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LED
TX/
TORCH
SDA
SCL
IN
STROBE
OUT
SW
GND
10 PF
CIN
10 PF
J20
30310-6002HB
PWM0
3.3 V
PWM2
SCL
PWM1
GND
SDA
1
2
3 4
5
6
7 8
9 10
21
VOUT
GND
A1 A2
A3
COUT
GND
J2
J1
L1
1µH
STROBE
1 2
1
2
GND
LM3642
B2
B3
VIN/VL
GND
C1 C2 C3
RSCL 1kRSDA 1k
12
TX/TORCH
GND
1
2
ILED
DIODE
B1
User's Guide
SNOU098A–November 2012–Revised April 2013
LM3642 Evaluation Board
1 Introduction
The LM3642 is a 4MHz fixed-frequency synchronous boost converter plus 1.5A constant current driver for
a high-current white LED. The high-side current source allows for grounded cathode LED operation
providing Flash current up to 1.5A. An adaptive regulation method ensures the current source remains in
regulation and maximizes efficiency.
The LM3642 is controlled via an I
2
C-compatible interface. Features include: a hardware flash enable
(STROBE) allowing a logic input to trigger the flash pulse and a TX input which forces the flash pulse into
a low-current Torch Mode allowing for synchronization to RF power amplifier events or other high-current
conditions.
The 4MHz switching frequency, over-voltage protection and adjustable current limit settings allows the use
of tiny, low-profile inductors and (10 µF) ceramic capacitors. The device is available in a small 9-bump
(1.615 mm × 1.665 mm × 0.6 mm) DSBGA package and operates over the −40°C to +85°C temperature
range.
The schematic for LM3642 is shown in Figure 1.
Figure 1. LM3642 Evaluation Board Schematic
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1
SNOU098A–November 2012–Revised April 2013 LM3642 Evaluation Board
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