Power USB VBUS from 3.7V Lithium battery?

Paul Singh

Other Parts Discussed in Thread: TPS61240, TPS61256, TPS61222

Hi,

We have an OTG USB design, and would like the board to be able to act as USB HOST even when powered only by 3.7V lithium battery.

This means we need an IC to buck-up from 3.7V to 5V for USB VBUS power supply to the USB peripheral. The peripheral is only going to be a USB flash drive and presumably would require much less power than 500mA. Could someone recommend a power IC (the simpler the better) for this purpose?

Additionally, probably we also need a current-limited (to prevent current from exceeding 500mA) switch for this purpose. Does any buck-up power IS also have current limting ability built-in for this purpose?

Paul

over 11 years ago

0 Chris Glaser over 11 years ago

TI__Guru*** 147950 points

The power quick search at power.ti.com can help you find ICs that meet power specs. A few that it should return and the extremely simple TPS61240 and TPS61256.

All power supplies have some sort of current limit in them to handle fault conditions. If this is not sufficient for a given application, then you might want to look at using a USB switch on the output. More information on those is found in the power interface forum.

Finally, I'll note that your battery voltage will vary based on its state of charge. So you'll likely need a boost that can provide sufficient output power at 3.3V or 3Vin.

0 Paul Singh over 11 years ago in reply to Chris Glaser

Expert 2750 points

Chris,

Thanks for suggestins, I found TPS61240 is very good for this.

However TPS61240 has max current 450mA. If my purpose is only to use USB's VBUS to power a peripheral USB flash drive, may I use TPS61222 (200mA limit) ?

And is 200mA enough to drive USB flash disks?

Paul

0 Chris Glaser over 11 years ago in reply to Paul Singh

TI__Guru*** 147950 points

If it meets your needed current, then yes you could use it instead.

But one note on boost converter currents: you need to look into the graphs in the D/S to determine how much output current you can get at your operating conditions. With a boost, this will be less than their switch current limit.

0 Paul Singh over 11 years ago in reply to Chris Glaser

Expert 2750 points

Chris,

This is from SLVS776 TPS61222 DS:

It appears for even when the battery is depleted (down to 3.3V), the maximum output current is still over 150mA. Does this warrant its use for powering USB flash drives?

Paul

0 Chris Glaser over 11 years ago in reply to Paul Singh

TI__Guru*** 147950 points

You will need to determine how much current your load requires.

0 Paul Singh over 11 years ago in reply to Chris Glaser

Expert 2750 points

I see it. Thanks.

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Power USB VBUS from 3.7V Lithium battery?