MCP73831: design a lithium battery charging circuit
From what I read (but I never used those ICs) if the open circuit voltage is 6.2V you can omit the 6V zener. In fact, the voltage at its output decreases with the load, and the maximum rating of the IC is 7V, so up to 7V it should not break. You can test it, or wait for someone more expert than me to come and say that I am completely wrong (but I hope I'm not).

As for the microcontroller and LED, your circuit is ok for the LED (it will light only when STAT is tied low), but I don't think the uC will like it. When STAT is tied to VCC the voltage can reach 6V, while usually the uC can bear Vcc+0.3V on their pins (so 5.3V if it is 5V powered or 3.6V if it is 3.3V powered). I suggest you modify your circuit in







simulate this circuit &ndash; Schematic created using CircuitLab

I refer to the graph in figure 13 and 14 in the TLMS1000 datasheet.
The scheme, with a VDD of 6V, provides you these data:


STAT = VDD:


voltage at STAT PIN = 6V
voltage on the whole LED branch = 0, current in LED = 0, luminosity = 0
voltage on ADC is 47/57*6V = 4.95V

STAT = GND:


voltage at STAT PIN = 0V
voltage on the whole LED branch = 6V, current in LED = 2mA, luminosity = 100% of specified luminosity
voltage on ADC is 0V

STAT = HI-Z:


if we estimate a current around 50uA-100uA, the voltage on the LED is not in the graph (the graph goes as low as 100uA). In any case, I expect it to be roughly around 1.5V-1.6V)
if the voltage on the LED is 1.5V, the current in the branch is (6-1.5)/(2.2+10+47) = 75uA. The luminosity of the LED is around 2-3% of the nominal luminosity (cannot be seen)
voltage on ADC is 47*75uA = 3.53V



If you have a 3.3V microcontroller, to keep almost the same values you can substitute the 10k and 47k resistors with, respectively, a 27k and 33k one. This way the LED will see the same circuit, while on the ADC


STAT = VDD: voltage on ADC is 33/60*6V = 3.3V
STAT = GND: voltage on ADC is 0V
STAT = HI-Z: voltage on ADC is 33*75uA = 2.48V