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DN70 ZXSC400 Driving 2 serial high power LEDs
Description
This design note shows the ZXSC400 driving 2 serial LEDs. The input voltage ranges from 2V to 3.6V with a maximum output current of 360mA from 2.6V input. Figure 1 shows a typical constant current solution with the ZXSC400 driving two 1W LEDs in series. The wide input voltage range allows the use of different battery cell combinations. This could be dual alkaline cells with voltage starting from 3V down to 2V or triple NiCad/NiMH cells with voltage starting from 3.6V down to 2.7V.
VIN=1.8V to 3.6V
L1
D1
Q1
U1
Vcc Stdn Vdrive Isense VFB
C2
C1
Gnd
ZXSC400 R1 R2
Figure 1 Ref. U1 Q1 D1 L1 R1 R2 R3 C1 C2 C3 2A 22 H 18m 820m 1K 22uF/10V 100uF/10V 220nF/10V Value Part number ZXSC400E6 ZHCS2000 Generic Generic Generic Generic Generic Generic Generic Table 1
Schematic diagram Manufacturer Zetex Zetex Generic Generic Generic Generic Generic Generic Generic Bill of materials 0805 size Comments LED driver in SOT23-6 Low sat. NPN transistor in SOT23 2A Schottky in SOT23 ISAT = 2A 0805 size 0805 size 0805 size
ZXTN25012EFH Zetex
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DN70
Typical operating characteristics
(For typical application circuit where Tamb = 25C unless otherwise stated)
100 90 80 70 60 50 3.6 3.4 3.2 3 2.8 2.6 2.4 2.2 2 Input Voltage (V) 0.4
Output Current (A)
Efficiency (%)
0.2
0.0 3.6 3.4 3.2 3 2.8 2.6 2.4 2.2 2 Input Voltage (V)
Input Voltage vs Efficiency
Input Voltage vs Output Current
1.6
8
Input Current (A)
Output Voltage (V)
1.2
6
0.8
4
0.4
2
0.0 3.6 3.4 3.2 3 2.8 2.6 2.4 2.2 2 Input Voltage (V)
0 3.6 3.4 3.2 3 2.8 2.6 2.4 2.2 2 Input Voltage (V)
Input Voltage vs Input Current
Input Voltage vs Output Voltage
Figure 2
Performance graphs
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Issue 3 - July 2007
(c) Zetex Semiconductors plc 2007
DN70
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(c) Zetex Semiconductors plc 2007
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DN70
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 labelling 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. Zetex sales offices Europe Zetex GmbH Kustermann-park Balanstrae 59 D-81541 Munchen Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 europe.sales@zetex.com Americas Zetex Inc 700 Veterans Memorial Highway Hauppauge, NY 11788 USA Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 usa.sales@zetex.com Asia Pacific Zetex (Asia Ltd) 3701-04 Metroplaza Tower 1 Hing Fong Road, Kwai Fong Hong Kong Telephone: (852) 26100 611 Fax: (852) 24250 494 asia.sales@zetex.com Corporate Headquarters Zetex Semiconductors plc Zetex Technology Park, Chadderton Oldham, OL9 9LL United Kingdom Telephone: (44) 161 622 4444 Fax: (44) 161 622 4446 hq@zetex.com
(c) 2007 Published by Zetex Semiconductors plc
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