Hello
My customer have a question following.
Would you please advise?
*** Question***
Q1 UVLO setting p13 eq(1) eq(2) is satisfied in case with external VCC only ?
Q2 also, internal 10uA Hysteresis current source supplied from VCC?
Q3 Customer want VOUT=28V in the actual design. So, customer cannot connect from VOUT to VCC by diode.
Please advise how to set RUV1 and RUV2 in case no external VCC supply.
*******************
Background of question
Customer had tested the UVLO function using LM5121EVM .
Customer want to set VHYS=1V, VIN(STRATUP)=5.64V , VIN(shutdown) = 4.64V, VOUT=12V( default ), also, not connect from VOUT to VCC.
R10 0ohm → removed ( use internal LDO )
R16 365kΩ → 100kΩ
R21 107kΩ → 27kΩ
Increase VIN = 0 to around 8V , then decrease to 0V using lab power supply, Monitor switching output (LO).
Result: Start Up voltage: 5.58V---OK ( almost 5.64V) Shutdown voltage: 4.06V---No Good (not 4.64V)
Then ,customer chaged R10 as inserted (EVM default): Shutdown voltage is :4.50V , and its OK
Please advise
Best Regards
