LMZ22008 Audible noise

Grant Downie2

Other Parts Discussed in Thread: LMZ22008, LMZ22005, LMZ22003, TPS62130, TPS84A20

Dear Sir/Madam,

I am using various Simple switcher parts:

2x LMZ22008 (master/slave) +1V0
1x LMZ22005 +1V5
1x LMZ22003 +1V8
1x LMZ22003 +2V5
1x LMZ22008 +3V3
1x TPS62130 +3V6

There is audible noise coming from what appears to be the LMZ22008 used on the +3V3 supply.
Each supply has a ferrite bead and filter capacitors on the +12V input side.
The layout, schematic and input/output capacitors are in accordance with the datasheet.

Before i start isolating each supply and running load tests are there any pointers on what could
cause this type of instability.

I can provide layout and schematic information.

Regards Grant

over 11 years ago

0 YangZhang over 11 years ago

TI__Genius 11085 points

Hi Grant,

Could you provide sch, layout and BOM for the LMZ22008 with 3.3Vout? Also what is the load level when you hear the audible noise? Was it there with any load or just a narrow range of load?

Thank you,

Yang

0 Grant Downie2 over 11 years ago in reply to YangZhang

Intellectual 390 points

Hi Yang,

Thank you for the response.

As there are so many simple switchers in the same area it is difficult to know exactly which one is causing the problem as i cant probe the SW node. Order is left to right +3V3, +1V8 and +1V5 (have not shown +1V0, +2V5 or +3V6).
All loads are low at this stage of testing because other circuitry ie. FPGA, ADCs not running.