ZXLD1322 Datasheet, PDF (1/17 Pages) Zetex Semiconductors – Buck/boost mode DC-DC converter for LED driving with 700mA output and current control

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ZXLD1322
BUCK/BOOST MODE DC-DC CONVERTER FOR LED DRIVING WITH 700mA OUTPUT AND CURRENT
CONTROL
Description
The ZXLD1322 is an inductive DC-DC converter, with an internal switch, designed for driving single or multiple LEDs in
series up to a total of 700mA output current. Applications cover input voltages ranging from 2.5V to 15V. Depending upon
supply voltage and external components, this can provide up to 12W of output power. The device employs a variable 'on'
and 'off' time control scheme with adjustable peak switch current limiting and operates in Buck/Boost mode, offering higher
power efficiency and lower system cost than conventional PFM buck/boost circuitry. The device includes the DC-DC
converter, a high-side current monitor and an NPN switching transistor to provide an integrated solution offering small PCB
size, competitive 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. The feedback control circuitry inside the
ZXLD1322 provides excellent load and current regulation, resulting in very stable LED current over the useful life of the
battery and over the full operating temperature range. The LED current can be adjusted from 100% down to 10% of the set
value by applying a dc voltage to the ADJ pin and down to 1% by applying a PWM signal. An on-chip LED protection circuit
also allows output current to be reduced linearly above a 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 can
be shut down by applying a continuous low level dc voltage to the ADJ pin.
Features
Pin Assignments
• 2.5V to 15V Input Voltage Range
• Up to 700mA output current
• Typical efficiency^# >80%
• User-defined thermal control of LED
• output current using external thermistor
• High output current stability over input
• voltage and temperature
• 12μA typical standby current
• LED current adjustable from 100%
• down to 2%
• Adjustable Soft-Start
• Capable of driving 3 LEDs in series
Applications
• High power LED flashlights
• LED back-up lighting
• General LED lighting
(Top View)
DFN4030-14 with Exposed Pad
4mm x 3mm
0.50mm pitch
1.5W @ T_A = 70°C
Typical Application Circuit
DFN4030-14 Package(Bottom View)
45° chamfer denote Pin 1
Notes: #. 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.
ZXLD1322
Document number: DS32166 Rev. 3 - 2
1 of 17
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April 2010
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