Short Circuit Detection Circuit

Abstract

The short circuit detection circuit (100) includes a first transistor (102), a switched load circuit (110), a second transistor (104), a switched capacitor circuit (120), and a comparator (130). The first transistor is configured to conduct a load current. The switched load circuit is coupled to the first transistor and configured to switchably draw a test current. The second transistor is coupled to the first transistor. The second transistor is configured to conduct a sense current. The sense current includes first and second portions representing the load current and the test current, respectively. The switched capacitor circuit is coupled to the second transistor and configured to generate a short circuit detection voltage representing the second portion. The comparator has a first comparator input coupled to the switched capacitor circuit. The comparator is configured to compare the short circuit detection voltage with a short circuit threshold voltage.

Description

[Technical Field]

[0001] Circuit protection devices, such as fuses and circuit breakers, protect electrical circuits from damage caused by overcurrent and short-circuit conditions. An overcurrent condition occurs when the current flowing through a circuit exceeds the circuit's design rating (e.g., due to load demands). A short-circuit condition occurs when conductive elements in a circuit establish contact, causing current to bypass the circuit's electrical load, potentially resulting in very high currents. Overcurrent and short-circuit conditions can damage conductors and other components of an electrical circuit due to overheating of the conductor wiring, potentially resulting in burned wiring insulation. Circuit protection devices detect the occurrence of an overcurrent or short-circuit condition and open an electrical switch or otherwise reduce the flow of current to the protected electrical circuit to prevent circuit damage.

[0002] Fuses, positive temperature coefficient resistors, and active circuit protection are examples of available circuit protection devices. Fuses are typically used to isolate overload or short-circuit faults from the main system. However, the fault current generally needs to be much higher than the fuse's rating, and response times range from milliseconds to seconds, making it difficult to predict the exact overcurrent level at which the fuse will open. Once a fuse opens, it must be physically replaced, thereby increasing system downtime and maintenance costs. Positive temperature coefficient resistors provide resettable overcurrent protection and, unlike fuses, do not require replacement. Positive temperature coefficient resistors' response times are in the range of milliseconds, and they increase in resistance with each activation.

[0003] Active circuit protection devices measure the current flowing through a field effect transistor (FET) and control the resistance of the FET to limit the current flowing to the load when a fault condition is detected. Active current protection devices can respond faster and provide more accurate fault detection than passive solutions. Summary of the Invention

[0004] Circuit elements for detecting a short circuit in or through a pass transistor are described herein. In one example, the short circuit detection circuit includes a first transistor, a first resistor, a second transistor, a current source, a second resistor, a switched capacitor circuit, and a comparator. The first transistor has a first current terminal, a second current terminal, and a first control terminal. The first resistor is coupled between the second current terminal and a ground terminal. The second transistor has a third current terminal, a fourth current terminal, and a second control terminal. The third current terminal is coupled to the first current terminal. The second control terminal is coupled to the first control terminal. The current source has a current output and a current input. The current input is coupled to the fourth current terminal. The second resistor is coupled between the current output and the ground terminal. The switched capacitor circuit is coupled between the current output and the ground terminal. The comparator has a comparator output, a first comparator input, and a second comparator input, the first comparator input coupled to the switched capacitor circuit, and the second comparator input coupled to the reference voltage terminal.

[0005] In another example, a short circuit detection circuit includes a first transistor, a switched load circuit, a second transistor, a switched capacitor circuit, and a comparator. The first transistor is configured to conduct a load current. The switched load circuit is coupled to the first transistor. The switched load circuit is configured to switchably draw a test current. The second transistor is coupled to the first transistor. The second transistor is configured to conduct a sense current. The sense current includes first and second portions. The first portion represents the load current and the second portion represents the test current. The switched capacitor circuit is coupled to the second transistor. The switched capacitor circuit is configured to generate a short circuit detection voltage representing the second portion. The comparator has an output, a first comparator input, and a second comparator input. The first comparator input is coupled to the switched capacitor circuit. The comparator is configured to compare the short circuit detection voltage with a short circuit threshold voltage.

[0006] In a further example, a system includes a power terminal, a load terminal, and an electronic fuse (EFUSE) circuit. The electronic fuse circuit includes a first transistor, a switched load circuit, a second transistor, a switched capacitor circuit, and a comparator. The first transistor is configured to conduct a load current from the power terminal to the load terminal. The switched load circuit is coupled to the first transistor. The switched load circuit is configured to switchably sink a test current. The second transistor is coupled to the first transistor. The second transistor is configured to conduct a sense current. The sense current includes first and second portions. The first portion represents the load current and the second portion represents the test current. The switched capacitor circuit is coupled to the second transistor. The switched capacitor circuit is configured to generate a short circuit detection voltage representing the second portion. The comparator has an output, a first comparator input, and a second comparator input. The first comparator input is coupled to the switched capacitor circuit. The comparator is configured to compare the short detection voltage with the short threshold voltage. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a schematic level diagram of an exemplary short circuit detection circuit.

[0008] [Figure 2] 2 is a schematic diagram of an exemplary current source suitable for use in the short circuit detection circuit of FIG. 1;

[0009] [Figure 3A] 2 is a diagram of an example signal generated in the short circuit detection circuit of FIG. 1. [Figure 3B] 2 is a diagram of an example signal generated in the short circuit detection circuit of FIG. 1.

[0010] [Figure 4] 1 is a flowchart of an example method for determining whether a short exists based on multiple short detection tests.

[0011] [Figure 5] 5 is a diagram of an exemplary short circuit defect signal generated in the short circuit detection circuit of FIG. 1 based on the method of FIG. 4.

[0012] [Figure 6] FIG. 1 is a block diagram for an example system including an electronic fuse with short circuit detection. [Figure 7] FIG. 1 is a block diagram for an example system including an electronic fuse with short circuit detection. DETAILED DESCRIPTION OF THE INVENTION

[0013] Many electrical systems include active circuit protection devices, such as electronic fuses (EFUSEs), to limit power to the system or to portions of the system in the event of a fault. However, if the defect is a failure of the EFUSE's pass transistor, the EFUSE cannot limit the power provided to the system. Failures related to the EFUSE's pass transistor include failure of the pass transistor itself, external short circuits caused by miswiring or unintended solder connections, and so on. Some systems attempt to protect against such short circuits by using two EFUSEs in series, so that if one EFUSE fails, the other EFUSE can limit power to the system. However, using multiple EFUSEs increases system size (circuit area) and cost.

[0014] The short circuit detection circuit described herein can be used in an EFUSE or other electronic system to detect internal or external short circuits in a pass transistor. The short circuit detection switchably connects a current source to the output of the pass transistor. The current flowing through the pass transistor is represented by a sense current flowing through a sense transistor. A short circuit is deemed to exist when the sense current due to the current source is below a threshold. The sense current due to the current source is detected by a switched capacitor circuit that generates a voltage representing the difference between the sense current flowing with and without the current source connected to the pass transistor.

[0015] 1 is a schematic level diagram of an exemplary short-circuit detection circuit 100. The short-circuit detection circuit 100 includes a pass transistor 102, a sense transistor 104, an amplifier 106, a transistor 108, a switched current source 110, a switched capacitor circuit 120, a comparator 130, a current source 132, a resistor 134, and a control circuit 136. The short-circuit detection circuit 100 is coupled between a voltage source 140 (e.g., a power terminal) and a load 142 (e.g., a load terminal) and passes power from the voltage source 140 to the load 142 through the pass transistor 102. The voltage source 140 may be a battery, a power supply circuit, or other voltage-generating device. The load 142 may be an electric or electronic circuit.

[0016] The pass transistor 102, the sense transistor 104, and the transistor 108 may be n-channel field effect transistors (NFETs). The sense transistor 104 is coupled in parallel with the pass transistor 102. A first current terminal (e.g., drain) of the pass transistor 102 is coupled to a first current terminal (e.g., drain) of the sense transistor 104, and a control terminal (e.g., gate) of the pass transistor 102 is coupled to a control terminal (e.g., gate) of the sense transistor 104. A sense current (ISENSE) flowing through the sense transistor 104 represents the current flowing through the pass transistor 102 to the load 142.

[0017] 1 , resistor Rext represents the external resistance across pass transistor 102, resistor Rfet represents the resistance of pass transistor 102, and resistor Rsns represents the resistance of sense transistor 104. If an external short is present across pass transistor 102, the resistance of Rext will be small (e.g., less than 40 milliohms). Similarly, if the pass transistor is defective, the resistance of Rfet may be less than a selected value (less than 30 milliohms). The sense transistor 104 may be a scaled replica of pass transistor 102. For example, the channel width of pass transistor 102 may be N times larger than the channel width of sense transistor 104 such that the current flowing through pass transistor 102 is N times larger than the sense current flowing through sense transistor 104.

[0018] Amplifier 106 and transistor 108 are coupled to sense transistor 104 to maintain the second current terminal of sense transistor 104 at the same potential as the second current terminal of pass transistor 102. A first input of amplifier 106 is coupled to the second current terminal of pass transistor 102, and a second input of amplifier 106 is coupled to the second current terminal of sense transistor 104. A first current terminal (e.g., a drain) of transistor 108 is coupled to the second input of amplifier 106, and a second current terminal (e.g., a source) of transistor 108 is coupled to a ground terminal. A control terminal (e.g., a gate) of transistor 108 is coupled to the output of amplifier 106. Transistor 108 sinks I Sense, and amplifier 106 controls the voltage of the control terminal of transistor 108 to make the voltage at the second current terminal of sense transistor 104 equal to the voltage at the second current terminal of pass transistor 102.

[0019] Because short circuit detection circuit 100 does not control load 142, short circuit detection circuit 100 cannot identify a short circuit based on the current flowing through load 142. Short circuit detection circuit 100 includes a switched current source 110 for receiving (sinking) a predetermined test current to determine whether a short circuit (internal or external) exists across pass transistor 102. Switched current source 110 includes an amplifier 112, a resistor 114, a transistor 116, and a switch 118. A first current terminal (e.g., drain) of transistor 116 is coupled to a second current terminal of pass transistor 102 via switch 118. A second current terminal (e.g., source) of transistor 116 is coupled to a first input (e.g., inverting amplifier input) of amplifier 112. A control terminal (e.g., gate) of transistor 116 is coupled to the output of amplifier 112. A second input (e.g., non-inverting amplifier input) is coupled to a reference terminal of bandgap voltage circuit 117. Resistor 114 is coupled between the second current terminal of transistor 116 and a ground terminal. Resistor 114 includes a first resistor terminal coupled to amplifier 112 and a second resistor terminal coupled to the ground terminal. Switch 118 includes a first terminal coupled to the second current terminal of pass transistor 102, a second terminal coupled to the first current terminal of transistor 116, and a control terminal coupled to control circuit 136. A signal provided at the amplifier output controls transistor 116 to equalize the voltage at the first input of amplifier 112 with the bandgap voltage provided at the second input of amplifier 112 and set the current flowing through switch 118, transistor 116, and resistor 114 when switch 118 is closed. Control circuit 136 closes switch 118 to test for a short across pass transistor 102.

[0020] Current source 132 generates a current equal to or representative of ISENSE flowing through sense transistor 104. Current source 132 may be implemented as a current mirror circuit having a current output coupled to resistor 134. Resistor 134 is coupled between current source 132 and a ground terminal. Current 148 generated by current source 132 flows through resistor 134 to create a sense voltage representative of the current flowing through pass transistor 102. A first terminal of resistor 134 is coupled to current source 132, and a second terminal of resistor 134 is coupled to the ground terminal. Resistor 134 and resistor 114 may be the same type of resistor (fabricated using the same manufacturing process) to cancel each other's variations and provide improved accuracy. Resistor 134 and resistor 114 may have a high sheet resistance. Resistor 134 may have a resistance of approximately 5 kilohms, and resistor 114 may have a resistance of approximately 53 ohms.

[0021] Switched capacitor circuit 120 includes capacitor 122, switch 124, switch 126, and switch 128. Capacitor 122 includes a top plate and a bottom plate. The top plate is coupled to a first terminal of resistor 134 via switch 126. Switch 126 includes a first terminal coupled to the first terminal of resistor 134, a second terminal coupled to the top plate of capacitor 122, and a control terminal coupled to control circuit 136. Switch 124 is coupled between the bottom plate of capacitor 122 and a ground terminal. Switch 124 includes a first terminal coupled to the bottom plate of capacitor 122, a second terminal coupled to the ground terminal, and a control terminal coupled to control circuit 136. Switch 128 is coupled between the bottom plate of capacitor 122 and a first input (e.g., a non-inverting comparator input) of comparator 130. Switch 128 includes a first terminal coupled to the bottom plate of capacitor 122, a second terminal coupled to a first input of comparator 130, and a control terminal coupled to control circuit 136. A second input (e.g., an inverting comparator input) of comparator 130 is coupled to a reference voltage terminal of reference voltage circuit 144. Reference voltage circuit 144 generates a short circuit threshold voltage that comparator 130 compares to the voltage at the bottom plate of capacitor 122 to identify a short circuit across pass transistor 102.

[0022] When control circuit 136 opens switch 118, current flows through pass transistor 102, and any short circuit across pass transistor 102 flows to load 142. The current generated by current source 132 and the voltage across resistor 134 represent the current flowing through pass transistor 102 to load 142. When switch 118 opens, switch 124 closes, connecting the bottom plate of capacitor 122 to ground, and switch 126 closes, connecting the top plate of capacitor 122 to resistor 134. When switch 118 is open, capacitor 122 charges to the voltage developed across resistor 134. When control circuit 136 closes switch 118, sinking current 146 through transistor 116 and resistor 114, switch 124 opens, disconnecting the bottom plate of capacitor 122 from ground. The current flowing through pass transistor 102 increases in proportion to the current 146 flowing through switched current source 110. If there is no short across pass transistor 102, all of the current flowing through switched current source 110 flows through pass transistor 102. If there is a short across pass transistor 102, only a portion of the current flowing through switched current source 110 flows through pass transistor 102. The voltage developed across resistor 134 corresponds to the current flowing through pass transistor 102.

[0023] When control circuit 136 closes switch 118, control circuit 136 closes switch 126, and the voltage across resistor 134 is present on the top plate of capacitor 122. The voltage on the bottom plate of capacitor 122 is equal to the difference between the voltage across resistor 134 when switch 118 is closed and the voltage across resistor 134 when switch 118 is open. Thus, when switch 118 is closed, the voltage at the bottom plate of capacitor 122 represents a portion of current 146 flowing through pass transistor 102.

[0024] The control circuit 136 closes the switch 128 to connect the bottom plate of the capacitor 122 to the comparator 130. The comparator 130 compares the short-circuit detection voltage (ΔVcopy) at the bottom plate of the capacitor 122 to a short-circuit threshold voltage (ΔVcopy(lim)) generated by the reference voltage circuit 144. If the voltage at the bottom plate of the capacitor 122 is greater than ΔVcopy(lim), the current through the pass transistor 102 is high enough that it is assumed that no short circuit exists across the pass transistor 102. If the voltage at the bottom plate of the capacitor 122 is less than ΔVcopy(lim), not all of the current flowing through the switched current source 110 flows through the pass transistor 102, and it is assumed that a short circuit exists across the pass transistor 102. The output of the comparator 130 is coupled to the control circuit 136. The control circuit 136 sets the state of a fault signal 138 provided at the output of the control circuit 136 based on the output signal (FET GOOD) provided at the comparator output. Fault signal 138 indicates whether a short across pass transistor 102 is detected.

[0025] Switch 118, switch 124, switch 126, and switch 128 may be implemented using one or more transistors (eg, NFETs and / or PFETs) configured to pass signals in response to a control signal.

[0026] 2 is a schematic diagram of an example current source 132. 132 includes transistor 202, transistor 204, and transistor 206. 202 may be an NFET. 204 and 206 may be PFETs. A control terminal (e.g., gate) of 202 is coupled to the output of amplifier 106 and to the control terminal of transistor 108. A first current terminal (e.g., source) of 202 is coupled to a ground terminal. A second current terminal of 202 is coupled to 204 and 206.

[0027] 204 and 206 are connected as a current mirror circuit. 204 is diode-connected. A first current terminal (e.g., source) of 204 is coupled to a power supply terminal. A second current terminal (e.g., drain) of 204 is coupled to a second control terminal of 202. A control terminal (e.g., gate) of 204 is coupled to a second control terminal of 204. A first current terminal (e.g., source) of 206 is coupled to a first current terminal of 204. A control terminal of 206 is coupled to a control terminal of 204. A second current terminal (e.g., drain) of 206 is coupled to 134 and 126.

[0028] The current flowing through 202 and 204 is the same as (or a scaled replica of) the sense current (ISENSE) flowing through 108. 148 flowing through 206 is the same as (or a scaled replica of) the current flowing through 204 and 202.

[0029] 3A is a diagram of example signals generated in short-circuit detection circuit 100. FIG. 3A shows current 146 flowing through switched current source 110, current 148 flowing through resistor 134, voltage ΔVcopy at the bottom plate of capacitor 122, and FET GOOD output by comparator 130. Current 146 increases when switch 118 is closed. In some implementations of switched current source 110, current 146 flowing through switched current source 110 is approximately 30 milliamps (ma). As switched current source 110 sinks current, current 148 increases and voltage ΔVcopy increases. During interval 302, no short circuit is present across pass transistor 102, voltage ΔVcopy exceeds ΔVcopy(lim), and FET GOOD is high during the test, indicating no short circuit is present across pass transistor 102. For example, if no short circuit is present, ΔVcopy may be approximately 30 millivolts (mv) and ΔVcopy(lim) may be approximately 19 mv. In interval 304, an external short circuit is present across pass transistor 102. As a result of the short circuit, the increase in current 148 due to current 146 and the increase in ΔVcopy are small (relative to the increase if no short circuit is present). ΔVcopy is less than ΔVcopy(lim), and FET GOOD is low during the test to indicate the presence of a short circuit across pass transistor 102. For example, if a short circuit is present, ΔVcopy may be approximately 10 millivolts (mv).

[0030] 3B is a graph of the signals in the short circuit detection circuit 100. FIG. 3B shows the signals θ generated by the control circuit 136 to control the switches 118, 124, and 128, respectively. 1、 TIFF2026504711000002.tif99, θ2 is shown. FIG. 3B also shows current 146, Vcopy, and ΔVcopy. Control circuit 136 activates θ1, closing the switch and increasing current 146. At approximately 2.1 milliseconds, a short circuit is formed across pass transistor 102. Prior to the formation of the short circuit, ΔVcopy increases by a relatively large amount in response to current 146. Following the formation of the short circuit, ΔVcopy increases by a relatively small amount in response to current 146, allowing detection of the short circuit by comparator 130.

[0031] Because the load 142 is not controlled by the short-circuit detection circuit 100, the current drawn by the load 142, flowing through the pass transistor 102, and shorting across the pass transistor 102 can change at any time, causing a change in ΔVcopy that can result in errors in short-circuit detection. For example, the current drawn by the load 142 can change during a short-circuit detection cycle (when the switch 118 is closed). To improve the accuracy of short-circuit detection, the control circuit 136 performs multiple randomly spaced short-circuit detection cycles and determines whether a short circuit exists based on the results provided by a majority of the short-circuit detection cycles. For example, the control circuit 136 may perform five randomly spaced 600-microsecond short-circuit detection cycles (times when the switch 118 is closed) at 200-millisecond intervals. The control circuit 136 identifies the presence or absence of a short circuit based on the short-circuit condition indicated by three of the five cycles.

[0032] 4 is a flowchart of an example method for determining whether a short circuit exists based on multiple short detection tests. While shown sequentially for convenience, at least some of the actions shown may be performed in a different order and / or in parallel. Also, some implementations may perform only some of the actions shown. The operations of method 400 may be performed by control circuit 136.

[0033] In block 402, control circuit 136 performs a short circuit detection test. The short circuit detection test involves opening switch 118 and closing switch 124 to charge capacitor 122 to the voltage across resistor 134, then closing switch 118 and opening switch 124, and comparing the voltage on the bottom plate of capacitor 122 to ΔVcopy(lim). The test is considered a pass if the voltage on the bottom plate of capacitor 122 is greater than ΔVcopy(lim), and is considered a fail if the voltage on the bottom plate of capacitor 122 is less than ΔVcopy(lim).

[0034] In block 404, control circuit 136 evaluates the results of the last N short detection tests performed in block 402. If M of the last N short detection tests fail, a short across pass transistor 102 is deemed to have been detected in block 406. For example, if the bottom plate of capacitor 122 is less than ΔVcopy(lim) in three of the last five short detection tests, control circuit 136 determines that a short across pass transistor 102 has been detected. Control circuit 136 may set fault signal 138 to indicate that a short has been detected.

[0035] If, at block 404 , M of the last N shorts detection tests have not failed, shorts testing continues at block 402 .

[0036] FIG. 5 is a diagram of an example short circuit fault signal generated in short circuit detection circuit 100 based on method 400. In FIG. 5, ΔVcopy is shown over eight short circuit detection tests. During short circuit detection tests 506, 508, and 510, a short across pass transistor 102 is present, so ΔVcopy is substantially lower than during short circuit detection tests 502, 504, 512, 514, 516, and 518. In FIG. 5, control circuit 136 determines whether a short circuit exists based on the last five tests performed. If three of the last five tests fail, a short circuit is deemed to exist. If three of the last five tests do not fail, a short circuit is deemed not to exist. Upon execution of short circuit detection test 510, control circuit 136 determines that a short circuit exists because short circuit detection tests 506, 508, and 510 failed. Testing continues and if the short detection tests 512, 514, and 516 pass three of the last five tests, the control circuit 136 determines in response to the short detection test 516 that no short circuit is present.

[0037] 6 is a block diagram of an example system 600 including an electronic fuse circuit 604 with short circuit detection. System 600 includes a power source 602, an electronic fuse circuit 604, a load circuit 606, and a switch 610. Power source 602 may be a battery, a DC-DC converter, an AC-DC converter, or other power source. Electronic fuse circuit 604 includes a short circuit detection circuit 608. Short circuit detection circuit 608 is one implementation of short circuit detection circuit 100. System 600 also includes a switch 610 coupled between power source 602 and electronic fuse circuit 604. Switch 610 may be implemented using a transistor (e.g., a PFET) coupled between power source 602 and electronic fuse circuit 604. Switch 610 includes a control terminal coupled to a fault output of electronic fuse circuit 604.

[0038] Short circuit detection circuit 608 tests for shorts (internal or external) across electronic fuse circuit 604 as described with respect to short circuit detection circuit 100. If a short is detected, electronic fuse circuit 604 opens switch 610 via fault signal 138, interrupting the flow of current from power supply 602 to electronic fuse circuit 604 and load circuit 606.

[0039] 7 is a block diagram of an example system 700 including an electronic fuse circuit 604 with short circuit detection. The system 700 includes a power supply 702, an electronic fuse circuit 604, and a load circuit 606. The power supply 702 may be a linear regulator, a DC-DC converter, an AC-DC converter, or other power source. The electronic fuse circuit 604 includes a short circuit detection circuit 608. The short circuit detection circuit 608 is one implementation of the short circuit detection circuit 100. The power supply 702 includes an input terminal coupled to a fault output of the electronic fuse circuit 604.

[0040] The short detection circuit 608 tests for shorts (internal or external shorts) across the electronic fuse circuit 604 as described with respect to the short detection circuit 100. If a short is detected, the electronic fuse circuit 604 changes the state of the fault signal 138 to indicate that a fault (short) has been detected. In response to the fault signal 138, the power supply 702 stops supplying current to the electronic fuse circuit 604 and the load circuit 606.

[0041] System 600 or system 700 may be a refrigerator, a washing machine, a clothes dryer, an oven, a range, or other appliance or electrical or electronic device.

[0042] The term "coupled" in this description may encompass a connection, communication, or signal path that enables a functional relationship consistent with this description. For example, if device A generates a signal that controls device B to perform a certain action, then (A) in a first example, device A is coupled to device B by a direct connection, or (b) in a second example, device A is coupled to device B via an intervening component C such that device B is controlled by device A via a control signal generated by device A, where intervening component C does not change the functional relationship between device A and device B.

[0043] Also, as used herein, the phrase "based on" means "based at least in part on." Thus, if X is based on Y, X can be a function of Y and any number of other factors.

[0044] A device that is "configured to" perform a certain task or function may be configured (e.g., programmed and / or hardwired) by a manufacturer at the time of manufacture to perform that function and / or may be configurable (or reconfigurable) by a user after manufacture to perform that function and / or other additional or alternative functions. Such configuration may be through firmware and / or software programming of the device, through the configuration and / or layout of hardware components, through the device's interconnections, or through a combination thereof.

[0045] As used herein, the terms "terminal," "node," "interconnect," "pin," and "lead" are used interchangeably. Unless otherwise noted, these terms are used generally to refer to an interconnection between, or termination of, a device element, circuit element, integrated circuit, device, or other electronic or semiconductor component.

[0046] A circuit or device described herein as including particular components may instead be coupled to those components and adapted to form the described circuit or device. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and / or inductors), and / or one or more sources (such as voltage and / or current sources) may instead include only the semiconductor elements in a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package) and may be adapted to be coupled to at least some of the passive elements and / or sources during or after manufacture, e.g., by an end user and / or third party, to form the described structure.

[0047] While the use of particular transistors is described herein, other transistors (or equivalent devices) can be substituted with little or no change to the remaining circuit elements. For example, field-effect transistors (“FETs”) (e.g., n-channel FETs (NFETs) or p-channel FETs (PFETs)), bipolar junction transistors (BJTs—e.g., NPN or PNP transistors), insulated-gate bipolar transistors (IGBTs), and / or junction field-effect transistors (JFETs) can be used in place of or in conjunction with the devices described herein. The transistors can be depletion-mode devices, drain-extension devices, enhancement-mode devices, natural transistors, or other types of device structure transistors. Additionally, the devices can be implemented in / on silicon substrates (Si), silicon carbide substrates (SiC), gallium nitride substrates (GaN), or gallium arsenide substrates (GaAs).

[0048] In the claims, reference may be made to a transistor's control input and its current terminals. In the context of a FET, the control input is the gate and the current terminals are the drain and source. In the context of a BJT, the control input is the base and the current terminals are the collector and emitter.

[0049] As used herein, a reference to a FET being "on" means that the FET's conduction channel is present and drain current can flow through the FET. As used herein, a reference to a FET being "off" means that the conduction channel is not present and drain current does not flow through the FET. However, a FET that is "off" may still have current flowing through the transistor's body diode.

[0050] The circuits described herein are reconfigurable to include additional or different components to provide functionality at least partially similar to that available before the component was replaced. A component shown as a resistor, unless otherwise noted, generally represents any one or more elements coupled in series and / or parallel to provide the amount of impedance represented by the depicted resistor. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in series between the same two nodes as the single resistor or capacitor.

[0051] While certain elements of the described examples are included in an integrated circuit and others are external to the integrated circuit, in other examples, additional or fewer features may be incorporated into the integrated circuit. Also, some or all of the features illustrated as being external to the integrated circuit may be included in the integrated circuit, and / or some features illustrated as being internal to the integrated circuit may be incorporated external to the integrated circuit. As used herein, the term "integrated circuit" means one or more circuits that are (1) incorporated in / on a semiconductor substrate, (2) incorporated in a single semiconductor package, (3) incorporated within the same module, and / or (4) incorporated within / on the same printed circuit board.

[0052] Use of the term "ground" in the foregoing description includes chassis ground, earth ground, floating ground, virtual ground, digital ground, common ground, and / or any other form of ground connection applicable to or suitable for the teachings herein. As used herein, unless specifically stated otherwise, the words "about," "approximately," or "substantially" preceding a parameter means within + / - 10% of that parameter.

[0053] Modifications may be made to the examples described, and other examples are possible, within the scope of the invention.

Claims

1. A short-circuit detection circuit, A first transistor having a first current terminal, a second current terminal, and a first control terminal, A first resistor coupled between the second current terminal and the ground terminal, A second transistor having a third current terminal connected to the first current terminal, a fourth current terminal, and a second control terminal connected to the first control terminal, A current source having a current output and a current input coupled to the fourth current terminal, A second resistor coupled between the current output and the ground terminal, A switched capacitor circuit coupled between the current output and the ground terminal, A comparator having a comparator output, a first comparator input coupled to the switched-capacitor circuit, and a second comparator input coupled to the reference voltage terminal, A short-circuit detection circuit, including one.

2. A short-circuit detection circuit according to claim 1, A short-circuit detection circuit further comprising a switch coupled between the second current terminal and the first terminal of the first resistor.

3. A short-circuit detection circuit according to claim 2, A third transistor having a fifth current terminal, a sixth current terminal coupled to the first terminal of the first resistor, and a third control terminal, An amplifier having a first amplifier input coupled to the first terminal of the first resistor, a second amplifier input coupled to a bandgap voltage circuit, and an amplifier output coupled to the third control terminal, It further includes, A short-circuit detection circuit in which the switch is coupled between the sixth current terminal and the second current terminal.

4. A short-circuit detection circuit according to claim 1, The switched-capacitor circuit includes a capacitor having a top plate and a bottom plate, and a first switch coupled between the top plate and the current output, wherein the short-circuit detection circuit includes a capacitor having a top plate and a bottom plate, and a first switch coupled between the top plate and the current output.

5. A short-circuit detection circuit according to claim 4, The aforementioned switched capacitor circuit, A second switch is coupled between the bottom plate and the grounding terminal, A third switch coupled between the bottom plate and the first comparator input, A short-circuit detection circuit, further including the following.

6. A short-circuit detection circuit according to claim 1, A short-circuit detection circuit in which the first current terminal is connected to a power terminal and the second current terminal is connected to a load terminal.

7. A short-circuit detection circuit according to claim 1, A short-circuit detection circuit including a current mirror circuit configured such that the current source generates a first current that is conducted by the second resistor based on a second current conducted by the second transistor.

8. A short-circuit detection circuit, A first transistor configured to conduct load current, A switchable load circuit coupled to the first transistor, configured to switchably draw out a test current, A second transistor coupled to the first transistor, configured to conduct a sensing current including first and second portions, wherein the first portion represents the load current and the second portion represents the test current, A switched capacitor circuit coupled to the second transistor, configured to generate a short-circuit detection voltage representing the second portion, A comparator having an output, a first comparator input coupled to the switched-capacitor circuit, and a second comparator input, wherein the comparator is configured to compare the short-circuit detection voltage with the short-circuit threshold voltage, A short-circuit detection circuit, including one.

9. A short-circuit detection circuit according to claim 8, The switchable load circuit is A first current source configured to receive the aforementioned test current, A switch coupled between the first transistor and the first current source, configured to switchably connect the first current source to the first transistor, A short-circuit detection circuit, including one.

10. A short-circuit detection circuit according to claim 9, The first current source is, A first resistor having a first terminal and a second resistor terminal connected to the ground terminal, A third transistor having a control terminal, coupled between the first resistor terminal and the switch, An amplifier having a first amplifier input connected to a first resistor terminal, a second amplifier input connected to a reference terminal, and an amplifier output connected to a control terminal, wherein the amplifier is configured to provide a control signal to the amplifier output in response to the voltages at the first and second amplifier inputs, Includes, A short-circuit detection circuit in which the third transistor is configured to conduct the test current in response to the control signal.

11. A short-circuit detection circuit according to claim 10, A second current source coupled to the second transistor, configured to generate a current representing the sensing current, A second resistor coupled between the second current source and the ground terminal, A short-circuit detection circuit, further including the following.

12. A short-circuit detection circuit according to claim 11, A short-circuit detection circuit comprising a current mirror circuit configured to generate the current representing the sensed current based on the sensed current, wherein the second current source is configured to generate the sensed current.

13. A short-circuit detection circuit according to claim 11, The aforementioned switched capacitor circuit, A capacitor having a top plate and a bottom plate, A first switch coupled between the second resistor and the top plate, configured to switchably connect the top plate to the second current source, A short-circuit detection circuit, including one.

14. A short-circuit detection circuit according to claim 13, The aforementioned switched capacitor circuit, A second switch coupled between the bottom plate and the grounding terminal, configured to switchably connect the bottom plate to the grounding terminal, A third switch coupled between the bottom plate and the first comparator input, wherein the third switch is configured to switchably connect the bottom plate to the first comparator input, A short-circuit detection circuit, further including the following.

15. A short-circuit detection circuit according to claim 8, A short-circuit detection circuit in which the second comparator input is coupled to a reference voltage circuit configured to generate the short-circuit threshold voltage.

16. It is a system, Power terminals and Load terminal and An electronic fuse (EFUSE) circuit, A first transistor configured to conduct load current from the power terminal to the load terminal, A switchable load circuit coupled to the first transistor, configured to switchably draw out a test current, A second transistor coupled to the first transistor, configured to conduct a sensing current including first and second portions, wherein the first portion represents the load current and the second portion represents the test current, A switched capacitor circuit coupled to the second transistor, configured to generate a short-circuit detection voltage representing the second portion, A comparator having an output, a first comparator input coupled to the switched-capacitor circuit, and a second comparator input, wherein the comparator is configured to compare the short-circuit detection voltage with the short-circuit threshold voltage, The electronic fuse (EFUSE) circuit includes, A system that includes this.

17. The system according to claim 16, The switchable load circuit is A first current source configured to receive the aforementioned test current, A switch coupled between the first transistor and the first current source, configured to switchably connect the first current source to the first transistor, A system that includes this.

18. The system according to claim 17, The first current source is, A first resistor having a first resistor terminal and a second resistor terminal connected to a ground terminal, A third transistor having a control terminal, coupled between the first resistor terminal and the switch, An amplifier having a first amplifier input connected to the first resistor terminal, a second amplifier input connected to the reference terminal, and an amplifier output connected to the control terminal, wherein the amplifier is configured to provide a control signal to the amplifier output in response to the voltages of the first and second amplifier inputs, Includes, A system in which the third transistor is configured to conduct the test current in response to the control signal.

19. The system according to claim 18, A second current source coupled to the second transistor, configured to generate a current representing the sensing current, A second resistor coupled between the second current source and the ground terminal, A system that further includes the following.

20. The system according to claim 19, The aforementioned switched capacitor circuit, A capacitor having a top plate and a bottom plate, A first switch coupled between the second resistor and the top plate, configured to switchably connect the top plate to the second resistor and the second current source, A system that includes this.

21. The system according to claim 20, The aforementioned switched capacitor circuit, A second switch coupled between the bottom plate and the grounding terminal, configured to switchably connect the bottom plate to the grounding terminal, A third switch coupled between the bottom plate and the first input of the comparator, the third switch configured to switchably connect the bottom plate to the first input of the comparator, It further includes, The system further comprises a second comparator coupled to a reference voltage circuit configured to generate the short-circuit threshold voltage.

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