AFE4490 - Diagnostics query

Hello Purushottam,

During the diagnostic operation, the AFE output will not be proper since the inputs INP, INN and outputs TXN and TXP are being used for diagnostic check. After diagnostics, the AFE output should become normal. During diagnostics it is not recommended to capture the PPG data. To avoid glitches in the PPG data, disable the timer before entering diagnostics. This freezes the device filter and when diagnostics is complete, enable the timer again to start the Timing Engine. After completion of the diagnostics function, time must be allowed for the device filter to settle.

Please follow the sequence to remove the glitches in the output signal.

1. Disable timer (Set the TIMEREN bit in the CONTROL1 register by setting the value to '0')
2. Wait for 2ms.
3. Enable Diagnostics (set DIAG_EN bit to '1')
4. Wait for tDIAG
5. Enable Timer (Set the TIMEREN bit in the CONTROL1 register by setting the value to '1')
6. Wait for tFilter_settle time (After completion of the diagnostics function, time must be allowed for the device filter to settle)

Hi Praveen,

Thanks for your reply. The steps mentioned are followed. Issue still exists. Please find the attached document.

1) Sampling rate is 500Hz.

2) On every 5 second, the diagnostics is enabled. From the captures on every 2500 samples, glitch can be seen. (due to loss of data).

Hi Praveen,

Any update on the query?

Hi Purushottam,

Do you capture the PPG data or wait during the filter settling time after the diagnostics complete?

How long do you wait?

Hi Praveen,

After enabling the diagnostics, software will poll for DIAG_END pin going high. Later 30mS is wait for filter settling time.