Other Parts Discussed in Thread: LMR14050, LM61460-Q1
Hi Team,
My customer now use LMR14050 to convert 12V to 3.375V. The point of load(POL) in LMR14050 are BUCK and PMIC, which means that LMR14050 has two loads, BUCK and PMIC.
The output current of LMR14050 is 2.67A(RMS), 1.8-4.23A(Peak-Peak)
Customer target noise need to lower than 3% (scope 20M band width) and 5% (scope 250M band width) of output voltage, so the values are as following, 101.25mVpp and 168.75mVpp.
However, the test result of customer are 219.1/182.7>101 and 251.2/241.9>168.
When testing to get the result, customer test the output of LMR14050, use AC coupling, and use 3 minute afterglow function of oscilloscope to get the noise value when fulling of load(POL1 and POL2).
Also customer use the standard test method: probe and earth ring.
It seems that the noise results are much higher than the target. May I ask for some advice?
Here is the SCH.LMR14050.pdf
|
Power network |
Voltage（V） |
Test point |
Target noise＜3％（mVpp） 20MHz |
Target noise＜5％（ mVpp ） 250MHz |
Noise/ mVpp 20MHz |
Noise/ mVpp 250MHz |
|||
|
MIN |
TPY |
MAX |
|||||||
|
VPH_PWR(U501)BUCK |
3.13 |
3.375 |
3.47 |
C504 |
3.375*3%=101.25 |
3.375*5%=168.75 |
219.1>101 |
251.2>168 |
POL1 |
|
VPH_PWR(U4)PMIC |
3.13 |
3.375 |
3.47 |
C48 |
3.375*3%=101.25 |
3.375*5%=168.75 |
182.7>101 |
241.9>168 |
POL 2 |
