LM2734: big overshoot and undershoot when we insert the power supply

user4822106

Prodigy 100 points

Part Number: LM2734

Hi all,

We have find a big overshoot and undershoot with LM2734 when we insert it to the power supply 5V.

We get the Vboost from the output 3.3V.

over 4 years ago

0 user4822106 over 4 years ago

Prodigy 100 points

0 user4822106 over 4 years ago in reply to user4822106

Prodigy 100 points

The waveform from SW and Boost seems to be some strange.

0 Tahar Allag over 4 years ago in reply to user4822106

TI__Mastermind 29560 points

Hello,

Can you please send me your layout, please make sure C9 is connected as close as possible to the VIN pin. Also, are you using low ESL rating input capacitor as recommended in the data sheet? Here are some SCH and BOM recommendations for 5Vin/3.3VOUT/ 1A.

https://webench.ti.com/power-designer/switching-regulator/customize/3?AppType=BOOST_FROM_SUPPLY&Flavor=NA&O1I=1&O1V=3.3&Topology=BUCK&VinMax=5&VinMin=5&VoltageOption=NA&base_pn=LM2734X&flavor=NA&lang_chosen=en_US&op_TA=30&optfactor=3&origin=ti_search

The VSW plot does not look right, is that plots just during the insertion of the input or during normal operation.

To help speed up our understanding of this issue, if you can plot VIN, VSW, BOOST, and I_Inductor all in one plot so we can see exactly what is going on with all of them. VIN need to be measure tight at the pin of the device.

Thanks!

Tahar

Power management

Power management forum

LM2734: big overshoot and undershoot when we insert the power supply