LTC3407A-2 as dual dcdc converter wrong voltage

Status
Not open for further replies.
O

onoffman

Member level 3
Joined
Feb 9, 2010
Messages
56
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,727
Refer to the circuit **broken link removed**

I am using the same except r4=887k and r3= 197k for getting 3.3V
and r2=887k and r1=442k for 1.8v

Vout is given by 0.6(1+r2/r1) volts and 0.6(1+r4/r3)


I have soldered the DFN10 pack chip and after that i am using this as a source for tests

9v batt>Lm7805>"LTC3407A-2 circuit"


But I am getting 1.4Volts and 3.4v. second one seems ok but the first voltage is way too low .. i used 1% tolerance resistors .
Please help me ,what may be the reason of low output? How to test it .
 

Begin by looking at the feedback pin voltage. If that's in
spec (bearing in mind that megohm meter input impedance
could bend the answer by over 10%, given the values
you used) then it's an external tolerance problem, a ground
offset, or something.

At that high an impedance things like ESD protection leakage,
input bias currents (if non-CMOS), even flux residue on the
board can all cause low-level grief. You might consider
knocking every one of those resistors down 1 decade
and see if things tighten up. Until the feedback ladder power
approaches 10% of no-load supply power, you're not doing
yourself any favors by using higher values.
 

    O

    onoffman

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…