DC507A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 507
SINGLE CELL WHITE LED DRIVER
LT1937
DESCRIPTION
Demonstration circuit 507 features the LT1937 constantcurrent white LED driver in a small SC70 package. The
demo board consists of two circuits: an efficiency circuit
designed to demonstrate high efficiency performance of
the LT1937 using the Murata inductor and a size circuit
highlighting the LT1937’s ability to work with a small
ceramic chip inductor and a small output capacitor
(0.22µF). The high efficiency and small circuit size are
made possible by a 95mV feedback voltage and 1.2MHz
switching frequency, making the LT1937-SC70 an ideal
solution for battery powered portable applications such
as cellular phones, digital cameras, MP3 players, GPS
receivers, and handheld computers (PDAs). The DC507
is specifically designed for white LED backlight applications using 2–4 LEDs in series. LT1937 offers numerous
LED-dimming circuit options, see the datasheet for more
detailed information on LED brightness control.
Design files for this circuit board are available. Call
the LTC factory.
QUICK START PROCEDURE
Demonstration circuit 507 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.
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. When measuring the
output ripple, see Figure 2 for proper scope probe technique.
TEST THE EFFICIENCY CIRCUIT (UPPER CIRCUIT)
2. Place jumper JP2 in the EFFICIENCY position.
3. Press the SW1 switch. Observe all four white LEDs
light up. The output voltage should measure about
13V across the Vout Test terminal to GND terminal.
4. Turn off the input power supply or disconnect the sin-
gle cell Li-Ion battery.
TEST THE SIZE CIRCUIT (LOWER CIRCUIT)
5. Place jumper JP2 in the SIZE position.
SET THE INPUT VOLTAGE SOURCE
1. The demo board can be powered from the 3V Lithium
battery installed on the demo board (B1) or other input source (bench top power supply) by selecting input source jumper (JP1).
a.
For battery (B1) input operation, place the jumper
(JP1) in the BATTERY position.
b.
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.
6. Turn on the input power supply or connect the single
cell Li-Ion battery.
7. Press the SW2 switch. Observe all four white LEDs
light up. The output voltage should measure about
13V across the Vout Test terminal to GND terminal.
LED BRIGHTNESS CONTROL
The brightness of the LEDs can be controlled by applying a PWM signal to the SHDN terminal (use the upper
SHDN terminal for the EFFICIENCY circuit and lower
SHDN terminal for the SIZE circuit). 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 on PWM dimming control.
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 507
SINGLE CELL WHITE LED DRIVER
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Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Scope Probe Placement for Measuring Input or Output Ripple
2
5
4
VIN
BATTERY
L1
JP2
22uH
3
E1
JP1
3
Vin
2.7V - 5V
3
2
2
D1
Vout Test
CMDSH-3
E3
EFFICIENCY
SIZE
2
1
LED1
SW1
1
1
D
D
LED2
ON/OFF
6
Vin
B1
BATTERY
+
C1
2.2uF
6.3V
R2
12mA
1
SW
LED3
C2
0.47uF
16V
U1
LT1937ESC6
LED4
WHITE
4
SHDN
100K
FB
3
GND GND
2
5
R1
8.06
1%
E5
SHDN
GND
GND
E2
E4
C
C
D2
L2
22uH
CMDSH-3
SW2
ON/OFF
C4
2.2uF
6.3V
B
R3
100K
4
6
1
Vin
SW
SHDN
FB
C3
0.47uF
16V
U2
LT1937ESC6
3
B
GND GND
2
5
E6
SHDN
CONTRACT NO.
A
APPROVALS
DRAWN
DATE
June Wu
2/13/02
DAVE KIM
2/13/02
TECHNOLOGY
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900
Fax: (408)434-0507
A
TITLE
CHECKED
LT1937ESC6, SINGLE CELL WHITE LED DRIVER
APPROVED
ENGINEER
SIZE CAGE CODE
DESIGNER
DWG NO
REV
DC507A
Thursday, March 21, 2002
5
4
3
SCALE:
2
FILENAME:
A
SHEET
1
1
OF
1
Bill Of Material
Demo Bd. #507A
Linear Technology Corporation
LT1937ESC6
6/17/2005
Item Qty Reference
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
0
2
1
1
2
2
2
6
2
2
4
1
2
2
2
1
B1
B1 HOLDER
L1
L2
C1,C4
C2,C3
D1,D2
E1,E2,E3,E4,E5,E6
JP1,JP2
JP1,JP2
LED1-LED4
R1
R2,R3
SW1,SW2
U1,U2
Part Description
BATTERY, AA
BATTERY HOLDER,
INDUCTOR, 22uH
INDUCTOR, 22uH
CAP., X5R, 2.2uF, 6.3V, 20% 0603
CAP., X5R, 0.47uF, 16V 20% 0603
DIODE, CMDSH-3, SOD-323
TESTPOINT, TURRET, .094"
JUMPER, 0.079, 3 PIN
SHUNT,
LED, NSCX SERIES, WHITE
RES., CHIP, 8.06, 1/16W, 1% 0402
RES., CHIP, 100K, 1/16W, 5% 0402
SWITCH MOMENTARY
IC., LT1937ESC6, SC70
PRINTED CIRCUIT BOARD
Page 1 - of - 1
Manufacture / Part #
SANYO., CR2,
KEYSTONE, 92
MURATA, LQH32CN220K51
TAIYO YUDEN, LB2012T220M
AVX, 06036D225MAT
AVX, 0603YD474MAT
Central Semi. CMDSH-3
MILL-MAX, 2501-2
COMM CON, 2802S-03G1
COMM CON. CCIJ2MM-138G
NICHIA, NSCW100
AAC., CR05-8R06FM
AAC., CR05-104JM
PANASONIC EVQ PJS 05K
LINEAR., LT1937ESC6
DEMO CIRCUIT 507A
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