LT1932
Constant-Current DC/DC
LED Driver in ThinSOT
FEATURES DESCRIPTIO
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Up to 80% Efficiency The LT 1932 is a fixed frequency step-up DC/DC converter
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Inherently Matched LED Current designed to operate as a constant-current source. Be-
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Adjustable Control of LED Current cause it directly regulates output current, the LT1932 is
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Drives Five White LEDs from 2V ideal for driving light emitting diodes (LEDs) whose light
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Drives Six White LEDs from 2.7V intensity is proportional to the current passing through
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Drives Eight White LEDs from 3V them, not the voltage across their terminals.
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Disconnects LEDs In Shutdown
With an input voltage range of 1V to 10V, the device works
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1.2MHz Fixed Frequency Switching
from a variety of input sources. The LT1932 accurately
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Uses Tiny Ceramic Capacitors
regulates LED current even when the input voltage is
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Uses Tiny 1mm-Tall Inductors
higher than the LED voltage, greatly simplifying battery-
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Regulates Current Even When V > V
IN OUT
powered designs. A single external resistor sets LED
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Operates with V as Low as 1V
IN
current between 5mA and 40mA, which can then be easily
TM
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Low Profile (1mm) ThinSOT Package
adjusted using either a DC voltage or a pulse width
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modulated (PWM) signal. When the LT1932 is placed in
APPLICATIO S
shutdown, the LEDs are disconnected from the output,
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ensuring a quiescent current of under 1m A for the entire
Cellular Telephones
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circuit. The devices 1.2MHz switching frequency permits
Handheld Computers
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the use of tiny, low profile chip inductors and capacitors to
Digital Cameras
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minimize footprint and cost in space-conscious portable
Portable MP3 Players
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applications.
Pagers
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
Li-Ion Driver for Four White LEDs Efficiency
85
L1
D1
6.8H
V
IN
V = 4.2V
IN
80
2.7V TO 4.2V
V = 2.7V
IN
75
C1
61
4.7F
V SW
IN
70
LT1932
PWM
5 3
C2
65
SHDN LED
DIMMING
1F
CONTROL
R GND
SET
15mA
60
4 2
R
SET
55
1.50k
0 510 15 20
LED CURRENT (mA)
C1: TAIYO YUDEN JMK212BJ475
1932 TA01
C2: TAIYO YUDEN EMK212BJ105
1932 TA02
D1:ZETEX ZHCS400
L1: SUMIDA CLQ4D106R8 OR PANASONIC ELJEA6R8
1932f
1
EFFICIENCY (%)
U
ULT1932
UUW
ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
V Voltage ............................................................. 10V
IN
NUMBER
TOP VIEW
SHDN Voltage ......................................................... 10V
SW Voltage ............................................................. 36V
SW 1 6 V
IN
LT1932ES6
GND 2 5 SHDN
LED Voltage ............................................................. 36V
LED 3 4 R
SET
R Voltage ............................................................. 1V
SET
S6 PART MARKING
Junction Temperature.......................................... 125 C
S6 PACKAGE
6-LEAD PLASTIC SOT-23
Operating Temperature Range (Note 2) .. 40 C to 85 C
LTST
T = 125 C, q = 250 C/ W
JMAX JA
Storage Temperature Range ................. 65 C to 150 C
Lead Temperature (Soldering, 10 sec).................. 300 C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The l denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T = 25 C. V = 1.2V, V = 1.2V, unless otherwise noted.
A IN SHDN
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage 1V
Quiescent Current V = 0.2V 1.2 1.6 mA
RSET
V = 0V 0.1 1.0 m A
SHDN
R Pin Voltage R = 1.50k 100 mV
SET SET
LED Pin Voltage R = 1.50k, V < V (Figure 1) 120 180 mV
SET IN OUT
LED Pin Current R = 562W , V = 1.5V 33 38 45 mA
SET IN
R = 750W , V = 1.2V 25 30 36 mA
SET IN
R = 1.50k, V = 1.2V 12.5 15 17.5 mA
SET IN
R = 4.53k, V = 1.2V 5 mA
SET IN
LED Pin Current Temperature Coefficient I = 15mA 0.02 mA/ C
LED
Switching Frequency V = 1V 0.8 1.2 1.6 MHz
IN
Maximum Switch Duty Cycle l 90 95 %
Switch Current Limit 400 550 780 mA
Switch V I = 300mA 150 200 mV
CESAT SW
SHDN Pin Current V = 0V 0 0.1 m A
SHDN
V = 2V 15 30 m A
SHDN
Start-Up Threshold (SHDN Pin) 0.85 V
Shutdown Threshold (SHDN Pin) 0.25 V
Switch Leakage Current Switch Off, V = 5V 0.01 5 m A
SW
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
Note 2: The LT1932E is guaranteed to meet specifications from 0 C to 70 C.
Specifications over the 40 C to 85 C operating temperature range are
assured by design, characterization and correlation with statistical process
controls.
1932f
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