Part Number: LM5085
I have designed a dc/dc converter from 10-60V to 5.00 V @ 1A with LM5085MYX/NOPB
After the build with exact the listed components the supply is working only between 7- 20 Volt
What is the solution our the common design fault that made this happen ?
Do you have the layout for your design?
Generally it is recommended to use similar layout as an EVM especially on the input capacitor, PFET and diode
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In reply to Arief Hernadi:
Thanks for your reply ,
I have enclosed the schematic and the pcb layout.
Everything operates perfect until dc 20V input , then the supply stops.
Hope you can help ..Celmonitor.pdf
In reply to Harm Lok:
It looks like the size of your R15 looks small. Is there anything gets hot when the fault happens?
Harm, has the issue been resolved?
Please let us know if we can be of anymore assistance, or let us know that this issue has been resolved so we dont continue to monitor this thread.
Marshall Beck Texas Instruments, Power Applications
If this response answered your questions/concerns, please click below.
In reply to Marshall_Beck:
Arief is trying to understand if it is a thermal issue or a stability issue.
You have reported that the device stops to regulate above 20V.
One experiment you can do for us to better understand the issue is set the input voltage just below the problem voltage (20V - 1V = 19V) Let the device regulate successfully for about 15min. After that time is elapsed, increase the input voltage just above the problem voltage (20 + 1V = 21V).
After this experiment, please answer the following:
Q1: Did the device stop regulaing instantly after increase the input voltage above the problem voltage
Q2: Did the device stop regulating during the soak time?
Hello Marchall, Arief,
Just want to check the output capacitor type, in your wenbench file, it is bulk cap with 0.65ohm ESR which will be helpful to LM5085 stable. if it is ceramic, it maybe need add external ESR for meet the stability.
if you can share the SW node waveform when Vo is falling at Vin=21V, it will be helpful for us.
Do you still this issue?
Please let us know if we can be of anymore assistance, or let us know that this issue has been resolved so we dont continue to monitor this thread. Thanks!
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