# Forum: Analog Circuits Circuit to measure current consumption of uC

 Author: Thomas (Guest) Posted on: 2011-04-15 17:30
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Hi guys,

I need to design a circuit that measures the power consumption of uP.
The uP has to be supplied by a voltage Vcc, and then using the shunt
resistor, the current drawn by the uC is converted to a voltage then
followed to the shunt monitor. The current range I want to measure is
1nA...150mA which is too large and cannot be reached with only one shunt
resistor, which is not a big deal first.
I went through all current shunt monitors of TI, simulated them and even
tested couple of them, but no one can return reasonable results when it
comes to measure currents from 1uA...10mA

I attached my circuit for your review.
Does any body habe any suggestion how can I reach my goal?!
Thx

 Author: oork (Guest) Posted on: 2011-04-16 10:20

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I'd try a 10 Ohm Shunt in the GND path and measure with a 24bit ADC.

 Author: henrik (Guest) Posted on: 2011-04-16 21:12

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1nA :) sounds like fun

Bandwith? Uncertancy?

All will be for naught if you don't monitor the voltage to keep it
stable....

and take some expensive low leakage components ...

and Jim Williams too (on crystals, however always worth the time)

One idea: Take a big (low leakage) cap for the supply of your DUT and
charge it with a small cap of a (slightly) higher constant voltage,
controlled by a comparator. The number of charge pulses per time is your
current.

Tricky is the switch :)

Or take a look at current output DAC ..

 Author: g457 (Guest) Posted on: 2011-04-16 21:36

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http://www.alternatezone.com/electronics/ucurrent/

HTH

 Author: tt4u (Guest) Posted on: 2011-04-17 17:12

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> http://www.alternatezone.com/electronics/ucurrent/

I have it (DIY), it is GREAT!

 Author: Thomas (Guest) Posted on: 2011-04-19 08:55

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@oork: this did not work unfortunately
@henrik: I want to have as much accurate results as possible. What do
you mean with Bandwidth?
@g457: yes but I need the circuit of it. I need to build my own
circuit...

 Author: Lothar Miller (lkmiller) (Moderator) Posted on: 2011-04-19 09:08

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g457 wrote:
> http://www.alternatezone.com/electronics/ucurrent/
Thomas wrote:
> @g457: yes but I need the circuit of it. I need to build my own
> circuit...
Just scroll down and you will see this:
http://www.alternatezone.com/electronics/ucurrent/...

BTW: 1nA...150mA
This is a dynamic range of 1:150000000. And that equals more than 27
bits. A VERY demanding task...

 Author: Thomas (Guest) Posted on: 2011-04-19 11:23

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Appreciate it!!
Thank you so much, it seems to be what I need... I'm gonna try to
simulate the circuit and hopefully it works.
thx again

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