Part Number: TPS53355
Hi.
We have 2 kinds of power.
First one has over 10ms raising time for power slop.
TPS53355 is working well with this power supply. Vout is ok and PGOOD is asserted.
However, Second one has almost 4~5ms raising time for power slop.
When using this power supply, it will work properly if turned on after the first about 8 seconds or more after the power is turned off. However, if I tunr on after less then 8 seconds after turned off, Vout is ok, but PGOOD is not asserted.
Therfore I tested one more with first power supply.
I added switch on power line.
And I turned on the power supply with the power line switch is off.
After that, I turned on the switch to supply power to TPS53355.
In this case, the power raising time was almost 0.
Then, Vout was ok, but PGOOD was not asserted.
And there is a different problem from second power supply.
With this way, PGOOD is never asserted.
But, If I turn on the power supply with the power line switch is on, Vout is ok and PGOOD is asserted.
It's the same result as the first power supply with out power line switch.
I changed Rtrip to 330K for the OCP.
But, it's the same result.
The Vin is 5V.
VIN and VDD is connected directly.
The EN is connecte to VDD through 100K resistor.
Therefore I delayed EN for 10ms through RC circuit, but it is nor work, too. (The voltage at EN rises to 1.2V for 10ms.)
RF is floating.
MODE is connected to PGOOD through 39.2K resistor.
PGOOD is connected to VREG through 100k resistor.
Please. I need your help.