First time using current limiting IC

[Pariston]

Hi,
Thanks for stopping by. I am trying to use MAX4787EXK,100mA, current limiting ic to charge 1.2 V NiMH battery. At the moment, I have 3.3 volt from power supply connected to pins ON&IN, 3k pullup resistor for #FLAG (which is not connect to mcu, basically remain high all the time), everything else is according to provided schematics. IC seems to be working (giving off around 110 mA) when I keep my finger on the ON pin(basically it is constantly forcing ic to turn on due to bitrate), from here, I get a feeling that chip is turning itself off. There is no output current when ON pin is connected straight to vdd or vcc.

I am missing something simple...

Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX4785-MAX4788.pdf

[langwadt]

it is not a constant current source, think of it as an electronic fuse. It turns off when the current limit is exceeded which will happen immediate when you connect at 1.2V battery to 3.3V

you need a charger IC not an IC intended to protect things like a USB port from a short

[Manul]

This is not a "current limiting ic" and not a current source either. This is a switch with a current limit (for protection). It is not in any way supposed to be used like you use it. And the behaviour which you observe does exactly match the information provided in the first page of the datasheet.

[pwlps]

page 6:

"The MAX4785 and MAX4787 do not have the autoretry
option and the switch remains in latch-off mode until
the ON pin or the input power is cycled from high to low
and then high again. "

It seems this is what happens here.

[Doctorandus_P]

If you want to charge batteries, then use a battery charger IC.