I hate to hear that..I had no luck in finding one in a DIP either.
DIP packages are generally no longer made.
Not deliberately.I hate to hear that..They want to bury the DIY or something??
Okay.A dedicated IC would have been better, because of the built-in calibration. But looks like your solution is the only choice. Btw, it's a 48V battery bank (64V maximum).
The slew rate won't significantly affect the response time since the opamp output voltage change is only what is required to control the MOSFET (a fraction of a volt).Thank you very much for your simulation. As I need a very quick response (short-circuit protection), I'm a little bit concerned about the LT1638 slew rate (0.4V/us). Does it have any effect on the above circuit topology? Also, does the Mosfet affect the output linearity?
Wouldn't be better to put a comparator on the high-side and only translate its output on the low-side (when a short-circuit condition occurs), to drive a realy and to shutdown the power Mosfets (H-bridge) drivers?
Actually, I was thinking of using the opamp as a fixed gain & low offset/drift amplifier (60mV -> 3V) followed by a comparator. The output of the comparator would be translated on the low-side using a BJT or something.Yes, for fastest response to a sudden overload you could use a rail-rail comparator.
The realy is used to disconnect the main 230V loads (most probably, the cause of the short-circuit). But, like I've just said, I'm using the comparator output signal to shutdown the H-bridge MOSFETs drivers (this is where I need a very fast response).But if you are concerned about speed you certainly don't want to use a (mechanical) relay to shut down the MOSFETs.
The bridge MOSFETS will be long gone before the relay even starts to operate.
Okay.Actually, I was thinking of using the opamp as a fixed gain & low offset/drift amplifier (60mV -> 3V) followed by a comparator. The output of the comparator would be translated on the low-side using a BJT or something. .............
Looks okay.........What do you think about this design?
View attachment 140463
Could it be faster?
I hope I could get a higher slew rate comparator and a high frequency BJT with very low propagation delays.
Yes, that's what the simulation shows..............
With your proposed circuit, I could get 5us propagation delay at the low-side resistor terminals?
Make sure you add some decoupling capacitors to the power, such as 0.1µF ceramics between the opamp and comparator plus power pins to ground (don't add one to the minus opamp pin or you will zap the op amp).That's perfect! I've already start designing the pcb.
........................... I'll post few scope screens when it's finished.
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