From: Terry Pinnell
Subject: Re: zero-power toggle circuit; was, how to master electronics
Date: Wed, 20 Nov 2002 07:33:55 +0000
References: <3DD39D90.firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: Wed, 20 Nov 2002 07:34:11 +0000 (UTC)
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"Helmut Sennewald" wrote:
>I analyzed(simulated) your circuit with SwitcherCADIII.
>The circuit switches on and off as required, even with the IRF9513,
>when you decrease the feedback resistor R2(e.g. 100k).
>This feedback resistor defines the holding gate voltage.
>The old IRF9513 has a much higher on resistance than the other two
>mosfets you used successfully. I measured 1V voltage drop above this
>mosfet with a 10 Ohm load(=0.9A).
>Accidentally, you designed not for worst case Vgs_th(2N7000) and
>You are too close to the typical threshhold voltage of the 2N7000.
>With some mosfets it would work in reality and with some not.
Thanks very much for taking the trouble, Helmut. First, as I assume
you have missed the earlier (long) thread, note that this was not my
design. I've been querying its reliability with its author, Wafer, and
developer/supporter, Win. That challenge was based solely on its
apparent failure to simulate here with 5 out of 7 power MOSFETs I
tried, using the component values specified.
As per my reply to Fred in
so far I've been unable to get correct working with IRF9513 even with
R2 = 10k. I wonder how the models in CM and SwitcherCADIII compare?
*80V 2A 1ohm Power MOSFET pkg:TO-220 2,1,3
.SUBCKT XIRF9513 10 20 40 40
* TERMINALS: D G S
M1 1 2 3 3 DMOS L=1U W=1U
RD 10 1 0.474
RS 40 3 26M
RG 20 2 60
CGS 2 3 150P
EGD 12 0 1 2 1
VFB 14 0 0
FFB 1 2 VFB 1
CGD 13 14 385P
R1 13 0 1
D1 12 13 DLIM
DDG 15 14 DCGD
R2 12 15 1
D2 15 0 DLIM
DSD 10 3 DSUB
LS 30 40 7.5N
.MODEL DMOS PMOS (LEVEL=3 VMAX=167K THETA=60M ETA=2M VTO=3 KP=0.978)
.MODEL DCGD D (CJO=385P VJ=0.6 M=0.68)
.MODEL DSUB D (IS=10.4N N=1.5 RS=0.3 BV=80 CJO=237P VJ=0.8 M=0.42
.MODEL DLIM D (IS=100U)
For comparison, as you may have seen from my reply to Tony, I also
found this spec in a library of MOSFET Spice models at
.model IRF9513 PMOS(Level=3 Gamma=0 Delta=0 Eta=0 Theta=0 Kappa=0.2
+ Tox=100n Uo=300 Phi=.6 Rs=.3715 Kp=10.54u W=.2 L=2u Vto=-3.923
+ Rd=.6523 Rds=266.7K Cbd=331.8p Pb=.8 Mj=.5 Fc=.5 Cgso=2.306n
+ Cgdo=551.8p Rg=.8973 Is=3.748E-18 N=3 Tt=2250n)
* Int'l Rectifier pid=IRFC9110 case=TO220
* 88-08-25 bam creation
Hobbyist, West Sussex, UK