Hi Rubens,
The INA138 from TI is a nice part for measuring current. Keep in mind
though that the minimum common mode input is 2.7V, so you couldn't use
it for charging a low voltage battery.
You might also use an instrumentation amplifier. It's simpler than
building a differential amplifier with an op amp, plus you can easily
set the output's reference voltage to whatever you like. I did a circuit
like yours once using an AD623 to control the output of a switching
current source at very low voltage (i.e. low resistance load). Worked
pretty well.
Chris
rlistas wrote:
{Quote hidden}> Hi,
>
>
> I need some suggestion on how to measure the output
> current in a buck dc-dc converter used to charge
> a battery.
>
> I´m using a PIC 16F88 as PWM generator and charge
> controller (MPPT).
> The problem of measuring the current is the ground referencial
> that the microcontroller uses. I´m using a N channel
> mosfet as the switch (so the negative is switched and the positive is
> always conected) and therefore I´m getting trouble using the AD of the PIC.
>
> I want to get the value of the current by means of a low value resistor
> connected to the battery.
>
> Any suggestion will be welcome.
>
> thanks
>
> Rubens
>
>
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