"High" voltage timer

Driving a dumb chopper: 24V supply, NMOS H-bridge, 12V gate drive, 50%
duty cycle at 200kHz. All I need is complementary drive to the left and
right-hand side gate drivers. Trouble is, my gate drive circuitry needs
12V. Old skool metal gate logic would suffice, but fancy that, no one
makes special circuits out of it. :)

Options:
- Use, e.g., LT's TimerBlox, or logic (e.g., Schmitt trigger oscillator
at 400kHz, followed by a T flip-flop to generate complementary outputs
and 50% duty) and level shifter. Ugly, the level shifter wastes all the
components the TimerBlox was supposed to save.
- I *could* use a TimerBlox, *if* I use logic level MOSFETs. But my
simulations show this will at least double the losses, based on typical
MOSFETs. I might go shopping to find others more suitable but Rds(on)
will always be higher than with 10-12V drive; the expense is an overkill
transistor with disproportionately higher Qg, which means more drive,
more supply consumption... - Skip the gate drive circuit I have, and use
one of those VCOs with gate drives included (e.g., IR27xxx), downside
being I need four gate outputs, not two. I don't know of any offhand
that do that in one chip; the 8-pin models don't support synchronization
so this would be a challenge (even more level shifting? fuggedaboudit).
- Do the Schmitt trigger + T flip-flop, but implement it in CD4000 MOS.
Downside: I'm pretty sure no one makes CDTinyLogic4000's, so that's two
SO-14's almost entirely wasted. - Use an SMPS controller. I'm intently
eyeballing UC3825, the "improved TL494". It's fast enough and has true
complementary outputs, but it has limited duty cycle (dead time), as do
most PP/ bridge controllers. I can tolerate plenty of deadtime, but it's
not as elegant as having simple complementary outputs. It's also an
SO-16 or whatever, when all I really need is an SOT-23-6, but still,
it's better than two SO-14s.
- Just make a fucking astable multivibrator*. We live in a world of
everything integrated, but hey, what works, works... Plus, it saves one
of those damn $5 chips. Not that the placement of all those resistors
is any cheaper.

Optimal solution: a TimerBlox (or CD4000 logic oscillator, or..) that
runs from 12V. CMOS outputs drive a nominal amount of current (>5mA) at
roughly supply voltages, give or take drop. Heck, crude bipolar outputs
would be acceptable too (e.g., a 555 with complementary outputs).

*Last time I had this same problem, I built the multivibrator out of the
very power stage itself (2N4401 for the win). And the time before that,
I had some FPGA outputs to spare, so I just clocked some square waves
out of that. Which still required a level shift, but a transistor per
phase happened to be enough in that case.

Tim

Driving a dumb chopper: 24V supply, NMOS H-bridge, 12V gate drive, 50%
duty cycle at 200kHz.  All I need is complementary drive to the left
and right-hand side gate drivers.  Trouble is, my gate drive circuitry
needs 12V.  Old skool metal gate logic would suffice, but fancy that,
no one makes special circuits out of it. :)

Options:
- Use, e.g., LT's TimerBlox, or logic (e.g., Schmitt trigger
oscillator at 400kHz, followed by a T flip-flop to generate
complementary outputs and 50% duty) and level shifter.  Ugly, the
level shifter wastes all the components the TimerBlox was supposed to
save.
- I *could* use a TimerBlox, *if* I use logic level MOSFETs.  But my
simulations show this will at least double the losses, based on
typical MOSFETs. I might go shopping to find others more suitable but
Rds(on) will always be higher than with 10-12V drive; the expense is
an overkill transistor with disproportionately higher Qg, which means
more drive, more supply consumption...
- Skip the gate drive circuit I have, and use one of those VCOs with
gate drives included (e.g., IR27xxx), downside being I need four gate
outputs, not two.  I don't know of any offhand that do that in one
chip; the 8-pin models don't support synchronization so this would be
a challenge (even more level shifting? fuggedaboudit).
- Do the Schmitt trigger + T flip-flop, but implement it in CD4000
MOS.  Downside: I'm pretty sure no one makes CDTinyLogic4000's, so
that's two SO-14's almost entirely wasted.
- Use an SMPS controller.  I'm intently eyeballing UC3825, the
"improved TL494".  It's fast enough and has true complementary
outputs, but it has limited duty cycle (dead time), as do most PP/
bridge controllers. I can tolerate plenty of deadtime, but it's not as
elegant as having simple complementary outputs.  It's also an SO-16 or
whatever, when all I really need is an SOT-23-6, but still, it's
better than two SO-14s.
- Just make a fucking astable multivibrator*.  We live in a world of
everything integrated, but hey, what works, works...  Plus, it saves
one of those damn $5 chips.  Not that the placement of all those
resistors is any cheaper.

Optimal solution: a TimerBlox (or CD4000 logic oscillator, or..) that
runs from 12V.  CMOS outputs drive a nominal amount of current (>5mA)
at roughly supply voltages, give or take drop.  Heck, crude bipolar
outputs would be acceptable too (e.g., a 555 with complementary
outputs).

*Last time I had this same problem, I built the multivibrator out of
the very power stage itself (2N4401 for the win).  And the time before
that, I had some FPGA outputs to spare, so I just clocked some square
waves out of that.  Which still required a level shift, but a
transistor per phase happened to be enough in that case.

Tim

Gee, that's an awfully wordy ramble Tim.

50% duty complementary outputs @ 200Khz?  Any CMOS flop will do that.
For a driver, IRS2101.  Or, translate your logic-level to 12v with a
couple 2n7002s, plus pull-ups.

On Wed, 25 Jan 2012 18:58:52 -0800, Tim Williams wrote:
Driving a dumb chopper: 24V supply, NMOS H-bridge, 12V gate drive, 50%
duty cycle at 200kHz.  All I need is complementary drive to the left and
right-hand side gate drivers.  Trouble is, my gate drive circuitry needs
12V.  Old skool metal gate logic would suffice, but fancy that, no one
makes special circuits out of it. :)

Options:
- Use, e.g., LT's TimerBlox, or logic (e.g., Schmitt trigger oscillator
at 400kHz, followed by a T flip-flop to generate complementary outputs
and 50% duty) and level shifter.  Ugly, the level shifter wastes all the
components the TimerBlox was supposed to save.
- I *could* use a TimerBlox, *if* I use logic level MOSFETs.  But my
simulations show this will at least double the losses, based on typical
MOSFETs. I might go shopping to find others more suitable but Rds(on)
will always be higher than with 10-12V drive; the expense is an overkill
transistor with disproportionately higher Qg, which means more drive,
more supply consumption... - Skip the gate drive circuit I have, and use
one of those VCOs with gate drives included (e.g., IR27xxx), downside
being I need four gate outputs, not two.  I don't know of any offhand
that do that in one chip; the 8-pin models don't support synchronization
so this would be a challenge (even more level shifting? fuggedaboudit).
- Do the Schmitt trigger + T flip-flop, but implement it in CD4000 MOS.
Downside: I'm pretty sure no one makes CDTinyLogic4000's, so that's two
SO-14's almost entirely wasted. - Use an SMPS controller.  I'm intently
eyeballing UC3825, the "improved TL494".  It's fast enough and has true
complementary outputs, but it has limited duty cycle (dead time), as do
most PP/ bridge controllers. I can tolerate plenty of deadtime, but it's
not as elegant as having simple complementary outputs.  It's also an
SO-16 or whatever, when all I really need is an SOT-23-6, but still,
it's better than two SO-14s.
- Just make a fucking astable multivibrator*.  We live in a world of
everything integrated, but hey, what works, works...  Plus, it saves one
of those damn $5 chips.  Not that the placement of all those resistors
is any cheaper.

Optimal solution: a TimerBlox (or CD4000 logic oscillator, or..) that
runs from 12V.  CMOS outputs drive a nominal amount of current (>5mA) at
roughly supply voltages, give or take drop.  Heck, crude bipolar outputs
would be acceptable too (e.g., a 555 with complementary outputs).

*Last time I had this same problem, I built the multivibrator out of the
very power stage itself (2N4401 for the win).  And the time before that,
I had some FPGA outputs to spare, so I just clocked some square waves
out of that.  Which still required a level shift, but a transistor per
phase happened to be enough in that case.

Tim

Use gate drivers that work at CMOS levels?  There's plenty out there.

*Last time I had this same problem, I built the multivibrator out of
the very power stage itself (2N4401 for the win).  And the time
before that, I had some FPGA outputs to spare, so I just clocked some
square waves out of that.  Which still required a level shift, but a
transistor per phase happened to be enough in that case.

Tim

Use gate drivers that work at CMOS levels?  There's plenty out there.

I've got the gate drive already -- a couple discrete transistors and
resistors are about the same size as an 8-pin driver, so I still have
the problem of generating the complementary clock to begin with.

Tim

On Jan 25, 9:26 pm, dagmargoodb...@yahoo.com wrote:

Gee, that's an awfully wordy ramble Tim.

Thanks?  I've had a few and I'm tired, conditions under which I tend
to get unusually verbose.  Sometimes good or bad, I suppose?!

50% duty complementary outputs @ 200Khz?  Any CMOS flop will do that.
For a driver, IRS2101.  Or, translate your logic-level to 12v with a
couple 2n7002s, plus pull-ups.

To a point, that's what I've got now (the 2N7002s, for the high sides;
high and low actually get to the gates via emitter followers, hence
the 12V source requirement), but that doesn't save me oscillator +
level shift gibberish.

Driving a dumb chopper: 24V supply, NMOS H-bridge, 12V gate drive, 50%
duty cycle at 200kHz.  All I need is complementary drive to the left
and right-hand side gate drivers.  Trouble is, my gate drive circuitry
needs 12V.  Old skool metal gate logic would suffice, but fancy that,
no one makes special circuits out of it. :)

Options:
- Use, e.g., LT's TimerBlox, or logic (e.g., Schmitt trigger
oscillator at 400kHz, followed by a T flip-flop to generate
complementary outputs and 50% duty) and level shifter.  Ugly, the
level shifter wastes all the components the TimerBlox was supposed to
save.
- I *could* use a TimerBlox, *if* I use logic level MOSFETs.  But my
simulations show this will at least double the losses, based on
typical MOSFETs. I might go shopping to find others more suitable but
Rds(on) will always be higher than with 10-12V drive; the expense is
an overkill transistor with disproportionately higher Qg, which means
more drive, more supply consumption...
- Skip the gate drive circuit I have, and use one of those VCOs with
gate drives included (e.g., IR27xxx), downside being I need four gate
outputs, not two.  I don't know of any offhand that do that in one
chip; the 8-pin models don't support synchronization so this would be
a challenge (even more level shifting? fuggedaboudit).
- Do the Schmitt trigger + T flip-flop, but implement it in CD4000
MOS.  Downside: I'm pretty sure no one makes CDTinyLogic4000's, so
that's two SO-14's almost entirely wasted.
- Use an SMPS controller.  I'm intently eyeballing UC3825, the
"improved TL494".  It's fast enough and has true complementary
outputs, but it has limited duty cycle (dead time), as do most PP/
bridge controllers. I can tolerate plenty of deadtime, but it's not as
elegant as having simple complementary outputs.  It's also an SO-16 or
whatever, when all I really need is an SOT-23-6, but still, it's
better than two SO-14s.
- Just make a fucking astable multivibrator*.  We live in a world of
everything integrated, but hey, what works, works...  Plus, it saves
one of those damn $5 chips.  Not that the placement of all those
resistors is any cheaper.

Optimal solution: a TimerBlox (or CD4000 logic oscillator, or..) that
runs from 12V.  CMOS outputs drive a nominal amount of current (>5mA)
at roughly supply voltages, give or take drop.  Heck, crude bipolar
outputs would be acceptable too (e.g., a 555 with complementary
outputs).

*Last time I had this same problem, I built the multivibrator out of
the very power stage itself (2N4401 for the win).  And the time before
that, I had some FPGA outputs to spare, so I just clocked some square
waves out of that.  Which still required a level shift, but a
transistor per phase happened to be enough in that case.

Tim

What James Arthur presumably had in mind was good old 4000 series
CMOS. MC14xxxB runs from 3V to 18V.

http://www.onsemi.com/pub_link/Collateral/MC14013B-D.PDF

You could use a couple of inverters (or 2n7002s) to make a non-50%
duty cycle oscillator and divide it with the 14013 to get exactly 50%.

irs2453 or ir2153 ?

555 + flipflop + 2/4 gatedrivers

On Jan 26, 7:33 am, "langw...@fonz.dk" <langw...@fonz.dk> wrote:

irs2453 or ir2153 ?

Has exactly the drive and size I need, but it's just not fast enough
-- 100kHz max, and too much dead time. :(

555 + flipflop + 2/4 gatedrivers

Yuck!  There must be a smaller solution out there.

Tim

two of these then?

http://www.irf.com/product-info/datasheets/data/auir2085s.pdf

500KHz, 50-200ns deadtime

On Jan 26, 12:10 pm, "langw...@fonz.dk" <langw...@fonz.dk> wrote:

two of these then?

http://www.irf.com/product-info/datasheets/data/auir2085s.pdf

500KHz, 50-200ns deadtime

Ahh, that looks good!  Doesn't mention how to synchronize, but I'd
guess RT from one (which comes from an internal flip-flop) could be
tied to CT on the other (flipping the thresholds at will), at a few
nanoseconds' expense in delay.  Hopefully not enough to care.

As for stock, Digikey doesn't have them.  Mouser and Newark do, which
isn't bad.  Hmmmmm...

Tim

Driving a dumb chopper: 24V supply, NMOS H-bridge, 12V gate drive, 50%
duty cycle at 200kHz. All I need is complementary drive to the left
and right-hand side gate drivers. Trouble is, my gate drive circuitry
needs 12V. Old skool metal gate logic would suffice, but fancy that,
no one makes special circuits out of it. :)

Optimal solution: a TimerBlox (or CD4000 logic oscillator, or..) that
runs from 12V. CMOS outputs drive a nominal amount of current (>5mA)
at roughly supply voltages, give or take drop. Heck, crude bipolar
outputs would be acceptable too (e.g., a 555 with complementary
outputs).