TE0820 Power Up Issues with REV04

[jan.blaesi]

Hi,

we are experiencing some issues with REV04 TE0820 modules.
After a brownout, or occasionally on initial startup, the module sometimes gets stuck, not booting anymore.
The red LED on the long side of the module stays lit up, the boot mode LED blinks as usual.
Doing a longer power cycle (~10 seconds), the module boots up just fine.

Our REV05 modules never show this kind of behaviour, it is just the REV04 ones.

The EN1, RESIN and NOSEQ lines are controlled by a microcontroller, but I did not find any way to get the module out of this state.
Do you have any idea what we could be doing wrong?

Best regards

[M Kirberg]

Might be related to TE0820 PCN item from:

https://wiki.trenz-electronic.de/display/PD/PCN-20220725+TE0820-04+to+TE0820-05+Hardware+Revision+Change

#9 Changed reset, enable and power-up structure with resistor R95, added transistor T2, and added resistor R128.

Maybe your control sequence is not compatible anymore?

[jan.blaesi]

Please excuse my late reply, the notification must have gotten lost in my inbox.

The microcontroller is connected to the same 3V3 input as the TE0820.

On startup, we do the following:
Put EN1 high, RESIN low, NOSEQ low.
Wait ~50ms, then put RESIN high.

Do you see any issue why this would get the TE0820-04 stuck?
As I said, the TE0820-05 has absolutely no issues and starts reliably.