Convert Li polymer to 3.3V and 5V

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Convert Li polymer to 3.3V and 5V

Post by Dunno » Wed Apr 01, 2009 5:55 am

Post by Dunno
Wed Apr 01, 2009 5:55 am

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

Post by Dunno » Wed Apr 01, 2009 5:59 am

Post by Dunno
Wed Apr 01, 2009 5:59 am

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]
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]
Dunno offline
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Posts: 3
Joined: Wed Apr 01, 2009 5:39 am

Post by StuartL » Wed Apr 15, 2009 7:10 am

Post by StuartL
Wed Apr 15, 2009 7:10 am

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.
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.
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Post by Dunno » Wed Apr 15, 2009 8:08 am

Post by Dunno
Wed Apr 15, 2009 8:08 am

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
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
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Post by StuartL » Sat Apr 18, 2009 8:00 am

Post by StuartL
Sat Apr 18, 2009 8:00 am

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