Forums

Low RDSon Logic CMOS Gate

Started by Klaus Kragelund October 1, 2012
On Oct 3, 1:15=A0pm, "k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz>
wrote:
> On Tue, 2 Oct 2012 19:43:44 -0700 (PDT), dagmargoodb...@yahoo.com wrote: > >On Oct 1, 10:09=A0pm, "Vladimir Vassilevsky" <nos...@nowhere.com> wrote: > >> "John Larkin" <jjlar...@highNOTlandTHIStechnologyPART.com> wrote in me=
ssage
> > >>news:n5bk68h59kckkcmb8ntr5ecfauefjkmq6l@4ax.com... > > >> > If a CMOS gate's input is roughly midway between Vcc and ground, bot=
h
> >> > p-channel and n-channel fets can be partially turned on in the front > >> > end. > > >> This problem is greatly overstated. > >> While ago I tested static cross conduction of HCT04 gate powered at +5=
V.
> >> The worst case was about 4mA, at 0.9V at the input. > > >> Vladimir Vassilevsky > >> DSP and Mixed Signal Consultantwww.abvolt.com > > >I've destroyed 74AC parts that way. =A0Smoked 'em. > > HCT stuff isn't tuned for speed so has little crossover current (none, > ideally). =A0AC logic is a whole different kettle. =A0Better decouple AC =
gates
> well. =A0 ;-)
I was experimenting using one as a VHF amplifier. That works well, until the smoke comes out. Another guy put a resistor in the supply line with some success. I switched to 'HC. Cool as a cucumber, and it just worked. -- Cheers, James Arthur
On Thursday, October 4, 2012 6:34:46 AM UTC+2, (unknown) wrote:
> On Oct 3, 1:15=A0pm, "k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz> >=20 > wrote: >=20 > > On Tue, 2 Oct 2012 19:43:44 -0700 (PDT), dagmargoodb...@yahoo.com wrote=
:
>=20 > > >On Oct 1, 10:09=A0pm, "Vladimir Vassilevsky" <nos...@nowhere.com> wrot=
e:
>=20 > > >> "John Larkin" <jjlar...@highNOTlandTHIStechnologyPART.com> wrote in =
message
>=20 > > >=20 > > >>news:n5bk68h59kckkcmb8ntr5ecfauefjkmq6l@4ax.com... >=20 > > >=20 > > >> > If a CMOS gate's input is roughly midway between Vcc and ground, b=
oth
>=20 > > >> > p-channel and n-channel fets can be partially turned on in the fro=
nt
>=20 > > >> > end. >=20 > > >=20 > > >> This problem is greatly overstated. >=20 > > >> While ago I tested static cross conduction of HCT04 gate powered at =
+5V.
>=20 > > >> The worst case was about 4mA, at 0.9V at the input. >=20 > > >=20 > > >> Vladimir Vassilevsky >=20 > > >> DSP and Mixed Signal Consultantwww.abvolt.com >=20 > > >=20 > > >I've destroyed 74AC parts that way. =A0Smoked 'em. >=20 > > >=20 > > HCT stuff isn't tuned for speed so has little crossover current (none, >=20 > > ideally). =A0AC logic is a whole different kettle. =A0Better decouple A=
C gates
>=20 > > well. =A0 ;-) >=20 >=20 >=20 > I was experimenting using one as a VHF amplifier. That works well, >=20 > until the smoke comes out. Another guy put a resistor in the supply >=20 > line with some success. >=20 >=20 >=20 > I switched to 'HC. Cool as a cucumber, and it just worked. >=20 >=20
Some measurements of supply current: For NC7SZ14: 100kHz, 3 gates in parallel, one gate feeding the 3 gates for fast switchin= g of inputs, no output load: 3.3V, 366uA 5V, 1400uA 1MHz: 3V3,1280uA 5V, 3100uA Cheers Klaus
On Thu, 4 Oct 2012 01:12:24 -0700 (PDT), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

>Some measurements of supply current: > >For NC7SZ14: > > 100kHz, 3 gates in parallel, one gate feeding the 3 gates > for fast switching of inputs, no output load: > >3.3V, 366uA >5V, 1400uA > >1MHz: > >3V3,1280uA >5V, 3100uA
Linear assumption, then: 3.3V: I =3D 265uA + 1.02uA*f (in kHz) 5.0V: I =3D 1210uA + 1.89uA*f (in kHz) Jon
Jon Kirwan a &#2013265929;crit :
> On Thu, 4 Oct 2012 01:12:24 -0700 (PDT), Klaus Kragelund > <klauskvik@hotmail.com> wrote: > >> Some measurements of supply current: >> >> For NC7SZ14: >> >> 100kHz, 3 gates in parallel, one gate feeding the 3 gates >> for fast switching of inputs, no output load: >> >> 3.3V, 366uA >> 5V, 1400uA >> >> 1MHz: >> >> 3V3,1280uA >> 5V, 3100uA > > Linear assumption, then: > > 3.3V: I = 265uA + 1.02uA*f (in kHz) > 5.0V: I = 1210uA + 1.89uA*f (in kHz) > > Jon
Which seems a lot... Also, the "static" (1210uA) current is way too big. 1.89uA/kHz -> 1.89nC/switch event and a *big* 380pF Cpd under 5V 380pF/4 gates, mean 95pF/gate which is 3 time the Fairchild figure... -- Thanks, Fred.
On Thursday, October 4, 2012 1:00:39 PM UTC+2, Fred Bartoli wrote:
> Jon Kirwan a =E9crit : >=20 > > On Thu, 4 Oct 2012 01:12:24 -0700 (PDT), Klaus Kragelund >=20 > > <klauskvik@hotmail.com> wrote: >=20 > >=20 >=20 > >> Some measurements of supply current: >=20 > >> >=20 > >> For NC7SZ14: >=20 > >> >=20 > >> 100kHz, 3 gates in parallel, one gate feeding the 3 gates >=20 > >> for fast switching of inputs, no output load: >=20 > >> >=20 > >> 3.3V, 366uA >=20 > >> 5V, 1400uA >=20 > >> >=20 > >> 1MHz: >=20 > >> >=20 > >> 3V3,1280uA >=20 > >> 5V, 3100uA >=20 > >=20 >=20 > > Linear assumption, then: >=20 > >=20 >=20 > > 3.3V: I =3D 265uA + 1.02uA*f (in kHz) >=20 > > 5.0V: I =3D 1210uA + 1.89uA*f (in kHz) >=20 > >=20 >=20 > > Jon >=20 >=20 >=20 > Which seems a lot... >=20 > Also, the "static" (1210uA) current is way too big. >=20 >=20 >=20 > 1.89uA/kHz -> 1.89nC/switch event and a *big* 380pF Cpd under 5V >=20 >=20 >=20 > 380pF/4 gates, mean 95pF/gate which is 3 time the Fairchild figure... >=20 >=20 >=20
The static consumption is unmeaserable (or at least below 1uA) Regarding the high consumption, they are in parallel, so might be cross con= duction from device to device if propagation times are no equal I'll dig further and post back here Cheers Klaus
On Wed, 3 Oct 2012 21:14:26 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

>On Oct 3, 1:48&#2013266080;pm, John Larkin <jlar...@highlandtechnology.com> wrote:
[snip]
>> >> Even a break-before-make CMOS analog switch has several CMOS gate >> driver sections, each of which will have shoot-through. Then the final >> switch capacitance behaves just like a Cpd effect, wasting energy on >> every transition. No free lunch. > >The lunch doesn't have to be free. If it's smaller, cheaper, and all >wrapped up in a nicer box, that counts too.
An interesting thought sprung into my head. The driver sections don't have to have shoot-thru, they can be time staggered all the way back to the basic on-off control. I'll have to implement that in my next H-bridge controller ;-) ...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 Thu, 04 Oct 2012 08:38:20 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Wed, 3 Oct 2012 21:14:26 -0700 (PDT), dagmargoodboat@yahoo.com >wrote: > >>On Oct 3, 1:48&#2013266080;pm, John Larkin <jlar...@highlandtechnology.com> wrote: >[snip] >>> >>> Even a break-before-make CMOS analog switch has several CMOS gate >>> driver sections, each of which will have shoot-through. Then the final >>> switch capacitance behaves just like a Cpd effect, wasting energy on >>> every transition. No free lunch. >> >>The lunch doesn't have to be free. If it's smaller, cheaper, and all >>wrapped up in a nicer box, that counts too. > >An interesting thought sprung into my head. The driver sections don't >have to have shoot-thru, they can be time staggered all the way back >to the basic on-off control. I'll have to implement that in my next >H-bridge controller ;-) > > ...Jim Thompson
If they switch, they have to at least charge node capacitances. If a chip has a narrow specified Vcc range, I guess you can avoid overlap fet conduction, at the cost of speed. Another requirement with analog switches is low charge/glitch injection, which puts constraints on staggering the drives to the analog switch devices. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On Wed, 3 Oct 2012 21:34:46 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

>On Oct 3, 1:15&#2013266080;pm, "k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz> >wrote: >> On Tue, 2 Oct 2012 19:43:44 -0700 (PDT), dagmargoodb...@yahoo.com wrote: >> >On Oct 1, 10:09&#2013266080;pm, "Vladimir Vassilevsky" <nos...@nowhere.com> wrote: >> >> "John Larkin" <jjlar...@highNOTlandTHIStechnologyPART.com> wrote in message >> >> >>news:n5bk68h59kckkcmb8ntr5ecfauefjkmq6l@4ax.com... >> >> >> > If a CMOS gate's input is roughly midway between Vcc and ground, both >> >> > p-channel and n-channel fets can be partially turned on in the front >> >> > end. >> >> >> This problem is greatly overstated. >> >> While ago I tested static cross conduction of HCT04 gate powered at +5V. >> >> The worst case was about 4mA, at 0.9V at the input. >> >> >> Vladimir Vassilevsky >> >> DSP and Mixed Signal Consultantwww.abvolt.com >> >> >I've destroyed 74AC parts that way. &#2013266080;Smoked 'em. >> >> HCT stuff isn't tuned for speed so has little crossover current (none, >> ideally). &#2013266080;AC logic is a whole different kettle. &#2013266080;Better decouple AC gates >> well. &#2013266080; ;-) > >I was experimenting using one as a VHF amplifier. That works well, >until the smoke comes out. Another guy put a resistor in the supply >line with some success. > >I switched to 'HC. Cool as a cucumber, and it just worked.
Some of the TinyLogic gates could be used as RF power amps. One of the hidden gems is the LVDS line receiver. These are essentially r-r comparators with screaming-fast CMOS output stages. They make great RF oscillators. Dirt cheap. SN65LVDS2DBVR and such. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On Thu, 04 Oct 2012 09:08:57 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

[snip]
> >One of the hidden gems is the LVDS line receiver. These are >essentially r-r comparators with screaming-fast CMOS output stages. >They make great RF oscillators. Dirt cheap. SN65LVDS2DBVR and such.
Yep. I designed a couple for Fairchild. (Portland, ME, division. Wonderful town. The car rental people warm up the car interior before they bring it around to you :-) ...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 Thu, 04 Oct 2012 09:04:29 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 04 Oct 2012 08:38:20 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Wed, 3 Oct 2012 21:14:26 -0700 (PDT), dagmargoodboat@yahoo.com >>wrote: >> >>>On Oct 3, 1:48&#2013266080;pm, John Larkin <jlar...@highlandtechnology.com> wrote: >>[snip] >>>> >>>> Even a break-before-make CMOS analog switch has several CMOS gate >>>> driver sections, each of which will have shoot-through. Then the final >>>> switch capacitance behaves just like a Cpd effect, wasting energy on >>>> every transition. No free lunch. >>> >>>The lunch doesn't have to be free. If it's smaller, cheaper, and all >>>wrapped up in a nicer box, that counts too. >> >>An interesting thought sprung into my head. The driver sections don't >>have to have shoot-thru, they can be time staggered all the way back >>to the basic on-off control. I'll have to implement that in my next >>H-bridge controller ;-) >> >> ...Jim Thompson > >If they switch, they have to at least charge node capacitances. If a >chip has a narrow specified Vcc range, I guess you can avoid overlap >fet conduction, at the cost of speed.
Nope, not necessary. Ask Klaus. I sent him my whole chip design... minus customer-identifying information. Of course YOU are not allowed to see it >:-)
> >Another requirement with analog switches is low charge/glitch >injection, which puts constraints on staggering the drives to the >analog switch devices.
Big difference between analog switch needs and those for a 500mA H-bridge. ...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.