Microchip Voltage Boost regulator

[rocky79]

Hello,
I am trying to build a boost voltage regulator that converts 2.5 v to 5v. So I found the MCP1623 from Microchip and I followed the recomended application on the datasheet.
I made a prototype board following the recommended layout but I am getting an output of 3.5 v instead of 5v.
One thing to note is the that feedback voltage is 0.8 v instead of 1.2 v as mentioned in the datasheet. What's causing this discrepancy?
Schematics attached.

Input voltage is 2.5v
Inductor is 4.7uH
Rtop =976K
Rbottom=309K

<a href="http://obrazki.elektroda.pl/83_1310758637.png"><img src="http://obrazki.elektroda.pl/83_1310758637_thumb.png" alt="83_1310758637.png" /></a>

 

[john blue]

VOUT = 5.0V
VFB = 1.21V
RBOT = 309 k
RTOP = 967.9 k (Standard Value = 976 k)

You may need to get close to 967.9k

 

[rocky79]

Thank you for the reply but doesn't change the output. I believe the problem lies within the feedback voltage of being 0.8 rather than 1.2v