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Linear Technology Electronic Components Datasheet

LT1932 Datasheet

Constant-Current DC/DC LED Driver

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FEATURES
s Up to 80% Efficiency
s Inherently Matched LED Current
s Adjustable Control of LED Current
s Drives Five White LEDs from 2V
s Drives Six White LEDs from 2.7V
s Drives Eight White LEDs from 3V
s Disconnects LEDs In Shutdown
s 1.2MHz Fixed Frequency Switching
s Uses Tiny Ceramic Capacitors
s Uses Tiny 1mm-Tall Inductors
s Regulates Current Even When VIN > VOUT
s Operates with VIN as Low as 1V
s Low Profile (1mm) ThinSOTTM Package
U
APPLICATIO S
s Cellular Telephones
s Handheld Computers
s Digital Cameras
s Portable MP3 Players
s Pagers
TYPICAL APPLICATIO
Li-Ion Driver for Four White LEDs
VIN
2.7V TO 4.2V
L1
6.8µH
D1
C1
4.7µF
PWM
DIMMING
CONTROL
61
VIN SW
LT1932
5
SHDN
3
LED
RSET
GND
4
RSET
1.50k
2
15mA
C1: TAIYO YUDEN JMK212BJ475
C2: TAIYO YUDEN EMK212BJ105
D1:ZETEX ZHCS400
L1: SUMIDA CLQ4D106R8 OR PANASONIC ELJEA6R8
LT1932
Constant-Current DC/DC
LED Driver in ThinSOT
DESCRIPTIO
The LT®1932 is a fixed frequency step-up DC/DC converter
designed to operate as a constant-current source. Be-
cause it directly regulates output current, the LT1932 is
ideal for driving light emitting diodes (LEDs) whose light
intensity is proportional to the current passing through
them, not the voltage across their terminals.
With an input voltage range of 1V to 10V, the device works
from a variety of input sources. The LT1932 accurately
regulates LED current even when the input voltage is
higher than the LED voltage, greatly simplifying battery-
powered designs. A single external resistor sets LED
current between 5mA and 40mA, which can then be easily
adjusted using either a DC voltage or a pulse width
modulated (PWM) signal. When the LT1932 is placed in
shutdown, the LEDs are disconnected from the output,
ensuring a quiescent current of under 1µA for the entire
circuit. The device’s 1.2MHz switching frequency permits
the use of tiny, low profile chip inductors and capacitors to
minimize footprint and cost in space-conscious portable
applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
C2
1µF
1932 TA01
Efficiency
85
80 VIN = 4.2V
75 VIN = 2.7V
70
65
60
55
0
5 10 15
LED CURRENT (mA)
20
1932 TA02
1932f
1


Linear Technology Electronic Components Datasheet

LT1932 Datasheet

Constant-Current DC/DC LED Driver

No Preview Available !

LT1932
ABSOLUTE AXI U RATI GS
(Note 1)
VIN Voltage ............................................................. 10V
SHDN Voltage ......................................................... 10V
SW Voltage ............................................................. 36V
LED Voltage ............................................................. 36V
RSET Voltage ............................................................. 1V
Junction Temperature .......................................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SW 1
GND 2
LED 3
6 VIN
5 SHDN
4 RSET
S6 PACKAGE
6-LEAD PLASTIC SOT-23
TJMAX = 125°C, θJA = 250°C/ W
ORDER PART
NUMBER
LT1932ES6
S6 PART MARKING
LTST
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The q denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VSHDN = 1.2V, unless otherwise noted.
PARAMETER
Minimum Input Voltage
Quiescent Current
RSET Pin Voltage
LED Pin Voltage
LED Pin Current
LED Pin Current Temperature Coefficient
Switching Frequency
Maximum Switch Duty Cycle
Switch Current Limit
Switch VCESAT
SHDN Pin Current
Start-Up Threshold (SHDN Pin)
Shutdown Threshold (SHDN Pin)
Switch Leakage Current
CONDITIONS
VRSET = 0.2V
VSHDN = 0V
RSET = 1.50k
RSET = 1.50k, VIN < VOUT (Figure 1)
RSET = 562, VIN = 1.5V
RSET = 750, VIN = 1.2V
RSET = 1.50k, VIN = 1.2V
RSET = 4.53k, VIN = 1.2V
ILED = 15mA
VIN = 1V
ISW = 300mA
VSHDN = 0V
VSHDN = 2V
Switch Off, VSW = 5V
MIN TYP MAX UNITS
1V
1.2 1.6
0.1 1.0
mA
µA
100 mV
120 180
mV
33 38 45
25 30 36
12.5 15 17.5
5
mA
mA
mA
mA
– 0.02
mA/°C
0.8 1.2 1.6
MHz
q 90
95
%
400 550 780
mA
150 200
mV
0 0.1
15 30
µA
µA
0.85 V
0.25 V
0.01 5
µA
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
2


Part Number LT1932
Description Constant-Current DC/DC LED Driver
Maker Linear Technology
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LT1932 Datasheet PDF






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