Integrated circuit for smoke detector compatible with multiple power sources

Abstract

An AFE chip (101) for a smoke detector includes a DC / DC boost converter (102) having a boost input, a boost output, and a boost power-on input (110). The boost input is coupled to a first pin (P1) suitable for coupling to a battery through an inductor (L), and the boost output is coupled to a second pin (P2). The DC / DC boost converter (102) is configured to not switch when a voltage on the second pin (P2) is greater than a programmed boost voltage (VPGM). A set of power regulator circuits (113) has a power input coupled to a third pin (P3), and a power output. The third pin is suitable for receiving an input voltage, the power output is coupled to provide an internal voltage (Vint), and the set of power regulator circuits (113) is further coupled to the boost power-on input (110).

Description

BACKGROUND

[0001] The smoke alarm market requires a variety of power supply platforms to accommodate the needs of various applications, so smoke alarm suppliers often develop and sell different power supply versions of their products. Each platform uses a different hardware configuration by replacing discrete components or integrated circuit (IC) chips. It is desirable to have multiple power options with the same components. SUMMARY

[0002] The described embodiments provide an analog front end (AFE) chip for a smoke detector. The AFE chip can accept a wide range of power supply inputs while also supporting the 2020 UL requirements for smoke detectors. A pre-regulator on the AFE chip can accept a power supply input with a voltage between approximately two (2) volts and approximately fifteen (15) volts and provide a safe voltage to other circuits on the AFE chip. This capability has the output of a DC / DC boost converter on the AFE chip coupled to the AFE power input. The DC / DC boost converter is enabled by default, but can sense when a higher input voltage is provided and turn off the DC / DC boost converter when not needed. These two capabilities enable the AFE chip to be used with a variety of smoke detector power configurations.

[0003] In one aspect, embodiments of an AFE chip for a smoke detector are described. The AFE chip includes a DC / DC boost converter having a boost input, a boost output, and a boost upper power input, the boost input coupled to a first pin, the boost output coupled to a second pin, the first pin adapted to be coupled to a battery through an inductor, and the DC / DC boost converter configured to not switch when a voltage on the second pin is greater than a programmed boost voltage; and a set of power regulator circuits having a power input and a power output, the power input coupled to a third pin, the third pin adapted to receive an input voltage, the power output coupled to provide an internal voltage to a digital upper power input, the set of power regulator circuits further coupled to the boost upper power input.

[0004] In another aspect, embodiments of a smoke detection device are described. The smoke detection device includes an AFE chip and a trace, the AFE chip including a DC / DC boost converter having a boost input, a boost output, and a boost upper power input, the boost input coupled to a first pin, and the boost output coupled to a second pin, and a set of power regulator circuits having a power input and a power output, the power input coupled to a third pin, the third pin adapted to receive an input voltage, the power output coupled to provide an internal voltage; and the trace coupling the second pin to the third pin.

[0005] In yet another aspect, embodiments of a method of operating a smoke detector are described. The method couples, by a trace, an output pin of a DC / DC boost converter on an analog front end (AFE) chip to an input pin of a set of power regulator circuits on the AFE chip; and couples a power supply to the AFE chip. BRIEF DESCRIPTION OF DRAWINGS

[0006] Embodiments of the present description are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like references indicate similar elements. In the present description, different references to "an" or "one" embodiment do not necessarily refer to the same embodiment, and such references can mean at least one. In addition, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the purview of one of ordinary skill in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicit description of the same is provided. As used herein, the term "coupled" means either an indirect or direct electrical connection, unless the context requires otherwise, including a wireless connection, in accordance with the requirements of "communicatively coupled." Thus, if a first device is coupled to a second device, the connection can be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

[0007] The accompanying drawings are incorporated in and constitute a part of this specification, and together with the description of the specification, serve to explain one or more exemplary embodiments in the present description. Various advantages and features of the present description will be understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0008] Figure 1A A power configuration is depicted in accordance with embodiments of the present description, in which an IC chip is coupled to an AC / DC converter with a backup battery;

[0009] Figure 1B A power configuration is depicted in accordance with embodiments of the present description, in which an IC chip is coupled to an AC / DC converter with a backup battery;

[0010] Figure 1C A power configuration is depicted in accordance with embodiments of the present description, in which an IC chip is coupled to an AC / DC converter with a backup battery;

[0011] Figure 2 An example of a smoke detection device including an IC chip is depicted in accordance with embodiments of the present description;

[0012] Figure 2A A more detailed version of a digital core is depicted in accordance with embodiments of the present description;

[0013] Figure 3 A process of operating a smoke detector is described in accordance with embodiments of the present description; and

[0014] Figures 3A-3I A process of operating a smoke detector is described in accordance with embodiments of the present description; andFigure 3 elements that can be included in the process. DETAILED DESCRIPTION

[0015] Specific embodiments of the present application will now be described in detail with reference to the figures. In the following detailed description of embodiments of the application, numerous specific details are set forth in order to provide a more thorough understanding of the application. However, it will be apparent to one of ordinary skill in the art that the application can be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0016] The smoke alarm market requires multiple power supply platforms. Commercial smoke alarms and many residential smoke alarms use a combination of DC power from the main power, with battery power as backup when the main power is lost. For example, one power supply platform uses a combination of 12V DC input and 3V backup battery. Other power supply platforms rely solely on battery power, and can utilize low voltage inputs, such as 3V batteries, or high voltage inputs, such as 9V-12V batteries. These three platforms require different power management configurations, as the smoke alarm functions require different voltages, which can be lower or higher than these input voltages. For example, the horn driver function requires 10V-12V, while the smoke chamber AFE requires 2V-3V.

[0017] Depending on the power supply of the particular platform, a smoke alarm can have a DC / DC boost converter to provide a higher voltage from a lower input voltage, or a buck converter to provide a lower voltage from a higher input voltage; some configurations use both. An example DC / DC boost converter generates 10V-12V from a lower voltage input, such as 3V, while an example buck converter generates 2V-3V from a higher voltage input, such as 9V or 12V. Smoke alarm vendors historically develop and sell different power supply versions of their products. Each platform uses a different hardware configuration, differing by discrete components or IC chips. This situation is not ideal, as the development cost of multiple platforms, and the need to stock each of the components of the multiple platforms. Within these platforms, the AFE IC for the smoke detector typically only accepts lower voltage inputs, such as up to 5V, as the AFE can be configured to utilize 2V-3V.

[0018] Applicants have designed a single IC chip that integrates an AFE and power management to support multiple power combinations; this IC chip can be referred to herein as an AFE chip. The power input of the AFE chip is designed to have a wide input range, for example between 2V-15V. At the same time, a DC / DC boost converter on the AFE chip is enabled by default and is designed to be coupled to the power input of the AFE. The power input of the AFE receives at a pre-regulator that is designed to receive a high voltage and provide a power output in the 4V-5V range. The output of the pre-regulator provides power to the DC / DC boost converter and to an additional voltage regulator that provides power to other elements of the smoke detector.

[0019] The combination of a pre-regulator that can receive a high voltage and a default enabled DC / DC boost converter whose output is coupled to the input of the pre-regulator provides the AFE chip with multiple power configurations. Using this combination, the described AFE chip is able to support power configurations that can include a low voltage battery (3V) dedicated platform, a high voltage battery (9V) dedicated platform, and a platform that combines 12V DC power with a 3V backup battery.

[0020] Not only does the described IC chip provide versatility for use with different power platforms, but the overall power requirements are also low. Underwriters Laboratories (UL) introduced new requirements for smoke alarm certification in 2018 and implementation of these requirements will be completed in early 2020. These requirements include the ability of a smoke alarm to be powered by a 3-volt lithium battery for the ten-year life of the smoke alarm, which puts very strict limits on power usage. The described AFE chip supports this requirement.

[0021] Figures 1A-1C Each depicts a portion of a smoke detection device 100 that includes an AFE chip 101 according to embodiments of the present specification. The AFE chip 101 can contain multiple circuits for detecting smoke and / or carbon monoxide (CO), which are not specifically shown in these figures in order to emphasize the distinctions of the described embodiments. The AFE chip 101 includes a DC / DC boost converter 102 and a set of power regulator circuits 113 that provide the required power levels. In one described embodiment, the set of power regulator circuits 113 includes a pre-regulator circuit 104, an internal LDO regulator 106, and a microcontroller unit (MCU) LDO regulator 108. It can be noted that the set of power regulator circuits 113 can be greater than or less than the set specifically shown in these figures. For example, if the AFE chip does not power an MCU, then the MCU LDO can be omitted. Similarly, if the internal LDO regulator 106 and the MCU LDO regulator 108, if present, are adapted to work with the voltage on the third pin, then the pre-regulator circuit 104 is not needed.

[0022] The DC / DC boost converter 102 has a boost input coupled to the first pin P1, a boost output coupled to the second pin P2, and a boost power in 110. The first pin P1 can be coupled to a low voltage battery, such as a battery providing 3.0-3.6V voltage, although over time the battery power can decrease to about 2V, but can still provide power to the AFE chip 101, attached sensors, and attached MCU (not specifically shown in these figures). The DC / DC boost converter 102 operates with a wide range of input and output voltages, and can support multiple battery configurations and driver voltages. A program boost voltage VPGM can be set to indicate a desired boost output voltage Vbst. The DC / DC boost converter 102 provides a power good signal BST_PG that can be sent to a register in the digital core (not specifically shown in this figure) to inform the MCU when the boost converter is above 95% of the program boost voltage VPGM. When the DC / DC boost converter 102 is disabled, the power good signal BST_PG is set low.

[0023] Several register bits can be used to control the activity of the DC / DC boost converter 102. If the DC / DC boost converter 102 is to be enabled, the boost enable register bit BST_EN is set to “1”, and if the DC / DC boost converter 102 is to be disabled, the boost enable register bit BST_EN is set to “0”. If the DC / DC boost converter 102 is to be disabled during sleep mode (e.g., for low voltage battery operation), the boost sleep register bit SLP_BST can be set to “1”, and if the DC / DC boost converter 102 is to remain unchanged during sleep mode (e.g., when operating from an AC / DC converter), the boost sleep register bit SLP_BST can be set to “0”. When the smoke detection device 100 is in sleep mode (which will be described in more detail below), the boost sleep register bit SLP_BST disables the DC / DC boost converter 102 if it is enabled by the boost enable register bit BST_EN. The boost charge register bit BST_CHARGE can enable the boost converter until the power good signal BST_PG is high, at which point the boost charge register bit BST_CHARGE is reset to “0” and the DC / DC boost converter 102 is disabled. Other register bits can be used to enable the DC / DC boost converter 102 in the event of certain errors in the pre-regulator circuit 104 or the MCU LDO regulator 108.

[0024] The default-enabled DC / DC boost converter 102 can be powered from an AC / DC power supply providing approximately 12V and a backup battery providing approximately 3V. When the AC / DC power supply is connected and the power at pin 2 P2 is greater than the boost output voltage Vbst, the DC / DC boost converter 102 will not switch or draw power from the battery. When the AC / DC power supply is lost, the DC / DC boost converter 102 automatically enables and generates the boost output voltage Vbst based on the battery voltage Vbat. If only a 3V battery is connected, the default-enabled DC / DC boost converter can provide a higher voltage. This ensures that the power input of the AFE chip 101 can be powered with a high voltage when a battery, a 12V DC power supply, or either is connected.

[0025] The pre-regulator circuit 104 has a pre-regulator input coupled to pin 3 P3 and a pre-regulator output 112 coupled to the boost power input 110 and also coupled to pin 4 P4. As previously described, the pre-regulator circuit 104 can receive an input voltage Vcc ranging from approximately 2V (e.g., during startup) to approximately 15V. When the power input is less than approximately 4V, the pre-regulator circuit 104 simply passes the input voltage Vcc to other circuits using power. Once the power input rises above approximately 4V, the output of the pre-regulator circuit 104 is regulated, with its output ranging from approximately 4V to approximately 5.5V.

[0026] The internal LDO regulator 106 has an internal LDO on-power input 114 coupled to the pre-regulator output 112 and an internal LDO output coupled to pin 5 P5. During operation, the internal LDO regulator 106 receives a voltage provided by the pre-regulator circuit 104, which is not as tightly regulated as some internal circuitry requires, and provides a well-regulated internal voltage Vint to the analog block and digital core, which are not specifically shown in these figures. In one embodiment, the voltage provided by the internal LDO regulator 106 is approximately 2.3V.

[0027] The MCU LDO regulator 108 has an MCU-LDO power input 116, an MCU-LDO output, and an MCU select input 118. The MCU-LDO power input 116 is coupled to a pre-regulator output 112, the MCU-LDD output is coupled to pin 6 (P6), and the MCU select input 118 is coupled to pin 7 (P7). In one embodiment, the MCU LDO regulator 108 is also coupled to receive an MCU voltage setting signal VMCUSET 122 and an MCU enable signal MCUENA 120. In one embodiment, the MCU LDO regulator 108 can provide an MCU voltage Vmcu that can be set between approximately 1.5V and approximately 3.3V. The MCU select input 118 and pin 7 (P7) are used to set the initial value of the MCU voltage Vmcu from a selection of possible settings, while the MCU voltage setting signal VMCUSET 122 is stored in an internal register (not specifically shown in the figure) on the AFE chip 101, which can be programmed by the MCU to the final voltage setting once the MCU is operational. The MCU enable signal MCUENA 120 is an internal signal used to notify when the MCU should wake up after entering a sleep cycle. Similar to the DC / DC boost converter 102, if the MCU sleep register bit SLP_MCU is set to "1", the MCU LDO regulator 108 can be disabled during sleep mode, and if the MCU sleep register bit SLP_MCU is set to "0", the MCU LDO regulator 108 can remain unchanged during sleep mode. If the MCU LDO 108 was enabled before entering sleep mode, it is re-enabled when exiting sleep mode.

[0028] As a whole, this set of power regulator circuits 113 has a power input and a power output. In this embodiment, the power input is coupled to a third pin to receive the input voltage Vcc, and the power output is coupled within AFE 100 to multiple analog blocks and digital cores (none specifically shown in this figure) to provide the internal voltage Vint. This set of power regulator circuits 113 is also coupled to the boost on-supply input 110. Although Figures 1A-1C Each depicts the same AFE chip 101, but utilizes three different power configurations to illustrate the flexibility of the AFE chip 101's power regulation circuitry. Figure 1AIn this smoke detection device 100A, an AC / DC converter 103 and a backup battery 105 are coupled to an AFE chip 101. In one embodiment, the AC / DC converter 103 provides an 11.5V power supply, and the backup battery 105 is designed to deliver 3V-3.6V of power, although the battery may only provide about 2V near the end of the smoke alarm's ten-year lifespan. The backup battery 105 is coupled to a first pin P1 via an inductor L. A second pin P2 is coupled to a third pin P3 via a trace T1 on a circuit board (not specifically shown). A first diode D1, such as a Schottky diode, is coupled between the first pin P1 and the second pin P2.

[0029] AC / DC converter 103 is coupled to trace T1 via a second diode D2. It can be noted that the voltage on pin P2 is referred to here as the boost output voltage Vbst, even when DC / DC boost converter 102 is not supplying power. This convention is used because the boost output voltage Vbst on pin P2 is supplied via an internal metallization layer to other circuitry on the AFE chip 101, such as the speaker driver circuitry and interconnect I / O buffers (neither of which is specifically shown in this figure). When main power is available, AC / DC converter 103 supplies the boost output voltage Vbst, which can be equal to or greater than the programmed boost voltage VPGM, for example, approximately 11.5V-15V. DC / DC boost converter 102 senses the voltage on pin P2, and when the boost output voltage Vbst is equal to or greater than the programmed boost voltage VPGM, DC / DC boost converter 102 does not switch, thus not drawing power from the battery. When main power fails, the current supplied by AC / DC converter 103 disappears. When a voltage drop is sensed, the DC / DC boost converter is automatically activated and generates a boost output voltage Vbst from the 3V backup battery 105 at the programmed boost voltage VPGM.

[0030] A charging cycle begins when the boost output voltage Vbst is lower than the programmed boost voltage VPGM. When the boost output voltage Vbst is higher than the programmed boost voltage VPGM, the DC / DC boost converter does not switch. In a backup battery system, power is not drawn from the battery while the AC / DC converter provides a boost output voltage Vbst higher than the boost regulation voltage. If the AC / DC supply decreases, boost switching begins, drawing power from the battery to regulate the boost output voltage Vbst. In one embodiment, a boost timer BST_nACT monitors the time during which boost switching is not performed and notifies the MCU if boost activity is present. The boost timer BST_nACT can be programmable, for example, from 100 microseconds to 100 milliseconds, and can be used to determine whether power is received from the battery with a voltage higher than the programmed boost voltage VPGM or from the AC / DC converter.

[0031] Several power-saving options are incorporated into the AFE chip 101. Like other circuits powered by the pre-regulator circuit 104, the pre-regulator circuit 104 is capable of operating with only 2V-3V as the power supply. However, the attached speaker and other circuits described below require higher voltages provided by the DC / DC boost converter 102. When the AFE chip 101 operates at 3V battery power and the boost voltage VPGM is not currently required—for example, when none of the circuits requiring the boost voltage VPGM are active—the DC / DC boost converter 102 can be disabled, and the first diode D1 provides current flowing directly from the battery to the pre-regulator circuit 104, bypassing the DC / DC converter 102. However, when powered by a low-voltage battery, the attached MCU may require an MCU voltage Vmcu that is greater than the battery voltage but less than the voltage required by the speaker driver. In this case, the DC / DC boost converter 102 is modified to provide an intermediate voltage, thereby providing the necessary MCU voltage Vmcu.

[0032] Figure 1B An AFE chip 101 with a battery 107 is depicted, which is coupled to a first pin P1 via an inductor L. (See diagram below.) Figure 1A As shown, trace T1 is coupled between the second pin P2 and the third pin P3, and the first diode D1 is coupled between the first pin P1 and the second pin P2. Figure 1B Battery 107 and Figure 1A The main difference between the backup batteries 105 and 107 is that battery 107 operates as the sole power source for AFE chip 101, while backup battery 105 serves as a backup power source for the main power supply. Battery 107 again has an initial voltage in the range of approximately 3.0V-3.6V, but during the life of smoke alarm 100B, the voltage on battery 107 may drop to approximately 2V without affecting the operation of smoke alarm 100B.

[0033] During operation of the smoke alarm 100B, the DC / DC boost converter 102 will turn on during periods requiring higher voltage, such as during horn (not specifically shown) operation or during operation of other circuits requiring higher voltage. These additional circuits will be described below. When higher voltage is not required, power is received directly from the battery 107 at the pre-regulator circuit 104 via the first diode D1 and supplied directly by the pre-regulator circuit 104 to the internal LDO regulator 106 and the MCU LDO regulator 108. When needed, the DC / DC boost converter 102 generates 10V-12V from the battery 107 for horn driver supply. This DC / DC boost converter 102 is automatically enabled upon power-up to support battery power from as low as 2V. Once the device is powered on, the battery voltage can drop further, maintaining the device powered by the DC / DC boost converter.

[0034] Of particular interest is the scenario where battery 107 or backup battery 105 is coupled to AFE chip 101, but the battery has been depleted to 2V and no other supply has been pre-coupled. In this setup, if the MCU coupled to AFE chip 101 requires 3.3V, there is no means of supplying power to the MCU except by turning on DC / DC boost converter 102. DC / DC boost converter 102 turns on automatically and determines the voltage required by the MCU, for example, based on how pin 7 P7 is coupled. DC / DC boost converter 102 then provides a voltage suitable for turning on the MCU without any external programming.

[0035] Figure 1C A third configuration of the smoke detector 100C is depicted, in which a high-voltage battery 109, such as a 9V or 12V battery, is used, thus typically eliminating the need for a DC / DC boost converter 102. As shown in the smoke detector 100C, trace T1 is coupled between pin 2 P2 and pin 3 P3, and battery 109 is coupled to trace T1. Pin 1 P1 does not receive any input and remains floating. When power is applied to the smoke detection device 100C, the DC / DC boost converter 102 is automatically enabled, sensing a high voltage on pin 2 P2 to verify that the device is ready to power on, and can be disabled during operation. Pre-regulator circuitry 104 provides a voltage in the 4V-5V range to internal LDO regulator 106 and MCU LDO regulator 108, and when a higher voltage is required, such as through a horn driver (not specifically shown), a higher voltage is obtained using internal coupling with pin 2 P2 (not specifically shown).

[0036] Figure 2A block diagram of a smoke detector (also referred to as smoke detection device 200) according to an embodiment of this specification is depicted, the smoke detector being adapted to utilize an input voltage range between approximately 2 volts and approximately 15 volts. Smoke detection device 200 includes five basic components: an AFE chip 201, a power source 203, one or more sensors 205, an alarm system 207, and an MCU chip 209.

[0037] The AFE chip 201 includes a DC / DC boost converter 202, a pre-regulator circuit 204, an internal LDO regulator 206, an MCU LDO regulator 208, and a voltage divider 210. As shown in the smoke detection device 200, the DC / DC boost converter 202, the pre-regulator circuit 204, the internal LDO regulator 206, and the MCU LDO regulator 208 correspond to... Figures 1A-1C Each of these components has its corresponding counterpart and is coupled as previously described in those figures. In one embodiment, the DC / DC boost converter 202 provides a boost output voltage Vbst of approximately 11.5V, the pre-regulator circuit 204 provides a pre-regulator output voltage Vprereg between approximately 4V and approximately 5.4V, the internal LDO regulator 106 provides an internal voltage Vint of approximately 2.3V, and the MCU LDO 108 is capable of providing an optional MCU voltage Vmcu between approximately 1.2V and approximately 3.3V. In one embodiment, the MCU LDO regulator 208 is further coupled to receive an MCU select input 215 from pin 7 P7, which can be used to set an initial value for the MCU voltage Vmcu, and an MCU voltage setting signal VMCUSET 213, which is available from the MCU chip 209 once the MCU is operational. The MCU LDO regulator 208 may also receive an MCU enable signal MCUENA 211, which indicates when the MCU should be woken up after it has entered a sleep period. In one embodiment, pin 7 P7 can be coupled via a 620Ω resistor to a) ground, b) left float, c) internal voltage Vint, and d) ground, where each possible connection is related to the initial MCU voltage Vmcu.

[0038] The AFE chip 201 also includes sensor drivers, such as a CO detection circuit 212, a light detection circuit 214, and an ion detection circuit 216. In one embodiment, as shown, the CO detection circuit 212 has a CO-on-power input coupled to receive power from an internal LDO 206; the CO detection circuit 212 is further coupled to a plurality of CO pins 220. The light detection circuit 214 has a light-on-power input coupled to receive power from an internal LDO 206; the light detection circuit 214 is further coupled to a plurality of light detection pins 222. In one embodiment, the light detection circuit 214 includes a first light-emitting diode (LED) driver 224 and a second LED driver 226. The ion detection circuit 216 has an ion-on-power input coupled to receive power from a DC / DC boost converter 202; the ion detection circuit 216 is further coupled to a plurality of ion pins 228.

[0039] To supply the information collected by sensor 205, multiplexer 230 is coupled to the CO output of CO detection circuit 212, the first and second light outputs of light detection circuit 214, the ion output of ion detection circuit 216, and VCC divider 210 providing a voltage divider Vccdiv. By passing the voltage divider Vccdiv to MCU chip 209, MCU chip 209 is able to monitor the voltage that pre-regulator circuit 204 can provide. This may be particularly important when smoke detection device 200 is operated by a low-voltage battery such as backup battery 105 or battery 107. Multiplexer 230 has a power input on the MUX coupled to receive power from internal LDO 206. Multiplexer 230 is further coupled to selectively provide data from the detection circuitry to the MUX pin Pmux via buffer amplifier 232. As shown, the final elements of the AFE circuitry system in AFE chip 201 are interconnect I / O buffer 234 and speaker driver 236. Interconnect I / O buffer 234 has an upper power input coupled to receive power from DC / DC boost converter 202, and interconnect I / O buffer 234 is further coupled to a first interconnect pin Pi1 and a second interconnect pin Pi2, as will be described further below. Speaker driver 236 is also coupled to receive power from boost output voltage Vbst, and is further coupled to a plurality of speaker pins 238.

[0040] Power source 203 will typically include a battery that can be used as a backup power source in the event of a power outage or as the main power source for smoke detection device 200, and may also include a connection to the main power source via an AC / DC converter. For example... Figure 2As shown, power source 203 includes AC / DC converter 240 and backup battery 242, but may include other power configurations, including any power configurations described herein.

[0041] Sensor 205 may include a CO sensor 244, one or more light sensors 246, an LED 248, and an ionization sensor 250, or some combination of these sensors. For example, not every smoke detection device 200 will include a CO sensor 244, and not every smoke detection device 200 will include an ionization sensor 250. When present, the CO sensor 244 is coupled to the CO detection circuit 212 via a plurality of CO pins 220, and the ionization sensor 250 is coupled to the ionization detection circuit 216 via a plurality of ion pins 228.

[0042] Current UL standards require the ability to distinguish between different types of fires with varying particle sizes. To address this, many smoke detection devices 200 now include two distinct LEDs 248, such as a blue LED and an infrared LED. Each LED 248 is coupled to either a first LED driver 224 or a second LED driver 226, and each LED is used in conjunction with a different light sensor 246. Both the light sensor(s) 246 and the LEDs 248 are coupled to a light detection circuit 214 via multiple light detection pins 222.

[0043] Alarm system 207 is a device that can communicate a problem detected by smoke detection device 200 to people inside and / or monitoring the affected building. As shown, alarm system 207 may include an attached horn 252, horn driver 236, and interconnection capabilities for connecting to a centralized alarm system, such as interconnect I / O buffer 234. When using a horn, horn 252 may be attached to horn pin 238. If it is desired to connect multiple residential smoke detection devices 200 together, interconnect I / O buffer 234 provides a means for the smoke detection devices to communicate with each other. Commercial smoke detection systems typically do not use horns or interconnection functions within a single smoke alarm, but instead use signal line circuitry (SLC). Interconnect I / O buffer 234 and horn driver 236 are also designed to be SLC compatible, and both multiple horn pins 238 and the second interconnect pin Pi2 can be used to couple to and communicate with the centralized alarm system. As can be seen, the first pin Pi1 is coupled to MCU chip 209, enabling MCU chip 209 to communicate with the centralized alarm system.

[0044] The MCU chip 209 is coupled to the AFE chip 201 via multiple MCU pins 254, including a sixth pin P6, a MUX pin Pmux, a first interconnect pin Pi1, and multiple additional pins for general-purpose I / O, for programming registers in the digital core 256 (not specifically shown in the figure), and for controlling various functions via the AFE chip 201.

[0045] In one embodiment, AFE chip 201 integrates a sleep timer to help manage critical analog and regulator circuitry independent of MCU chip 209. The sleep timer starts when MCU chip 209 enables sleep mode. Several circuits on AFE chip 201 can be disabled, such as portions of MCU LDO regulator 208, DC / DC boost converter 202, multiplexer 230, light detection circuitry 214, and ion detection circuitry 216. In one embodiment, whether DC / DC boost converter 202, MCU LDO regulator 208, and analog block are disabled depends on the corresponding settings in the boost sleep register bit SLP_BST, MCU sleep register bit SLP_MCU, and analog sleep register bit SLP_ADALOG. After the sleep timer expires, AFE chip 201 notifies MCU chip 209 that it can exit sleep mode. When AFE chip 201 exits sleep mode, the circuitry on AFE chip 201 is set to its pre-sleep state.

[0046] Sleep mode reduces power consumption in three ways:

[0047] • By quickly disabling the simulation block;

[0048] • By turning off the power to the DC / DC boost converter 202 and the MCU LDO regulator 208 during sleep mode; and.

[0049] • By putting the MCU into its lowest power idle state.

[0050] During sleep mode operation, MCU chip 209 can enter its lowest power idle state and monitor general-purpose I / O pins to indicate when to exit the sleep cycle. This monitoring disables the clock on MCU chip 209 as AFE chip 201 signals the MCU to wake up after a precise programming time, which in one embodiment is programmable.

[0051] Figure 2AA more detailed version of the digital core 256 and its corresponding connections to the MCU chip 209 are depicted. In this embodiment, what is shown as part of the digital core 256 is the bus interface 258 and a memory device containing register bits 260, although these elements could also be implemented as separate circuits coupled to the digital core. The bus interface 258 is coupled to the serial data pin SDA and the serial clock pin SCL; in the smoke detection device 200, the serial data pin SDA and the serial clock pin SCL are coupled to a bus interface (not specifically shown) in the MCU chip 209. In one embodiment, the bus interface 258 is an internal integrated circuit (I2C) interface utilizing the I2C communication protocol. Because the bus interface 258 needs to operate in two separate voltage domains to work with both the digital core 256 and the MCU 209, the digital core 256 receives the MCU voltage Vmcu at the MCU power input 257 and the internal voltage Vint at the digital power input 259.

[0052] Register bit 260 contains a large number of registers / register bits that can be used to provide parameters and control for smoke detection device 200. Figure 2A Only a few of register bits 260 are shown. The programming boost voltage VPGM is set by MCU chip 209 and stored in programming boost voltage register bit VPGMR 262. The power good signal BST_PG is set by DC / DC boost converter 202 and stored in power good register bit BST_PGR 264 to notify MCU chip 209 when DC / DC boost converter 202 is above 95% of the programming boost voltage VPGM. Boost enable register bit BST_EN 266 can be used to enable or disable DC / DC boost converter 202 and can be controlled by MCU chip 209. If DC / DC boost converter 202 is turned off during sleep mode, boost enable register bit BST_EN 266 can also be controlled by a sleep timer. The boost charge register bit BST_CHARGE 268 can be configured to provide additional control over the DC / DC boost converter 202. For example, when enabled, the DC / DC boost converter 202 is enabled until the programmed boost voltage register bit VPGMR 262 is enabled; when disabled, the boost enable register bit BST_EN 266 provides control. The boost activity monitor register bit BST_nACTR 270 is enabled by the DC / DC boost converter 202 when the boost timer BST_nACT indicates that the DC / DC boost converter 202 has not switched for a pre-selected amount of time. The MCU chip 209 can use the boost activity monitor register bit BST_nACTR 270 to determine that the current power configuration is not using the DC / DC boost converter 202, for example, because a power supply providing a voltage greater than the programmed boost voltage VPGM is coupled to provide the input voltage VCC.

[0053] The boost sleep register bit SLP_BST 272, the MCU sleep register bit SLP_MCU 274, and the analog sleep register bit SLP_ANALOG 276 are used to determine whether the DC / DC boost converter 202, the MCU LDO regulator 208, and the analog block are disabled during sleep mode. The analog block may include, for example, high-power amplifiers and drivers, such as multiplexer 230, speaker driver 236, interconnect I / O buffer 234, and light detection circuitry 214, which includes a first LED driver 224 and a second LED driver 226. The MCU voltage setting signal VMCUSET 213 is set by the MCU chip 209, stored in the MCU voltage setting register VMCUSETR 278, and indicates the operating voltage supplied to the MCU chip 209 by the MCU LDO regulator 208. The MCU enable signal MCUENA 211 can be provided to the MCU LDO regulator 208 from the MCU enable register bit MCUENAR 280 or from the sleep timer. In one embodiment, the sleep timer is provided as the sleep timer register SLP_TIMER 282.

[0054] Figure 3 A process 300 for operating a smoke detector according to an embodiment of this specification is described. Process 300 begins by coupling a boost output pin (e.g., second pin P2) on the analog front-end (AFE) chip 305 to an input pin (e.g., third pin P3) of a set of power regulator circuitry on the AFE chip via a trace, and coupling power supply 310 to the AFE chip. By coupling the boost output pin to the input pin of this set of power regulator circuitry, the first IC chip is able to couple to at least three power configurations described in embodiments of smoke detection devices 100A, 100B, and 100C.

[0055] Figures 3A-3I Each of these describes an additional action that can be part of process 300. Figure 3A In the middle, a battery with a rated voltage between approximately 9V and approximately 12V (inclusive) is coupled to trace 320, and the boost input pin remains floating at 325, as... Figure 1C The smoke detection equipment is shown. Figure 3B In this configuration, a battery with a rated voltage between approximately 2V and approximately 3.6V (inclusive) is coupled to the boost input pin via an inductor 330, and a diode 335 is coupled between the boost input pin and the boost output pin. Figure 1B The smoke detection equipment is shown. Figure 3C In the middle, the DC output of the AC / DC converter is coupled 340 to trace T1; this is combined Figure 3BThe components were completed, and in Figure 1A The diagram in the middle is shown.

[0056] exist Figure 3D In this configuration, it can be combined with any of the aforementioned components. The power supply pin on the MCU chip is coupled to the MCU LDO pin on the AFE chip, and the MCU select pin on the AFE chip (e.g., pin 7, P7) is also coupled to the MCU LDO pin on the AFE chip. Figure 2 The 355 timer is coupled to reflect the desired initial voltage on the MCU LDO pin, which is selected from a set of available initial voltages. Figure 3E In this context, the coupled MCU select pin is further defined as including coupling using 360 selected from the group consisting of: coupling the MCU select pin to ground to select a first voltage; coupling the MCU select pin to ground via a 620Ω resistor to select a second voltage; coupling the MCU select pin to an internal LDO pin to select a third voltage; and floating the MCU select pin to select a fourth voltage.

[0057] exist Figure 3F In process 300, in response to the DC / DC boost converter determining that the voltage at the boost output pin is equal to or greater than the programmed boost voltage VPGM, the MCU chip stops the DC / DC boost converter on the AFE chip from switching. Furthermore, when the DC / DC boost converter does not switch for a programmable amount of time, for example because the AC / DC converter is coupled to track T1, the MCU chip can also disable the DC / DC boost converter until the conditions change. Figure 3G In response to the MCU chip determining that the smoke detector operates on 3.6 volts or less of battery power and that no circuitry requiring higher voltages is active, such as horn driver circuitry, interconnect I / O buffers, or MCU LDOs to supply the MCU chip, the DC / DC boost converter on the AFE chip can be disabled 370. Figure 3H In the AFE chip, a set of power regulator circuitry receives an input voltage between approximately 2 volts and approximately 15 volts and provides an output voltage between approximately 2 volts and approximately 5 volts. This ability of the pre-regulator circuitry to accept a wide voltage range and provide a safe output voltage for the low-voltage circuitry on the AFE chip offers great flexibility in powering smoke detectors. Finally, in Figure 3I In response to entering sleep mode, the indicated circuit is disabled 380. The indicated circuit can be selected from a circuit set that includes a DC / DC boost converter, an MCU LDO regulator, a multiplexer, portions of a photodetector circuit, and portions of an ion detection circuit.

[0058] The applicant has described an AFE chip for smoke detection devices and a smoke detection device using the described AFE chip. The AFE chip is designed for versatility with a variety of power sources, allowing use with batteries rated between 2V and 15V, or accepting mains power via an AC / DC converter. The DC / DC boost converter on the AFE chip is capable of detecting the voltage at the boost output and accessing additional information to determine if a DC / DC boost converter is needed. The pre-regulator circuitry can accept a wide range of input voltages and provides a safe output voltage for other power circuitry on the AFE chip. The process of operating the smoke detector is also described.

[0059] Although various embodiments have been shown and described in detail, the claims are not limited to any particular embodiment or example. None of the above detailed descriptions implies that any particular component, element, step, action, or function is necessary and must therefore be included within the scope of the claims. Unless expressly stated otherwise, references to the singular form of an element do not mean "one and only one," but rather "one or more." All structural and functional equivalents of the elements of the above embodiments known to those skilled in the art are expressly incorporated herein by reference and are included in these claims. Therefore, those skilled in the art will recognize that the exemplary embodiments described herein can be implemented with various modifications and alterations within the spirit and scope of the appended claims.

Claims

1. An analog front end (AFE) chip for a smoke detector, the AFE chip comprising: a DC / DC boost converter having a boost input, a boost output, and a boost power-on input, the boost input coupled to a first pin, the boost output coupled to a second pin, the first pin adapted to be coupled to a battery through an inductor, and the DC / DC boost converter configured to not switch when a voltage on the second pin is greater than a programmed boost voltage; and a set of power regulator circuits having a power input and a power output, the power input coupled to a third pin, the third pin adapted to receive an input voltage, the power output coupled to provide an internal voltage, the set of power regulator circuits further coupled to the boost power-on input.

2. The AFE chip of claim 1, wherein the set of power regulator circuits comprises: a pre-regulator having a pre-regulator input and a pre-regulator output, the pre-regulator input coupled to the third pin, the pre-regulator output coupled to the boost power-on input and a fourth pin; an internal low dropout (LDO) regulator having an internal LDO power-on input and an internal LDO output, the internal LDO power-on input coupled to the pre-regulator output, and the internal LDO output coupled to a fifth pin; and a microcontroller unit (MCU) LDO regulator having an MCU-LDO power-on input, an MCU-LDO output, and an MCU select input, the MCU-LDO power-on input coupled to the pre-regulator output, the MCU-LDO output coupled to a sixth pin, and the MCU select input coupled to a seventh pin, the sixth pin adapted to be coupled to an MCU.

3. The AFE chip of claim 2, comprising: a carbon monoxide (CO) detection circuit having a CO power-on input and a CO output, the CO power-on input coupled to the internal LDO output, the CO detection circuit coupled to a plurality of CO pins; a light detection circuit having a light power-on input, a first light output, and a second light output, the light power-on input coupled to the internal LDO output, and the light detection circuit coupled to a plurality of light pins; an ion detection circuit having an ion power-on input and an ion output, the ion power-on input coupled to the boost output, and the ion detection circuit coupled to a plurality of ion pins; a multiplexer (MUX) having a MUX power-on input, a MUX output, a first MUX input, a second MUX input, a third MUX input, and a fourth MUX input, the MUX power-on input coupled to the internal LDO output, the first MUX input coupled to the CO output, the second MUX input coupled to the first light output, the third MUX input coupled to the second light output, and the fourth MUX input coupled to the ion detection output; and a multiplexer (MUX) having a MUX power-on input, a MUX output, a first MUX input, a second MUX input, a third MUX input, and a fourth MUX input, the MUX power-on input coupled to the internal LDO output, the first MUX input coupled to the CO output, the second MUX input coupled to the first light output, the third MUX input coupled to the second light output, and the fourth MUX input coupled to the ion detection output; and ​ a buffer amplifier coupled between the MUX output and a MUX pin.

4. The AFE chip of claim 3, comprising: a horn driver having a horn upper power input coupled to the boost output and a horn enable signal, the horn driver coupled to a plurality of horn pins; and an interconnect I / O buffer coupled between a first interconnect pin and a second interconnect pin.

5. A smoke detection device, comprising: an analog front end chip (AFE chip) comprising: a DC / DC boost converter having a boost input, a boost output, and a boost upper power input, the boost input coupled to a first pin and the boost output coupled to a second pin, and the DC / DC boost converter configured to not switch when a voltage on the second pin is greater than a programmed boost voltage, and a set of power regulator circuits having a power input coupled to a third pin adapted to receive an input voltage and a power output coupled to provide an internal voltage; and a trace coupling the second pin to the third pin.

6. The smoke detection device of claim 5, comprising: a battery coupled to the first pin through an inductor, the battery having a voltage between 2 volts and 3.6 volts; and a first diode coupled between the first pin and the second pin.

7. The smoke detection device of claim 6, comprising an AC-DC converter having a DC output coupled to the trace through a second diode.

8. The smoke detection device of claim 5, comprising: the first pin being floating; and a battery coupled to the trace, the battery having a voltage of 9 volts or greater.

9. The smoke detection device of claim 5, wherein the set of power regulator circuits comprises: a pre-regulator having a pre-regulator input coupled to a third pin and a pre-regulator output, the pre-regulator output coupled to the boost upper power input and a fourth pin, an internal low dropout regulator (LDO) having an internal LDO upper power input coupled to the pre-regulator output and an internal LDO output, the internal LDO output coupled to a fifth pin, and a microcontroller unit (MCU) LDO regulator having an MCU-LDO upper power input coupled to the pre-regulator output, an MCU-LDO output coupled to a sixth pin, and an MCU select input coupled to a seventh pin; and wherein the AFE chip comprises: a carbon monoxide detection circuit (CO detection circuit) having a CO upper power input coupled to the internal LDO output and a CO output, the CO detection circuit coupled to a plurality of CO pins; a light detection circuit having a light-on power input coupled to the internal LDO output and a first light output and a second light output, the light detection circuit coupled to a plurality of light pins; an ion detection circuit having an ion-on power input coupled to the boost output and an ion output, the ion detection circuit coupled to a plurality of ion pins; a multiplexer (MUX) having a MUX-on power input coupled to the internal LDO output, a MUX output, a first MUX input coupled to the CO output, a second MUX input coupled to the first light output, a third MUX input coupled to the second light output, and a fourth MUX input coupled to the ion detection output; and the MUX output coupled to a MUX pin; an interconnect I / O buffer coupled between a first interconnect pin and a second interconnect pin; and a horn driver having a horn-on power input coupled to the boost output and a horn enable signal, the horn driver coupled to a plurality of horn pins.

10. The smoke detection device of claim 9, comprising: a microcontroller unit (MCU) chip having an MCU-on power pin coupled to the sixth pin and a plurality of MCU I / O pins, a first MCU pin of the plurality of MCU I / O pins coupled to the MUX pin, and a second pin of the plurality of MCU I / O pins coupled to the first interconnect pin.

11. The smoke detection device of claim 10, comprising: a carbon monoxide (CO) detector having a plurality of CO terminals coupled to the plurality of CO pins; first and second light emitting diodes (LEDs) having a plurality of LED terminals; a photodiode having a plurality of photodiode terminals, the LED terminals and the photodiode terminals coupled to the plurality of light pins; an ion sensor having a plurality of terminals coupled to the plurality of ion pins; and a horn having a plurality of terminals coupled to the plurality of horn pins.

12. A method of operating a smoke detector, comprising: coupling, by a trace, an output pin of a DC / DC boost converter on an analog front end (AFE) chip to an input pin of a set of power regulator circuits on the AFE chip; coupling a power source to the AFE chip; and stopping switching of the DC / DC boost converter in response to the DC / DC boost converter determining that a voltage at the output pin is equal to or greater than a programmed boost voltage. ​ ​ 13. The method of claim 12, wherein coupling the power source to the AFE chip comprises coupling a battery to the trace and floating an input pin of the DC / DC boost converter, the battery having a voltage between 9V and 12V, inclusive.

14. The method of claim 12, wherein coupling the power source to the AFE chip comprises: coupling a battery to an input pin of the DC / DC boost converter through an inductor, the battery having a voltage between 3 volts and 3.6 volts; and coupling a diode between the input pin of the DC / DC boost converter and the output pin of the DC-DC boost converter.

15. The method of claim 14, comprising coupling a DC output of an AC-DC converter to the trace.

16. The method of claim 12, comprising: coupling a power-on pin on an MCU chip to a microcontroller unit low dropout pin, MCU LDO pin, on the AFE chip; and coupling an MCU select pin on the AFE chip to reflect a desired initial voltage on the MCU LDO pin, the desired initial voltage selected from a set of available initial voltages.

17. The method of claim 16, wherein coupling the MCU select pin comprises using a coupling selected from the group consisting of: coupling the MCU select pin to ground to select a first voltage; coupling the MCU select pin to ground via a 620Ω resistor to select a second voltage; coupling the MCU select pin to an internal LDO pin to select a third voltage; and floating the MCU select pin to select a fourth voltage.

18. The method of claim 16, comprising disabling the DC / DC boost converter on the AFE chip in response to the MCU chip determining that the smoke detector is operating on battery power of 3.6 volts or less and that no circuit requiring a higher voltage is active.

19. The method of claim 12, comprising the set of power regulator circuits on the AFE chip receiving an input voltage between 2 volts and 15 volts and providing an output voltage between 2 volts and 5 volts.

20. The method of claim 16, comprising disabling an indication circuit in response to entering a sleep mode, the indication circuit selected from a set of circuits comprising the DC / DC boost converter, the MCU LDO regulator, a multiplexer, a portion of a light detection circuit, and a portion of an ion detection circuit.

Images