Hi Sir,
My customer used the LM33630CRNXR and TPS62A02 on the power system.
They heard the buzzing noise from inductor with LM33630C, we also measured the waveform for SW and Vout pins.
Could you please review and share some comments to fix this issue? Thanks!
Test condition:
V-in: 12V
P-out: 5V/3A
Inductor: SPM4020T-1R5M-DZ
schematics:
LMR33630_waveforms
Hi Henry,
Can you zoom in when the SW node turns on? See below:
Try increasing the inductor value to a 1.8uH-2.2uH, reducing the output capacitance and repeat test.
Ben
Hi Sir,
Sorry for the delay in responding, the customer is waiting the vendor to provide the 1.8uH-2.2uH inductors.
They provided the below figure for zoom in when the SW node turns on.
My thoughts on the layout:
1. VCC GND trace should be thicker
2. More vias on the VIN trace (pin2)
3. There is no high frequency capacitor for VIN (pin 10)
4. The bulk capacitance (C4 and C5) should be distributed between both VIN pins, not just one VIN pin.
5. AGND should have more metal and vias.
6. FB to R9 to GND loop should be short to AGND
Below is the layout suggestion found in the datasheet:
Ben
