Texas Instruments LM22670 3A SIMPLE SWITCHER regulator LM22670EVAL/NOPB LM22670EVAL/NOPB Datenbogen
Produktcode
LM22670EVAL/NOPB
Component Selection
5
Component Selection
Before changing the default components, refer to LM22670/LM22670Q 42V, 3A SIMPLE SWITCHER,
Step-Down Voltage Regulator with Features (
Step-Down Voltage Regulator with Features (
) for information regarding component selection.
The WEBENCH
®
designer online circuit simulation tool is also available on the
The output voltage is adjustable with resistors R1 and R2, shown in
. Any changes to these
evaluation board feedback resistors may require changes to the inductor and output capacitor values. It is
especially important to change the output capacitor, C4, if the output voltages are adjusted higher than 5V.
The Schottky diode, D1, has a voltage rating of 60V to allow for a 42V maximum input voltage. If the input
voltage is below 38V, a 40V Schottky diode may be used with a lower forward voltage to improve
efficiency. For improved heat dissipation, a Schottky diode in a D2PAK package may be selected for
higher efficiency. The input capacitor, C2, is not always required. This capacitor is placed on the
evaluation board to make the application robust and minimize input voltage ringing if power is suddenly
applied. Capacitor C2 also helps stabilize the transfer function of the converter loop. The input capacitor
C1 provides the main contribution to the switch current. Both capacitors are selected with appropriate
values intended only for the evaluation of the LM22670. For production designs, the impedance of the
power source as well as the ripple current rating of the selected input capacitors need to be taken into
consideration and modified accordingly. See the LM22670 datasheet (
especially important to change the output capacitor, C4, if the output voltages are adjusted higher than 5V.
The Schottky diode, D1, has a voltage rating of 60V to allow for a 42V maximum input voltage. If the input
voltage is below 38V, a 40V Schottky diode may be used with a lower forward voltage to improve
efficiency. For improved heat dissipation, a Schottky diode in a D2PAK package may be selected for
higher efficiency. The input capacitor, C2, is not always required. This capacitor is placed on the
evaluation board to make the application robust and minimize input voltage ringing if power is suddenly
applied. Capacitor C2 also helps stabilize the transfer function of the converter loop. The input capacitor
C1 provides the main contribution to the switch current. Both capacitors are selected with appropriate
values intended only for the evaluation of the LM22670. For production designs, the impedance of the
power source as well as the ripple current rating of the selected input capacitors need to be taken into
consideration and modified accordingly. See the LM22670 datasheet (
) for more information.
Output capacitor C5 is not populated but space is provided to add a second output capacitor. This second
output capacitor may be used to further reduce output voltage ripple.
output capacitor may be used to further reduce output voltage ripple.
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Bill of Materials
Table 1. LM22670EVAL Bill of Materials
Ref #
Value
Supplier
Part Number
C1
6.8 µF 50V ceramic
TDK
C4532X7R1H685M
C2
22 µF 63V electrolytic
Panasonic
EEEFK1J220XP
C3
10 nF 50V ceramic
TDK
C1608X7R1H103K
C4
120 µF 6.3V 24mohm
Nippon Chemi-Con
APXE6R3ARA121ME61G
C5
Not populated
-
C6
Not populated; not applicable for LM22670
-
D1
60V 5A CMSH5-60
Central Semiconductor
CMSH5-60
L1
8.2 µH 6.25A WE-PD L
Wurth
744771008
Coilcraft
MSS1260-822MX
R1
976
Ω
1%
-
CRCW0603976RFKEA
R2
1.54 k
Ω
1%
-
CRCW06031K54FKEA
R3
Not populated
-
U1
Texas Instruments
LM22670
3
SNVA361D – September 2008 – Revised April 2013
AN-1885 LM22670 Evaluation Board
Copyright © 2008–2013, Texas Instruments Incorporated