nRF52840 HFCLK

[Al Bundy]

What kind of high frequency clock source is less current 'hungry', internal RC or external XO? I can not find any information in nRF52840 product specification?

It is possible to provide CPU core with 16 MHz or 32 MHz instead of 64 MHz for saving power consumption?

[Sigurd]

Hi,

Q1: What kind of high frequency clock source is less current 'hungry', internal RC or external XO?

A1: The internal RC uses less power, but the RC clock accuracy is much lower compared to using a crystal. If you are using BLE/Radio peripheral, you have to use an external crystal with a frequency tolerance of max 40 ppm.

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Q2: It is possible to provide CPU core with 16 MHz or 32 MHz instead of 64 MHz for saving power consumption?

A2: You can only run the CPU at 64MHz. Using a 64MHz clock will execute your tasks faster and overall you wont save power reducing the clock speed. We chose not to implement a clock divider because we found 64MHz to be most effective in terms of current consumption.