I have a project I'm working on, that amongst other things monitors a battery pack (voltage can be between 50-100V). What is the best way to get 5V from this high voltage to power the monitoring circuit? Obviously a regular voltage regulator (7805 etc) will not work as the input voltage is too high. The circuit's total current draw will be around 150-200mA. Even with this current draw, that's a LOT of heat to dissipate with the big voltage drop.
I have found a few components, e.g. 5283 & TL783 that can handle the input voltages, but I have very limited space so not much room for heatsinks. Any ideas?
I've avoided switching regulators up to this point, as the implementation usually takes a lot more components, but this is actually a good option if I can get the power suppply circuit small enough. The switching reg will definitely avoid the heat generated by the linear regs.
If the input voltage was limited to 72 volts the Linear Technology LTM8008 would be a candidate for a very simple switching regulator.
Another option is to build a switching regulator, but there will be much more of a learning curve. If you are operating in the world of 7805 regulators the jump to your first switcher is a long one. 100 volts to 5 volts is quite a voltage transformation for a Buck regulator as the switch ON time will be only 5% of the cycle period. Another topology such as a Flyback might be more attractive.
And if you don't mind burning 20 watts a simple series pass regulator can be used. A circuit as simple as a TL431 and two transistors will do the job. Current limiting can be added with a third transistor. If you'd like a schematic I will post it here.
I know this doesn't fit the entire range, but RECOM make a switching regulator that can accept between 9V and 72V (75V absolute max). It is a module so there is no other components or heatsink needed. You just drop it in. R-78HB5.0-0.5.
It has 17.5 x 11.5 x 8.5 mm dimensions, horiztonal or vertical orientation.
One part that does cover your range is an isolated DC/DC converter, so I don't know if you have enough space to fit a DIP24 (through hole or SMD). RP08-11005SAW.
Digikey stocks has a possible candidate in the Vicor V72C5C100BL.
Input 43-110 V
Output 5 V
Output current 20 A
Voltage Isolation 3 kV
2.28" x 1.45" x 0.62"
Digikey stocks another off-the-sheld solution in the Power-one 70IMX4-05-8. Note that this part is not in stock and the minimum order is 25.
Input 40-121 volts
Output 5 volts
Output current 350 mA
Voltage isolation 2 kV
24-Dip module, 1.30" x 0.79" x 0.33"