TPIC8101 enables remote adjustment of engine knock sensor
The purpose of the engine knock sensor is to improve engine efficiency and performance by monitoring engine vibration. The engine control unit (ECU) uses this data to adjust the fuel-to-air ratio to reduce "engine crash" and correct engine timing. TI's TPIC8101 can be used as a signal conditioner for such engine knock sensors. The new solution sometimes integrates this functionality into one MCU of the engine ECU, but this means that the process may be done more remotely (due to the lower temperature rating of the microcontroller), which may result in a signal Deterioration. The performance of the TPIC8101 can be verified by looking at the extraction of the signal from the knock sensor (compared to the noise of the system). Brief working principle: The TPIC8101 performs signal conditioning of the knock sensor components, which are resonant piezoelectric sensor components. After passing through the input amplifier, noise is filtered out of the signal (concentrating a bandpass filter on the center frequency of the sensing element). The signal is then rectified and integrated. This output can then be transmitted digitally or via an analog signal. The ECU monitors the strength of this signal to determine when knocking occurs. Figure 1: TPIC8101 internal block diagram One of the purposes of the knock sensor signal conditioner is to suppress all out-of-band noise because the engine is already an inherently noisy environment. Therefore, the signal-to-noise ratio (SNR) provided by the system is very important. Specifically, the band pass filter determines the case where noise is suppressed from the system. To measure the performance of the bandpass filter, the following steps must be performed. Parameters such as bandpass filter center frequency, integrated time constant, amplifier gain, and integrated time window are selected (as described in Section 9.2.2 of the TPIC8101 datasheet). These parameters must be set according to system level requirements, or you can use the values ​​from the sample test settings in Table 1. A sine wave is generated at a specified frequency and amplitude using a function generator to mimic the output of the knock sensor element. Record the peak voltage of the signal. Adjust the frequency of the input signal and re-measure the signal. An output voltage map (relative to the input frequency) is then generated, from which the relative SNR value of the bandpass filter can be viewed. Test Data: This test data compares the TPIC8101 with competing devices to show how differences in the bandpass filter affect device performance and SNR. TI devices and competitor devices are configured in the same way as Table 1. Table 1: Test Settings byte data Configuration value Configured as 1st 0100 0110 Prescaler 11 8MHz 2nd 1110 0001 MUX 1 Ch2 Third 0010 1001 BPF 41 6.94Khz 4th 1100 0000 Integration time constant 0 40uS 5th 1010 0010 Amplifier gain 34 0.381 Table 2 shows the test data for the output signal amplitude of various frequency input signals. The bandpass filter for each device has been programmed to have a center frequency of 6.94 kHz, so input signals away from this center frequency should be suppressed. Table 2: Test Data At 1KHz Amplitude (V) At 3KHz Amplitude (V) At 6KHz Amplitude (V) At 7KHz Amplitude (V) At 8KHz Amplitude (V) At 10KHz Amplitude (V) At 50KHz Amplitude (V) TPIC8101 maximum 0.53 1.12 3.36 3.84 2.72 2.04 0.6 intermediate 0.4 0.76 1.84 2.32 1.84 1.4 0.47 Minimum 0.34 0.68 1.44 1.84 1.36 1 0.4 Competitor product maximum 0.5 0.5 2.52 2.88 2.08 0.72 0.5 intermediate 0.3 0.25 1.16 1.6 1.22 0.06 0.2 Minimum 0.04 0.04 0.56 1 0.48 0 0 The formula for SNR is: Interacive Display,Interactive Display Stand,2.3 Inch 16080 Lcd Display,Smart Board Interactive Display Kindwin Technology (H.K.) Limited , https://www.ktl-led.com