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PGA 308 1W to output

Sudheer Beligere
Intellectual 270 points
Other Parts Discussed in Thread: PGA308

Hello Ian,

We are exploring to have 1W pin connected to output of the product which is expected to provide full scale output of 6V.  Since a buffer is required between between PGA output and final output to scale upto 6V, we have the challenge of connecting PGA output and 1W together. 

1W pin max ratings upto 5.5V only but output is at 6V in full scale, can we tie 1W output and buffer output together and can still communicate over the same one line using PGA308 EVM? or any other methods availible? we are planning to have a zener connected to 1W pin to limit the voltage to 5V to protect from output pin which can go upto 6V and 1W and final Output shorted.

Thanks and regards,

Sudheer

  • 0
    TI__Mastermind 27715 points

    Hello Sudheer,

    This is a difficult problem - I don't see a quick and easy way to implement this type of system.

    What allows the 1W-to-VOUT feature on the PGA308 to be possible is that the VOUT pin goes to a high-impedance state during digital communication. In your proposed system, the 1W connection would go to the final amplifier's output, which is low impedance. Some kind of switching circuit would be necessary to connect or disconnect the final amplifier's output from the total module output. You would also have to provide overvoltage protection to the PGA308 1W pin, as you mentioned.

    I recommend using a four-wire implementation, where 1W and VOUT are on separate connections, in this type of circuit.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps