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  • Author Author: Jan Cumps
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MAX32660 Evaluation Kit - part 2: Mod the PCB for Power Measurement

Jan Cumps

I'm road testing the  Ultra-Low Power Arm Cortex-M4 Darwin MCU EVM.

In this blog post I modify the PCB to isolate the power going to the MAX32660.

image

 

 

Where to Measure the Current Consumtion

 

Measuring the voltage is easy. You can do that on the upper right breakout pin.

To measure the current, you could use the TARGET VDD jumper on the debuger / programmer side, and use a low Burden current meter instead of the jumper.

This will work, but there are a few (low current) consumers on the debug circuit.

image

 

To rule those out in the power measurements, I chose to get the signal further downstream, where only the controller and peripherals use power.

 

image

 

The way to be able to measure the current is to break the existing PCB trace and replace it by a jumper that can either be shortcut, or where you can insert a current meter.

I soldered a wire on the positive supply line at both sides of the mouse bites in the middle of the PCB.

After checking that all was soldered correctly, I cut the copper trace for the power on the breakout mouse bites in the middle of the board.

Then I soldered pin headers at the end of the two wires, protected by heat shrink.

The two wires are hot glued on the PCB bottom side for strain relief.

 

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When I put a little jumper over the header pins, the board works as before.

 

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When I want to measure current, I can remove the jumper and put a sensitive, low Burden meter in between.

 

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I will use this together with the Low Power example from Maxim. That project can cycle the controller through the different modes by pressing the button on the board.

That is going to be my next blog post ...

 

part 1: IDE install and Build First Example
part 2: Mod the PCB for Power Measurement
part 3: Power Measurement
part 4a: Low Power Sensor design - Barometer Hardware
part 4b: Low Power Sensor design - Barometer i2c and Init
part 4c: Low Power Sensor design - Barometer, Not Yet Power Optimised
MAX32660 Evaluation Kit - part 5: FreeRTOS Example
side note A: C++ Eclipse Project
side note B: Create a Release Configuration
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  • First measurements, using two different multimeters, 1.8 V

     

    Running in ACTIVE mode                         6.72 mA
All unused RAMs placed in LIGHT SLEEP mode     6.72 mA
All unused RAMs shutdown                       6.71 mA
Entering SLEEP mode                            2.73 mA
Entering DEEPSLEEP mode                        3.57 mA
Entering BACKUP mode                           0.21 mA

     

    For some reason, DEEPSLEEP seems to pull more current then SLEEP.

    This is measured without debugger, and with enabeling USB/UART0 clock.

     

    It would be interesting to see other tester's measurements.

     

    With 3.3 V supply:

    7,57
7,56
7,55
3,48
5,21
0,74

     

     

    A trace of the current, switching between modes every 5 seconds, with 1.8 V

    image

  • in reply to Jan Cumps

    For my own reference:

    1.8 V

    measured with µCurrent in 1 mV/mA mode

    console off

    button off

    RTC, 10 s / mode

     

     

    image

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