Power test SDRAM

Assemble test stand for checking power consumption of SDRAM in different operating modes.
1. Structure. Connection diagram.
Today wireless devises are everywhere. They always need a battery power, so the problem of power consumption measurement during device development is very important. And this is what we needed to do also. For this purpose we've assembled a consumption testing stand. Flexibility that has Fork allows us to use it also at Quality control (QC) during production. Generally the stand can measure consumption of different devices, but for this article we'll measure only some operating modes.

For measurements we've chisen this modes of device with SDRAM
  • stand-by
  • read
  • write
  • power-down

For stand we need
  • Fork
  • Accurate shunt 0.47 Om
  • device with SDRAM
  • some wires
Circuit diagram of stand:
Breaking the power supply we put a shunt resistor if small Om resistance, this is where we'll measure consumption according to voltage drop using Fork differential input. We should be careful as maximum input voltage is +-1V.

Photo of testing stand, but sorry the testing device is hidden I can't show it for now.
Here is a set of shunt resistors
2. Control via Python script
For getting data we will use Fork Stream ability. It'll be easy to convert Fork data directly to measurements. For this we can use function

First parameter is for set of AI channels for reading, then your callback function that is called after a packet received, then data format and data rate of sampling.
The most important for us is a callback function. Data is received as raw ADC data. After receving some packets we can convert them to power consumption measurements. For convenience we'll make it in two steps. Firstly convert raw data to voltage on input

V = ADC/4095*2.2-1.1
where V is voltage on shunt resistor, ADC – raw ADC data.
Then voltage to current

I = V/Rshunt
where R is Om of shunt resistor

Now we've started measurements and changed modes by hands.
Here we see write(1) into SDRAM and read(2) from SDRAM. With 180 mA, and 156 mA.
Here we see switching of SDRAM from stand-by to power-down.

So we have such table.
Thanks to Fork we've got a very good and simple stand for measuring different devices power consumption in different modes.
3. References to the code examples
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