I need an LDO to reduce 36V-52V down to 30V. It is not really a critical application and current draw is very low, >5mA. Any ideas?
36v as a minimum input down to 30v isn't really low dropout territory. Your load current is small. If you can meet the minimum current requirement the LM317AHV could be ideal. It is the high voltage version of the LM317 adjustable regulator. It has a minimum load current for correct operation and 5 milliamps is just about there... any shortfall can be made up by appropriate choice of the two voltage setting resistors.
1) no LDO needed, what for?
You have 20V leeway!
2) you shun resistor + Zener which is proper for meager 5mA load but if you wish you van use an LM7815 with a 15V Zener between its ground/sensor leg and ground.
3) Rube Goldberg is your friend: you can drive a 50V motor which will then drive a 30V generator.
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You have 20V leeway!
2) you shun resistor + Zener which is proper for meager 5mA load but if you wish you van use an LM7815 with a 15V Zener between its ground/sensor leg and ground.
3) Rube Goldberg is your friend: you can drive a 50V motor which will then drive a 30V generator.
If a zener is too simple for you, you can opt for a varicap regulator: it looks physically similar, but is a notch above with greatly improved characteristics, lower dynamic resistance, better stability, lower tempco etc.
Their voltage selection ranges from ~25V to 35V, thus you should be able to find a 30V one relatively easily.
Examples: https://www.radiomuseum.org/tubes/tube_tda1550.html
If you want to handle a wide input voltage range whilst consuming a minimal input current, the series resistor can be substituted with a simple CCS, transistor-based or also a current regulator diode, in the same form factor.
It will also improve the already excellent regulation
Their voltage selection ranges from ~25V to 35V, thus you should be able to find a 30V one relatively easily.
Examples: https://www.radiomuseum.org/tubes/tube_tda1550.html
If you want to handle a wide input voltage range whilst consuming a minimal input current, the series resistor can be substituted with a simple CCS, transistor-based or also a current regulator diode, in the same form factor.
It will also improve the already excellent regulation
I remember those, the venerable 33 volt regs used for varicap tuners in CTV's. Slightly OT but it brings back memories. We had a whole batch of new Toshiba flat screen TV's and all had massive tuner drift out of the box. It turned out the ZTK33B that should have been fitted was in fact a IN4148 😱
In this case an LDO is the opposite of what is needed. An LT783 (below 2 Euro a piece) will do with below 5V dropout voltage at less than 15 mA. A high(er) voltage regulator may come in handy, certainly when power on peak voltages are higher than 52V. Bonus is that any LM317 small PCB can be used as the pinout is the same. It always helps to predefine some requirements like the possible need of the PSU being short-circuitproof. Most simple solutions are not that simple when that is required. Using obsolete parts is fun to those that like to solve puzzles/have all the time/are sitting on stockpiles of old stuff 🙂
Please note that many regulators need a minimum load current to be able to regulate correctly. With less than 5 mA load current you could add a power on LED glowing at a few mA. My standard is 2.5 mA with modern green LEDs otherwise the whole room is lit.
Edit: did not read post #4 but please add the LED just in case.
Please note that many regulators need a minimum load current to be able to regulate correctly. With less than 5 mA load current you could add a power on LED glowing at a few mA. My standard is 2.5 mA with modern green LEDs otherwise the whole room is lit.
Edit: did not read post #4 but please add the LED just in case.
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