Texas Instruments LM53625 QEVM Series, User Manual, Page: 12 / 23

GND
when laying out the board, keep the EMI fi lter away from Switch Node.
IN+
IN-
GND
VIN1
100µF
Cbulk
4.7µF
CF1
4.7µF
CF2
0.1µF
CHF1
0.1µF
CHF2
EMI FILTER
2.2µH LF1
IHLP2020CZER2R2M11
1
2 3
4
LCM
VIN
GND1
IN+
IN-
600 ohm
FB1
4 A 2220
0
R1
0
R2
Copyright © 2016, Texas Instruments Incorporated
Operation and Test Setup
www.ti.com
12 SNVU526 – May 2016
Submit Documentation Feedback
Copyright © 2016, Texas Instruments Incorporated
LM53625xQEVM and LM53635xQEVM User's Guide
5.2 Measure Load Transient
1. Connect power supply to posts VIN1 and GND1 and make sure the power supply can provide
sufficient peak current.
NOTE: There is no reverse polarity protection or fuse on the evaluation board.
2. Connect transient load to posts VOUT and GND. For all power wires use preferable twisted lab wires.
If the power supply wires are very long > 50 cm; solder additional 470 µF, 50 V bulk capacitor to posts
VIN1 and GND1. Use sufficient power wires to avoid voltage drops and use short sense probe
connection for the measurement.
3. To accurately sense the output voltage, the scope probe should be placed directly over the output
capacitors C01 or C02. Make sure to connect scope probe GND ring directly to the output capacitor
GND pad for minimal ground loop. Ground loops can introduce ringing in observed waveforms which is
an artifact; not present on the PCB. Alternatively use differential probe over output capacitors C01 or
C02. Do not use wires to differential probe and always probe directly with shortest possible pins.
Make sure the IC is enabled by having jumper J2 set to [EN-VIN] and check test point EN is driven
high and not drooping during the load transient.
5.3 Measure EMI
1. Connect power supply cable from LISN to posts IN+ and IN- and make sure the board is placed 5 cm
above the table.
NOTE: The length of the LISN cable to VIN+/VIN- should be between 20 cm to 40 cm for conducted
EMI CISPR 25.
2. Connect resistive load directly to posts VOUT and GND. Use extremely short leads.
NOTE: To accurately measure EMI make sure the table has good ground connection to the
chamber, connect the battery GND cable to ground table, and do not touch the board and
setup or close the switch node. The board has a very effective 3-stage EMI filter where the
common mode choke is not assembled by default. If the common mode choke is added,
remove the bypass resistors R1 and R2.
Figure 12. 3-Stage EMI Filter Schematic