DC484A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 484
SINGLE CELL WHITE LED DRIVER
LT1937
DESCRIPTION
white LED backlight applications using 2–4 LEDs, making LT1937-SOT23 an ideal solution for battery powered
portable applications such as cellular phones, digital
cameras, MP3 players, GPS receivers, and handheld
computers (PDAs). LT1937 offers numerous LED dimming circuit options, see the datasheet for details.
Demonstration circuit 484 features the LT1937 constantcurrent white LED driver in a small SOT23 ThinSOT
package. The demo board is designed to demonstrate
the high efficiency performance and the small size of the
LT1937. The LT1937 features a 95mV feedback voltage,
1.2MHz switching frequency and a special internal compensation network, which allows small (0603) input and
output capacitors. DC484 is specifically designed for
Design files for this circuit board are available from
the LTC factory.
QUICK START PROCEDURE
For bench supply input, place the jumper (JP1) in the
Vin position and connect a 3.3V, 500mA Bench supply
to the Vin and GND terminals.
Demonstration circuit 484 is easy to set up to evaluate
the performance of the LT1937. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
2. Turn on the input power supply or connect the single
cell Li-Ion battery. Turn on the LT1937 LED driver circuit by pushing down SW1. Observe all four white
LEDs light up. The output voltage should measure
about 13V across the Vout Test terminal to GND terminal.
NOTE: When measuring the input or output voltage rip-
ple, care must be taken to avoid a long ground lead on
the oscilloscope probe. Measure the input or output
voltage ripple by touching the probe tip directly across
the Vin or Vout and GND terminals. See Figure 2 for
proper scope probe technique.
3. The brightness of the LEDs can be controlled by ap-
plying a PWM signal to the SHDN terminal. The typical frequency range recommended for PWM dimming
is 1KHz–10KHz with the signal magnitude of the PWM
signal higher than 1.5V. See the LT1937 data sheet for
more information about PWM dimming control.
1. The demo board can be powered from a 3V Lithium
battery installed on the demo board (B1) or other input source (bench top power supply) by selecting input source jumper (JP1).
For battery (B1) input operation, place the jumper
(JP1) to the “BATTERY” position.
OPTIONAL SUPPLY TO
ON-BOARD BATTERY
–
+
+
+
–
–
+
OPTIONAL
DIMMING
CONTROL VIA
1KHz-10KHz
PWM SIGNAL
(>1.5V)
SEE LT1937
DATASHEET
FOR DETAILS
–
GND
VIN
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Ripple
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 484
SINGLE CELL WHITE LED DRIVER
Vin
2.7V - 5 V
3
E1
JP1
2
VIN
BATTERY
D1
Vou t Test
CMDSH-3
E3
L1
1
22uH
LED1
SW1
LED2
ON/OFF
5
1
Vin
SW
12mA
LED3
U1
LT1937E S5
LED4
B1
BATTERY
+
C1
1uF
6.3V
R2
100K
WHITE
4
SHDN
FB
3
C2
0. 22uF
16V
GND
2
E5
R1
7. 5
1%
SHDN
GND
GND
E2
E4
Figure 3. Schematic
2
5
4
3
2
1
Vin
2.7V - 5V
D
D
3
E1
JP1
2
VIN
BATTERY
D1
L1
22uH
Vout Test
E3
1
CMDSH-3
LED1
SW1
LED2
ON/OFF
C
5
1
Vin
SW
12mA
LED3
U1
LT1937ES5
C
LED4
B1
BATTERY
+
C1
1uF
6.3V
R2
WHITE
4
SHDN
100K
FB
3
C2
0.22uF
16V
GND
2
R1
7.5
1%
E5
SHDN
B
B
GND
GND
E2
E4
CONTRACT NO.
APPROVALS
DRAWN
DATE
June Wu
11/27/01
TECHNOLOGY
TITLE
CHECKED
LT1937ES5, SINGLE CELL WHITE LED DRIVER
APPROVED
A
ENGINEER
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900
Fax: (408)434-0507
David Chen 11/27/01
DESIGNER
SIZE CAGE CODE
DWG NO
REV
A
DEMO DC484A
Friday, December 14, 2001
5
4
3
SCALE:
FILENAME:
2
SHEET
A
1
OF
1
1
Bill Of Material
Demo Bd. #484A
Linear Technology Corporation
LT1937ES5
6/17/2005
12:34 PM
Item Qty Reference
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
1
2
1
1
1
1
5
1
1
4
1
1
1
1
1
B1
B1 HOLDER
L1
C1
C2
D1
E1,E2,E3,E4,E5
JP1
JP1 (BATTERY SIDE)
LED1-LED4
R1
R2
SW1
U1
Part Description
BATTERY, AA
BATTERY HOLDER,
INDUCTOR, 22uH
CAP., X5R, 1.0uF, 6.3V, 20% 0603
CAP., X7R, 0.22uF, 16V 20% 0805
DIODE, CMDSH-3, SOD-323
TESTPOINT, TURRET, .094"
JUMPER, 0.079, 3 PIN
SHUNT,
LED, NSCX SERIES, WHITE
RES., CHIP, 7.5, 1/16W, 1% 0402
RES., CHIP, 100K, 1/16W, 5% 0402
SWITCH MOMENTARY
IC., LT1937, SOT23-S5
PRINTED CIRCUIT BOARD
Page 1 - of - 1
Manufacture / Part #
SANYO., CR2
KEYSTONE, 92
MURATA, LQH32CN220K51L
TAIYO YUDEN, JMK107BJ105MA
TAIYO YUDEN, EMK212BJ224MG
Central Semi. CMDSH-3
MILL-MAX, 2501-2
COMM CON, 2802S-03G1
COMM CON. CCIJ2MM-138G
NICHIA, NSCW100
AAC., CR05-7R50FM
AAC., CR05-104JM
PANASONIC EVQ PJS 05K
LINEAR., LT1937ES5 (Bulk)
DEMO BOARD DC484A
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