BQ25504: Schematic with MPPT to micro controller.

Thanks for the reply Jeff!

After the first look at the reference design, I think an I2C communication betwen the charger IC (bq25895) and the MCU (MSP430) is necessary for the MPPT to work in this case.

However, bq25504 does not offer any such provision. All we can do is pass a reference MPP voltage to the REF_SAMP pin. The question is how do we synchronize the MCU with the 16 sec sampling interval of bq25504?

Kawsar,

What is the purpose the synchronization? In other words, what do you want the MCU to do when the bq25504 is trying to find the MPP?

Also, keep in mind that the REF_SAMP pin is very sensitive to leakage. Any attempt to read the voltage at that pin needs to be with a very high impedance node. You could sample the VRDIV pin voltage.

Hi Jeff,
Assuming that we are doing MPPT using the MCU, the MCU should pass the MPP reference voltage to the VREF_SAMP pin of bq25504. One way of doing this, which I can think of, is -- use a PWM signal from the MCU, pass it through a low pass filter (RC) and connect it to the VREF_SAMP pin. However, for this I need to keep the PWM on all the time, otherwise the VREF_SAMP pin will leak quickly through the RC network connected.

The issue is that keeping the PWM on all the time needs a lot of energy, which I can't afford in an energy harvesting application. So, I was wondering if there is a way to pass the MPP reference quickly and disconnect from the VREF_SAMP pin for the rest of the 16 seconds. I understand that this may sound a bit ridiculous to say the least. Thanks for your support!