ppk2 ampere meter measure error.not correct

Question

hi nordic, 
 when ppk2 entry Ampere meter. the measure current not correct.(it seem the scale and offset error ,but can be enable/disable output) 
 (test circuit only vdd(3.3 extern power)->resistor5.1k->ppk2(in)-->ppk2(out)-->gnd(ppk2 gnd) it should be 0.6mA,but the ppk2 only 60uA.? and other case it get error value(nrf52840 dk blinkly example same issue*1) 
 when ppk2 entry soure meter.it be work it is right value. (it test use nrf52840 dk ,blinkly example) https://i.imgur.com/pMqRzEY.png 
 measure example(error): https://i.imgur.com/o41SGHp.png 
 app version: https://i.imgur.com/TlxZCIo.png 
 ppk2 F.W version: 15:37:32.160 Validating firmware for device with s/n D55B03750145 15:37:32.177 Opening device with s/n D55B03750145 
 os: # nRFConnect System Report - 2020-12-30T10-21-15.621Z - System: xxxx - BIOS: xxxx - CPU: 1 x Intel Core i5-8265U 1.60 GHz 8 cores (4 physical) - Memory: 1.2 GB free of 7.9 GB total - Filesystem: C: (NTFS) 120 GB 94.9% used - OS: Microsoft Windows 10 Pro (10.0.19041) win32 ia32 - Versions - kernel: 10.0.19041 - git: 2.21.0.windows.1 - node: 12.13.0 - python: 2.7.13 - python3: 
 
 *1: 
 https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_ppk2%2FUG%2Fppk%2Fmeasure_current_ampere_meter.html

2020-12-30T02:18:09.168Z INFO Deselecting device
2020-12-30T02:18:27.807Z INFO Validating firmware for device with s/n D55B03750145
2020-12-30T02:18:27.814Z INFO Opening device with s/n D55B03750145
2020-12-30T02:18:28.606Z INFO PPK started
2020-12-30T02:18:28.624Z INFO PPK opened
2020-12-30T02:18:36.925Z INFO DUT ON
2020-12-30T02:18:40.149Z INFO Sampling started
2020-12-30T02:18:51.021Z INFO Sampling stopped
2020-12-30T02:18:59.541Z INFO DUT OFF
2020-12-30T02:19:54.636Z INFO Deselecting device
2020-12-30T02:19:54.698Z INFO PPK closed
2020-12-30T02:19:58.355Z INFO Validating firmware for device with s/n D55B03750145
2020-12-30T02:19:58.362Z INFO Opening device with s/n D55B03750145
2020-12-30T02:19:58.729Z INFO PPK started
2020-12-30T02:19:58.748Z INFO PPK opened
2020-12-30T02:20:06.226Z INFO DUT ON
2020-12-30T02:20:07.538Z INFO Sampling started
2020-12-30T02:20:14.812Z INFO Sampling stopped
2020-12-30T02:20:15.640Z INFO DUT OFF

hmolesworth · Accepted Answer

The original problem about not measuring in Ampere Mode is caused because the PPK2 has been incorrectly connected to the board you are testing: 
 Change (3.3 extern power)->resistor5.1k->ppk2(in)-->ppk2(out)-->gnd(ppk2 gnd) 
 To (3.3 extern power)->ppk2(in) ppk2(out)->resistor5.1k->gnd(ppk2 gnd) 
 The PPK2 takes the difference in measured voltages because the measurement loads the input and output with 120k+30k each.

hmolesworth · Answer

This is more of a problem than at first sight. Alternating between Source Mode and Ampere Mode with Source Mode voltage set to the same as the CR2032 coin cell in Source Mode indicates 20uA in Source Mode and 10uA in Ampere Mode. (I tried to edit original response but the Reply/More/Edit stuff defeats me). This test is with nRF52832 in sleep, all outputs static no peripherals enabled, no connections to any pins, just LDO skipping and all 32 pins as outputs low driving . All 32 pins left as on reset figures are 18uA Source Mode and 7uA Ampere Mode when in both cases actual current is 1.16uA. 
 EXT+POWER_IN and VLDO on the PPK2 have the same 10uF capacitor on the PPK2, but the LDO impedance will be less than a coin cell; maybe the SAADC sampling requires adjustment to compensate for this although both readings are high which implies LDO skipping pulse peak "looks" longer than reality.. 
 Edit: The original problem about not measuring in Ampere Mode is caused because the PPK2 has been incorrectly connected to the board you are testing: 
 Change (3.3 extern power)->resistor5.1k->ppk2(in)-->ppk2(out)-->gnd(ppk2 gnd) 
 To (3.3 extern power)->ppk2(in) ppk2(out)->resistor5.1k->gnd(ppk2 gnd) 
 The PPK2 takes the diffference in measured voltages because the measurement loads the input and output with 120k+30k each. 
 // <- Supply to DUT From VOUT External Battery To VIN
// +------------------------------+ +-------------------------+
// | | | |
// | +---------+ | | +-----------+ |
// | | GND | | VOUT VIN | | GND | |
// +---------O---------+ | +----O-----O------------------------O-----O----+ | | Battery
// | Vdd | | | | | | | | | | + 3 volts
// | | | | | | AMPERE \ | | | | +-O-+
// | | | | | | \ | | | | | |
// | | | | | #----#-----------O O----# | | | | |
// | Device Under Test | | | | | | | | | | | |
// | DUT | | | | 120k| | |120k | | | | |
// | | | | | +++ | \ SOURCE +++ | | | | |
// | | | | | | | | \ | | | | | +-O-+
// | | | | | | | +-O O-- PPK LDO | | | | | | Gnd
// | | | | | | | | | | | +-------+
// | | | | | +++ +++ | |
// | | | | | | | | |
// | | | | | #-- VDUT VIN --# | |
// | | | | | | Sense Sense | | |
// | | | | | +++ +++ | |
// | | | | | | | | | | |
// | | | | | | | | | | |
// | | | | | | | | | | |
// | | | | | +++ +++ | |
// | | | | | | 30k 30k | | |
// | | | | +--#--+ +--#--+ |
// | | | | | | |
// | | | | ===== ===== |
// | | | | === === |
// | Gnd | | | = = |
// +---------O---------+ | +----------------------------------------------+
// | | PPK-II
// +--------------+