Electronics > Projects, Designs, and Technical Stuff
Overvoltage clamp/limiter
ubbut:
Hi,
I have a circuit that needs to run from a 3.3V to 5V power supply and I want to protect it against over voltage. (Should withstand 15V). Current is below 100mA
I am therefore looking for a simple circuit that passes voltage below 5V with a maximum drop of 100mV and Clamps the supply voltage to 5V.
My first thought is to use an LDO, unfortunately most datasheets do not specify operation below the normal output voltage. And when they do (for example MIC5504 or similar) it is only for the 3.3V part, not the 5V part.
I also found other solutions, like the LTC4360, but it turns off the output completely rather then clamping it.
Also found the TPS25200 which looks very good, but seems overkill given its 2.5A max operation. Wondering if there is a simpler and cheaper solution ?
The datasheet also states:
--- Quote ---TPS25200is designed for 2.7 V < VIN< 5 V (typical) voltage rails.While there is a VOUT clamp,it is not intended to be used to regulate VOUT at ~5.4V with 6 V < VIN< 7 V. This is a protection feature only.
--- End quote ---
Might be fine because of the low current I need, but certainly not optimal..
thanks
Jeroen3:
The TPS25200 will clamp until thermal limit. Which may be hit very quickly depending on circuit load. Just like a regular linear regulator.
But I think you are contradicting yourself here a bit.
You want overvoltage protection for a 3-5 Vdc circuit, which suggests there can be a failure condition that you want to harden your circuit against (eg: no damage).
Then you also write that you'd like to keep operating at 15V.
To me it then sounds like you're looking at a circuit which has a 3-15Vdc input that needs a voltage regulator.
There are parts for protection, like the NCP361. (UVLO might not fit here)
But I guess you'd be better of choosing the right power supply strategy with a buck-boost converter for example.
If all you want is to protect during a short non-repetitive temporary overvoltage and keep operating a power resistor and zener diode may be used.
I think you may also abuse an LM317 set at 6V for this, but I never used much LM317, you could also make one yourself with a depletion fet and zener diode.
ubbut:
--- Quote ---To me it then sounds like you're looking at a circuit which has a 3-15Vdc input that needs a voltage regulator.
--- End quote ---
The circuit needs to run at a voltage close to the supply voltage (which can be between 3..5V), but needs to be protected against a failure mode (user connecting it incorrectly).
So a boost, or sepic with a fixed output voltage would not work (because the voltage needs to be matched), neither would any circuit that only protects against short time over voltage.
Jeroen3:
Does it need to remain operational in the failure condition?
ubbut:
--- Quote from: Jeroen3 on June 02, 2020, 11:27:53 am ---Does it need to remain operational in the failure condition?
--- End quote ---
Would be great, but not necessarily
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