UCC29002: UC39002 for HV application( 28V output) - Rbias1,Rbias2

i get only around 2.8V at VDD pin of UCC39002, i think the IC gets damaged, can anyone let know how to correctly setup this 

Hi thanks for reply,

ok, i will very soon check this and connect a 12V zener for safety,

i see when i connect the controller to 12V VDD without bias resistors, it does not fetch much current, so controller looks to be safe,

the bias resistors Rbias1 also driving transistor, which may be taking some current,and that curretn results in drop across Rbias1 and so voltage gets reduced to very little on Rbias2,

i just randomly picked these values of Rbias1 and Rbias just keep in mind to divide the voltage, but current has to be taken card also,

 can you let know to choose Rbias1 and Rbias2 

should'nt there be a third resistor on transistor base to limit base current

i) i tried with 1K and 470 ohm, and get around 9.05V when ic is powered , out of 4 board two boards i see sharing approx same current, but other two boards totally different results, there is very little output on those modules LS output when powered standalone without sharing, 

ii)in the high voltaeg applicaton with bias resistors, Rbias2 is connected to SNS-, and UC39002 is sensing current below its GND, in datahseet it says upto -0.3V it tolerates, 

my question is that why Rbias2 cannot be connected to VOUT-, so voltage sensed on CS+ and CS- pins is always above its GND terminal

helo sir,

one board working with Rbias1 = 2k8, Rbias2 = 2K

other board is working with Rbias1 = 1K ,Rbias2 = 470E,

i tried to divide 30V by 510E and 510E divider for Rbias1 and Rbias 2, the voltage i see is around 9V, when IC is connected and 

15V when ic is not connected, so 11mA is consumption in this case, i doubt if ucc39002 ic is ok in this case,

the board which is working is working with higher value divider also, 

 i) C37 = 1uF 

i) is it could be beacuse of error amplier compensation also 

ii) do i need to measure crossover frequency as below, set set error amplifier compensation, is there a way to measure this on oscilloscope,spectrum analyzer 

Hi hkul.

I suggest you add the system parameter in the calculator, then we can further discuss this.

there are also excel version on TI.com if you cannot open the mathcad.

1111loadshare_worksheet_web_UCC29002.xmcd

HI thanks for reply, 

the values which i do not knw are cross over frequencies of load share loop and power supplies 

i have excel file with me and filled with parameters that  i know , how i can share excel file with you, is there option to share here 

2086.UCC29002_Calc.xlsx

hi attached file with parameters filled