A method for eliminating interference of isolator chip radiation on radio frequency system

Abstract

The present invention discloses a method for eliminating the interference of isolator chip radiation on the radio frequency system. The method can measure the frequency of the low-frequency RC oscillator during the chip wafer test or the finished product test stage after packaging, and flexibly burn the corresponding frequency control signal of the storage unit according to the needs of the customer's product communication system to adjust the local oscillator frequency and its harmonic frequency of the isolator chip to avoid the customer's communication frequency band. This method uses a low-temperature drift RC oscillator circuit combined with frequency-locked loop technology to ensure that the frequency deviation of the local oscillator signal is controlled within 3% within different process deviations and the full temperature range. In addition, by accurately adjusting the frequency of the high-frequency oscillator until it is close to the target frequency, and storing these configuration parameters in a non-volatile storage module, the isolator chip will not interfere with other communication systems during actual operation, thereby improving the stability and reliability of the entire communication system.

Description

Technical Field

[0001] The present invention belongs to the technical field of isolator integrated circuits, and in particular relates to a method for eliminating interference of isolator chip radiation on a radio frequency system. Background Art

[0002] At present, the mainstream technology used by capacitive isolation chips is radio frequency OOK modulation and demodulation technology, such as Figure 1 The figure shows a two-channel isolation chip in an 8-pin package. The four pins on the left are for power, ground, and two data channels. The right pins also provide power, ground, and two data channels. The power and reference ground on the left are separate from the power and reference ground on the right. During chip production, the left and right chips are bound or configured separately. The pad0_sel and pad1_sel pins on chip 1 and chip 2 are configured to determine whether channel A or channel B is a transmit channel or a receive channel.

[0003] The current local oscillator RF generation circuit generally uses a simple ring oscillator. The data is input from the PAD of chip 1 to the modulation circuit, modulated through OOK to the isolation capacitor and output to the isolation capacitor of chip 2. The demodulation circuit of chip 2 uses envelope detection to demodulate the OOK RF signal transmitted by chip 1 and output the PAD data output.

[0004] Current OOK local oscillator (LO) RF generation circuits typically use simple ring oscillators. Because the ring oscillator's frequency is highly sensitive to process and temperature, its frequency range is extremely wide. This complicates demodulation for the receiving chip and can easily lead to yield issues during mass production. Furthermore, if the ring oscillator's frequency or its harmonics fall within the frequency band of a system's communication modules or adjacent channels, they can generate co-channel interference and lead-channel interference, significantly degrading the system's reception performance and shortening communication distances. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for eliminating interference of isolator chip radiation on the radio frequency system, thereby reducing the problem of communication quality degradation caused by interference of the radio frequency signal of the isolator chip, ensuring the efficient operation of the communication system, and solving the problems raised in the above background technology.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for eliminating interference of isolator chip radiation on a radio frequency system, comprising the following steps:

[0007] The isolator chip is put into a calibration test mode, wherein the calibration test mode is triggered by identifying the voltage code stream m0 through the power detection circuit; in the calibration test mode, a low-frequency oscillator frequency f_ck is output through channel A of the chip; the low-frequency oscillator frequency f_ck is measured, and a frequency control signal f_ctl is calculated based on the target local oscillator frequency f_lo; the chip is put into a burning mode, and the frequency control signal f_ctl is burned into the memory module of the chip; the chip is put into an operating mode, and based on the burned frequency control signal f_ctl, a high-frequency oscillator is controlled to output a local oscillator frequency ck_lo that avoids the communication frequency band.

[0008] Preferably, the voltage code stream m0 is realized by inputting alternating voltages of 6.5V and 5V through a power pin.

[0009] Preferably, the calculation formula of the frequency control signal f_ctl is: , where f_lo is the target local oscillator frequency and f_ck is the measured low-frequency oscillator frequency.

[0010] Preferably, the low-frequency oscillator adopts a low-temperature drift RC oscillation circuit, and the frequency f_ck thereof varies with temperature and power supply voltage within a range of less than 3%.

[0011] Preferably, the method of controlling the high-frequency oscillator to output a local oscillator frequency ck_lo that avoids the communication frequency band based on the burned frequency control signal f_ctl includes: using a frequency-locked loop technology to control the local oscillator frequency ck_lo, specifically including: dividing the low-frequency oscillator frequency f_ck to generate a time window signal Twin; counting the high-frequency oscillator clock during the high level period of the time window signal Twin; comparing the count value cnt<11:0> with the burned f_ctl<11:0>; and adjusting the high-frequency oscillator control code c<7:0> according to the comparison result to make ck_lo approach the target frequency.

[0012] Preferably, the method further includes frequency sweep control, specifically including: updating the frequency sweep code fs<2:0> at each clock edge of the low frequency oscillator frequency f_ck, so that the high frequency oscillation frequency changes in a polling range of 4%.

[0013] Preferably, the step of making the chip enter the programming mode and programming the frequency control signal f_ctl into the storage module of the chip includes: triggering the programming mode by inputting a voltage code stream m1, at which time channel A and channel B constitute a serial port to transmit the frequency control signal f_ctl and the pdet_enn parameter.

[0014] Preferably, the programming parameters in the programming mode include f_ctl<11:0>, pdet_enn, pad1_sel and pad0_sel, wherein pdet_enn=1 indicates that the chip has completed calibration.

[0015] Preferably, in the working mode, channel A and channel B are configured to be in the transmitting input mode or the receiving output mode according to the programmed pad1_sel and pad0_sel.

[0016] Technical effects and advantages of the present invention: Compared with the prior art, the method of eliminating the interference of isolator chip radiation on the radio frequency system proposed by the present invention has the following advantages:

[0017] The present invention can measure the frequency of the low-frequency RC oscillator during the chip wafer test or finished product test stage after packaging, and flexibly burn the corresponding frequency control signal of the storage unit according to the needs of the customer's product communication system to adjust the local oscillator frequency and its harmonic frequency of the isolator chip so that it avoids the customer's communication frequency band. This method uses a low-temperature drift RC oscillator circuit combined with frequency-locked loop technology to ensure that the frequency deviation of the local oscillator signal is controlled within 3% within different process deviations and the full temperature range. In addition, by accurately adjusting the frequency of the high-frequency oscillator until it is close to the target frequency, and storing these configuration parameters in a non-volatile storage module, the isolator chip will not interfere with other communication systems during actual operation, thereby improving the stability and reliability of the entire communication system. This method significantly reduces the problem of communication quality degradation caused by interference from the radio frequency signal of the isolator chip, ensuring the efficient operation of the communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the architecture diagram of a traditional isolator chip;

[0019] Figure 2 This is a diagram of the architecture of the two-channel isolation chip of the present invention;

[0020] Figure 3 This is a diagram of the frequency locking circuit architecture of the present invention;

[0021] Figure 4 This is a flow chart of the isolator chip test and calibration of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] The present invention provides a method for eliminating interference of an isolator chip radiation on a radio frequency system, comprising the following steps:

[0024] The isolator chip enters a calibration test mode, which is triggered by the power detection circuit identifying the voltage code stream m0; the voltage code stream m0 is achieved by inputting alternating voltages of 6.5V and 5V through the power pin.

[0025] In the calibration test mode, the low frequency oscillator frequency f_ck is output through channel A of the chip;

[0026] The low-frequency oscillator frequency f_ck is measured, and the frequency control signal f_ctl is calculated according to the target local oscillator frequency f_lo. The calculation formula of the frequency control signal f_ctl is: , where f_lo is the target local oscillator frequency and f_ck is the measured low-frequency oscillator frequency. The low-frequency oscillator uses a low-temperature drift RC oscillator circuit, and its frequency f_ck varies less than 3% with temperature and supply voltage.

[0027] The chip enters programming mode and programs the frequency control signal f_ctl into the chip's memory module. This includes triggering programming mode by inputting a voltage code stream m1. Channels A and B form a serial port to transmit the frequency control signal f_ctl and the pdet_enn parameter. Programming parameters in programming mode include f_ctl<11:0>, pdet_enn, pad1_sel, and pad0_sel. pdet_enn = 1 indicates the chip has completed calibration.

[0028] The chip enters working mode, and based on the programmed frequency control signal f_ctl, the high-frequency oscillator is controlled to output a local oscillator frequency ck_lo that avoids the communication frequency band. Specifically, the frequency-locked loop technology is used to control the local oscillator frequency ck_lo, which includes: dividing the low-frequency oscillator frequency f_ck to generate a time window signal Twin; counting the high-frequency oscillator clock during the high level period of the time window signal Twin; comparing the count value cnt<11:0> with the programmed f_ctl<11:0>; and adjusting the high-frequency oscillator control code c<7:0> according to the comparison result to make ck_lo approach the target frequency.

[0029] In working mode, configure channel A and channel B as transmit input or receive output mode according to the programmed pad1_sel and pad0_sel.

[0030] Furthermore, the above method also includes frequency sweep control, specifically including: updating the frequency sweep code fs<2:0> at each clock edge of the low frequency oscillator frequency f_ck, so that the high frequency oscillation frequency changes in a polling range of 4%.

[0031] In order to more clearly introduce the specific operation of the above-mentioned method of eliminating the interference of the isolator chip radiation on the radio frequency system, the following will be further explained with reference to the accompanying drawings:

[0032] This method tests the low-frequency RC oscillator frequency f_ck during wafer testing (CP) or final product testing (FT) after packaging. Based on the customer's product's communication system requirements, the isolator chip's local oscillator frequency and its harmonics can be adjusted to avoid the customer's communication system's frequency band by flexibly programming the corresponding frequency control signal in the memory unit. This prevents the isolator chip's RF signal from interfering with the customer's communication system. The isolator chip's low-frequency oscillator circuit uses a low-temperature RC oscillator circuit, and the local oscillator frequency utilizes frequency-locked loop technology. This ensures that the local oscillator signal's frequency deviation is within 3% across various process variations and the full temperature range.

[0033] The frequency of the local oscillator signal ck_lo of the isolator chip is as follows:

[0034] ;

[0035] The frequency control signal f_ctl is as follows:

[0036] ;

[0037] Because the frequency of a low-frequency RC oscillator is primarily dependent on resistance R and capacitance C, its frequency f_ck varies very little with temperature and power supply voltage. As long as each isolator chip is programmed with the corresponding memory cell control signal f_ctl, the isolator's local oscillator signal f_lo is determined and remains stable over temperature, voltage, and process.

[0038] Isolators are available in single, dual, triple, quad, 5, and 6-channel versions. Because the 2-channel SOP8 packaged chip has fewer IO pins, IO multiplexing is required. Channel A and Channel B function as data ports in operating mode.

[0039] In calibration test mode, Channel A functions as the chip's clock output port, measuring the chip's oscillator clock frequency. In programming mode, Channels A and B function as programming serial ports. This method uses a two-channel configuration as an example to eliminate isolator interference with the customer's communication system.

[0040] The isolator chip architecture of this method is as follows Figure 2 As shown, the circuit includes:

[0041] Two channels, Channel A and Channel B. Channel A includes the pad0 (IO) circuit, multiplexer circuit, modulation circuit, and demodulation circuit module A. Channel B includes the pad1 (IO) circuit, modulation circuit, and demodulation circuit module B. Four isolation capacitors (iso_c0, iso_c1, iso_c2, iso_c3). A power detection circuit. Digital circuits, storage modules, and frequency modules. Their connections are described as follows:

[0042] Channel A connects to the pad0 (IO) general-purpose input / output (GPIO) circuit. Whether the PAD is an input or output is controlled by pad0_sel. When pad0_sel = 0, pad0 (IO) is in input mode. When pad0_sel = 1, pad0 (IO) is in output mode. The pad0 (IO) output signal, pad0_in, connects to the modulation and demodulation circuit modules A, the digital circuit, and the storage module.

[0043] The output of modulation and demodulation circuit module A is connected to isolation capacitors iso_c0 and iso_c1. Another output, demA, of modulation and demodulation circuit module A is connected to an input of a multiplexer circuit. Another input of the multiplexer circuit is connected to the low-frequency output f_ck of the frequency module. The multiplexer circuit's selection signal is connected to the output adj_sel of the digital circuit and storage module. When adj_sel = 0, f_ck is output to pad0_out. When adj_sel = 1, demoA is output to pad0_out. adj_sel is connected to inverter INV1. The output of INV1 is connected to one input of an OR gate OR1. The other input of OR1 is connected to the output pad0_sel of the digital circuit and storage module. The output of OR1 is connected to the input / output control signal pad0_sel of pad0 (Io).

[0044] Channel B is connected to the pad1 (IO) general-purpose input / output PAD circuit. Whether the PAD is an input or output PAD is controlled by pad1_sel. When pad1_sel = 0, pad0 (IO) is in input mode. When pad1_sel = 1, pad1 (IO) is in output mode. Pad1 (IO) output signal pad1_in is connected to modulation and demodulation circuit module B and the digital circuit and storage module. The output of modulation and demodulation circuit module B is connected to isolation capacitors iso_c2 and iso_c3. Another output of modulation and demodulation circuit module B, demB, is connected to the input of the pad1 (IO) general-purpose input / output PAD circuit. pad1_sel is the output of the digital circuit and storage module.

[0045] The signals of pad1_sel and pad0_sel are stored in the non-volatile storage module.

[0046] When the chip is powered on, the digital circuit reads data from the memory module and stores it in registers. pdet_enn, f_ctl<11:0>, pad1_sel, and pad0_sel represent the contents of the memory module. Before the chip is programmed, the contents of the memory cells are "0." Therefore, pdet_enn, f_ctl<11:0>, pad1_sel, and pad0_sel are all "0." The default value of mod_sel upon power-on is "1." When pdet_enn = 0, the power detection circuit operates. This circuit monitors the chip's power supply voltage, VDD. When VDD > 5.8V, the circuit outputs a logic signal of "1." When VDD < 5.8V, the circuit outputs a logic signal of "0." During chip testing, by inputting 6.5V and 5V bit streams to the power supply, the power detection circuit outputs corresponding bit streams to the digital circuit and memory module inputs. The digital circuit verifies whether the specific codes in these bit streams are the preset specific codes, m0 or m1.

[0047] If the code stream is m0, then mod_sel = 0, adj_sel = 0, pad_1_sel = 0, and pad0_sel = 0, and the chip enters frequency calibration measurement mode. When mod_sel = 0, the modulation and demodulation circuits (Module A and Module B) are forced to shut down. When adj_sel = 0, the multiplexer outputs the f_ck signal to Pad0(io). When OR1 output Pad0_sel = 1, Pad0(io) becomes an output. Channel A outputs the f_ck clock signal, allowing the tester to measure the f_ck frequency. When pad1_sel = 0, Pad1(io) becomes an input. The signal from Channel B is fed through Pad1(io) to pad1_in, which then connects to the digital circuit and storage module.

[0048] If the power detection circuit detects bit stream m1, the chip enters programming mode, adj_sel = 1. OR1 outputs a high level to pad0_sel, and Pad0(io) is in input mode. Channel A's signal is input to pad0_in via Pad0(io), connecting to the digital circuit and memory module. Channel B is also in input mode, and its signal is input to pad1_in via Pad1(io), connecting to the digital circuit and memory module. In other words, Channel A and Channel B form a serial port operating mode, connecting to the digital circuit and memory module. The tester can then program the chip's configuration parameters into the memory module and simultaneously program the memory cell corresponding to pdet_enn to "1."

[0049] The frequency module receives inputs from the digital circuit and storage module, f_ctl<11:0>. It outputs two clock signals: f_ck, which connects to the multiplexer circuit. The other, ck_lo, is the RF local oscillator signal and connects to the modulation and demodulation circuit modules A and B. This serves as the OOK modulated local oscillator signal for channels A and B.

[0050] After programming the chip, power on again, set pdet_enn=1, and disable the power detection circuit. Program pad1_sel and pad0_sel to the appropriate parameters based on the product configuration. For example, you can program channels A and B to be both transmit inputs, or both receive outputs, or one channel to be a transmit input and the other to be a receive output. Program f_ctl<1:0> to the appropriate parameters based on the customer's system and f_ck frequency, avoiding the customer's communication frequency band.

[0051] Figure 3 This is the architectural block diagram of the frequency module, which includes: a low-frequency oscillator, a frequency divider (which divides the low-frequency oscillator's clock by 16), a counter circuit, a logic control circuit, a high-frequency oscillation circuit, and a frequency sweep circuit.

[0052] The low-frequency oscillator adopts a low temperature drift RC oscillator structure, and its output f_ck is connected to the frequency divider and the sweep frequency control circuit. At the same time, the output module is connected to the chip's multiplexer circuit.

[0053] After dividing f_ck by 16, the frequency divider outputs Twin to the counter as the control signal for the start and end latches. Twin is a 50% duty cycle signal. When Twin is high, the counter starts and ends. When Twin transitions from high to low, counting ends. The count result is then latched and output to cnt<11:0>. The counter is then reset and waits for the next high level of Twin to resume counting.

[0054] Cnt<11:0> is output to the control logic circuit. After Twin transitions from high to low and cnt<11:0> latches the new count result, the control logic circuit compares the input cnt<11:0> with f_ctl<11:0>. If cnt is less than f_ctl, the high-frequency oscillator frequency is less than the target frequency. The control logic increments c<7:0> by 1. c<7:0> is connected to the high-frequency oscillator circuit, increasing the frequency of its output ck_lo. If cnt is greater than f_ctl, the high-frequency oscillator frequency is greater than the target frequency. The control logic decrements c<7:0> by 1, decreasing the frequency of its output ck_lo.

[0055] The low-frequency oscillator's output, f_ck, is also connected to a frequency sweep circuit. The sweep control circuit changes its output, fs<2:0>, at every f_ck clock edge. Every eight f_ck clock cycles, the code value of fs<2:0> is polled. fs<2:0> is connected to a high-frequency oscillator circuit, which causes the clock frequency of the high-frequency oscillator to vary within 4%, compressing the average radiated power.

[0056] The frequency calibration of the chip can be done during wafer testing or after packaging. The workflow is as follows: Figure 4 shown.

[0057] The chip starts testing by first powering on and initializing the isolator chip.

[0058] The initialization process will copy the contents of the storage module to the corresponding register and output it to the corresponding module.

[0059] When pdet_enn = 0, the chip has not been factory calibrated or programmed into the operating mode. After powering on, the tester inputs a specific code, m0, into the chip's power supply. The power supply voltage fluctuates between 6.5V and 5V according to the data value. After the chip detects this specific code, m0, it enters calibration test mode.

[0060] Mod_sel = 0, adj_sel = 0, pad1_sel = 0, and pad0_sel = 0. F_ck is output from pad0 (io) to channel A. The tester measures the frequency of f_ck on channel A. The tester then calculates the chip configuration parameter f_ctl using Equation 2. The tester then inputs another specific code m1 into the power supply. The chip detects this code and enters serial port programming mode. The tester then programs the isolation chip's frequency parameters f_ctl<11:0> and other chip parameters into the chip's memory module. Simultaneously, the memory cell marked with pdet_enn is programmed to "1." Finally, the chip is powered back on and enters normal operating mode.

[0061] Through this method, the OOK modulated RF signal frequency and its harmonic frequencies of the isolator chip will not fall on the communication frequency band of the customer system, and will not interfere with the communication system.

[0062] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for eliminating interference of isolator chip radiation on radio frequency system, characterized in that: The following steps are involved: The isolator chip enters a calibration test mode, wherein the calibration test mode is triggered by the power detection circuit identifying the voltage code stream m0; In the calibration test mode, the low frequency oscillator frequency f_ck is output through channel A of the chip; Measuring the low frequency oscillator frequency f_ck and calculating the frequency control signal f_ctl according to the target local oscillator frequency f_lo; Put the chip into a burning mode, and burn the frequency control signal f_ctl into the storage module of the chip; The chip enters a working mode, and based on the programmed frequency control signal f_ctl, a high-frequency oscillator is controlled to output a local oscillator frequency ck_lo that avoids the communication frequency band. This includes: using a frequency-locked loop (FLL) technology to control the local oscillator frequency ck_lo, specifically including: dividing the low-frequency oscillator frequency f_ck to generate a time window signal Twin; counting the high-frequency oscillator clock during a high-level period of the time window signal Twin; comparing the count value cnt<11:0> of the high-frequency oscillator clock count with the programmed f_ctl<11:0>; and adjusting the high-frequency oscillator control code c<7:0> based on the comparison result to make ck_lo approach the target frequency.

2. The method for eliminating interference of isolator chip radiation on radio frequency system according to claim 1, characterized in that: The voltage code stream m0 is realized by inputting 6.5V and 5V alternating voltages through the power pin.

3. The method for eliminating interference of isolator chip radiation on radio frequency system according to claim 1, characterized in that: The calculation formula of the frequency control signal f_ctl is: , where f_lo is the target local oscillator frequency and f_ck is the measured low-frequency oscillator frequency.

4. The method for eliminating interference of isolator chip radiation on radio frequency system according to claim 1, characterized in that: The low frequency oscillator adopts a low temperature drift RC oscillation circuit.

5. The method for eliminating interference of isolator chip radiation on radio frequency system according to claim 4, characterized in that: The method further includes frequency sweep control, specifically including: updating the frequency sweep code fs<2:0> at each clock edge of the low frequency oscillator frequency f_ck, so that the high frequency oscillation frequency changes in a polling range of 4%.

6. The method for eliminating interference of isolator chip radiation on radio frequency system according to claim 5, characterized in that: The step of causing the chip to enter a programming mode and programming the frequency control signal f_ctl into a storage module of the chip includes: The programming mode is triggered by inputting voltage code stream m1. At this time, channel A and channel B constitute the serial port transmission frequency control signal f_ctl and pdet_enn parameter.

7. The method for eliminating interference of isolator chip radiation on radio frequency system according to claim 6, characterized in that: The programming parameters in the programming mode include f_ctl<11:0>, pdet_enn, pad1_sel, and pad0_sel, where pdet_enn=1 indicates that the chip has completed calibration.

8. The method for eliminating interference of isolator chip radiation on radio frequency system according to claim 1, characterized in that: In working mode, configure channel A and channel B as transmit input or receive output mode according to the programmed pad1_sel and pad0_sel.

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