RE: NRF52820 as 3LED high-side driver using internal LDO?

Kazi Afroza Sultana — Thu, 17 Jul 2025 14:45:51 GMT

Hello,

1. ''driving the LEDs with up to 15mA is well within the LDO's capability?''

Internal LDO regulator is designed to supply the nRF52840 and it's peripherals. But the maximum current that can be sunk by all GPIOs is 15mA. You should not exceed this limit.

''2: We could use high current drive to drive the LEDs with ~5mA without issue?''

Yes, you can use the high drive setting on the GPIOs to drive LEDs at around 5 mA without issue, as long as the total current sunk by all GPIOs does not exceed 15 mA. The internal pad resistance should be considered when calculating the series resistor for the LED, as the voltage drop across the pin increases with current.

''3: Any additional consideration such as increased Decap etc? ''

For adding decap, you need to follow our reference design. If you want to switch multiple output at a time and use the high drive mode it is important to have sufficient decap close to the VDD pins.

4: Could the NRF52805 operate down to VDDH=2.7V or lower even though we set the linear regulator to 2.7V? Would it passthrough the voltage and then VDD(reg)=VDDH?

You may look at this case (+) VDD and VDDH out-of-spec consequences - Nordic Q&A - Nordic DevZone - Nordic DevZone.