Q: 0-Nodes in .SUBCKT

Dec 11, 2015 13 Replies
J

The problem was simpulating with LTspice: I have this irl3103s.spi from the IR website. I am trying to use the MOSFET hi-side as a sync-rectifier(backwards).... I am driving with IRL2110 (2Amps,15V). I sill get 200 Amp spikes that look like dv/dt turn on(when the lower FET(IRFZ44) switches on). I tried adding capacitor from gate to source. stopped(unsuccessfully) at around 100nF. looked at the .spi file. They have a bunch of components connected to the 0 node(diodes, behavoiral sources...). Is that ok? I suspect that only works in lo-side applications?



posting the spi..



8 Drain
  • Node 2 -> Gate
  • Node 3 -> Source M1 9 7 8 8 MM L=100u W=100u
  • Default values used in MM:
  • The voltage-dependent capacitances are
  • not included. Other default values are:
  • RS=0 RD=0 LD=0 CBD=0 CBS=0 CGBO=0 .MODEL MM NMOS LEVEL=1 IS=1e-32

+VTO=2.15365 LAMBDA=0 KP=53.1202
+CGSO=1.37063e-05 CGDO=1.00138e-11 RS 8 3 0.00857705 D1 3 1 MD .MODEL MD D IS=8.21594e-09 RS=0.00671808 N=1.42559 BV=30
+IBV=0.00025 EG=1.2 XTI=3.26374 TT=9.99995e-05
+CJO=1.50815e-09 VJ=0.5 M=0.379369 FC=0.500065 RDS 3 1 1.2e+06 RD 9 1 0.0001 RG 2 7 3.42076 D2 4 5 MD1
  • Default values used in MD1:
  • RS=0 EG=1.11 XTI=3.0 TT=0
  • BV=infinite IBV=1mA .MODEL MD1 D IS=1e-32 N=50

+CJO=2.61157e-09 VJ=0.5 M=0.545522 FC=1e-08 D3 0 5 MD2
  • Default values used in MD2:
  • EG=1.11 XTI=3.0 TT=0 CJO=0
  • BV=infinite IBV=1mA .MODEL MD2 D IS=1e-10 N=0.4 RS=3e-06 RL 5 10 1 FI2 7 9 VFI2 -1 VFI2 4 0 0 EV16 10 0 9 7 1 CAP 11 10 4.07694e-09 FI1 7 9 VFI1 -1 VFI1 11 6 0 RCAP 6 10 1 D4 0 6 MD3
  • Default values used in MD3:
  • EG=1.11 XTI=3.0 TT=0 CJO=0
  • RS=0 BV=infinite IBV=1mA .MODEL MD3 D IS=1e-10 N=0.4 .ENDS
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M

Good guestion and I don't look at node 0 as being connected directly to Node 0 outside the sub unless it is via one of the input parameters. I see node 0 as a common for itself, just like a device being connected to another device, both having their own power source.

I can see why this would be needed for example using "E", voltage dependent voltage source. etc.

Getting to your original problem, you may have shoot through currents on the output, where one is still on while turning the otehr on. There are ways to get around that if that is really what's happening? Slow on, Fast off or simply have a gated feed back to know when you can safely turn on the other side, etc..

Just my comments, really..

Jamie

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M

[...]

Node 0 is global ground. If you want to separate the subcircuit internal ground from global ground you'll have to name that net something else and provide a connection through a subcircuit port.

Grizzly H.
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J

Wrong. Node 0 (zero) is _global_. which can lead to treacherous/misleading results... better to use %COM.

...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
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M

Ok, have it your way but, that is not the way I understood it back when it was introduced to me, years ago. My understanding of it makes it perfectly clear and sensible as to how it works. I guess I don't think like you do, and I don't seem to have any issues with that, so what ever.

Thanks anyway..

Jamie

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J

You be wrong.

Reread and digest.

Don't try to be gratuitous or we'll chew you up and spit you out >:-} ...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
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M

Do all the spitting yuo want Jim, it may back fire on you.

Jamie

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J

Stay away from my backfire... I just has Chili Relleno at Cass de Mina

...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
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J

I took the time to figure this one out.... The 0 nodes seem2be part of the charge injection mechanism(capacitances or somesuch parasitics). Yes, it's global, but no they should not cause problems, because it's disconnected from the actual FET(voltages). seems it's really dv/dt turn on...

I have a schematic but thunderbird won't let me send it(lines 2 long and rewrap doees not work)

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J

It helps to understand by creating a schematic of the subcircuit...

I've highlighted the ground paths. There are no direct connections from ground to any of the active nodes of the subcircuit (DRAIN/GATE/SOURCE).

The ground/node-zero connection is necessary to avoid floating node issues. ...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
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J
[snip]

I forgot the snarky part... the 4 and 5-place component values means the model was concocted by a PhD, and is thus suspect as to quality of performance, and likelihood of convergence >:-} ...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
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J

[snip]

It shouldn't matter high-side or low. Post _your_ asc (LTspice schematic file). You probably have some drive overlap. ...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
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