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John Larkin Highland Technology Inc
Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
ON has products along this line too. They all seem to be based on SenseFets. The current limits are a bit large for that 10ish ma range in the original post.
The current limits are a bit large for that 10ish ma range in the original post.
It would be nice of the limit went lower, and was more accurate, but it is self-protecting, and does work up to 20 volts. I've been wanting a good programmable current limiter for years, and this is sort of getting there.
The current limits are a bit large for that 10ish ma range in the original post.
The current limits are a bit large for that 10ish ma range in the original post.
Being realistic, it's not going to be a 2-terminal device. So it has as a minimum 4 pins...
Vin +2.5 to +32 volts range Vout To load Gnd Ilim_set probably a resistor to ground, 0-1 amp maybe
It would have low drop from in to load, except it would current limit and thermal limit. The current limit could be a linear limit, or might be a shutdown/retry. Another pin could select that.
Ilim_set might be 2 pins, for an external shunt resistor, since it's hard to get good milliohm sense resistors on-chip. The current limit should be accurate, 5% or better maybe.
Most existing current limiters are low-voltage, special-purpose USB types.
Another way to look at this would be to call it an LDO, a good voltage regulator, but add a settable current limiter mechanism. We sometimes use voltage regulator chips solely for their current limiting function, when it accidentally hits a limit that we can use. I've used LM317L's for that. Polyfuses have their own problems.
The other family of useful parts would be lower-current (signal level) precise constant-current sources.
I've told LTC and TI and ADI to make these, but for some reason they haven't.
The current limits are a bit large for that 10ish ma range in the original post.
It is quite possible to make a very accurate current source, three pins... external resistor.
But you're looking at 1.25V headroom for the bandgap, so maybe a 2V minimum device. ...Jim Thompson
SenseFets. The current limits are a bit large for that 10ish ma range in the original post.
That's essentially an LM1117 and a resistor.
It would be sensible to add one pin to an LDO, to connect an external shunt resistor, against Vin, as an optional, precise current limit. I wonder why nobody (that I know of) has done this.
nc
eFets. The current limits are a bit large for that 10ish ma range in the or iginal post.
That sounds useful! I'm always playing with the load or supply voltage to make something that won't 'burn out' no matter what someone asks of it.
A minimum current of maybe 10mA would be OK.
I've used some power opamps OPA569 that have a built in current limit.
George H.
.highlandtechnology.com jlarkin at highlandtechnology dot com
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