Diodes ZXLD381 User Manual
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Diodes Incorporated
ZXLD381
SINGLE OR MULTI CELL LED DRIVER SOLUTION
Summary
The ZXLD381 is a single cell LED driver designed for a pplications where step-up voltage conversion from a very low input
voltage is required. These applications mainly operate from 1.5V or 1.2V c ells. The IC generates constant current pulses that
are ideal for driving single or multiple LEDs over a wide range of operating voltages.
The ZXLD381 uses a PFM control technique to drive an internal switching transistor which a low saturation resistance. This
ensures high efficiency, even for input voltages as low as 1V.
The IC can start up under full load and operates down to an input voltage of only 0.9V.
The ZXLD381 is offered in the space saving SOT23 packag e or in die form, offering an excellent cost vs performance s olution
for single cell LED driving applications.
Features
• 85% Efficiency
• User adjustable output current
• Single cell operation (0.9V minimum)
• Low saturation voltage switching transistor
• SOT23-3 package
• Available also in Die form
• Simple Application circuit
Application
Pin Assignments
SOT23-3
(Top View)
• LED flashlights and torches
• LED backlights
• White LED driver
Typical Application Circuit
V
IN
V
CC
V
OUT
GND
ZXLD381
ZXLD381
Document number: DS32188 Rev. 3 - 2
L1
LED
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Block Diagram
1.5V
VCC
ZXLD381
Pulse
Control
Cof fCon
Rsense
GND
Fig 1. ZXLD381 Block Diagram
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ZXLD381
L1
VOUT
LED
Pin Description
Pin No. Name Description
1 GND Ground
2
3
V
V
OUT
CC
ZXLD381
Document number: DS32188 Rev. 3 - 2
Switch output external inductor/LED
Supply voltage, generally Alkaline, NiMH or NiCd single cell
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Absolute Maximum Ratings
Parameter Rating Unit
Supply Voltage (VCC)
Output Voltage (V
Supply Current 20 mA
Output Switch Current 800 mA
Power Dissipation SOT23-3 450 mW
Power Dissipation Die 1 W
Operating Temperature Range 0 to 85 °C
Storage Temperature Range -55 to 150 °C
OUT
)
-0.6 to 10 V
-0.6 to 20 V
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ZXLD381
Electrical Characteristics Measured at T
Parameter Conditions
Supply Voltage Operating Range L = 10μH 0.9 2.2 V
Minimum Supply Start-up Voltage L = 10μH 0.8 0.9 V
Switch Current At turn-off 250 320 400 mA
Switch Saturation Voltage
Switch Leakage Current
Mean LED Current
Efficiency
Operating Frequency
Discharge Pulse Width 0.7 1.5 2.5 µs
I
OUT
V
V
V
V
OUT
LED
LED
LED
= 200mA
= 25°C, L = 4.7µH and VCC = 1.5V unless otherwise specified.
AMB
Min Typ. Max
100 300 mV
= 20V
= 3.5V
= 3.5V
= 3.5V
40 70 120 µA
40 55 70 mA
85 %
350 kHz
Limits
Units
ZXLD381
Document number: DS32188 Rev. 3 - 2
3 of 9
www.diodes.com
May 2010
© Diodes Incorporated
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