4 Apr
2010
4 Apr
'10
10:25 a.m.
I will have to do some digging on this. I used a PIC625 from Unitrode
in designing a 12 to 5 volt switching regulator. It is a switch mode
transistor with a flyback diode in it if I remember correctly. The
device is a four pin can (smaller than a TO3 case). Just not sure if the
900 was in the same family.
Yes, I've come across some of the PIC6xx parts in HP swithcing
regulators. The 9845B PSU is full of them (in the secondary-side
switching regulators), I think there's at least one in the 9915, but I
dont ahve the schematic in front of me. They were, as you said, a chopper
transistor and flyback diode in one can
I've had anohter look at the PIC900C. From the connections, and finding
diode-drops between the pins, it might be noting more than 2 NPN
transistorsm 2 PNP transistors, a couple of diodes connected between the
collector of each of one flavour of transistor and a spare pin, and a
couple of uncommitted dioddes. That accounts for all the pines (2*3 (plain
transistor) + 2*4 (transitor + diode) + 2*2 (diode) =18, the number of
pins on the package). But I would like ot see a data sheet if it's around
anywhwere...
-tony