LM5156H: LM5156H - Can't get UVLO Low Threshold to work

Tool/software:

Hello guys,

I am designing a boost flyback controller using LM5156HPWPR. So far everything work fine except for the UVLO low voltage threshold is not following my calculations:

My settings are as below:

V_supply(on) = 7.8V

V_supply(off) = 7.0V

By calculations, here are the values I got:

R_UVLOT = 100k

R_UVLOB = 23.2k

From my test, I can get the driver to turn on correctly at +V_BATT = 7.8V. However, the driver will immediately stop driving when the voltage drops to +V_BATT = 7.7V and below.

What is the issue here?

I have done the following:

1. Reconfirm the values for soldered R_UVLOT & R_UVLOB.
2. Swap R_UVLOB GND to PGND and AGND.
3. Resolder LM5156H IC.
4. Replaced LM5156H IC.

Here's my schematic for reference: