Nordic Dongle Power Off mode

Question

I have been struggling to reduce the current on the Nordic Dongle to the sub 3 uA levels that the specs suggest I should be able to achieve. 
 I am stuck at achieving a 9-10 uA current in POWER off mode. 
 Here is an output from the PPK-II in power off mode. 
 
 To achieve this I set up 4 GPIO pins to wakeup the nrf52840 from POWER_OFF mode as follows:

// this will enable wakeup from ultra low power mode (any button press) 
 nrf_gpio_cfg_sense_input ( PLUS__PIN , GPIO_PIN_CNF_PULL_Pullup , GPIO_PIN_CNF_SENSE_Low ); 
 nrf_gpio_cfg_sense_input ( MINUS__PIN , GPIO_PIN_CNF_PULL_Pullup , GPIO_PIN_CNF_SENSE_Low ); 
 nrf_gpio_cfg_sense_input ( ENTER__PIN , GPIO_PIN_CNF_PULL_Pullup , GPIO_PIN_CNF_SENSE_Low ); 
 nrf_gpio_cfg_sense_input ( STANDBY__PIN , GPIO_PIN_CNF_PULL_Pullup , GPIO_PIN_CNF_SENSE_Low ); 
 
 I also disable the button on the board as follows: 
 
 nrf_drv_gpiote_in_event_disable ( BUTTON_1 ); 
 
 I also turned off the following 
 1.ram retention 
 2. logging in sdk_config.sys. 
 3. NRF_SPI0 -> ENABLE = 0 ; 
 4.NRF_UART0 -> ENABLE = 0 ; 
 
 I am using the s340 SD in low power mode:

//set up the pwr configuration 
 sd_power_mode_set ( NRF_POWER_MODE_LOWPWR ); 
 
 power is from a 3v coin battery connected to the VDD pin, not VBUS to avoid the first conversion stage 
 
 Does anybody have any ideas on how I can get below 9 uA in POWER_OFF mode? 
 I am developing for a CR2032 and pwr is everything!

rananna · Accepted Answer

Yes, I am powering on VDD out. 
 You were right, I did not properly disconnect SB2 on the first dongle. 
 When I did, the poweroff current fell to 0.5uA. 
 However, this was measure before I shorted SB1. 
 I then shorted SB1 on both boards, and there was, as expected, no difference in the poweroff current. 
 So , I have the answer, thank you! 
 I see the reference design has it in, but would there be any downside to leaving VDDH floating and not tying it to VDD through the SB1 short? 
 I wanted to simplify the preparation of the dongle, and leaving out the SB1 short would simplify things at little bit by only requiring the sb2 open.

Stian Røed Hafskjold · Answer

rananna said: I see the reference design has it in, but would there be any downside to leaving VDDH floating and not tying it to VDD through the SB1 short? 
 All I can say is that the regulator is designed this way (VDD and VDDH shorted) and all production testing we have done to verify our product is with this configuration. So we cannot guarantee that every device will work as expected without VDD and VDDH shorted. So for mass production I would definitely follow the reference design, but for prototyping and testing purposes you will probably be fine by leaving out the SB1 short.

Stian Røed Hafskjold · Answer

Hi, so I tried measuring here, and I see the same 10 uA in system off. 
 I took a closer look at the schematic and you actually have to cut SB2 when powering only on VDD. Otherwise VBUS_nRF will be powered as well, and this is where the leakage occurs. VBUS_nRF should only be powered when the USB is in use, otherwise the USB peripheral will be consuming current. From the spec:

Symbol 
 Description

Min. 
 Typ. 
 Max. 
 Units

I USB,DISABLED,VDD 
 
 Current from VDD supply, USB disabled, VBUS supply connected, 256 kB RAM retention, regulator=LDO, CPU sleeping

3 
 7 
 11 
 µA

https://infocenter.nordicsemi.com/topic/ps_nrf52840/usbd.html?cp=4_0_0_5_34_13#unique_518559908

rananna · Answer

Thanks again for your help with this. 
 Great support!

Nordic Dongle Power Off mode

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