W
Winfield Hill
- Jan 1, 1970
- 0
Some years ago Unitrode, now TI, introduced the uc3875
phase-shift resonant PWM controller. Four years ago
they introduced an advanced cmos version, the ucc3895.
This IC can run up to 1MHz and is well suited to high-
power zero-voltage-transition dc-dc converters.
I'm using a '3895 with my favorite Intersil HIP4081 to
drive four MOSFETs in a 600W H-bridge at 300 and 600kHz
to energize a resonant high-voltage (10kV) transformer.
The intended frequency is crystal derived, so I'm trying
to synchronize the '3895 as described in the data sheet,
http://focus.ti.com/docs/prod/folders/print/ucc3895.html
via the SYNC pin. Although this pin is an output, it's
a "weak" one with 400uA drive and 100uA sink capability.
I'm trying to overdrive it via a diode and 1k resistor,
but it's not working - the RAMP pin doesn't respond well.
Before I spend a chunk of time characterizing the exotic
clocking properties of this chip, can anyone who's "been
there and done that" give me some guidance?
Thanks,
- Win
whill_at_picovolt-dot-com
phase-shift resonant PWM controller. Four years ago
they introduced an advanced cmos version, the ucc3895.
This IC can run up to 1MHz and is well suited to high-
power zero-voltage-transition dc-dc converters.
I'm using a '3895 with my favorite Intersil HIP4081 to
drive four MOSFETs in a 600W H-bridge at 300 and 600kHz
to energize a resonant high-voltage (10kV) transformer.
The intended frequency is crystal derived, so I'm trying
to synchronize the '3895 as described in the data sheet,
http://focus.ti.com/docs/prod/folders/print/ucc3895.html
via the SYNC pin. Although this pin is an output, it's
a "weak" one with 400uA drive and 100uA sink capability.
I'm trying to overdrive it via a diode and 1k resistor,
but it's not working - the RAMP pin doesn't respond well.
Before I spend a chunk of time characterizing the exotic
clocking properties of this chip, can anyone who's "been
there and done that" give me some guidance?
Thanks,
- Win
whill_at_picovolt-dot-com