LNK304 -5v Problem
Hello
I designed these values for a -5v supply ,where return or Neutral is Vcc.
I have F/b Resistors R3(2k) & R6(4k7) so that i get 5v but what i actually get is 4.45v.
When i try to increase this voltage by changing the F/b resistors ,the LNK goes out of regulation and i get voltages close to zero.
Why is this?..is something wrong with the design?
Please help
Thanks and regards
EDIT: When I can easily regulate & reduce the o/p voltage to 3.3v but cant increase beyond 4.5v
Comments
Hello Sudarshana
Thanks for replying.
As u can see in the attachment that i have 4.7k & 2k as the resistors which set the voltage at 5v but i get 4.45v.Now i increased the 4.7k to 5.1k and next by 1k to 5.7k thats where it restarts (i think).Why is this happening
pl reply
Can you measure the voltage across the feedback pin? It should be 1.65V.Why dont you try 3.9k instead of 4.7k?
Hello
When i reduce the feedback resistor from 4.7k to lesser values,i get lesser voltage.I get 3.3v when i put 4.7k across the 4.7k (2.35k)..Also when i designed it for +5v i did get that voltage..Its a problem with -5v
pl get back
have you measured the feedback pin voltage?
Hello
The problem is solved.The o/p supply was getting an unsual short ckt. path through a pair of diodes.My mistake.
Its working now.
Thanks for the support and concern anyways.. :)
What resistor values you have tried?