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LMH6882: Unused SDO (MISO) Pin

Part Number: LMH6882

Hi!

Copied from the datasheet: "The SDO pin is a current output and requires external bias resistor to develop the correct logic voltage. Resistor values of 180 to 400 are recommended."

We don't need to read out the registers via SPI MISO.

So just to be sure: I assume that we can let the SDO pin floating as long as we don't need to read out register data. Correct? Or does the SDO current output causes any problems without the external resistor?

Regards,

Andre


  • Hello Andre,

       Yes, that is correct. SDO is a high-impedance state, unless CS (chip select pin) is asserted. You can leave SDO pin floating, but pin 14 is both SDO (serial interface) and D0 (parallel interface). If the device is in parallel mode and you need 0.25dB gain change steps, you would need to control this logic state. 

         This is from the datasheet in section 7.5.2: "The attenuator control pins are internally biased to logic high states with weak pull-up resistors, with the exception of D0 (pin 14) which is biased low due to the shared SDO function. If the control bus is left unconnected, the amplifier gain will be set to 6dB." 

    Thank you,
    Sima 

  • Thank you for the confirmation.

    Have a nice day!
    Andre