REG0 power consumption

Question

Hello Nordic, 
 today I'm curious about power management! 
 
 Background 
 We are in development of two products (let's say A & B) both featuring Minew MS88F3 module (based on nRF52840 IC) and with two different power management topologies. 
 
 Product A 
 
 USB and Li-Po battery (3.7V nominal) supply 
 High Voltage mode
 
 REG0 as LDO. 
 REGOUT0 is set to 2.7V 
 REG1 as DC/DC

Schematic:
 
 VDD: LDO output 
 VDDH: diode-ored with BAT and USB (VCCM on shematic) 
 VBUS: connected to USB plug

Product B 
 
 2xAA bateries (3.0V max) supply 
 Normal Voltage mode (SB1 ON) or High Voltage mode (SB1 OFF) 
 REGOUT0 is set to 1.8V (when in High Voltage mode) 
 Schematic:
 
 VDD: if SB1 ON, then shorted to VDDH, 
 VDDH: connected to 2xAA battery 
 VBUS: not connected

NOTICE: Product B is prepared for evaluation purposes, therefore it has SB1 jumper to easy change voltage modes! 
 
 Platform description: 
 
 IC: nRF52840 
 Module: Minew MS88SF3 
 SDK: nRF5_SDK_17.1.0_ddde560 
 Softdevice: s140_nrf52_7.2.0 
 IDE: SEGGER Embedded Studio for ARM Release 7.10a Build 2022121504.52072 
 OS: Windows 10

Observations/Measurements 
 Current consumption measurements were taken using Power Profiler Kit II, at 100ksamp/sec and 2 minute window. Current consumption was measured on five different B products in both (normal and high) voltage modes and at different power supply levels. In all cases device was in connection with central device. Measurements were taken in three different configurations: 
 
 Normal voltage mode (SB1 ON), REG1 LDO 
 High voltage mode (SB1 OFF), REG1 LDO, REG0 LDO 
 Normal voltage mode (SB1 ON), REG1 DC/DC 
 
 In all three test cases there was the same software, regarding calling " sd_power_dcdc_mode_set( NRF_POWER_DCDC_ENABLE ); " in 3. test case. Purpose of that measurements was to compare the power consumptions in various power configurations. 
 Results are following with Iavg (average current in uA) and Imax (max. current in mA) within 2 min window: 
 
 Notice the current consumption increase when in High voltage mode at battery voltage of 2.5V (REGOUT0 is set to 1.8V). Current increase from 2.0V -> 2.5V was ~10x for all 5pcs! Same increase can be observed from 2.5V->3.0V! 
 On the other hand product A has in High Voltage mode current consumption around ~50uA, measured from 4.2V to 3.0V. 
 
 Questions: 
 
 Why does the current consumption raise proportional to supplied voltage in test case 2.? 
 On product B, when enabled high voltage mode, current consumption increases by ~100uA, but not in the product A. What can be the reason for that? One should expect at least 100uA current consumption on product A as this was measured on product B. 
 Schematic difference between A & B is that A have a VBUS connected and B does not. Can this have any effect on increased current consumption on product B, when in High voltage mode? 
 What amount of current consumption does REG0 consume by itself when operating in LDO and when in DC/DC mode?

Thank you! 
 BR, Žiga

Ziga Miklosic · Accepted Answer

Hi Jared, 
 thanks for reply! 
 
 Jared said: In the meantime, would you be willing to share the schematics of the products just to make the difference more clear? 
 Unfortunately sharing a complete schematic is against the company policy. I already provided all power related connections to the chip, if you need any more information, I&rsquo;m happy to give you in text format or sketch it out. Hope that will be enough for you guys to analyze. 
 Please note that we are making relative comparisons here and not focusing on absolute consumption values. I'm curious of consumption levels in different power management topologies, when using same HW & SW and only changing power part of it. 
 
 Jared said: Also, do you have a PPK2 
 Yes, I've already provide that info. I have a feeling that you read initial post superficially. 
 Ziga Miklosic said: Observations/Measurements 
 Current consumption measurements were taken using Power Profiler Kit II, at 100ksamp/sec and 2 minute window. 
 
 Jared said: Could you share a PPK2 trace that shows the current for the 3 configurations? 
 I will capture it and post current traces later that day or tomorrow. 
 
 Jared said: I noticed that some of avg current that you have listed has a very high difference compared to the others. 
 Avg. current in Normal Voltage mode: 
 
 Normal Voltage mode, LDO only: 8.52uA 
 Normal Voltage mode, REG1 DC/DC: 6.37uA 
 
 which is 25% reduction when enabled REG1 DC/DC. That seems close though. But on the other hand current consumption in High Voltage mode is enormous (100uA+). 
 What is confusing to me is that when REG0 is used (either LDO or DC/DC mode), current consumption spikes to 100uA+ and it gets worst with raising battery supply. Current consumption is then direct proportional to battery supply voltage. 
 
 Thank you for all the help! 
 BR, Žiga

Stian Røed Hafskjold · Answer

Hi Žiga, 
 My analysis of the issue is as follows: 
 
 Product A has low current consumption in high voltage mode, while product B has high current consumption in high voltage mode
 
 This means that quiescent current in REG0 is most likely not the issue here 
 This is also in line with what I would expect. You should not see that much higher current consumption by just enabling REG0

VBUS is not connected on product B
 
 This should not have any impact on the current consumption. Actually connecting VBUS will add a few microamps, not the other way around.

The current increases linearly with voltage on VDDH
 
 Means that we have a resistive load on VDDH. (delta I with 0.5V increase => 0.5V/100uA ~ 5kOhm)

You do not see the increased current in normal voltage mode, but you see high current in high voltage mode
 
 The difference in these two modes would be the voltage difference between VDD and VDDH 
 Since we are looking at a resistive load on VDDH, and the fact that you do not see the elevated current in normal voltage mode, my guess is that this resistive load is placed between VDD and VDDH
 
 GPIOs (and SWD, nRESET, etc) are powered from the VDD domain, not VDDH.
 
 Having a pullup to VDDH (VBAT, VBUS, etc), on one of the GPIOs will allow for current to flow between VDDH and VDD.

Things to check:
 
 External pullups on GPIOs, including SWD and nRESET lines 
 If the Vref on the SWD header is connected to VDDH, not VDD (relevant only when the debugger is connected) 
 External components, and their GPIO voltages. If external components are powered by VDDH, they will have a different voltage level, and current will flow between the devices. Level shifters must be used. 
 Without being able to look at your schematic it's difficult to pinpoint exactly where the current flows, but my guess is that the issue is something similar to the above suggestions. We can make the ticket private if that makes it easier for you to share the schematic.

Best regards, Stian

REG0 power consumption

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