My GLCD requires a separate negative bias supply. It needs to be sequenced on after Vdd is on and off before Vdd is off. Initially, I am using a Max851 that has a shutdown pin, mainly because I had one in my parts boxes. It requires 4 capacitors plus the chip. I am unclear of its decay time when it is shut down, but will measure it.
Eventually, I will consider using a PWM pin from my 16F1519 chip to power a charge pump of two capacitors and two diodes. I may also include a negative voltage switch or drain resistor to switch/drain the capacitors producing Vee. New Haven Displays says having Vee applied without Vdd will destroy its displays.
What is your opinion on using a simple charge pump versus a dedicated chip for that function? Has anyone here used a negative-voltage switch to control the sequence?
John
Eventually, I will consider using a PWM pin from my 16F1519 chip to power a charge pump of two capacitors and two diodes. I may also include a negative voltage switch or drain resistor to switch/drain the capacitors producing Vee. New Haven Displays says having Vee applied without Vdd will destroy its displays.
What is your opinion on using a simple charge pump versus a dedicated chip for that function? Has anyone here used a negative-voltage switch to control the sequence?
John