Current consumption difference nRF51422 and nRF51822

[Bart de Kramer]

I'm had develloped some software and tested it on the nRF51-DK. After that I made my own PCB design where only the nRF51422 is replaced by a nRF51822. When I flash both with exactly the same software, the nRF51-DK consumes about 5.6uA and my own PCB about 2350uA. Is there a difference between the nRF51422 and nRF51822 which can cause this big difference?

I'm using softdevice s110_nrf51_8.0.0.

[Hung Bui]

Hi Bart,

I would need to see your schematics, to investigate more. Have you made sure you don't have any extra components that may consume more power ? Do you have the 32 KHz crystal on the board ? Beside consuming more power, would it still works at it should ? What kind of application did you test ? with or without softdevice ?

[Bart de Kramer]

Hi Hung, I have some extra components, but I add these to the development board too. I removed the 32kHz crystal from my own PCB but also from the development board. I've only tested with an softdevice application (starting with ble_app_hrs_s110_with_dfu_pca10028 but add my own functionality to it). The softdevice init in the function BLE_Stack_Init is now like SOFTDEVICE_HANDLER_INIT(NRF_CLOCK_LFCLKSRC_RC_250_PPM_TEMP_4000MS_CALIBRATION, NULL);

At my own PCB I cannot establish a Bluetooth connection because I need to tune my antenna but the software is running on it. I have a serial port on it at which I can print some chars.

[Hung Bui]

@Bart: I would suggest you to test the board with some simple code. Try to use some simple peripheral, or simply put the CPU to sleep. Just to check it's not from other part of the board. Then you can try the example with softdevice in the SDK.

[Bart de Kramer]

Hung,

I made a very simple main loop:

int main(void) { ble_stack_init(); for (;;) { sd_power_system_off(); } }

Current draw is now 8.3uA, so for me it look likes the nRF51822 draws that excessive current.

[Hung Bui]

Yes, but we need to know why on our board it doesn't draw more current but on yours it does.

I suspecting the RF part causing the issue. You can try to test with an example that advertise something. Also you can try to test with the radio_test example (the simple one, not with softdevice). You can open a case on our Support Portal (My Page) and send your schematic and layout there, then we can do better investigation.