HFINT has frequency tolerance of +/-1.5% typ and +/-8% max

RE: HFINT has frequency tolerance of +/-1.5% typ and +/-8% max

Håkon Alseth — Mon, 03 Sep 2018 07:44:03 GMT

1 and 2) Yes, I meant the HFXO. Using a stable clock source is the only way you can get a stable baudrate over the whole temperature spectrum.

3. There is no definite way to check this. You could check the temperature (TEMP peripheral) or if you get framing errors on the UART, then start the HFXO.

4. Depends on the crystal chosen. If you do not turn it off before going to sleep, you'll get an added suspend current of the HFXO, provided that no other devices are requesting the HFCLK.

Best regards,

Håkon

RE: HFINT has frequency tolerance of +/-1.5% typ and +/-8% max

Mahendra Tailor — Mon, 03 Sep 2018 07:30:44 GMT

Also I will be most grateful if you could explain what to do with regards to uart operation when the tolerance is +/- 8% as to how to detect that so that I can use the HFXO

RE: HFINT has frequency tolerance of +/-1.5% typ and +/-8% max

Mahendra Tailor — Mon, 03 Sep 2018 07:27:21 GMT

Thank you for getting back to me.

(1) I thought the HCLK is always ON? Otherwise the uart rx would never receive anything at anytime.
(2) Did you mean the HFXO?
(3) Please explain how I can detect that I am getting into that operation zone?
(4) What is the extra current consumption I could expect to see with HFXO?

RE: HFINT has frequency tolerance of +/-1.5% typ and +/-8% max

Håkon Alseth — Mon, 03 Sep 2018 06:49:44 GMT

Hi,

In this scenario, I'd recommend starting the external HFCLK to ensure a stable tolerance of your UART.

Best regards,

Håkon