Unable to get 1.5V Output Voltage

Saufi said:

I am unable to raise the voltage at that pin. Is there any ways to yield 1.5V output voltage?

What did you try to increase Vout from 1.46v? Did you try to lower R5 by 2%? Lower the feedback will increase Vout.

Saufi said:

But problem occurs when the output voltage is only 1.46V (400mV offset). Where does this 400mV go to?

400mv doesn't go anywhere.

1.46v is 2.7% less than 1.5v and it is within the spec of the chip. So just adjust R5 to get what you wanted. 

Brian

Saufi said:

I am unable to raise the voltage at that pin. Is there any ways to yield 1.5V output voltage?

What did you try to increase Vout from 1.46v? Did you try to lower R5 by 2%? Lower the feedback will increase Vout.

Saufi said:

But problem occurs when the output voltage is only 1.46V (400mV offset). Where does this 400mV go to?

400mv doesn't go anywhere.

1.46v is 2.7% less than 1.5v and it is within the spec of the chip. So just adjust R5 to get what you wanted. 

Brian

One thing I am curious about is that I have already set the Vout through Iset to be 1.5V, I also set the potential divider at PGFB according to 1.5V output as well. I want to know which pin is the ultimate one that set the output voltage because even though the SET pin has already been configure to 1.5V output, the potential divider at PGFB still affect the overall output voltage. 

Saufi said:

I want to know which pin is the ultimate one that set the output voltage because even though the SET pin has already been configure to 1.5V output, the potential divider at PGFB still affect the overall output voltage. 

The Vout is set solely by the R at SET pin, and the divider at PGFB have nothing to do with Vout. 

Brian