Datasheet

C
O
D1
R
OV2
R
OV1
R
SNS
R
FS
C
FS
C
OV
8V ± 28V
1A
I
LED
Q2
OVP
nDIM
LM3421
AGND
V
IN
PGND
DDRV
DAP
GATE
EN
COMP
VIN
CSH
RCT
IS
HSP
RPD
VCC
HSN
L1
C
BYP
R
LIM
Q1
C
CMP
R
CSH
R
T
R
UV2
R
UV1
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
R
HSN
R
HSP
Q3
PWM
R
UVH
C
T
C
IN
D2
LM3421, LM3421-Q1
LM3423, LM3423-Q1
SNVS574E –JULY 2008–REVISED MAY 2013 www.ti.com
APPLICATIONS INFORMATION
The following designs are provided as reference circuits. For a specific design, the steps in the Design Procedure
section should be performed. In all designs, an RC filter (0.1 µF, 10Ω) is recommended at VIN placed as close
as possible to the LM3421/23 device. This filter is not shown in the following designs.
DESIGN #2 - LM3421 BOOST Application
Features
• Input: 8V to 28V
• Output: 9 LEDs at 1A
• PWM Dimming up to 30kHz
• 700 kHz Switching Frequency
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Product Folder Links: LM3421 LM3421-Q1 LM3423 LM3423-Q1