RoboSavvy Forum

Convert Li polymer to 3.3V and 5V

2009-04-18T08:00:04+01:00

What's the current draw of the circuit and desired run time? What are the size and weight constraints?

Statistics: Posted by StuartL — Sat Apr 18, 2009 8:00 am

Convert Li polymer to 3.3V and 5V

2009-04-15T08:08:48+01:00

Hello
Thanks for your response!

Wanted to use LiPo because it is lightweight, has good energy density compared to others like Ni-Cd, LI-ion etc. Our application demands our circuit to be as compact as possibe.
I was planning to use a buck boost circuit to regulate the output to the 3.3V & 5V and some of the chips can accommodate teh large variation that you mentioned.

Any comments would be welcome.

Tharshan

Statistics: Posted by Dunno — Wed Apr 15, 2009 8:08 am

Convert Li polymer to 3.3V and 5V

2009-04-15T07:10:58+01:00

Do you have a specific reason to use LiPo? It doesn't seem the most logical choice for powering sensors...

You're going to have a serious problem with LiPo for your application as the discharge voltage range is ~3.2 - 4.2v. Given that you need a minimum of 0.6v drop across a regulator the maximum voltage you'll be guaranteed to get is 2.6v.

I suggest instead that you generate 6v from an appropriate power source (if it's just microcontrollers and sensors how about a pair of 18650 cells? That'd give 6.4 - 8.4v with plenty of slack) and use a pair of switching three-pin regulators. A couple of capacitors each side of the regulators would smooth out any interference.

Statistics: Posted by StuartL — Wed Apr 15, 2009 7:10 am

Convert Li polymer to 3.3V and 5V (updated output current)

2009-04-01T05:59:44+01:00

Hello

I am new and not sure if this is the right forum to ask but thought I'd give it a shot anyway.

I am very keen to know whether anyone has used a single Li Polymer battery rated at 3.7V (say @ 1100mAh) to power up 2 separate IC chips that operate at 3.3V supply (@50mA) AND another chip at 5V (@50mA). I have two sensors that I want to power up with a single battery and space, size, weight is an issue thus compactness is very critical.

Is there a single chip that anyone is aware of which can accept this single voltage of 3.7V and give TWO outputs?

The MaximMAX856/857 is a step-up DC-DC converter that can output 3.3V/5V depending upon a digital input on one of the pins but it does NOT give BOTH outputs.

Any help on this matter will be greatly appreciated.

Donkey

p.s
if I should be posting this question here, any pointers to where I should be asking this question will also be very helpful.[/quote]

Statistics: Posted by Dunno — Wed Apr 01, 2009 5:59 am

Convert Li polymer to 3.3V and 5V

2009-04-01T05:55:14+01:00

Hello

I am new and not sure if this is the right forum to ask but thought I'd give it a shot anyway.

I am very keen to know whether anyone has used a single Li Polymer battery rated at 3.7V (say @ 1100mAh) to power up 2 separate IC chips that operate at 3.3V supply AND another chip at 5V. I have two sensors that I want to power up with a single battery and space, size, weight is an issue thus compactness is very critical.

Is there a single chip that anyone is aware of which can accept this single voltage of 3.7V and give TWO outputs?

The MaximMAX856/857 is a step-up DC-DC converter that can output 3.3V/5V depending upon a digital input on one of the pins but it does NOT give BOTH outputs.

Any help on this matter will be greatly appreciated.

Donkey

p.s
if I should be posting this question here, any pointers to where I should be asking this question will also be very helpful.

Statistics: Posted by Dunno — Wed Apr 01, 2009 5:55 am