Low RDSon Logic CMOS Gate

Hi

I need a CMOS gate with low voltage drop at about 30mA current source and s ink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

I am searching for a device with less than 5-10 ohms and it would need to b e ok to parallel to get lower resistance. Also, it must not have to much cr ossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

Any one have a part in mind?

Thanks

Klaus

Reply to
Klaus Kragelund
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The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

How about a 6-pack of '04's paralleled? ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
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Reply to
Jim Thompson

The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

Use something like an HC14, with one section buffering the input, then driving several other sections, up to 5, in parallel.

More extreme on speed - sub ns edges - would be an NL37WZ17US, again with one section buffering the input to drive the other two.

Reply to
John Larkin

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

Massive shoot-through.

Reply to
John Larkin

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

I don't think that will fix shoot-thru. 'HC14 only fixes slow inputs, so maybe the simple-minded solution is to simply slow down the input to get firm turn-off of drive-low before drive-high (and vice-versa) is activated... say take 10-20ns to get thru the hysteresis ?:-)

Or maybe a 1/2-H bridge driven by non-overlapping drives... as demonstrated recently with my delay block? I use that scheme quite successfully in a 500mA full-H driver for a magnetic field sensor... allowing smooth control of a heavy truck clutch ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
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Reply to
Jim Thompson

Please describe shoot-through.

Reply to
hamilton

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

Oooops! That won't work with '14... the hysteresis isn't configured as non-overlap like my H-bridge drives are.

...Jim Thompson

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| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
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Reply to
Jim Thompson

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

Or go whole hog...

formatting link
...Jim Thompson

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| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
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Reply to
Jim Thompson

nd sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18 ohm RDS on.

to be ok to parallel to get lower resistance. Also, it must not have to muc h crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

Been through some posts, but did not find it. Can you point me in the right direction? :-)

Regards

Klaus

Reply to
Klaus Kragelund

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

be ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

direction? :-)

This is the way I generate precise delays (on-chip)...

formatting link

This delayed signal is then used to create non-overlapping drives for such things as full-H bridges, and commutating switches used in synchronous rectification and integrate control loops.

Analysis is left as an exercise for the student ;-)

Hints:

(1) These are 10ps inverters (TSMC 0.18u process) (2) This is internal to a monolithic chip, so no ESD to get in your way, so left end of the cap flys above VDDD and below GNDD without clamping or consequence.

This snap-shot is from a chip I designed last fall when I did an extended stay (:-) on Long Island and met Martin Riddle.

Designed entirely on my laptop, the chip worked perfectly to specifications first pass thru the foundry, as do ALL of my designs... I never do "designs" without component values >:-)

Klaus, I'll see if I can excise a clip showing how it inputs into the H-bridge without breaking any NDA restrictions.

Is your posted E-mail address valid? ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
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Reply to
Jim Thompson

Shoot-through is the term for what happens when both transistors in a half-bridge turn on at the same time: you end up with a connection from

+V to ground through a low-resistance connection, and the current just shoots on through -- sometimes with a BANG, even, and scattered bits of epoxy from the active devices' cases.
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Reply to
Tim Wescott

Klaus Kragelund a écrit :

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

Mucho thanks for posting this...

In an attempt to answer I had a look at a recent design and noticed that a 5V powered LVC14 escaped all the design reviews :-(

It survived all the stress test: 27MHz switching, with PCB temp=100°C while driving a 250pF Ciss Mosfet...

How did you know ?-)

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Thanks, 
Fred.
Reply to
Fred Bartoli

d sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18o hm RDS on.

o be ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have l ow dissipation at high operational frequency (1-10MHz)

I found maybe a slightly better one, the NC7SZ14. The device lists CPD of 2

4 (Power dissipation capacitance, but no information on the unit. Icc = C pd * V * f.

(page 5 of

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I guess it's in pC (pico coloumb), which corresponds to 100uA/MHz.

Regards

Klaus

Reply to
Klaus Kragelund

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

One can use discrete complementary MOSFETs to make a CMOS-like inverter, of course. Ferrite beads can help with the shoot-through problem, your frequency of interest seems low enough not to care. It may matter what voltage you're powering from, as well. At 5V, there's more options than at 2V.

Reply to
whit3rd

e and sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

ed to be ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must ha ve low dissipation at high operational frequency (1-10MHz)

n

ght direction? :-)

f

Hi Jim

Thank you for taking time to elaborate on this ;-)

The email is:

snipped-for-privacy@hotmail.com

It is valid and hotmail spamfilter works, I hardly get spam any more...

Regards

Klaus

Reply to
Klaus Kragelund

nd sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18 ohm RDS on.

to be ok to parallel to get lower resistance. Also, it must not have to muc h crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

That's a secret ;-)

Funny how some circuit work when they are not supposed to and other circuit s that look clean and nice has "gotchas"....

Cheers

Klaus

Reply to
Klaus Kragelund

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

be ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

direction? :-)

No way to clip you a shot... too hierarchical, but it's straight forward:

Delay your up/down command by the amount of desired dead-time.

From the up/down command and its delayed replica, NAND/NOR your way to a sequence like this...

Lower NMOS gate (turns it off) Wait Lower PMOS gate (turns it on) Hold for desired on-time Raise PMOS gate (turns it off) Wait Raise NMOS gate (turns it on) Hold for desired on-time | |

You just rig it so you cannot have a crowbar current path.

I also had a power-up sensor that kept both PMOS and NMOS off until a digital reset made everything copasetic ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
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Reply to
Jim Thompson

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

I have 3.3V, can make 5V if I need to. This is for a high efficiency device, so any powerloss is critical. Shoot through if a FET pair can easily go up to several amps, which won't be noticed if you are not looking.

Cheers

Klaus

Reply to
Klaus Kragelund

sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18ohm RDS on.

ok to parallel to get lower resistance. Also, it must not have to much crossover shoot-through (so probably schmitt trigger type) and must have low dissipation at high operational frequency (1-10MHz)

(Power dissipation capacitance, but no information on the unit. Icc = Cpd * V * f.

The unit is pF. Multiply by 1/2 Vsupply^2 and you have the energy quantum lost at each switching.

Total power loss is PL = f x Cpd x Vsupply^2

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Thanks, 
Fred.
Reply to
Fred Bartoli

Maybe look for a MOSFET driver chip.

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Reply to
Nico Coesel

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