when nrf52840 open dcdc and usb ,it will reboot.

[Terrel]

Hi There

 

Here we have been encountering some problems and would appreciate if you could help.

 

We are designing the hardware based on the following schematic, please refer to the official profile 7.3.4.(VDDH connected Battery) , software VDD_NRF=1.8V)

 

The problems are as below:

 

1, DCDC works well after power ON, but it will probably be reset while connecting/disconnecting from the USB, or the program fails to run. The measuring VDD_NRF=1.8V and it’s provided by the inner LDO. Because there is a stable 1.8V before & after L11. The failure rate is about 30%+. The reset rate is more than 30%.

2, If we turn OFF the software configured DCDC and change to inner LDO output 1.8V and all will be fine.

 

 

[Andreas]

Hi,

 

What revision chip is on the boards, C or D (is the marking on top QIAAC0 or QIAAD0)?

Is there anything else being supplied on VDD_nRF? Is there any change in behaviour if the REGOUT is higher than 1.8 V? Can you share a scope plot of what the VDDH line and VDD line look like when you plug/unplug the USB cable, is there any difference between failing and non-failing boards?

 

Best regards,

Andreas

[Terrel]

1.The mcu marking is QIAAC0.

2.VDD_nRF is only for nRF52840,it donot connect anything.

3.If REGOUT is higher than 1.8v, the system will still work.Because nrf52840 is now set to 2.1VLDO mode, the system is running normally.

4.If turn off the USB code and then plug/unplug USB, nrf52840 is not reset

[Andreas]

Hi,

 

Revision C should not be used due to errata 197 and 202. You should contact your sales manager to get some samples of revision D and test this.

 

Best regards,

Andreas