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Problems in setting up power profiler kit PPK

Aravinth

We have a product that uses nrf51422_CE_AA, Revision 3, 256KB ROM, 16KB RAM, PCA10028, SDK 8.0.0, S110. We are now in the stage of power optimization. Therefore we bought Nordic Power Profiler Kit. We have problems in setting it up to show accurate readings. Therefore decided to test it with a known load and measurement was way beyond the actual current. I have adjusted the calibration resistors and brought the current measurement close to the real. However, if i change the load to consume less current, the current measurement on PPK doesn't change. Following is my setup.

As shown in the image 3-led-load.jpg

I have connected three LEDs with 330 Ohm resistors respectively. PPK's SW2 is set to "External", SW4 is set to "Reg" and COM is set to "EXT". Multimeter in mA range is connected in series with positive of P16 (External DUT) and positive rail of breadboard. PPK is powered via USB and J-Link is connected via COM to computer. In PPK Voltage regulator VDD is set at 3V and resistor calibration "Hi" is changed from 1.8 to 19.4 get 7.73 mA where multimeter shows 7.73 mA. That was pretty successful.

However, one LED and a resistor was removed as shown in the image 2-led-load.jpg

and there was no change in the measurement. It just stays at 7.73 mA even after restarted and powered on/off where multimeter shows 5.63 mA. What should be done to make it work?

image description

Additionally, power profiling should be done on our real system. Our product uses 3.7 V (nominal voltage) LiPo battery (max voltage is 4.2 V and min voltage is 2.7 V). When i use our LiPo battery and put SW4 to "External", will software voltage regulator work? or voltage from the battery should be regulated to 3.6V before applying to P22 (External DUT Supply)?

UPDATE on 10-Nov-2016

If i disconnect PPK and reconnect, then it starts from 0mA but then goes to 7.7 mA even though Multimeter measures 5.6 mA (2 LEDs) as shown in the image.

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If i disconnect external DUT, then it shows noise as shown in the image.

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If i remove one more LED and Multimeter measures 2.9 mA, then i see noise and average of 4.5 mA (still wrong) as shown in the image.

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UPDATE on 14-Nov-2016

Started without Load. Measurement is around 0 mA with noise.

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While connecting the load and HI resistor calibration updated at 2 and it is around 0 mA with noises goes from 0 to 74 mA.

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After connected the load with HI resistor calibration updated at 2. Measurement stays at 74 mA. Actual load is 2 LEDs with 330 Ohm resistors which consume 5.63 mA.

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UPDATE on 15-Nov-2016

1 MΩ (998 KΩ) resistor load measures average 3.04 uA.

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470 KΩ (466 KΩ) resistor load measures average 6.39 uA

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UPDATE on 18-Nov-2016

270 Ω (268 Ω) resistor load measures 83.32 mA

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    @wilhelmsen Please check the original post for the updates with images (UPDATE on 14-Nov-2016) because i can't attach images in the reply. Measurements were around 74 mA with load and increasing the HI resistor calibration brought it down. As you said, i have update the calibration to 2 ohm and restarted. Yes. it shows a small window at startup about Calibration. If load is removed, then it is around 0 mA with noises as shown in the first image. Without load VDD at external pin is 3015 mV for Software VDD regulator at 3000 mV. When Load is connected it drops to 2830 mV. As soon as load is connected (without multimeter in between), it goes from 0 to 74 mA as shown in the second image. After that it stays at 74 mA with "Hi" resistor at 2 as shown in the third image. Load is 2 LEDs with 330 Ohm resistors each as shown in the post.

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    @avarinth okay, I see that the ppk is maxing out. Again, can you please just connect a known resistor instead of the LED's? E.g 1MOhm and 500kOhm and post the results?

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    @wilhelmsen 1 MΩ (998 KΩ) resistor load measures average 3.04 uA and 470 KΩ (466 KΩ) measures average 6.39 uA. Resistor calibrations are set to default and updated. VDD is set at 3000 mV and P16 (DUT) measures 3015 mV. Please check the original post for the updates with images (UPDATE on 15-Nov-2016).

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    That sounds very good for that range at least, and how about in the range of 270 Ohm?

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    @wilhelmsen thanks for your continuous support. 270 Ω (268 Ω) resistor load measures 83.32 mA. Please check the original post for the updates with images (UPDATE on 18-Nov-2016).

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