How to Set Undervoltage Lockout for TPS63001?

[samski]

Hey, i am using one of these ICs to provide a 3.3V power supply from a li-ion battery. it works well but has an undervoltage lockout of 1.8v, much too low for a lithium ion battery.

here is the datasheet:
http://focus.ti.com/lit/ds/symlink/tps63000.pdf

now it says on the pin descriptions that Vina is the control stage supply... this is also the pin that the undervoltage lockout is measured from. so could i create a potential divider for this pin so that when the li-ion voltage drops to ~2.8V, the chip locks out? what should be the minimum input current for this pin? i can't find a value given in the electrical characteristics -there is a circuit on page 11 which uses a 100R to the vina and other pins. using this and a Vin cut off of 2.9, i calculated 61ohms for the paired resistor. but this gives 18ma current leak, a little high if the battery is left for any time... (its a 1Ah)

sorry if this is in wrong forum

thanks for any help

sam

 

[Chandra214]

samski.

Rig up the circuit in your lab and find out the results.
The current shouldn't matter at that pin..
If its going into PCB then provide an option for voltage divider, and check it out
after you get the PCB

 

[samski]

hmm i thought it might being the "power supply for control stage" ill stick a pot on it and ill also try one on EN...