PowerProfiler 2: How to set up ampere-mode properly?

RE: PowerProfiler 2: How to set up ampere-mode properly?

danielschultz — Tue, 11 Jun 2024 07:01:51 GMT

Hi,
Thank you for clarification. That did the trick regarding the triangle-wave measurements. Guess also I caught the change of resistor in the 5 mA range was caught here (0.5Vpk, 2V offset):

Will try to see if I can get good results with the good suggestion by hmolesworth !

RE: PowerProfiler 2: How to set up ampere-mode properly?

Kenneth — Mon, 10 Jun 2024 16:17:26 GMT

Hello,

Do check:
https://docs.nordicsemi.com/bundle/ug_ppk2/page/UG/ppk/ppk_power_supply_specs.html

DUT voltage must be between 0.8-5V. Can you repeat the test for instance with offset 3V and 300mV amplitude?

Edit: I believe the measurement resistors will be changed around 50uA, 500uA, 5mA and 50mA, with some hysteresis depending on whether current is increasing or decreasing.

Kenneth

RE: PowerProfiler 2: How to set up ampere-mode properly?

hmolesworth — Mon, 10 Jun 2024 16:16:54 GMT

I never found out the transition switching times for the different measurement ranges, but with some loss of precision some of the switching disturbances can be defeated by using a known calibrated constant current in addition to the DUT current by using (say) a 0.1% (or even 1%) resistor in parallel with the DUT (to minimise number of current ranges used) and subtracting that constant current from the result.


data-mode="c_cpp">// Resistor Rc for current sense is 1k0 in parallel with one or more of 110R, 11R0, 1R0 and 0R051 +ve Supply to DUT From VOUT                               External Battery +ve To VIN --------------------+                             +-----------------------+ |                             |                       | +---------+     |                             |     +---------+       | |     GND |     | VOUT                   VIN  |     | GND -ve |       | |    +====O=====O=============================O=====O====+    |       | Battery |    |    |    |     #----+                        |     |    |    |       | + 3 volts |    |    |    |     |    |Rc        AMPERE \      |     |    |    |     +-O-+ |    |    |    |     |   +++                 \     |     |    |    |     |   | |    |    |    |     |   | |   +-----------O  O----#     |    |    |     |   | |    |    |     |   | |   |                   |     |    |    |     |   | |    |    |    | 120k|   | |   |                   |120k |    |    |     |   | |    |    |    |    +++  +++   |   \  SOURCE      +++    |    |    |     |   | |    |    |    |    | |   |    |    \             | |    |    |    |     +-O-+ |    |    |    |    | |   +----#--O  O-- PPK LDO  | |    |    |    |       | Gnd (-) |    |    |    |    | |                           | |    |    |    +-------+ |    |    |    |    +++                           +++    |    | |    |    |    |     |                             |     |    | |    |    |    |     #-- VDUT                VIN --#     |    | |    |    |    |     |  Sense                Sense |     |    | |    |    |    |    +++                           +++    |    | |    |    |    |    | |                           | |    |    | |    |    |    |    | |                           | |    |    | |    |    |    |    | |                           | |    |    | |    |    |    |    +++                           +++    |    | |    |    |    |     | 30k                     30k |     |    | |    |    |    +--#--+                             +--#--+    | |    |    |       |                                   |       | |    |    |     =====      <<== Common Gnd ==>>     =====     | |    |    |      ===           (Common -ve)          ===      | |    |    |       =                                   =       | |    +===================================================+ |     PPK-II

RE: PowerProfiler 2: How to set up ampere-mode properly?

danielschultz — Mon, 10 Jun 2024 13:25:46 GMT

Using setup 1, I applied a 1Vp triangle with 1V offset and measured the current through a 470 ohm resistor to span over approximately the same current range as my DUT in deepsleep:

Something strange happens in some of these transitions, not outputting a triangular symmetric waveform. About ~500 uA a rapid transition occurs downwards. However, peak values are as they should be (~1.28 mA).

When going down to peak values of ~500 uA, symmetric triangle-waves are seen on the output. However, the current values are off by a factor of 10. With 250 mVpeak, 250mV offset trangle wave over 470 ohm resistor, peak currents are measured to be 50 uA.

Even though the transients first discussed cannot be replicated by this, maybe this approves what have been discussed regarding switching of shunt resistors??

RE: PowerProfiler 2: How to set up ampere-mode properly?

danielschultz — Mon, 10 Jun 2024 13:00:32 GMT

Hi again,

I thought about that too - hence my question if someone knew what threshold values are for current ranges to switch the internal shunt resistors.

Either that or the internal regulator's operating in refresh mode. Do you know at what rate the internal cap is charged? Does this depend on DUT current consumption?

RE: PowerProfiler 2: How to set up ampere-mode properly?

Kenneth — Mon, 10 Jun 2024 12:44:42 GMT

Hello again,

It may be that the spikes are caused by the PPK when it switches between two measurement resistors, because of the frequent change in current consumption.

Kenneth

RE: PowerProfiler 2: How to set up ampere-mode properly?

danielschultz — Mon, 10 Jun 2024 11:47:27 GMT

Hi Kenneth,

Thank you for your answer. I also noticed setup #2 wouldn't work whatsoever- so that was a bummer by me!

DUT is an ESP32 with some peripherals connected to it, everything powered by the same Li-Ion battery. Measuring while the DUT and the peripherals are in deep-sleep.

So the question is if the very light but dynamic load (the DUT) can cause the above mentioned behaviour with transients in the measurements, even if this is not seen with a passive load (470 ohm - 1Mohm)?

RE: PowerProfiler 2: How to set up ampere-mode properly?

Kenneth — Mon, 10 Jun 2024 10:56:39 GMT

Hello,

Only setup #1 will work, you need to have ground between PPK and DUT for them to ensure they have the same ground potential:
https://infocenter.nordicsemi.com/topic/ug_ppk2/UG/ppk/measure_current_ampere_meter.html?cp=11_9_5_2

Normally "spikes" in measurements are caused by the internal regulator is operating in refresh mode, which means it only turn ON for short periods to charge it's decoupling capacitor. This overall reduce current consumption quite a lot.

It's difficult to provide any more details here without actually knowing what hardware and software is doing here, without knowing more of your DUT I would say setup #1 seems to be most correct, both in terms of what they look like and actual current.

Kenneth

RE: PowerProfiler 2: How to set up ampere-mode properly?

danielschultz — Mon, 10 Jun 2024 09:52:11 GMT

Hey everyone,

I found myself having made a rookie mistake on the measurements. I see that with passive loads, setup (2) is yielding incorrect results. So I guess this method can be discarded.

I observed there is a ~4 sec of obtaining a correct result when powering the (in this case passive) load. I must've been fooled by this "delay" and concluded upon the result within 4 seconds earlier ...

Q1: Is this behaviour to be expected? I'm curious if someone, with a reference to schematics can explain this behaviour if so.

This is some tests I have done with our 5 PPK2's. With "ampere mode" i am referring to test setup 1 mentioned above:

This yields a difference of ~40 uA from ampere mode to source mode on the same PPK2. Generally source mode is less. Can't figure this out if this is to be expected, but I guess it is expected behaviour when it's seen on all PPK2's

In ampere mode, there is a difference of max. 21 uA (~10%) from PPK2 to PPK2. With passive loads I don't see that much of a variance. Maybe this is the difference from deep-sleep cycle to deep-sleep cycle on the IoT devices.

Q3: Will switching of the sense resistor be captured in measurements? For which current thresholds will they be switched?

Q4: The incorrect measurements on PPK2 no. (2) is due to the control of the source mode supply is malfunctioning. 3.6V output setting gives 4.15V out. When obtaining these tests, another device suddenly got this error aswell. Have you seen other instances of this failure to occur and what might be causing it?

Hope relevant answers to this post might serve to other trying to obtain reference measurements for further optimizing battery usage. Hopefully getting an answer to be sure to obtain measurements as should be done so one can question the DUT instead of the measurement gear.

Br Daniel