F
Frank Miles
I have a small 3V-battery-operated device which has a switching power converter.
The power converter gets turned off when not needed; when on, it generates
two power supplies of ~ +/- 15V. Unfortunately, the analog output (much closer
to a current source than a voltage source) running off the converted voltages
emits transients on power-supply turn-on and turn-off. I need to clamp these
transients to ground during this transition, without degrading the current-mode
output during normal operation, and without taking up much board space, which
is nearly as limited as the battery power.
Simply turning off a series switch between source and load tends to upset the
current source driver, making the eventual turn-on even more problematic.
I haven't found any traditional analog switches that have the kind of power
supply range (3V vs. 30+v). MOSFETs have those obnoxious parasitic diodes,
and it would be ugly to control a pair of them (though it would work, albeit
with series diodes that would prevent clamping tighter than a diode drop
either side of ground).
Is there something obvious that I'm missing? Some magical part that I have
forgotten or simply didn't know about? Something small, simple, available,
and low power? Sure, I can dream can't I?
Thanks for any clues, hints, or commiseration!
-f
The power converter gets turned off when not needed; when on, it generates
two power supplies of ~ +/- 15V. Unfortunately, the analog output (much closer
to a current source than a voltage source) running off the converted voltages
emits transients on power-supply turn-on and turn-off. I need to clamp these
transients to ground during this transition, without degrading the current-mode
output during normal operation, and without taking up much board space, which
is nearly as limited as the battery power.
Simply turning off a series switch between source and load tends to upset the
current source driver, making the eventual turn-on even more problematic.
I haven't found any traditional analog switches that have the kind of power
supply range (3V vs. 30+v). MOSFETs have those obnoxious parasitic diodes,
and it would be ugly to control a pair of them (though it would work, albeit
with series diodes that would prevent clamping tighter than a diode drop
either side of ground).
Is there something obvious that I'm missing? Some magical part that I have
forgotten or simply didn't know about? Something small, simple, available,
and low power? Sure, I can dream can't I?
Thanks for any clues, hints, or commiseration!
-f
