0
\$\begingroup\$

i working on 3W DC to DC boos converter using LM2733YMF IC

Specs are- Vin- 12V Vout- 36V, 100mA FSW- 600KHz

Schematic and components selected as per WEBENCH design tool. find attached file

enter image description here board work fine without load all parameters ok like SW, FB, SHDN, VIN.

but when i test with load suddenly after suppy turning ON IC get damage due to spike at SW pin.

Any suggetion..?

\$\endgroup\$
9
  • 1
    \$\begingroup\$ Probably the ringing at SW is exceeding 40V. Show your setup with complete schematic and part values. \$\endgroup\$ – Rohat Kılıç Sep 26 '20 at 6:46
  • 2
    \$\begingroup\$ I see the schematic but the diode's P/N is missing. We can't estimate what diode you used. TI Webench suggests CD214A-B150LF but you may not have this at hand. So maybe you've put an alternative and maybe it's slow. Who knows? That's why I said "complete schematic with part values". Also, you still didn't show the setup i.e. how you hooked up the circuit. Please note that the IC does not have an on-board snubber for the internal NMOS, so the performance depends on the layout. You may expect the SW node voltage to be 30.5V but it can jump to as high as 50+V. \$\endgroup\$ – Rohat Kılıç Sep 26 '20 at 7:23
  • 1
    \$\begingroup\$ Are you testing it with a load at all times? \$\endgroup\$ – Andy aka Sep 26 '20 at 8:00
  • 1
    \$\begingroup\$ What is the load? \$\endgroup\$ – ocrdu Sep 26 '20 at 8:49
  • 1
    \$\begingroup\$ Show layout. Show oscillogram of said spike at SW pin. \$\endgroup\$ – winny Sep 26 '20 at 8:56
0
\$\begingroup\$

If the coil is physically too small and it saturates with the load on, the SW can be damaged from the high current. Without load the coil doesn't saturate because of the short switch on time. If the diode is slow then the spike without load is higher and more risk of damage, so it's not likely the diode.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.