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Forum: Analog Circuits Circuit to measure current consumption of uC


Author: Thomas (Guest)
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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)
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I'd try a 10 Ohm Shunt in the GND path and measure with a 24bit ADC.

Author: henrik (Guest)
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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 ...

Bop Pease had some stories about low current measurements on 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)
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Author: tt4u (Guest)
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> http://www.alternatezone.com/electronics/ucurrent/

I have it (DIY), it is GREAT!

Author: Thomas (Guest)
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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)
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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)
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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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