RTC battery causing boot issues

[scott104]

Hello all

We have been evaluating our custom carrier PCB for months without any boot issues

But when you connect an RTC backup battery to the PMIC_BBAT pin, it causes the boot cycle to stop the Orin powering up until you remove power and reapply power again …

Why is this? As the backup battery is only connected to ground and not connected to any other circuit on the carrier PCB

As the Orin is a “black box” there is no way of knowing is that voltage present on the BBAT pin is leaking into another circuit on the carrier out of one of the other Orin pins ?

[Trumany]

As said in DG: Note: This pin is input only and rechargeable cells or devices such as Super Caps cannot be supported.

Could you share the schematic of this part?

[scott104]

yes we only use a non rechargeable cell - a CR1216 3V lithium coin cell.

See the image, there is nothing more than that connected to BBAT pin 235.

But its strange as when you disconnect power (i dont have a power button, power is simply lost and then reconnected) and then reconnect power, it doesnt start, then disconnect and reconnect again and it starts.

[Trumany]

Please add 1k ohm as that in P3768_A04 design. If still fail with 1k resistor, then it looks more like other part issue of your board.

[scott104]

ok thanks, whats does that resistor do?

[Trumany]

It’s to limit current. Any result?

[scott104]

i had to end up adjusting the enable time constant , then it worked.

that resistor you mentioned didnt help unfortunately.

[stanley.adams]

Hi, I am having this exact same problem on a custom carrier board. With the battery installed, the Jetson will only boot every second time. Can you please describe how you adjusted the enable time constant.

[stanley.adams]

Ok, never mind. I increased the capacitance on the Power Enable pin (Pin 237 on the module) and that solved it. Thank you for pointing me in the right direction.