Power supply question

[cgraf]

Hi everybody

I am stuck with a supply question.
I would like to use the circuit I am working on (it will be an onboard device)
either for electric gliders (2s-5s Lipo) PLUS also for nonpowered small gliders (60") with 4 Nicad or a very small one with 1 Lipo...

One of the sensors needs a supply voltage of 5V (no problem with fully charged battery) but with as less drift as possible.

For the larger 2s-5s configs there is of course no problem, but how do I provide stable 5V output for 3.6-5.x V input?
Power consumption is round 20mA. Looked around step up datasheets, but did not find a nice solution...
Any help ?

Thanks a lot

Christoph

[AndyKunz]

Look for buck-boost converters. They will drop to 5V when above, boost to 5V when below. Many designs get "interesting" when Vin=Vout, so you would do well to make sure your input V is either always above or always below your 5V target on a particular plane. That will give you the wide range you want, without the issues of Vin=Vout.

Andy

[rmteo]

Christoph,

Here is one for you:
• Inductorless, Buck/Boost, DC/DC Converter
• Low Power: 80 μA (Typical)
• High Output Voltage Accuracy:
- ±2.5% (VOUT Fixed)
• 120 mA Output Current
• Wide Operating Temperature Range:
- -40°C to +85°C
• Thermal Shutdown and Short-Circuit Protection
• Uses Small Ceramic Capacitors
• Switching Frequency:
- MCP1252: 650 kHz
- MCP1253: 1 MHz
• Low Power Shutdown Mode: 0.1 μA (Typical)
• Shutdown Input Compatible with 1.8V Logic
• VIN Range: 2.0V to 5.5V
• Selectable Output Voltage (3.3V or 5.0V) or Adjustable Output Voltage
• Space-saving, 8-Lead MSOP
• Soft-Start Circuitry to Minimize In-Rush Current

Less than $2 and you can get a datasheet here:
http://ww1.microchip.com/downloads/en/DeviceDoc/21752a.pdf

[village_idiot]

Is the answer to all these new receiver reboots really as simple as that chip? Would be nice if it would take a higher voltage like 6 to 12 volts, but as a secondary regulator to keep the MCU from rebooting that seems like a decent answer.

[cgraf]

Thanks guys

The microchip solution is a nice idea. Searching for the buck-boost converters sorts also the max877/878. Same thing but needs a coil....

Regards,
Christoph

[AndyKunz]

Is the answer to all these new receiver reboots really as simple as that chip? Would be nice if it would take a higher voltage like 6 to 12 volts, but as a secondary regulator to keep the MCU from rebooting that seems like a decent answer.

If you put an LDO in front you will lose a little at the low end but can run up to the VinMax of the LDO.

Andy

[village_idiot]

You could also be crude and put a zener on it to get within the max voltage.