UCC2894: Initial Testing of UCC2894D

Hi, 

Thank you for the reply. 

Observations are as follows:

1.  VREF is about 5V;

Vref = 5.1V generated  (pin number 4)

2. OV and UV threshold are within the normal range

 LineUV= 1.31V generated  (pin number 15)

LineOV= 0.95V generated  (pin number 16)

3. CS pin voltage is low;

0V at CS pin

4. SS pin voltage is normal

It is low value, 0.95V is obtained at SS/SD pin (pin number 10)

5. FB voltage is high

2.2V is applied using external power supply. 

As per datasheet, SS pin voltage is 1.25V to 4.5V, but the generated voltage is below 1.25V. Please suggest if any modifications are required. 

Thank you

Umamaheswararao

Hello,

SS pin need be higher voltage than 1.25V. How many devices did you test? 

Thanks,

Hi, 

I have tested three devices, I have observed the same and the corresponding waveforms are given below

Vref and SS signals

Please suggest. 

I think something wrong with SS pin. It tries to ramp up but couldn't ramp high enough. OV/UV voltage look ok. I am not sure why SS ramps down.

Can you try to increase RTON? RTON produces current for SS charging current.

Hi,

Thank you for your inputs. I have increased the VDD capacitance to 220uF, Now, SS pin charged to 5V and at OUT pin pules are OK and varying duty ration with Vfb.

Thank you

Umamaheswararao