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PGA117: How to verify SPI sent correctly?

Edmond Chiu
Prodigy 170 points
Other Parts Discussed in Thread: PGA117, PGA112, PGA113

Hello,

I currently am trying to write to the PGA 0x2a and 0x09 (mux CH9 with gain 1). Here is the scope snapshot of what I am sending to the PGA:

 http://imgur.com/rZo8slL.

However, I am unable to get anything out of Vout. On Page 27, there are SPI commands for the PGA112 and PGA113 but I don't see the commands for the PGA117. Are they the same? If not, where is the reference for the SPI commands to send to the PGA117. Thank you.

  • 0
    TI__Mastermind 27715 points

    Hello Edmond,

    I have a few suggestions for getting the PGA117 configured properly:

    • Make sure to provide the SPI /CS signal which remains low for the duration of each SPI command
    • Keep a logic "high" voltage applied to pin 13, ENABLE, to keep the PGA in an enabled state
    • The power-on-reset settings place the device in gain = 1, mux = CH0. Try to connect your input signal to CH0 (pin 7) and see if the device is enabled and passing the signal through to the output pin.
    • Use Table 4 - SPI Daisy Chain Commands - to write to the PGA117. According to this table, the command to set up the device for gain = 1, mux = CH9 is 0x3A 0x09.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps