Module specifies 3.6v max: How do I easily power it from a LiPo?

[poodyp]

I'm going to try using a Microchip MRF24J40MA in a project, and in the datasheet it states a min-max voltage of 2.5 to 3.6. I'm going to be powering some 3v motors, and I'd like to be able to use a LiPo for density, weight, and compatibility with the motors.

So what's an easy way to drop 4.2v to 3.6v while also keeping it powered to 2.5v?

Thanks.

[T4P]

Use LiFEPo4.
Or you can use a buck-boost converter

[amyk]

Looking at the datasheet for your device it's really designed for 3.3V and draws <50mA so a 50mA 3.3V LDO should be sufficient.

If those "3V" motors are the standard brushed types, they'll probably be quite fine with 4.2V (which you get only from a fully charged cell.)

[poodyp]

Use LiFEPo4.
Or you can use a buck-boost converter

Most LiFEPo4's have a pretty flat discharge curve so that'll probably work, I'll just need to look for some charge controllers.

I've been looking for info on buck-boost converters, but there isn't much to be had. So far I've found the LTC3444 and TPS53020/30, but other than datasheets I can't find much.

Looking at the datasheet for your device it's really designed for 3.3V and draws <50mA so a 50mA 3.3V LDO should be sufficient.

If those "3V" motors are the standard brushed types, they'll probably be quite fine with 4.2V (which you get only from a fully charged cell.)

Anything besides maximum current and lowest dropout I should look out for? Am I wrong in assuming this doesn't have a minimum load current like an LM317?

[RCMR]

I've been facing the same problem recently -- how to run a 3.3V device from a single-cell lipo (3.1v - 4.2V)

I thought of using a shunt regulator (anyone remember those) but figured it would be an awful waste of the meagre energy resources on offer.

I looked at LDO linear regulators but once the battery voltage got to 3.4V or so then the regulator would no longer be "regulating"

So I opted for a boost/buck converter.  More components, more weight, more bulk -- but the ideal solution.

An LiFePO4 cell would have been an option except that 3.6V was too high for this device (absolute 3.3V maximum) and besides which, I couldn't find an LiFePO4 cell with a small enough capacity (or low enough weight) for this application.

[T4P]

Ahh, shunt regulators

[poodyp]

I've been facing the same problem recently -- how to run a 3.3V device from a single-cell lipo (3.1v - 4.2V)

I thought of using a shunt regulator (anyone remember those) but figured it would be an awful waste of the meagre energy resources on offer.

I looked at LDO linear regulators but once the battery voltage got to 3.4V or so then the regulator would no longer be "regulating"

So I opted for a boost/buck converter.  More components, more weight, more bulk -- but the ideal solution.

An LiFePO4 cell would have been an option except that 3.6V was too high for this device (absolute 3.3V maximum) and besides which, I couldn't find an LiFePO4 cell with a small enough capacity (or low enough weight) for this application.

Have you decided on a controller? I found the TPS63001, which looks to be a TPS63030, but fixed at 3.3v. Only problem is it's $2.5 in single quantity, and I have no SMPS experience.

The amp or so from the motors will dwarf even the extra draw of a shunt regulator powering maybe 40mA, so I'm not too worried about efficiency .