Choosing SMT diodes for LinkSwitch-TN
Hello,
The app note for the LinkSwitch TN chip (buck topology) gives a few model number suggestions for both the freewheeling diode and the feedback diode.
However, they are all through-hole components. I'm looking for good smt alternatives.
For the Freewheeling diode, I'm looking for an alternative to the UF4004. Trr<75ns, >=220V reverse, 1A continuous. I chose the Fairchild ES1F - similar specs, with only slightly higher forward voltage.
However, this is more tricky: What is a good SMT alternative for the feedback diode? The application note says:
For the feedback diode, use a glass passivated 1N4005GP or
1N4937GP device with a voltage rating of ≥1.25 × VMAX
Surely they don't mean that these are the only options. Any suggestions on selecting an alternative?
Thanks!
Comments
Great! That what I'd hoped to hear. I had taken some time trying to find a good smt alternative.
I suspect that the ratings for the 1N4937GP feedback diode are much higher than necessary. 1A, 600V, 200ns Trr, 1.2Vf.
It seems to me that this diode should not have much more than the output voltage across it and never conduct even 1/2A continuous.
With that said, for anyone interested, the Fairchild RS1G seems to be a good choice for a comparable cost.
Thanks for your input!
You need to choose the voltage rating on Dfb to be greater than Vinput. See page 10 of AN37.
http://www.powerint.com/sites/default/files/product-docs/an37.pdf
-The Traveler
The SMT alternatives to the UF4004 and the 1N4005GP are numerous. It will ultimately come down to what SMT package you want. I would start by just pulling up the basic specs of the diodes and then going to Digikey or Mouser and finding SMT versions with similar specs.
-The Traveler