I am working with an nRF52840 on a custom board with an SD card connected on SPI, running Zephyr 3.2.99/NCS 2.2.0.
I would like to use SPI frequency >8 MHz for the SD card, which would require using the SPIM3 instance. When using an Otii Arc to measure current consumption, I observe that even when only configuring for 8 MHz speed, SPIM3 results in a much larger current consumption than SPIM2. In the same application idle condition with BLE advertising, but nothing else happening, and not actively using SPI, using SPIM2 for the SD card results in ~136µA current draw (with the majority going to the sleeping SD card), while changing to SPIM3 increases this to ~529µA.
I am aware of anomaly 195 "SPIM3 continues to draw current after disable", but this only refers to current consumption after disabling the SPIM3 instance. In nrfx_spim.c, the anomaly workaround is implemented only when un-initializing the instance, not every time a transfer is completed. Does the HW issues with SPIM3 also explain an increased current consumption while it is still enabled, but not actively used, or should a workaround be required after every data transfer (e.g. when CS goes high)? Or, is it simply expected the SPIM3 uses more power due to being more capable, supporting up to 32 MHz?
