LM358A for high-side current sensing
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Posted by Hammy on July 13, 2008, 12:41 pm
Please log in for more thread options 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 | ||||||||||||||||
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Posted by John Popelish on July 13, 2008, 1:00 pm
Please log in for more thread options With that low supply voltage, they probably will not overheat. But you don't have a very determinate situation, either. The diodes are a good idea. > 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. Same answer. -- Regards, John Popelish | ||||||||||||||||
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Posted by Jamie on July 13, 2008, 1:51 pm
Please log in for more thread options Hammy wrote:
> I'm using an LM358A for high-side current sensing. I would like to be
I would feed the R4 Via the extra OP-AMP. Also, I don't think you'll
> 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 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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> 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?