Zetex ZXLD1321EV2 User manual

Issue 2 - April 2008 www.zetex.com
© Zetex Semiconductors plc, 2008
ZXLD1321EV2 USER GUIDE
DESCRIPTION
The ZXLD1321 is an inductive DC-DC converter,
with an internal switch, designed for driving single or
multiple LEDs in series up to a total of 1A output
current.
Applications cover commercial environments with
input voltages ranging from 1.2V to 12V.
The device employs a variable ‘on’ and ‘off’ time
control scheme with adjustable peak switch current
limiting and supports step-up (Boost) mode and self-
powering Bootstrap operating modes, offering higher
power efficiency and lower system cost than
conventional PFM 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
ZXLD1321 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 to
the ADJ pin. 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
• 1.2V to 12V Input Voltage Range
• Up to 1A output current
• Typical efficiency (*) : >85%
• Bootstrap operation enables input voltage down to
1V
• User-defined thermal control of LED output current
using external thermistor
• 12µA typical standby current
• Adjustable Soft-Start
• Drives up to 5 white LEDs in series
APPLICATIONS
•High power LED flashlights
•LED back-up lighting
•General LED lighting
ORDERING INFORMATION
ORDER NUMBER
ZXLD1321EV2
Please note evaluation boards
are subject to availability and
qualified leads.
TYPICAL APPLICATION CIRCUIT

ZXLD1321EV2
Issue 2 – April 2008 www.zetex.com
© Zetex Semiconductors plc, 2008
2
REFERENCE DESIGN
ZXLD1321EV2 evaluation board is designed with LED output connector which is compatible with the FLS Emitter
Board connection standard. The target application is 700mA/1000mA high current LED driver for single or
multiple LEDs with wide input voltage range.
If the ZXLD1321EV2 is connected to 1 off-board LED, the supply voltage is: VIN=2V ~ 3.4V.
The ZXLD1321EV2 boards are initially set at LED current of around 700mA with150mΩ(R3) current sensing
resistor. In order to boost the LED current to 1000mA, on-board 300mΩ(R3A) could made parallel to R3 by
means of soldering jumper pad JP1.
For other reference designs or further applications information please refer to the ZXLD1321 datasheet.
SCHEMATIC DIAGRAM
Materials List
Ref Value Package Part Number Manufacturer Contact Details
U1 LED Driver DFN14 ZXLD1321DCA Zetex www.zetex.com
D1 Schottky Diode SOT23-6 ZHCS2000 Zetex www.zetex.com
L1 10uH 2A
MSS7341-103ML
NPIS64D100MTRF
744-777910
Coilcraft
NIC Comps.
Wurth
www.coilcraft.com
www.niccomp.com
www.we-online.com
C1 10nF 10V 0603 Generic Generic
C2 2.2uF 25V 1206 GRM31MR71E225K Murata www.murata.com
C3 4.7uF 50V 1206 GRM31CR71H475K Murata www.murata.com
R1 430Ω0805 Generic Generic
R2 25mΩ0603 Generic Generic
R3 150mΩ0805 Generic Generic
R3A 300mΩ0805 Generic Generic
R4 5.1KΩ0603 Generic Generic
Z1 18V 3W Zener DO-214AC BZG03C18 Vishay www.vishay.com

ZXLD1321EV2
Issue 2 – April 2008 www.zetex.com
© Zetex Semiconductors plc, 2008
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PERFORMANCE
Graphs

ZXLD1321EV2
Issue 2 – April 2008 www.zetex.com
© Zetex Semiconductors plc, 2008
4
ZXLD1321EV2 OPERATION
Connection diagram
ZXLD1321EV2 Set-up and Test
1. Preset PSU to 3V with current limit around 1.8A
2. Connect the FLS Emitter board to LED output socket respectively.
3. Connect V
IN
and GND to positive and zero volts of PSU supply respectively.
4. Turn on PSU.
5. The LED should illuminate and be regulated at 700mA/1000mA +/-5%.
6. Input current should measure between 0.9A and 1.1A for 700mA board and between 1.4 A and 1.6A for 1A
board.
Caution: Please make sure the FLS Emitter board is connected to the EV board before applying of power.
FLS Emitter board with appropriate current rating should be used.

ZXLD1321EV2
Issue 2 – April 2008 www.zetex.com
© Zetex Semiconductors plc, 2008
5
Layout considerations
PCB tracks should be kept as short as possible to minimize ground bounce, and the ground pin of the device
should be soldered directly to the ground plane. It is particularly important to mount the coil and the input/output
capacitors close to the device to minimize parasitic resistance and inductance, which will degrade efficiency. The
VIN pin is prone to noise. Input decoupling capacitor C2 should be kept as close as possible between the VIN
and GND pin. Enough copper should be attached to the GND pin (exposed pad) for heat-sinking purposes. In this
EV board, the copper area is at the bottom layer, connected to the exposed pad through a few plated through
holes.
Below is the recommended layout of the ZXLD1321EV2.
Top Silk Top Copper
Bottom Copper Drill File

ZXLD1321EV2
Issue 2 – April 2008 www.zetex.com
© Zetex Semiconductors plc, 2008
6
Definitions
Product change
Zetex Semiconductors reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or service.
Customers are solely responsible for obtaining the latest relevant information before placing orders.
Applications disclaimer
The circuits in this design/application note are offered as design ideas. It is the responsibility of the user to ensure that the circuit is fit for the
user’s application and meets with the user’s requirements. No representation or warranty is given and no liability whatsoever is assumed by Zetex
with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or
otherwise. Zetex does not assume any legal responsibility or will not be held legally liable (whether in contract, tort (including negligence), breach
of statutory duty, restriction or otherwise) for any damages, loss of profit, business, contract, opportunity or consequential loss in the use of these
circuit applications, under any circumstances.
Life support
Zetex products are specifically not authorized for use as critical components in life support devices or systems without the express written
approval of the Chief Executive Officer of Zetex Semiconductors plc. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body
or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions
for use provided in the labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to
cause the failure of the life support device or to affect its safety or effectiveness.
Reproduction
The product specifications contained in this publication are issued to provide outline information only which (unless agreed by the company in
writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating
to the products or services concerned.
Terms and Conditions
All products are sold subjects to Zetex’ terms and conditions of sale, and this disclaimer (save in the event of a conflict between the two when the
terms of the contract shall prevail) according to region, supplied at the time of order acknowledgement.
For the latest information on technology, delivery terms and conditions and prices, please contact your nearest Zetex sales office.
Quality of product
Zetex is an ISO 9001 and TS16949 certified semiconductor manufacturer.
To ensure quality of service and products we strongly advise the purchase of parts directly from Zetex Semiconductors or one of our regionally
authorized distributors. For a complete listing of authorized distributors please visit: www.zetex.com/salesnetwork
Zetex Semiconductors does not warrant or accept any liability whatsoever in respect of any parts purchased through unauthorized sales
channels.
ESD (Electrostatic discharge)
Semiconductor devices are susceptible to damage by ESD. Suitable precautions should be taken when handling and transporting devices. The
possible damage to devices depends on the circumstances of the handling and transporting, and the nature of the device. The extent of damage
can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time. Devices suspected of
being affected should be replaced.
Green compliance
Zetex Semiconductors is committed to environmental excellence in all aspects of its operations which includes meeting or exceeding regulatory
requirements with respect to the use of hazardous substances. Numerous successful programs have been implemented to reduce the use of
hazardous substances and/or emissions.
All Zetex components are compliant with the RoHS directive, and through this it is supporting its customers in their compliance with WEEE and
ELV directives.
Product status key:
“Preview” Future device intended for production at some point. Samples may be available
“Active” Product status recommended for new designs
“Last time buy (LTB)” Device will be discontinued and last time buy period and delivery is in effect
“Not recommended for new designs” Device is still in production to support existing designs and production
“Obsolete” Production has been discontinued
Datasheet status key:
“Draft version” This term denotes a very early datasheet version and contains highly provisional
information, which may change in any manner without notice.
“Provisional version” This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance.
However, changes to the test conditions and specifications may occur, at any time and without notice.
“Issue” This term denotes an issued datasheet containing finalized specifications. However, changes to
specifications may occur, at any time and without notice.
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© 2006 Published by Zetex Semiconductors plc.