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Q: TPS61070 UVLO by 1166021
I'm using TPS61070 with single cell NiMH battery(0.9-1.2V). TPS61070 has a UVLO at 0.8V. But as the battery reaches o.8V the device shutdiowns but it starts again as the battery voltage rises due to removal of Load from battery. So it oscillates. They want to shutdown TPS61070 or disconnect the Load from TPS61070 as battery voltage goes below 0.9V. Can I use TPS61028 or a Low voltage opamp(TLV341) and a switch with TPS61070. Is there any other better way to implement this?
A: Re: TPS61070 UVLO by 1090425
Other than using some kind of comparator to drive the EN pin, there is no way around this. The comparator solution is tricky--you don't want to power it from the battery as it will continue to discharge the battery indefinitely. Powering from the output makes starting more difficult without power on the comparator.
I wouldn't recommend the TPS61028 family. Instead, the TPS61220 or TPS61200 are other options. Note that the TPS61220 has a diode from input to output, so the output is always powered. This may or may not be desirable.
A: Re: TPS61070 UVLO by 10449
There are many ways to implement their requested functionality. They need to find a way to add additional hysteresis to their enable function. You can use the TLV341, but you still need an additional reference. Using the TPS61200 is a good option. It works down to 0.3V and has a built in UVLO circuit that is externally adjustable. If you need more hysteresis than the TPS61200 UVLO pin, refer to application notes http://focus.ti.com/analog/docs/litabsmultiplefilelist.tsp?literatureNumber=slva287a&docCategoryId=1&familyId=751 and http://focus.ti.com/analog/docs/litabsmultiplefilelist.tsp?literatureNumber=slva373&docCategoryId=1&familyId=751 for more information
TPS61070 - in the datasheet, figure 26 shows a design for use with white leds. What I'm a little confused about is the led & the text adjacent.
Are you saying that the TPS61070 should only drive one white LED to a maximum of 30mA - or am I interpreting that wrong. I figured that since this IC can deliver up to 150mA output in or around 3.3V from 2 healthy alkaline batteries, that it must be capable of driving more than one white LED at just 30mA?!!
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