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ZXSC300
SINGLE OR MULTI CELL LED DRIVER SOLUTION
DESCRIPTION
The ZXSC300 is a single or multi cell LED driver designed for applications where step-up voltage conversion from very low input voltages is required. These applications mainly operate from single 1.5V or 1.2V battery cells. The circuit generates constant current pulses that are ideal for driving single or multiple LED's over a wide range of operating voltages. The ZXSC300 is a PFM controller IC that drives an external Zetex switching transistor with a very low saturation resistance. These transistors are the best switching devices available for this type of switching conversion enabling high efficiency conversion with input voltages below 1 volt. The drive output of the ZXSC controller generates a dynamic drive signal for the switching transistor. The circuit can start up under full load and operates down to an input voltage of 0.8 volts. The solution configuration ensures optimum efficiency over a wide range of load currents, several circuit configurations are possible depending on battery life versus brightness considerations. The ZXSC300 is offered in the SOT23-5 package which, when combined with a SOT23 switching transistor, generates a high efficiency small size circuit solution. The IC and discrete combination offers the ultimate cost vs performance solution for single cell LED driving applications.
FEATURES
* 94% efficiency * Minimum operating input voltage 0.8V * Fixed output current * Low saturation voltage switching transistor * SOT23-5 package
APPLICATIONS
* LED flashlights and torches * LED backlights * White LED driving * Multiple LED driving * Solar Equipment
TYPICAL APPLICATION CIRCUIT
VBATT
ORDERING INFORMATION
DEVICE ZXSC300E5TA Reel 7" Tapewidth 8mm Quantity per reel 3,000
L1
100H
U1
Vcc Vdrive Isense Gnd ZXSC300
Q1
FMMT617
LED1
WHITE LED
DEVICE MARKING C300
Package SOT23-5
R1
0.33R
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ZXSC300
ABSOLUTE MAXIMUM RATING
Supply Voltage -0.3 to 10V Maximum Voltage Other Pins -0.3 to VCC+0.3V Power Dissipation 450mW Operating Temperature Storage Temperature -40 to 85C -55 to 150C
ELECTRICAL CHARACTERISTICS: Test conditions unless otherwise stated: VCC=1.5V, TAMB=25C
SYMBOL V CC PARAMETER Efficiency
1
CONDITIONS
MIN.
TYP.
MAX. UNITS 94 % V
Recommended supply voltage range Minimum startup and operating voltage Quiescent current 2 Base drive current Supply current
3
0.8
8
V CC(min)
I DRIVE =-600A, V DRIVE =0.7V I DRIVE =-600A, V DRIVE =0.7V, T AMB =-10C 3
0.8 0.9 0.2
0.92
V
IQ I VDRIVE I CC V VDRIVE(high) V VDRIVE(low) V ISENSE (threshold) T CVISENSE I ISENSE T DRV
mA 3.6 4 V CC 0.2 mA mA V V mV
V DRIVE = 0.7V, V ISENSE = 0V V DRIVE = 0.7V, V ISENSE = 0V V ISENSE = 0V, I VDRIVE =-0.5mA V ISENSE = 50mV, I VDRIVE = 5mA
1.5 2 V CC -0.3 0 14 19
High level drive voltage Low level drive voltage Output current reference voltage I SENSE voltage temp co. 2 I SENSE input current Discharge pulse width
24
0.4 V ISENSE = 0V 1.2 0 -30 1.7 -65 3.2
%/C A s
OPERATING CONDITIONS
SYMBOL F OSC
1 2 3 4
PARAMETER Recommended operating frequency
4
CONDITIONS
MIN.
TYP.
MAX. 200
UNITS kHz
Application dependent, see reference designs. These parameters guaranteed by design and characterisation Total supply current =IQ + IVDRIVE, see typical characteristics Operating frequency is application circuit dependent. See applications section.
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ZXSC300
FMMT617
For the circuits described in the applications section, Zetex FMMT617 is the recommended pass transistor. The following indicates outline data for the transistor, more detailed information can be found in the Zetex surface mount data book or at www.zetex.com
ELECTRICAL CHARACTERISTICS (at TA = 25C unless otherwise stated).
PARAMETER Collector-Emitter Saturation Voltage Collector-Emitter Breakdown Voltage SYMBOL MIN. V CE(sat) TYP. 8 70 150 15 18 MAX. 14 100 200 UNIT mV mV mV V CONDITIONS I C =0.1A, I B =10mA* I C =1A, I B =10mA* I C =3A, I B =40mA* I C =10mA*
V (BR)CEO
*Measured under pulsed conditions. Pulse width=300s. Duty cycle 2%
ZHCS1000
For the circuits described in the applications section Zetex ZHCS1000 is the recommended Schottky diode. The following indicates outline data for the diode, more detailed information is available at www.zetex.com
ELECTRICAL CHARACTERISTICS (at Tamb = 25C unless otherwise stated).
PARAMETER Forward Voltage Reverse Current Reverse Recovery Time SYMBOL VF IR t rr 50 12 MIN. TYP. MAX. 400 500 100 UNIT mV mV A ns CONDITIONS I F =500mA I F =1A V R =30V Switched from IF = 500mA to IR = 500mA. Measured at IR=50mA
*Measured under pulsed conditions. Pulse width=300s. Duty cycle 2%
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ZXSC300
TYPICAL CHARACTERISTICS
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ZXSC300
DEVICE DESCRIPTION
The ZXSC300 is PFM, controller IC which, when combined with a high performance external transistor, enables the production of a high efficiency boost converter for use in single cell LED driving applications. A block diagram is shown for the ZXSC300 in Figure 1. With every on pulse the switching transistor is kept on until the voltage across the current-sense resistor exceeds the threshold of the ISENSE input. The on-pulse length, and therefore the switching frequency, is determined by the programmed peak current, the input voltage and the input to output voltage differential. See applications section for details. The Driver circuit supplies the external switching transistor with a fixed drive current. To maximise efficiency the external transistor switched quickly, typically being forced off within 30ns.
Pinout Diagram
Figure 1 ZXSC300 Block Diagram
The on chip comparator forces the driver circuit and therefore the external switching transistor off if the voltage at ISENSE exceeds 19mV. This threshold is set by an internal reference circuit and divider. The Voltage at ISENSE is taken from a current sense resistor connected in series with the emitter of the switching transistor. A monostable following the output of the comparator forces the turn-off time of the output stage to be typically 1.7s. This ensures that there is sufficient time to discharge the inductor coil before the next on period.
Pin Descriptions
Pin No. 1 2 3 4 5 Name V CC Gnd N/C I SENSE V DRIVE Description Supply voltage, generally Alkaline, NiMH or NiCd single cell Ground Not connected Inductor current sense input. Internal threshold voltage set to 19mV. Connect external sense resistor Drive output for external switching transistor. Connect to base of external switching transistor
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ZXSC300
REFERENCE DESIGNS
Two typical LED driving applications are shown. Firstly a maximum brightness solution and secondly an optimised battery life solution.
Maximum brightness solution
This circuit provides a constant current output to the LED by rectifying the switching pulses. This ensures maximum LED brightness.
VBATT
L1
100H
D1
ZHCS1000
U1
Vcc Vdrive Isense Gnd ZXSC300
Q1
FMMT617
C1
2.2F
LED1
WHITE LED
R1
0.1R
Material List
Ref U1 Q1 D1 R1 C1 L1 LED1 Value N/A N/A 1A 100mW 2.2mF 100H 5600mcd Part Number ZXSC300E5 FMMT617 ZHCS1000 Generic Generic DO1608P-104 NSPW500BS Manufacture Zetex Plc Zetex Plc Zetex Plc Various Various Coilcraft Nichia Comments Single cell converter, SOT23-5 Low V CE(sat) NPN, SOT23 1A Shottky diode, SOT23 0805 Size Low ESR ceramic capacitor Surface mount inductor White LED
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ZXSC300
Maximum battery life solution
To ensure optimum efficiency, and therefore maximum battery life, the LED is supplied with a pulsed current. Maximum efficiency is ensured with the removal of rectifier losses experienced in the maximum brightness solution.
100
VBATT
L1
100H
Single LED Load
Efficiency (%)
U1
Vcc Vdrive Isense Gnd ZXSC300
Q1
FMMT617
95
LED1
WHITE LED
90
R1
0.33R
85
1.0
1.5
2.0
2.5
3.0
3.5
Input Voltage (V)
Input Voltage v Efficiency
Materials list
Ref U1 Q1 R1 L1 LED1 Value N/A N/A 330mW 100mH 5600mcd Part Number ZXSC300E5 FMMT617 Generic DO1608P-104 NSPW500BS Manufacture Zetex Plc Zetex Plc Various Coilcraft Nichia Comments Single cell converter, SOT23-5 Low V CE(SAT) NPN, SOT23 0805 Size Surface mount inductor White LED
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ZXSC300
APPLICATIONS INFORMATION
The following section is a design guide for optimum converter performance. Switching transistor selection The choice of switching transistor has a major impact on the converter e fficiency. F or optim um performance, a bipolar transistor with low VCE(SAT) and high gain is required. The Zetex FMMT617 is an ideal choice of transistor, having a low saturation voltage. A data sheet for the FMMT617 is available on Zetex web site or through your local Zetex sales office. Outline information is included in the characteristics section of this data sheet.
Schottky diode selection
For the maximum battery life solution a Schottky rectifier diode is required. As with the switching transistor the Schottky rectifier diode has a major impact on the converter efficiency. A Schottky diode with a low forward voltage and fast recovery time should be used for this application. The diode should be selected so that the maximum forward current is greater or equal to the maximum peak current in the inductor, and the maximum reverse voltage is greater or equal to the output voltage. The Zetex ZHCS1000 meets these needs. Datasheets for the ZHCS Series are available on Zetex web site or through your local Zetex sales office. Outline information is included in the characteristics section of this data sheet. For the maximum brightness solution a pulsed current is supplied to the LED therefore a Schottky rectifier diode is not required. Inductor selection The inductor value must be chosen to satisfy performance, cost and size requirements of the overall solution. For the reference designs we recommend an inductor value of 100uH with a core saturation current rating greater than the converter peak current value and low series resistance. Inductor selection has a significant impact on the converter performance. For applications where efficiency is critical, an inductor with a series resistance of 500m or less should be used. Peak current definition The peak current rating is a design parameter whose value is dependent upon the overall application. For the high brightness reference designs, a peak current of was chosen to ensure that the converter could provide the required output power to the LED. In general, the IPK value must be chosen to ensure that the switching transistor, Q1, is in full saturation with maximum output power conditions, assuming worse-case input voltage and transistor gain under all operating temperature extremes. Once IPK is decided the value of R SENSE can be determined by: RSENSE = VISENSE IPK
where VISENSE=19mV
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ZXSC300
Output Power Calculation
By making the above assumptions for inductance and peak current the output power can be determined by: POUT = (VOUT- VIN) x (IPK + IMIN) TOFF x (TON + TOFF ) 2 Operating frequency can be derived by: 1 F= (TON + TOFF ) Capacitor selection For pulsed operation, as in the maximum battery life solution, no capacitors are required at the output to the LED. For rectified operation, as in the maximum brightness solution, a small value ceramic capacitor is required, typically 2.2uF. Generally an input capacitor is not required, but a small ceramic capacitor may be added to aid EMC, typically 470nF to 1uF. Demonstration board T (V - VIN) = OFF OUT VIN A demonstration board for the Maximum battery life solution, is available upon request. These can be obtained through your local Zetex office or through Zetex web pages. For all reference designs Gerber files and bill of materials can be supplied.
Note: VOUT = output voltage + Schottky rectifier voltage drop
where TOFF 1.7s (internally set by ZXSC300) and TON and IMIN = IPK - ( VOUT - VIN ) x TOFF L
Layout of Maximum battery life solution
Top Copper
Drill Holes
Bottom Copper
Silk Screen
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ZXSC300
SUPPLIER LISTING
Manufacturer EUROPE Zetex GmbH Germany (49) 894549490 ASIA Zetex Asia Hong Kong (852) 2610 0611 http://www.zetex.com AVX UK (44) 1252 770000 AVX Asia Singapore (65) 6286 7555 http://www.avxcorp.com Coilcraft Europe UK (44) 1236 730595 http://www.coilcraft.com Nichia Europe B.V. The Netherlands (31) 20 5060900 Nichia Corporation Japan (81) 3 3456 3784 Nichia America Corporation Head Office (1) 717 285 2323 San Jose (1) 408 573 0933 Coilcraft Inc (1) 847 639 6400 AVX USA (1) 843 448 9411 USA Zetex Inc (1) 631 543 7100
Zetex
Tel: URL:
AVX
Tel: URL:
Coilcraft
Tel: URL:
Nichia Corporation
Tel:
URL:
http://www.nichia.co.jp
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ZXSC300
PACKAGE OUTLINE PACKAGE DIMENSIONS
Millimeters DIM MIN. A A1 A2 b C D E E1 e e1 L a 0.90 0.90 0.20 0.09 2.70 2.20 1.30 MAX. 1.45 0.15 1.30 0.50 0.26 3.10 3.20 1.80 MIN. 0.0354 0.0354 0.0078 0.0035 0.1062 0.0866 0.0511 MAX. 0.0570 0.0059 0.0511 0.0196 0.0102 0.1220 0.1181 0.0708 Inches
0.95 REF 1.90 REF 0.10 0 0.60 30
0.0374 REF 0.0748 REF 0.0039 0 0.0236 30
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ZXSC300
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 or visit: www.zetex.com 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" "Last time buy (LTB)" "Not recommended for new designs" "Obsolete" Datasheet status key: "Draft version" "Provisional version" "Issue" Product status recommended for new designs Device will be discontinued and last time buy period and delivery is in effect Device is still in production to support existing designs and production Production has been discontinued This term denotes a very early datasheet version and contains highly provisional information, which may change in any manner without notice. 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. This term denotes an issued datasheet containing finalized specifications. However, changes to specifications may occur, at any time and without notice.
(c) Zetex Semiconductors plc 2006 Europe Zetex GmbH Kustermann-Park Balanstrae 59 D-81673 Munchen Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 europe.sales@zetex.com
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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
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