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PGA411Q1EVM: PGA411Q1 EVM single configure AFE function question

Eric Zheng
Prodigy 200 points

Part Number: PGA411Q1EVM

Dear Team：

Because of sensor specification limitations, PGA411 only use input open and input mutual short for the AFE system faults monitored. Whether register can be configured independently for AFE system faults monitored? if EVM not connect senor or input signal failure, can I configuration register the exciter output signal? thanks.

Following are the configured registers:

Figure 1:

Figure 2:

Figure 3:

Figure 4:

Figure 5:

  • 0
    TI__Mastermind 23810 points

    Eric,

    First, let me explain the difference between "FAULT pin mask bits" and "exciter override bits":

    The exciter override bit is completely independent of the FAULT pin mask bit. When this bit is set for a particular fault, then even if the fault is detected, the exciter output and tracking loop will continue to run. In general, we do not recommend setting these bits unless for debugging purposes.

    When the FAULT pin mask bit is set for a particular fault, then even if the fault is detected, the fault pin will remain in the low state (meaning that the MCU will not be notified of the fault unless it reads the DEV_STAT registers)

    This means that if you set MEXTMON, the fault pin mask bit for exciter-monitor high and low, then if that fault occurred, the fault pin would not interrupt the MCU, but the exciter would still turn off. This can be undesirable behavior, so you need to be careful how you use these bits.

    Now for your question, how to only use the open and mutual short faults:

    • You cannot use the AFE input fault override (ENINFAULT bit).
    • This is because it will also override the exciter even for the faults that you want to detect. Additionally, if a mutual short or open circuit fault were to actually occur and then be fixed, the PGA411 would still need for the tracking loop to be reset to have a fresh start
    • If you do not use ENINFAULT, then you cannot use any of the fault pin mask bits for the AFE.
      • This is because if one of the other faults occurred, then the exciter would be turned off, but the MCU would not get the appropriate interrupt.

    • The best way to "ignore" the other AFE faults is to set all of them to the maximum thresholds and maximum deglitch times.
    • OVIZH = 11b   (VCC*0.9)
    • OVIZL = 11b    (VCC*0.1)
    • IZTHL = 111b  (15.2us)

    I hope that this helps! Also, the "PGA411-Q1 Fault Reporting Summary" table in the datasheet is really useful when working with diagnostics.

  • 0 in reply to Clancy Soehren
    Prodigy 200 points

    Dear Clancy:

    Thanks for your support！

        I set the following register according to your recommended configuration.(Attachment configuration screenshot)

    • OVIZH = 11b   (VCC*0.9)
    • OVIZL = 11b    (VCC*0.1)
    • IZTHL = 111b  (15.2us)

    I hope to see the output open circuit and output short circuit fault state did not succeed.  Test PGA411EVM, I have open drain sensor SIN+. The Angle data can still be collected, but the data is random.

    The collection waveform is as follows:

    According to slaa684 (http://www.ti.com.cn/cn/lit/an/slaa684/slaa684.pdf) Page 23-24 5.22-5.25 documentation. I comprehend that the configuration of OVIZH and OVIZL function is that the sensor has normal access to PGA411. The signal amplitude of Cosine input and Sine input is greater than or less than the present value for diagnosis. Input signal open drain and short circuit haven’t relation.

    Do you have any better Suggestions?

    Thanks very much.

    PGA411_config.rar

  • 0 in reply to Eric Zheng
    Prodigy 200 points
    Dear Clancy:
    Is there more recommended configuration debugging available?
    Thanks！
  • 0 in reply to Eric Zheng
    TI__Mastermind 23810 points
    Eric,

    The waveform you see makes sense if there is no input signal.

    Can you describe in more detail the faults that you want to detect? For instance, does "detecting a short circuit" mean a mutual short between COS+ and COS- ? Or does it mean that you want to detect a short circuit to GND? Here is a brief description of what each fault is supposed to detect:

    FIZHx: SIN+, SIN-, COS+, or COS- shorted to battery
    FIZLx: SIN+, SIN-, COS+, or COS- shorted to ground
    FOSHORT: SIN+/SIN- shorted together or COS+/COS- shorted together
    FOSINOPH/FOSINOPL: SIN+ or SIN- disconnected
    FOCOSOPH/FOCOSOPL: COS+ or COS- disconnected
  • 0 in reply to Clancy Soehren
    Prodigy 10 points

    Dear Clancy:

      The faulst we want to detect are FOSHORT，FOSINOPH/FOSINOPL，FOCOSOPH/FOCOSOPL。The parameters we configure  are as followd:

  • 0 in reply to YD M
    Prodigy 200 points

    Dear Clancy:

        The pga411-configuration is described by YD M screen capture. Could you give us some advice for debugging pga411 ?

    Thanks!

  • 0 in reply to Eric Zheng
    TI__Mastermind 23810 points
    Eric,

    FOSHORT: You will only detect this when both the SIN and COS signals appear to be shorted. In practice, this will occur when one is shorted and the actual angle is at 0, 90, 180, or 270 degrees.

    FOSINOPH/FOSINOPL，FOCOSOPH/FOCOSOPL: With the EVM AFE resistors, you will only ever see the FOSINOPL/FOCOSOPL. Also, you need to make the following changes in the GUI:
    COS GAIN = 2.25 (block diagram page of the GUI)
    SIN GAIN = 2.25 (block diagram page of the GUI)
    OSIN/OCOS Open - Low = 25% (Analog Front End page)

    To use COS/SIN gain of 1, you will need to modify the resistors on the board. Either reduce the pull-up and pull-down resistors (they can go to 20kOhms) or reduce the gain setting resistors.

    Thanks,

    -Clancy