PRoblem with TPS61130...cannot get 3.3V out of LDO out

Hi All,

I recently made a power supply cct using TPS61130 (see the attached pdf for the schematic) but I only could obtain 5.2V out of the SEPIC converter and only can get that amount out of LDOOUT as well no matter how i tried to change it with the feedback resistors. Any Idea what is wrong here? did I miss something in the cct? helpful feecback is welcome and thank you!

-ISRU

The key is the voltage on the LDOSENSE pin, pin 11. In normal operation, this pin should be at 0.5V. If the voltage is higher than 0.5V, then one of two conditions exist. Either something external to the TPS61130 is pulling the LDO to a higher voltage, or the load current on VDD is so small that the LDO cannot regulate.

If the voltage is lower than 0.5V on the LDOSENSE pin then either the pin is externally shorted to another trace, the voltage divider resistors are bad, or the chip itself is bad. To check for a bad chip, remove all power and allow all capacitors to discharge. Unsolder pin 10 to isolate it. Then check the resistance between pins 9 and 10. This should measure across the internal MOSFET pass transistor. If this reading is low ohms in both directions, then the internal MOSFET is shorted and the chip must be replaced.

I want to make a transformer for ups of 500 watts . I need a formula and core size.

Hi Banjo,
Thanks for your reply! I'll check through and keep you updated =)