• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 534 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

AFE5808: Register difference between AFE5808A and AFE5808

AFE5808: Writing to register 0x32 adverse affects

MThorne
Prodigy 40 points

Part Number: AFE5808
Other Parts Discussed in Thread: , AFE5807, AFE5803

We are currently looking at temporarily replacing the AFE5808A with AFE5808 due to supply issues. One of the differences between the parts seems to be that it does not have the -6dB PGA Clamp

From AFE5808A data sheet (table 6)

50[10] 0x32[10] 0 PGA_CLAMP_-6dB

0: No clamp enabled.
1: The PGA output linearity will be degraded when PGA output signal is
higher than –6 dBFS, 1 VPP. The PGA output is limited to about 1.6 VPP.
50[10] 0x32[10] 0 PGA_CLAMP_-6dB ADC is not overloaded while its dynamic range is reduced by 2 dB. This
setting will reduce the channel gain by about 1.5 dB. Note: 0x33[7:5]
needs to be set as 000 in the low noise mode or 100 in the low/medium
power mode.

We currently write to this register, enabling and disabling bit 10 as required. What will be the affect of doing this with the AFE5808 which does not mention this register in it's data sheet? Will it ignore the use of the not supported -6dB PGA Clamp or produce undefined behavior?

Thanks in advance.

  • 0
    TI__Expert 7140 points

    Hi,

    Thanks for writing to us.

    The PGA clamp -6dB setting is not available in AFE5808. So, the clamp level is set to -2dBFs by default.

    Thanks & regards,

    Abhishek

  • 0 in reply to Abhishek Vishwa1
    Prodigy 40 points

    Thanks for the reply, I understand the PGA clamp -6dB is unavailable in the AFE5808. As this is a replacement in a production board I would like to confirm the affect of writing to register 0x32 in the AFE5808? Are we at risk of causing unwanted behavior by writing to this register or will it simply be ignored?

  • 0 in reply to MThorne
    TI__Expert 7140 points

    Hi,

    The PGA clamp feature is not implemented in AFE5808. By default it is set at -2dBFS level. Setting bit 10 in 5808 will not introduce any undefined behavior. On a different note, there is a color noise issue in AFE5808 which was fixed in AFE5808A, AFE5807 and AFE5803. Have you considered using any of these parts before going with AFE5808 ?

    Thanks & regards,

    Abhishek