Forums

New 555 Spice Model

Started by Jim Thompson March 18, 2011
On Thu, 24 Mar 2011 16:06:23 -0500, John Fields
<jfields@austininstruments.com> wrote:

>On Thu, 24 Mar 2011 12:33:07 -0400, Bitrex ><bitrex@de.lete.earthlink.net> wrote: > >. >. >. > >>I don't believe the bipolar 555 model included with LTSpice is >>modeling the supply spikes accurately. > >--- >Here's the circuit I'm using to test Linear's NE555 model: > >Version 4 >SHEET 1 880 748 >WIRE 224 192 -128 192 >WIRE 544 192 448 192 >WIRE -128 256 -128 192 >WIRE -80 256 -128 256 >WIRE 32 256 0 256 >WIRE 64 256 32 256 >WIRE 224 256 144 256 >WIRE 512 256 448 256 >WIRE 32 320 32 256 >WIRE 176 320 32 320 >WIRE 224 320 176 320 >WIRE 608 320 448 320 >WIRE 480 384 448 384 >WIRE 608 416 608 320 >WIRE 176 480 176 320 >WIRE 512 480 512 256 >WIRE 512 480 176 480 >WIRE 544 496 544 192 >WIRE -128 512 -128 256 >WIRE 480 512 480 384 >WIRE 480 512 -128 512 >WIRE -128 528 -128 512 >WIRE 176 544 176 480 >WIRE -128 624 -128 608 >WIRE 176 624 176 608 >WIRE 176 624 -128 624 >WIRE 544 624 544 576 >WIRE 544 624 176 624 >WIRE 608 624 608 496 >WIRE 608 624 544 624 >WIRE -128 688 -128 624 >FLAG -128 688 0 >SYMBOL Misc\\NE555 336 288 M0 >SYMATTR InstName U1 >SYMBOL voltage -128 512 M0 >WINDOW 123 0 0 Left 0 >WINDOW 39 0 0 Left 0 >SYMATTR InstName V1 >SYMATTR Value 5 >SYMBOL res -96 240 M90 >WINDOW 0 0 56 VBottom 0 >WINDOW 3 32 58 VTop 0 >SYMATTR InstName R1 >SYMATTR Value 40k >SYMBOL res 48 240 M90 >WINDOW 0 0 56 VBottom 0 >WINDOW 3 32 56 VTop 0 >SYMATTR InstName R2 >SYMATTR Value 19.8k >SYMBOL res 624 400 M0 >WINDOW 0 -45 40 Left 0 >WINDOW 3 -59 71 Left 0 >SYMATTR InstName R3 >SYMATTR Value 1000 >SYMBOL cap 192 544 M0 >WINDOW 0 -33 32 Left 0 >WINDOW 3 -39 58 Left 0 >SYMATTR InstName C1 >SYMATTR Value 1e-7 >SYMBOL res 528 480 R0 >SYMATTR InstName R4 >SYMATTR Value 1 >TEXT 88 656 Right 0 !.tran .1 startup uic >TEXT 456 176 Left 0 ;1 >TEXT 456 240 Left 0 ;2 >TEXT 456 304 Left 0 ;3 >TEXT 456 360 Left 0 ;4 >TEXT 200 368 Left 0 ;5 >TEXT 200 304 Left 0 ;6 >TEXT 200 240 Left 0 ;7 >TEXT 200 176 Left 0 ;8 > > >I've just posted a query to: > > http://groups.yahoo.com/group/LTspice/ > >for clarification re. the accuracy of the model, and I'll post what >comes back as soon as I get it. > >Maybe Helmut will post here first.
The NE555 model in LTspice is virtually all behavioral modeling. Just a quick observation of the switches (6 Ohms) suggest a whopping spike ;-) ...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 | Remember: Once you go over the hill, you pick up speed
"John Fields" <jfields@austininstruments.com> schrieb im Newsbeitrag 
news:hdcno6ptlutkbpnekqprakhet3i7ot06qc@4ax.com...
> On Thu, 24 Mar 2011 12:33:07 -0400, Bitrex > <bitrex@de.lete.earthlink.net> wrote: >>I don't believe the bipolar 555 model included with LTSpice is >>modeling the supply spikes accurately. > .... > I've just posted a query to: > http://groups.yahoo.com/group/LTspice/ > for clarification re. the accuracy of the model, and I'll post what > comes back as soon as I get it. > Maybe Helmut will post here first. > -- > JF
Hello John, The NE555 in the Misc-folder of LTspice may be just a gift from Mike. I guess he made it because so many people asked for a 555. LTC doesn't have a 555. So we can't expect that Mike spends time to tweak the model for shoot-through current. I tried a little bit with a capacitive load. Adding 100pF to the output has given a significant current peak in the power supply (V-source). Maybe this is a reasonable workaround if somebody wants it more realistic.. Best regards, Helmut
On Thu, 24 Mar 2011 23:24:52 +0100, "Helmut Sennewald"
<helmutsennewald@t-online.de> wrote:

>"John Fields" <jfields@austininstruments.com> schrieb im Newsbeitrag >news:hdcno6ptlutkbpnekqprakhet3i7ot06qc@4ax.com... >> On Thu, 24 Mar 2011 12:33:07 -0400, Bitrex >> <bitrex@de.lete.earthlink.net> wrote: >>>I don't believe the bipolar 555 model included with LTSpice is >>>modeling the supply spikes accurately. >> .... >> I've just posted a query to: >> http://groups.yahoo.com/group/LTspice/ >> for clarification re. the accuracy of the model, and I'll post what >> comes back as soon as I get it. >> Maybe Helmut will post here first. >> -- >> JF > > >Hello John, > >The NE555 in the Misc-folder of LTspice may be just a gift from Mike. >I guess he made it because so many people asked for a 555. >LTC doesn't have a 555. So we can't expect that Mike spends >time to tweak the model for shoot-through current. > >I tried a little bit with a capacitive load. Adding 100pF >to the output has given a significant current peak in the >power supply (V-source). Maybe this is a reasonable workaround >if somebody wants it more realistic.. > >Best regards, >Helmut
--- Hello Helmut, As always, with you, reason prevails. :-) Thank you for your advice. -- JF
On Sat, 19 Mar 2011 01:01:39 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

>On Friday, March 18, 2011 5:15:23 PM UTC-7, Helmut Sennewald wrote: >> "Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> schrieb=20 >> im Newsbeitrag news:bus7o6drmsa2vbhrtajn2gsalp6qrcinqf@4ax.com... >> > On Sat, 19 Mar 2011 00:52:38 +0100, "Helmut Sennewald" >> > <helmuts...@t-online.de> wrote: >> > >> >>"Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> schrieb >> >>im Newsbeitrag news:tep7o6p6m5phjofimc1336tulv7919h7ht@4ax.com... >> >>> Got annoyed at the flaky 555 models that are out there, so I =
rolled my
>> >>> own... >> >>> >> >>> http://www.analog-innovations.com/SED/MyLMC555.zip >> >>> >> >>> Based on old AMI 20V CMOS device models > >> I have to use ".ic V(timing_cap)=3D0" to get the simulation quickly =
started.
> >It's possible that would miss some real behaviors, of course; could the >flip-flop transistors get some explicit gate capacitors? Those would =
hold the
>state info of the flip-flop, and allow the initial timing cap charges of >low, medium, high, to have different initial effects. > >I'm curious, why is the differential amplifier 'tanh'? That isn't the >analytic form for square-law MOSFETs, is it?
It is standard for base input, collector output bipolar differential = pairs for sure. Had to grind the physics for my semiconductor physics course. 8:-P
On Thu, 24 Mar 2011 23:24:52 +0100, "Helmut Sennewald"
<helmutsennewald@t-online.de> wrote:

>"John Fields" <jfields@austininstruments.com> schrieb im Newsbeitrag >news:hdcno6ptlutkbpnekqprakhet3i7ot06qc@4ax.com... >> On Thu, 24 Mar 2011 12:33:07 -0400, Bitrex >> <bitrex@de.lete.earthlink.net> wrote: >>>I don't believe the bipolar 555 model included with LTSpice is >>>modeling the supply spikes accurately. >> .... >> I've just posted a query to: >> http://groups.yahoo.com/group/LTspice/ >> for clarification re. the accuracy of the model, and I'll post what >> comes back as soon as I get it. >> Maybe Helmut will post here first. >> -- >> JF > > >Hello John, > >The NE555 in the Misc-folder of LTspice may be just a gift from Mike. >I guess he made it because so many people asked for a 555. >LTC doesn't have a 555. So we can't expect that Mike spends >time to tweak the model for shoot-through current. > >I tried a little bit with a capacitive load. Adding 100pF >to the output has given a significant current peak in the >power supply (V-source). Maybe this is a reasonable workaround >if somebody wants it more realistic.. > >Best regards, >Helmut >
--- Hello Helmut, Thanks. :-) -- JF
On Thu, 24 Mar 2011 23:20:24 -0700, josephkk
<joseph_barrett@sbcglobal.net> wrote:

>On Sat, 19 Mar 2011 01:01:39 -0700 (PDT), whit3rd <whit3rd@gmail.com> >wrote: > >>On Friday, March 18, 2011 5:15:23 PM UTC-7, Helmut Sennewald wrote: >>> "Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> schrieb >>> im Newsbeitrag news:bus7o6drmsa2vbhrtajn2gsalp6qrcinqf@4ax.com... >>> > On Sat, 19 Mar 2011 00:52:38 +0100, "Helmut Sennewald" >>> > <helmuts...@t-online.de> wrote: >>> > >>> >>"Jim Thompson" <To-Email-Use-Th...@On-My-Web-Site.com> schrieb >>> >>im Newsbeitrag news:tep7o6p6m5phjofimc1336tulv7919h7ht@4ax.com... >>> >>> Got annoyed at the flaky 555 models that are out there, so I rolled my >>> >>> own... >>> >>> >>> >>> http://www.analog-innovations.com/SED/MyLMC555.zip >>> >>> >>> >>> Based on old AMI 20V CMOS device models >> >>> I have to use ".ic V(timing_cap)=0" to get the simulation quickly started. >> >>It's possible that would miss some real behaviors, of course; could the >>flip-flop transistors get some explicit gate capacitors? Those would hold the >>state info of the flip-flop, and allow the initial timing cap charges of >>low, medium, high, to have different initial effects.
The timing cap is what Helmut had to set a .IC, because .TRAN simulations don't have the noise of the real world. So "flip-flops" (weak plus strong inverter in this case) can queue up balance in the simulator.
>> >>I'm curious, why is the differential amplifier 'tanh'? That isn't the >>analytic form for square-law MOSFETs, is it? > >It is standard for base input, collector output bipolar differential pairs >for sure. Had to grind the physics for my semiconductor physics course. >8:-P
I use TANH a lot in my behavioral stuff because all derivatives exist, so convergence in a simulator is easy. ...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 | Remember: Once you go over the hill, you pick up speed