Purpose of LL101 diode used with ICL7660 in biasing circuit.

[Terminator3]

https://www.farnell.com/datasheets/1513917.pdf
ICL7660 is a negative voltage generator,
LL101 is a small signall schottky diode.
I want to know why LL101 diode is used here...

1. to protect gate of FET from positive voltage?
2. ESD protection of FET gates?
3. something else?

 

[betwixt]

The only thing I can think of is to prevent damage to the 7660 when the power is turned off. It is possible, although I wouldn't think likely, that the positive supply could couple throught the FETs to the output of the 7660. Other than that I can't see it ever conducts.

Brian.

 

[FvM]

I want to know why LL101 diode is used here...

The question presumes that the diode actually serves a purpose. You should also consider that it might be unnecessary.

ICL7660 has already a substrate diode which becomes forward biased when positive currents are fed to the output node. A schottky diode can be meaningful in cases when the current could cause latch-up. The 10k series resistor will prevent this safely.

Most likely, the author copied the diode from a different application without understanding it's purpose.

 

[mvs sarma]

Nice reply FvM.
Great of you.