LMR36006: heavy acoustic noise

christopher Krug

Prodigy 30 points

Part Number: LMR36006
Other Parts Discussed in Thread: LM5165

Hi,

I'm getting started working with LMR36006BRNXT on a PCB prototype.

I'm hearing acoustic noise.

Here my specs:

Vin: 13-40V
Vout: 5V (LDO with SMF is needed)
Iout: 0.05A

I tried inductor: WE-LQS-4025 footprint with 47µ or 100µ.

Any advises for better Design?

Regards
Christopher

over 6 years ago

0 Timothy Hegarty over 6 years ago

TI__Guru 72622 points

Hi Christopher,

The LMR36006 is rated for 600mA, so it will be in pulse skipping mode at 50mA. Please send the PCB layout for review.

Also, another option is the LM5165 as this is a lower current converter with adjustable current limit.

Regards,

Tim

0 Timothy Hegarty over 6 years ago

TI__Guru 72622 points

Also, this Wurth inductor is effectively unshielded. Try using a shielded or molded inductor construction more robust to the possibility of acoustic noise.

0 christopher Krug over 6 years ago in reply to Timothy Hegarty

Prodigy 30 points

Here the PCB:

Transparent:

L1 with GND-Poly:

L2 with GND-Poly, Vin:

L3: with GND-Poly and Vin:

L4 with GND-Poly and Vsense:

L5 with GND-Poly:

L6 with GND-Poly:

Thanks

Regards
Christopher

0 christopher Krug over 6 years ago in reply to christopher Krug

Prodigy 30 points

I'll try WE-MAPI 4020 Series.

Some hints for the Layout?

I tried to follow the layout recommendations in EVM and datasheet but i'm not sure how do it the best way in a 6-Layer Bord.

Regards
Christopher

0 Marshall_Beck over 6 years ago in reply to christopher Krug

TI__Mastermind 35210 points

The layout guidelines in the datasheet (http://www.ti.com/lit/ds/symlink/lmr36006.pdf), as well, the EVM will translate directly to a successful design on a 6-layer board.

The layers of the PCB that can often be seen to be most critical would be the component layer and the layer underneath, assuming that is the return path (ground layer) for the device.

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LMR36006: heavy acoustic noise