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PGA460-Q1: PGA460 not able to use full range

Yash Pandya
Prodigy 90 points
Part Number: PGA460-Q1
Other Parts Discussed in Thread: PGA460

Hello Everyone

I am using PGA460 to detect object.

I am extracting direct data using 8Mbps USART. My record length is 4.096*16 ms i.e. I am extracting 65536 data byte but after around 12240 byte my data is becoming 0xFF but there is no object at that distance. I am using 58kHz transducer. Let me know if I need to do some setting to increase its range other then setting it in REC_LENGTH Register.

Following are the default values that I'm using.

USER_DATA1 = 0x00;
USER_DATA2 = 0x00;
USER_DATA3 = 0x00;
USER_DATA4 = 0x00;
USER_DATA5 = 0x00;
USER_DATA6 = 0x00;
USER_DATA7 = 0x00;
USER_DATA8 = 0x00;
USER_DATA9 = 0x00;
USER_DATA10 = 0x00;
USER_DATA11 = 0x00;
USER_DATA12 = 0x00;
USER_DATA13 = 0x00;
USER_DATA14 = 0x00;
USER_DATA15 = 0x00;
USER_DATA16 = 0x00;
USER_DATA17 = 0x00;
USER_DATA18 = 0x00;
USER_DATA19 = 0x00;
USER_DATA20 = 0x00;
TVGAIN0 = 0x44;
TVGAIN1 = 0x44;
TVGAIN2 = 0x44;
TVGAIN3 = 0x08;
TVGAIN4 = 0x64;
TVGAIN5 = 0x9A;
TVGAIN6 = 0x98;
INIT_GAIN = 0x40;
FREQUENCY = 0x8F;
DEADTIME = 0x08;
PULSE_P1 = 0x4F;
PULSE_P2 = 0x12;
CURR_LIM_P1 = 0x80;
CURR_LIM_P2 = 0x00;
REC_LENGTH = 0xFF;
FREQ_DIAG = 0x11;
SAT_FDIAG_TH = 0x2E;
FVOLT_DEC = 0x3A;
DECPL_TEMP = 0x0F;
DSP_SCALE = 0x00;
TEMP_TRIM = 0x00;
P1_GAIN_CTRL = 0x0A;
P2_GAIN_CTRL = 0x02;

  • 0
    TI__Genius 14856 points

    Hello Yash,

     

    Have you been able to confirm the data (before 12240) is being captured properly by the MCU? Additionally, is the data dump error consistent in when the data gets set to 0xFF?

     

    The rec_length register is set properly as P1 and P2 are set to 4.096*16ms.

     

    Have you verified all output stages exude similar behavior? It may be beneficial to take the data dump from earlier stages of the signal chain to verify the response of 0xFF is from the PGA460 ADC.

    I will continue to look into what may be causing your issue.

    Please let me know if you have any questions.

    Thank you,

    Jacob

  • 0
    Prodigy 90 points

    This is how my output data looks like.

    I am taking output data after LPF i.e. 0x01.

  • 0 in reply to Yash Pandya
    TI__Genius 14856 points

    Hi Yash, 

    Thank you for the waveform. I have discussed the issue with other Engineers, however this is not an issue we have encountered before. Would you be able to change the MUX to output the data directly from the ADC instead of after the LPF. This will help us understand where the 0xFF result is coming from.

    Thank you,

    Jacob

  • 0 in reply to Jacob Nogaj
    Prodigy 90 points

    Hi Jacob,

    Sorry for late reply.

    I changed the MUX output to ADC as you told me. But it doesn't change anything for me. Please let me know if you find anything.

  • 0 in reply to Yash Pandya
    TI__Genius 14856 points

    Hi Yash,

    I appreciate the data you were able to take. This confirms the signal chain is not damaged. 

    Unfortunately, this still leaves many places as to where the issue could be sourcing from. Seeing as the output data returns to a state of 0 following the conclusion of the direct data bust, I would imagine the timing for acquiring data to be correct. 

    Would it be possible to test the output after changing the REC_LENGTH registers? This will help me understand if the recorded data scales with the recorded length of the data burst. 

    Additionally, has this condition been observed on multiple devices?

    Thank you,

    Jacob

  • 0 in reply to Jacob Nogaj
    Prodigy 90 points

    I tested it with different REC_LENGTH also. But its showing 0xFF after same position.

    I will try with different PGA460 IC and let you know the result.

  • 0 in reply to Yash Pandya
    TI__Genius 14856 points

    Thank you Yash,

    Please let me know when you obtain results for testing.

    Thank you,

    Jacob