Forums

Low RDSon Logic CMOS Gate

Started by Klaus Kragelund October 1, 2012
On Mon, 01 Oct 2012 12:35:52 -0600, hamilton wrote:

> On 10/1/2012 11:46 AM, John Larkin wrote: >> On Mon, 01 Oct 2012 10:42:16 -0700, Jim Thompson >>> >>> How about a 6-pack of '04's paralleled? >>> >>> ...Jim Thompson >> >> Massive shoot-through. >> >> >> > Please describe shoot-through.
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. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Klaus Kragelund a �crit :
> Hi > > I need a CMOS gate with low voltage drop at about 30mA current source and sink. 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 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) > > Any one have a part in mind? > > Thanks > > Klaus
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 ?-) -- Thanks, Fred.
On Monday, October 1, 2012 7:44:52 PM UTC+2, John Larkin wrote:
> On Mon, 1 Oct 2012 10:33:00 -0700 (PDT), Klaus Kragelund >=20 > <klauskvikyhyy@hotmail.com> wrote: >=20 >=20 >=20 > >Hi >=20 > > >=20 > >I need a CMOS gate with low voltage drop at about 30mA current source an=
d sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18o= hm RDS on.
>=20 > > >=20 > >I am searching for a device with less than 5-10 ohms and it would need t=
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)
>=20 > > >=20 > >Any one have a part in mind? >=20 > > >=20 > >Thanks >=20 > > >=20 > >Klaus >=20 >=20 >=20 > Use something like an HC14, with one section buffering the input, then >=20 > driving several other sections, up to 5, in parallel. >=20 >=20 >=20 > More extreme on speed - sub ns edges - would be an NL37WZ17US, again >=20 > with one section buffering the input to drive the other two.
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 =3D C= pd * V * f. (page 5 of http://www.fairchildsemi.com/ds/NC/NC7SZ14.pdf) I guess it's in pC (pico coloumb), which corresponds to 100uA/MHz. Regards Klaus
On Monday, October 1, 2012 10:33:01 AM UTC-7, Klaus Kragelund wrote:


> I need a CMOS gate with low voltage drop at about 30mA current source and sink. 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
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.
On Monday, October 1, 2012 9:28:11 PM UTC+2, Jim Thompson wrote:
> On Mon, 1 Oct 2012 12:15:09 -0700 (PDT), Klaus Kragelund >=20 > <klauskvik@hotmail.com> wrote: >=20 >=20 >=20 > >On Monday, October 1, 2012 8:07:17 PM UTC+2, Jim Thompson wrote: >=20 > >> On Mon, 01 Oct 2012 10:44:44 -0700, John Larkin >=20 > >>=20 >=20 > >> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >=20 > >>=20 >=20 > >>=20 >=20 > >>=20 >=20 > >> >On Mon, 1 Oct 2012 10:33:00 -0700 (PDT), Klaus Kragelund >=20 > >>=20 >=20 > >> ><klauskvikddd@hotmail.com> wrote: >=20 > >>=20 >=20 > >> > >=20 > >>=20 >=20 > >> >>Hi >=20 > >>=20 >=20 > >> >> >=20 > >>=20 >=20 > >> >>I need a CMOS gate with low voltage drop at about 30mA current sourc=
e and sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to= 18ohm RDS on.
>=20 > >>=20 >=20 > >> >> >=20 > >>=20 >=20 > >> >>I am searching for a device with less than 5-10 ohms and it would ne=
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)
>=20 > >>=20 >=20 > >> >> >=20 > >>=20 >=20 > >> >>Any one have a part in mind? >=20 > >>=20 >=20 > >> >> >=20 > >>=20 >=20 > >> >>Thanks >=20 > >>=20 >=20 > >> >> >=20 > >>=20 >=20 > >> >>Klaus >=20 > >>=20 >=20 > >> > >=20 > >>=20 >=20 > >> >Use something like an HC14, with one section buffering the input, the=
n
>=20 > >>=20 >=20 > >> >driving several other sections, up to 5, in parallel. >=20 > >>=20 >=20 > >> > >=20 > >>=20 >=20 > >> >More extreme on speed - sub ns edges - would be an NL37WZ17US, again >=20 > >>=20 >=20 > >> >with one section buffering the input to drive the other two. >=20 > >>=20 >=20 > >> > >=20 > >>=20 >=20 > >>=20 >=20 > >>=20 >=20 > >> I don't think that will fix shoot-thru. 'HC14 only fixes slow inputs, >=20 > >>=20 >=20 > >> so maybe the simple-minded solution is to simply slow down the input >=20 > >>=20 >=20 > >> to get firm turn-off of drive-low before drive-high (and vice-versa) >=20 > >>=20 >=20 > >> is activated... say take 10-20ns to get thru the hysteresis ?:-) >=20 > >>=20 >=20 > >>=20 >=20 > >>=20 >=20 > >> Or maybe a 1/2-H bridge driven by non-overlapping drives... as >=20 > >>=20 >=20 > >> demonstrated recently with my delay block?=20 >=20 > > >=20 > >Been through some posts, but did not find it. Can you point me in the ri=
ght direction? :-)=20
>=20 > > >=20 > >Regards >=20 > > >=20 > >Klaus >=20 >=20 >=20 > This is the way I generate precise delays (on-chip)... >=20 >=20 >=20 > http://www.analog-innovations.com/SED/DelayCircuitForNarrowPulseWidths.pd=
f
>=20 >=20 >=20 > This delayed signal is then used to create non-overlapping drives for >=20 > such things as full-H bridges, and commutating switches used in >=20 > synchronous rectification and integrate control loops. >=20 >=20 >=20 > Analysis is left as an exercise for the student ;-) >=20 >=20 >=20 > Hints: >=20 >=20 >=20 > (1) These are 10ps inverters (TSMC 0.18u process) >=20 > (2) This is internal to a monolithic chip, so no ESD to get in your >=20 > way, so left end of the cap flys above VDDD and below GNDD without >=20 > clamping or consequence. >=20 >=20 >=20 > This snap-shot is from a chip I designed last fall when I did an >=20 > extended stay (:-) on Long Island and met Martin Riddle. >=20 >=20 >=20 > Designed entirely on my laptop, the chip worked perfectly to >=20 > specifications first pass thru the foundry, as do ALL of my designs... >=20 > I never do "designs" without component values >:-) >=20 >=20 >=20 > Klaus, I'll see if I can excise a clip showing how it inputs into the >=20 > H-bridge without breaking any NDA restrictions. >=20 >=20 >=20 > Is your posted E-mail address valid? >=20
Hi Jim Thank you for taking time to elaborate on this ;-) The email is: klauskvik@hotmail.com It is valid and hotmail spamfilter works, I hardly get spam any more... Regards Klaus
On Monday, October 1, 2012 9:39:58 PM UTC+2, Fred Bartoli wrote:
> Klaus Kragelund a =E9crit : >=20 > > Hi >=20 > >=20 >=20 > > I need a CMOS gate with low voltage drop at about 30mA current source a=
nd sink. The tiny logic NL27WZ14 has 600mV drop at 32mA which equates to 18= ohm RDS on.
>=20 > >=20 >=20 > > I am searching for a device with less than 5-10 ohms and it would need =
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)
>=20 > >=20 >=20 > > Any one have a part in mind? >=20 > >=20 >=20 > > Thanks >=20 > >=20 >=20 > > Klaus >=20 >=20 >=20 > Mucho thanks for posting this... >=20 >=20 >=20 > In an attempt to answer I had a look at a recent design and noticed that=
=20
>=20 > a 5V powered LVC14 escaped all the design reviews :-( >=20 >=20 >=20 > It survived all the stress test: 27MHz switching, with PCB temp=3D100=B0C=
=20
>=20 > while driving a 250pF Ciss Mosfet... >=20 >=20 >=20 > How did you know ?-) >=20
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=20
On Mon, 01 Oct 2012 12:28:10 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Mon, 1 Oct 2012 12:15:09 -0700 (PDT), Klaus Kragelund ><klauskvik@hotmail.com> wrote: > >>On Monday, October 1, 2012 8:07:17 PM UTC+2, Jim Thompson wrote: >>> On Mon, 01 Oct 2012 10:44:44 -0700, John Larkin >>> >>> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>> >>> >>> >>> >On Mon, 1 Oct 2012 10:33:00 -0700 (PDT), Klaus Kragelund >>> >>> ><klauskvikddd@hotmail.com> wrote: >>> >>> > >>> >>> >>Hi >>> >>> >> >>> >>> >>I need a CMOS gate with low voltage drop at about 30mA current source and sink. 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 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) >>> >>> >> >>> >>> >>Any one have a part in mind? >>> >>> >> >>> >>> >>Thanks >>> >>> >> >>> >>> >>Klaus >>> >>> > >>> >>> >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. >>> >>> > >>> >>> >>> >>> 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? >> >>Been through some posts, but did not find it. Can you point me in the right direction? :-) >> >>Regards >> >>Klaus > >This is the way I generate precise delays (on-chip)... > >http://www.analog-innovations.com/SED/DelayCircuitForNarrowPulseWidths.pdf > >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
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 -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Monday, October 1, 2012 9:52:19 PM UTC+2, whit3rd wrote:
> On Monday, October 1, 2012 10:33:01 AM UTC-7, Klaus Kragelund wrote: > > > > > > > I need a CMOS gate with low voltage drop at about 30mA current source and sink. 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 > > > > 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.
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
Klaus Kragelund a &#2013265929;crit :
> On Monday, October 1, 2012 7:44:52 PM UTC+2, John Larkin wrote: >> On Mon, 1 Oct 2012 10:33:00 -0700 (PDT), Klaus Kragelund >> >> <klauskvikyhyy@hotmail.com> wrote: >> >> >> >>> Hi >>> I need a CMOS gate with low voltage drop at about 30mA current source and sink. 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 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) >>> Any one have a part in mind? >>> Thanks >>> Klaus >> >> >> 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. > > I found maybe a slightly better one, the NC7SZ14. The device lists CPD of 24 (Power dissipation capacitance, but no information on the unit. Icc = Cpd * V * f. > > (page 5 of http://www.fairchildsemi.com/ds/NC/NC7SZ14.pdf) > > I guess it's in pC (pico coloumb), which corresponds to 100uA/MHz. > > Regards > > Klaus >
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 -- Thanks, Fred.
Klaus Kragelund <klauskvik@hotmail.com> wrote:

>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.
Maybe look for a MOSFET driver chip. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------