CMOS IC Application Note
S-19902/19903 Series NOISE COUNTERMEASURES
AN
D
CI
S
PR25 MEASUREMEN
T
R
E
SULT
S
Rev.1.0_00
© ABLIC Inc., 2020
1
This application note is a reference describing recommended noise suppression parts and board layouts that help
reduce conductive noise and emission noise for the S-19902/19903 Series. It also summarizes CISPR25 compliant
measurement results.
Refer to the datasheets of the S-19902/19903 Series for details and specs.
CMOS IC Application Note
S-19902/19903 Series NOISE COUNTERMEASURES AND CISPR25 MEASUREMENT RESULTS
Rev.1.0_00
2
Contents
1. Need for Noise Suppression Parts ......................................................................................................... 3
2. Board Layout ............................................................................................................................................. 4
2. 1 Placement of input capacitors (C
IN0
, C
IN1
) and VIN and VSS layouts .............................................................. 4
2. 2 Placement and layout of Inductor (L1) .............................................................................................................. 4
2. 3 Placement and layout of output capacitor (C
OUT1
) ............................................................................................ 5
2. 4 Recommended board layout ............................................................................................................................. 5
3. Measurement Conditions and Measurement Results .......................................................................... 6
3. 1 Measurement condition 1.................................................................................................................................. 6
3. 2 Measurement condition 2.................................................................................................................................. 7
3. 3 Measurement results of voltage method........................................................................................................... 8
3. 4 Measurement results of ALSE method ............................................................................................................. 9
4. Precautions ............................................................................................................................................. 11
5. Related Sources ...................................................................................................................................... 11