1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
VIN
EN
COMP
CSH
RCT
AGND
OVP
nDIM
FLT
TIMR
LRDY
DPOL
PGND
GATE
VCC
IS
RPD
HSP
HSN
DDRV
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LM3423 TSSOP Pin Connection
Table 3. LM3423 Evaluation Board Test Points
Test Point Designation
Function or Use
TP1
Test point for "LED+" connector (LED anode).
TP2
Test point for "LED-" connector (LED cathode).
TP3
Test point for regulated output voltage.
TP5
Test point for L-RDY pin.
TP6
Test point for "PWM Dimming" input signal.
TP7
Test point for IS pin.
TP8
Test point for nDIM pin.
TP9
Test point for FLT pin.
TP10
Test point for GROUND.
TP11
Test point for TIMR pin.
TP12
Test point for switch-node.
4
LM3423 TSSOP Pin Connection
Figure 1. Top View
LM3423 Pin Connection
5
Board Features
This evaluation board has all the necessary connections and jumpers to evaluate the LM3423 controller in
a boost converter topology with the following operating features and options:
5.1
Setting Average LED Current
The LM3423 uses peak current-mode control to regulate the boosted output voltage. An external current
sense resistor R
SENSE
(i.e. R9) in series with the LED load is used to convert the LED current, I
LED
, into a
voltage that is sensed by HSP (pin 19) and HSN (pin 20). HSP and HSN are the inputs to a high side
sense amplifier that is used in combination with a resistor tied to CSH (pin 4) and an error amplifier to
program a desired I
LED
current.
3
SNVA376A – December 2008 – Revised May 2013
AN-1907 LM3423 Buck-Boost Configuration Evaluation Board
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