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LM358A for high-side current sensing

H

Hammy

Jan 1, 1970
0
I'm using an LM358A for high-side current sensing. I would like to be
able to use the other OP in the so-8 package as a thermal shutdown.
This means that both outputs would be connected to the same point R9&
R8 junction on the schematic. Q1 &Q2 are really a dual prebiased
MUN5311DW1T1-D I'm using as a latch.

Schematic

http://i37.tinypic.com/2z9csja.png

My question is do I have to place blocking diodes on the output of the
OP'S. If one output goes high it will place Vcc-1.5V on the output of
the other OP will this damage the OP?



I don't have any LM358A's on hand but I would like to be able to test
it with maybe a TLC27L2 so the same question for this OPAMP.

Thanks
 

neon

Oct 21, 2006
1,325
Joined
Oct 21, 2006
Messages
1,325
how are you going to get [-] anything out of your circuit ii see vcc and gnd. why try to reinvent the wheel try lm317 aand throw this away.
 
J

Jamie

Jan 1, 1970
0
Hammy said:
I'm using an LM358A for high-side current sensing. I would like to be
able to use the other OP in the so-8 package as a thermal shutdown.
This means that both outputs would be connected to the same point R9&
R8 junction on the schematic. Q1 &Q2 are really a dual prebiased
MUN5311DW1T1-D I'm using as a latch.

Schematic

http://i37.tinypic.com/2z9csja.png

My question is do I have to place blocking diodes on the output of the
OP'S. If one output goes high it will place Vcc-1.5V on the output of
the other OP will this damage the OP?



I don't have any LM358A's on hand but I would like to be able to test
it with maybe a TLC27L2 so the same question for this OPAMP.

Thanks
I would feed the R4 Via the extra OP-AMP. Also, I don't think you'll
get a full high side out on this op-amp. This may not be a problem in
your case how ever since the normal operation of your circuit would
require it to hold the output low in which case it looks like it should
do well.
I would how ever, use a hysteresis feed back in the (+) input to make
sure you don't develop a linear region at the critical point, this could
upset the current regulation a bit unless you don't want a latching
effect protect circuit.






http://webpages.charter.net/jamie_5"
 
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