ADPD1081 - Connect PDC pin to GND?

Hello ADI,


Our customer is developing an oximeter with ADPD1081, he is planning to use a standard Omeda probe.


On this type of probe the photodiode cathode is connected to GND (shield). On ADPD1081 block diagram, we see that the photodiode cathode is connected to PDC pin.


Customer would like to know if its possible to connect PDC pin to GND (through Omeda probe). On the datasheet I see that PDC pin can assume different voltage values (from 1v8 to 0v) depending on the value of register 0x54, in this case I would like to know if is there a workaround to allow the use of standard Omeda probes.


Thank you in advance,


  • 0
    •  Analog Employees 
    on Jul 19, 2021 3:18 PM

    Hi Matheus,

    The PDC pin is an analog output  to provide bias for the photodiode (PD). Connecting the PDC pin to GND causes short circuits.

    Although the PDC pin can be set to 0V during time slot A sampling, time slot B sampling, and sleep, the proper setting of PDC pin is 1.3V for zero bias of the PD or 1.55V for 0.25V reverse-bias of the PD. Setting PDC pin to 0V causes 1.3V forward-bias of the PD and hence low performance.


    Glen B.