ZXLD1321
Boost mode DC-DC converter for LED driving with 1A
output and current control
Description
The ZXLD1321 is an inductive DC-DC The feedback control circuitry inside the
converter, with an internal switch, designed ZXLD1321 provides excellent load and current
for driving single or multiple LEDs in series up regulation, resulting in very stable LED current
to a total of 1A output current.
over the useful life of the battery and over the
full operating temperature range.
Applications cover commercial environments
with input voltages ranging from 1.2V to 12V. The LED current can be adjusted from 100%
down to 10% of the set value by applying a dc
The device employs a variable 'on' and 'off'
voltage to the ADJ pin and down to 1% by
time control scheme with adjustable peak
applying a PWM signal to the ADJ pin. An on-
switch current limiting and supports step-up
chip LED protection circuit also allows output
(Boost) mode and self-powering Bootstrap
current to be reduced linearly above
a
operating modes, offering higher power
efficiency and lower system cost than
conventional PFM circuitry.
predetermined threshold temperature using an
external thermistor at the TADJ pin.
External resistors set nominal average LED
current and coil peak current independently.
The device includes the DC-DC converter, a
high-side current monitor and an NPN
switching transistor to provide an integrated The device can be shut down by applying a
solution offering small PCB size, competitive continuous low level dc voltage to the ADJ pin.
cost/performance, high power efficiency of
DC-DC conversion and maximum LED
brightness/reliability. More importantly, it
retains design flexibility to add customer
specific features.
Features
Applications
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1.2V to 12V Input voltage range
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High power LED flashlights
LED back-up lighting
General LED lighting
Emergency lighting
Up to 1A output current
#
Typical efficiency >85%
Bootstrap operation enables input voltage
down to 1V
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User-defined thermal control of LED
output current using external thermistor
High output current stability over input
voltage and temperature
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12µA typical standby current
LED current adjustable from 100%
down to 2%
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•
Adjustable soft-start
Drives up to 5 white LEDs in series
Note# : Using standard external components as specified under electrical characteristics. Efficiency is dependent upon
external component types and values. Higher efficiency is possible with alternative coils.
Issue 1 - January 2008
© Zetex Semiconductors plc 2008
1
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