ADPD188 - Registries for Separate PD Reading


I’m using an ADPD188GG with both photodiodes summed and connected to channel 1 (as in figure 16 of the data sheet), which works well. I would like experiment with reading the two PDs separately off channel 3 and 4 (as in figure 15), but can’t get that working. Does someone have a resource for the registry values that might get this to work or a .dcfg file that does this? I suspect I’m overlooking something in my values.  I’m currently doing this testing on the eval board and the included software – though we may eventually move to our own hardware.

Thank you,

  • +1
    •  Analog Employees 
    on Jun 29, 2021 8:44 PM

    Jeff,  There are 4 registers you need to check to get this working.  Register 0x14 sets the AFE connection, this is the one that is called out in figures 16 and 14.  If you are using the FIFO you need to make sure that the register 0x11 is set to be in one fo the 4-channel modes and not one of the "SUM" modes.  The ADC-Offset registers 0x18 to 0x1B; and ox1E to 0x21 need to be adjusted such that they do not force the channel output to zero.  A value of 0x3FFF will force the ouput to zero.  Generally a value of 0x2000 is ideally zero but may clip the noise when their is no light.  and offset of 0x1F00 or similar is often used for active channels when the no-light code case needs to be measured and subtracted.  Lastly registers  0x3C bits [8:3] need to be set to ensure that the amplifiers for channels 3 and 4 are on.  0x37 should also be set accordingly.  See Table 28.  

  • Dear Neal,

    Thank you for that.  It seemed to fix my issues.  I had neglected the ADC-Offset registers.
    All the best