Hi & tnx!
No;
C53 is not (only)to filtering the ripples needed, but more, and to first (with L10) is your only energy storager if the "switch is changing over"...
It MUST BE tenth of uF, practically 47uF & a good, low ESR type_I think these is yours Nr.1 failure! Than the C50 the second failure: its value is too high! :-( Select pls. one at 470pF instead drowed 0.47uF! Pls refer to pages 11 & 21.
Good progress!
K.
Hi Youngs,
Interesting! :-(
Than is maybe LT`s support to call...
Otherwise I would test it in steps but yet Im not on my PC_I dont have a Schema..
As I remember on the schema: it must be possible to check it as an oscillator/ Switch driver and so on, or is it possible that the pin functions are falsh documented?
For me is LT a very serious/accepted producer, but failures are over all possible.
K.
You have grounded the NC pin 7. I don't know what it does, but it may be a test mode pin. Try disconnecting it.
Keith.
Added after 2 minutes:
One other thing - as Karesz pointed out, C53 must be large, not small - 47uF. You said "I have taken L11, C53 and C54, only connected C55 with L11" but that will make it worse! Remove L11 and short it out.
Hi,
Keith has fully right_I have L11 in the answer overseen-sorry! Tnx!
Datasheet tolds us over pin7: "N/C (Pin 7): This pin should be tied to ground."
In all case_it is eventually a good idea to experiment with them to take it from GND...
K.
Added after 12 minutes:
Keith,
maybe you have really right with pin 7_I found a "Ref design", that has it NC!!
Second difference to datasheets circuit:
Run pin is over a 100K on the control voltage... http://cds.linear.com/docs/Reference Design/dc1313A.pdf
K.
Hi
@EDA_hg81, ,tnx!
@Keith & all,
its a good question, & as I wrote some earlier; C50?
Its 1000x higher value on the drowing is a possible problem for the amp too.
Otherweise was a news from "EDA_Hansi" over same problems :-(
@EDA_Hansi;
Whats your circuit Hansi?_ in details pls.
K.
I think you really need to be probing the circuit with an oscilloscope. Look for signs of switching the MOSFET gate. Look at the feedback pin.
What load do you have?
Are you using a bench power supply to power it? If so, does it have a current limit and what is it set to? Sometimes the surge current on DC-DC converters is quite high on switch-on so they can current limit if you set it too low.