MCP73213 IC status out is varying (NEED HELP PLEASE)

[Sai teja]

 Hello,
         I am using MCP73213 IC for my charging application. IC is working great. But I have an issue with status pin of MCP73213.

As per datasheet, status pin should gives HighZ(High impedence)  on charge completion and 0 volts during charge cycle.
Datasheet of MCP73213 IC : http://ww1.microchip.com/downloads/en/DeviceDoc/20002190C.pdf


Here are my observations: On charge completion it is giving 6.5 volts. And on charge completion it is giving 0 volts.

Later on,  I have added n-channel  mosfet to status pin for attaining switching functionality depending upon output of status pin.
Mosfet is connected as shown in the figure.
Gate of mosfet is attached to status pin of MCP73213 IC.
Drain is connected to GPIO and also pulled up to 3.3 volts with 12 k resistor
source is grounded.
On doing so the HighZ (High Impedence) voltage is reducing to 4.5 volts.

I am really confused why is this happening.Please help me in this regard.

[viperidae]

The chip might have ESD protection diodes on the pin, pulling down any voltage higher than its supply

[hcglitte]

Do you have a pull-up resistor from the charger status pin to your MCU positive power rail? This should work.

If your MCU positive power rail is higher than charger VDD (unlikely) by 0.3V there will flow a small current through the
ESD diode of the charger pin when HighZ.

HC

[Sai teja]

Datasheet says status output is High Z on charge completion.But that voltage is not  mentioned. What might be the value of High Z of MCP73213 datasheet?

[sleemanj]

Hi-Z means high impedance, effectively like having a switch turned off, or a wire hanging in mid-air, it does not make a lot of sense to talk about what voltage is found on an open-drain pin (either not connected (open) or ground (drain)) when it is open.

You need to pull it up to ensure that the output is a known state when open.  Indeed even the datasheet says this on page 13...
   
    "Alternatively, a pull-up resistor can be applied for interfacing to a host microcontroller. "