Copyright © 2009 Gary R. Van Sickle
The L200 linear voltage regulator from ST Microelectronics is a pretty sweet part. While it is not Low-Drop Out nor does it have a particularly low quiescent current, it is one of the few monolithic linear regulators with built-in user-adjustable current limiting. Even better, this current limiting feature requires only one additional resistor whose value is easily calculated.
In my never-ending quest to design and build the ultimate vacuum tube power supply, this part sounded like a natural for the heater supplies. For a 12AX7-type tube, I’d just set the voltage to 12.6V (heaters in series), set the current limit to, say, twice the hot heater current (i.e. 300ma), and I’d have a nice soft-start heater supply with one IC and 3 resistors per tube. Things rarely get more straightforward than that!
I was sold. Now to simply simulate it with LTSpice to make sure I hadn’t forgotten anything… and we come to a roadblock. ST doesn’t have a SPICE model available. Must be some new 21st-century marketing technique that I don’t quite understand. A thorough search of the World Wide Internet revealed that nobody else had one either. I was therefore forced to roll my own, which brings us to the main course of this banquet of information: Behold, The Shorted Turn‘s L200 / L200C Macromodel Version 1.0!:
The opamps shown are LTSpice’s default “1-pole” opamp models. Reference voltages VREF and VSC were divined from ST Microelectronics’ datasheet on the part. Transistors were chosen almost at random – the 2N2222 because it was there, and the BD137F pass transistor because it had the closest Vce(max) / maximum current handling capacity combination to the L200 of all the transistors currently in my transistor library. Even less thought was put into resistor selection, since the value of neither is especially critical to the operations of the circuit I wished to simulate.
A simple test circuit (for reference in further discussion) is shown in Figure 2:
A wise man once said, “Don’t trust any version under 2.0”, and if ever there was a place where that maxim applied, it’s here. In its current Version 1.0 form, this macromodel models the following:
- The voltage regulation equation given in the L200 datasheet, specifically:
V(OUT) = (1+R2/R1)
where R1 and R2 are the feedback resistors shown in Figure 2.
- The user-adjustable current limiting equation, also as (sort of) given by the L200 datasheet:
I(OUT)MAX = 0.45/R3
where R3 is the current sense resistor shown in Figure 2.
…and that’s it. Some of the many limitations of this model include:
- Absolutely no thought has been given to loop stability. It doesn’t oscillate in the circuit of Figure 2, nor in the slightly more complex heater regulator circuits I’ve been simulating which cause the current limiting to kick in, but that’s probably due to sheer luck more than anything else.
- While the user-selectable current limiting is modeled, the built-in current limiting (3.6A max) of the L200 is not modeled in any way. The model’s maximum current will be limited by the Q1 model, which as shown is a BD137F. Short-circuit output current of the macromodel simulates out to about 1.9A, considerably lower than the spec.
- Dropout voltage simulates out at about 1.5V, which is about half a volt better than the typical value listed in the datasheet.
- I haven’t even looked at such things as line or load regulation. They are probably considerably better in this model than in the real component due to the use of idealized opamps.
- I have also not looked at quiescent current, which I’m sure is wildly off.
So, there you have it, a macromodel for the L200 Voltage Regulator that’s better than any other you can’t find on the Internet ;-). Let me know if you find this useful, or if you have any ideas for improving the model’s fidelity.
Until next time, I remain,
Gary R. Van Sickle
President and CEO/Editor/Head Writer
The Shorted Turn
2013/03/21 at 10:51 AM
I am trying to create the l200 regulator for multisim student addition and need the spice model.
If this is what yall are refering to Can you send me a copy.
LikeLike
2012/10/24 at 6:28 AM
Hi Gary.
I wanted to simulate a Lithium Ion charger with the L200. Your model was very helpful, unfortunately the current limit was not working properly for me. So I changed a bit and eventually got it working.
Here is an example circuit, limiting voltage to 4.2V and current to 1A. The battery is simulated by a stepped resistor. Did not make any transient simulations, though.
Regards,
Lasse
Version 4
SHEET 1 2244 680
WIRE 1024 -320 512 -320
WIRE 192 -144 -368 -144
WIRE 256 -144 192 -144
WIRE 352 -144 256 -144
WIRE 800 -144 448 -144
WIRE 832 -144 800 -144
WIRE 944 -144 912 -144
WIRE 1232 -144 944 -144
WIRE 1600 -144 1232 -144
WIRE 800 -80 800 -144
WIRE 256 -48 256 -144
WIRE 400 -48 400 -80
WIRE 400 -48 352 -48
WIRE 1232 -48 1232 -144
WIRE 1600 16 1600 -144
WIRE 192 32 192 -144
WIRE 736 32 192 32
WIRE 1152 32 736 32
WIRE 304 96 304 16
WIRE 624 96 304 96
WIRE 736 112 736 32
WIRE 944 128 944 -144
WIRE 944 128 768 128
WIRE 704 144 688 144
WIRE 192 160 192 32
WIRE 800 160 800 0
WIRE 800 160 768 160
WIRE -176 176 -240 176
WIRE 160 176 -176 176
WIRE 304 192 304 96
WIRE 304 192 224 192
WIRE 160 208 80 208
WIRE 512 208 512 -320
WIRE 1024 208 1024 -320
WIRE 1024 208 512 208
WIRE 1152 208 1152 32
WIRE -368 224 -368 -144
WIRE 1600 224 1600 96
WIRE 1600 224 1184 224
WIRE 1712 224 1600 224
WIRE 1120 240 368 240
WIRE 1232 256 1232 32
WIRE 1232 256 1184 256
WIRE -176 272 -176 176
WIRE 80 272 80 208
WIRE 1712 304 1712 224
WIRE -368 448 -368 304
WIRE -176 448 -176 352
WIRE -176 448 -368 448
WIRE 80 448 80 352
WIRE 80 448 -176 448
WIRE 192 448 192 224
WIRE 192 448 80 448
WIRE 304 448 304 288
WIRE 304 448 192 448
WIRE 624 448 624 192
WIRE 624 448 304 448
WIRE 736 448 736 176
WIRE 736 448 624 448
WIRE 1152 448 1152 272
WIRE 1152 448 736 448
WIRE 1712 448 1712 384
WIRE 1712 448 1152 448
WIRE 1600 480 1600 224
WIRE 192 496 192 448
WIRE -240 576 -240 176
WIRE 1600 576 1600 560
WIRE 1600 576 -240 576
FLAG 192 496 0
FLAG 1712 224 batt
SYMBOL npn 352 -80 R270
SYMATTR InstName Q1
SYMATTR Value 2N3055
SYMBOL Opamps\\UniversalOpamp2 192 192 R0
SYMATTR InstName U1
SYMBOL Opamps\\UniversalOpamp2 1152 240 M0
SYMATTR InstName U2
SYMBOL voltage 1232 -64 R0
WINDOW 123 0 0 Left 2
WINDOW 39 24 124 Left 2
SYMATTR InstName V1
SYMATTR Value 0.45
SYMBOL voltage 80 256 R0
WINDOW 123 0 0 Left 2
WINDOW 39 24 124 Left 2
SYMATTR InstName V2
SYMATTR Value 2.77
SYMBOL res -192 256 R0
SYMATTR InstName R1.
SYMATTR Value 1k
SYMBOL res 1584 464 R0
SYMATTR InstName R2.
SYMATTR Value 500
SYMBOL res 1584 0 R0
SYMATTR InstName R3.
SYMATTR Value 440m
SYMBOL voltage -368 208 R0
WINDOW 123 0 0 Left 2
WINDOW 39 24 124 Left 2
SYMATTR InstName V3
SYMATTR Value 7.2
SYMBOL res 1696 288 R0
SYMATTR InstName batt
SYMATTR Value {RLOAD}
SYMBOL npn 256 16 R270
SYMATTR InstName Q2
SYMATTR Value 2N2222
SYMBOL npn 368 192 M0
SYMATTR InstName Q3
SYMATTR Value 2N2222
SYMBOL res 928 -160 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 10m
SYMBOL Opamps\\UniversalOpamp2 736 144 M0
SYMATTR InstName U3
SYMBOL voltage 800 -96 R0
WINDOW 123 0 0 Left 2
WINDOW 39 24 124 Left 2
SYMATTR InstName V4
SYMATTR Value 20m
SYMBOL npn 688 96 M0
SYMATTR InstName Q4
SYMATTR Value 2N2222
TEXT -400 584 Left 2 !.op
TEXT 1728 400 Left 2 !.step oct param RLOAD 1 100 10
TEXT -40 -160 Left 2 ;1 – IN
TEXT -56 424 Left 2 ;3 – GND
TEXT 1304 -168 Left 2 ;5 – OUT
TEXT 1304 200 Left 2 ;2 – CURRENT
TEXT -48 160 Left 2 ;4 – VOLTAGE
TEXT 656 -272 Left 2 ;Internal Current Limit
TEXT 672 -240 Left 2 ;V4=20m equals 2A
(EOF)
LikeLike
2012/07/04 at 7:03 AM
Hi!
Please can you share your model with me?
I have to design a circuit with an L200.
ThanX
Rick
LikeLike
2011/04/20 at 2:32 AM
Hi,
I’m also interrested in the model file mainly as a starting point for an l200 model that I can than refine if need be…
Like you say, it is burdensome to transcribe it just from the schematics…
I would like to do some simulations on a variable PSU that uses an L200 to set/limit the A and V.
I find it strange that such a model does not already exist in the LTSpice libraries… do you know why this is so ?
Thx
LikeLike
2010/12/03 at 4:38 AM
Hello!!!
good model!!!
Can you provide a downloadable example file/model?????
LikeLike
2011/01/09 at 6:57 PM
Hi Nicola,
Thanks! Unfortunately, due to the many limitations listed in the article, I don’t really feel comfortable releasing this model in a “ready-to-use” form. If I find the need to refine this model further, I probably will release the model files, as it will quickly become burdensome for my readers to easily transcribe the model from just the schematic.
LikeLike
2010/01/27 at 9:12 AM
Can you give it an animated icon – so it shows up in the schematic with a bouncing ball in the box or something?
LikeLike
2010/02/05 at 1:28 PM
It’s like you’re reading my mind, Mr. Winker. Unfortunately, I have been unable to convince Linear Technology to add the ability to embed Adobe Flash(tm) into LTSpice(tm) schematics. Unitl they see the light, I am afraid we will have to settle for boring, unanimated schematics.
LikeLike