Zetex zxld1350ev2 User's Manual
Contents
1. Rs 0 1V lour where lour the LED current Rs the sense resistor value in ohms Do not use a resistor value lower than 0 2790 0 1V is the nominal sense voltage with ADJ open circuit or set to 1 25V Follow the ZXLD1350EV2 Power Up sequence Using external LEDs or loads 1 Switch off the power supply Connect external LEDs across test pins LED a and LED K LED a is the LEDs anode connection point and LED k is the LEDs cathode connection point The number of external LEDs that can be connected depends on their operating power and forward voltage drop For an external load other than LEDs the positive terminal of the load should be connected to test pin LED a and the negative terminal of the load should be connected to test pin LED k Connector J1 is compatible with the Luxeon Emitter Board System from Future Electronics or can be used to connect LEDs via pin strip connectors Follow the ZXLD1350EV2 Power Up sequence ZXLD1350EV2 User Guide Iss 5 10 04 07 HZETEX ZXLD1350EV2 SEMICONDUCTORS PERFORMANCE The system efficiency depends on the sense resistor supply voltage switching inductor and the number of 1W LEDs connected in series The graph below shows the efficiency with a 0 33Q sense resistor Rs and a 100uH inductor for 1 to 3 series connected 1W LEDs With a 24V supply the switching frequency is typically 545kHz for three series connected 1 watt LEDs and 300kHz2. ZXLD1350 is now effectively being turned on and off at the PWM frequency The dimming ratios are in the region of 100 1 much greater than the DC dimming ratio The average LED current output current lout IS given by lour 0 1 D Rs where lout the average LED current Rs the sense resistor value in ohms Do not use a resistor value lower than 0 27Q D the duty cycle of the PWM dimming frequency 0 1V is the nominal sense voltage with ADJ open circuit or set to 1 25V Follow the ZXLD1350EV2 Power Up sequence Soft start 1 2 3 4 Switch off the power supply Solder a link across R1 pads Fit a capacitor at C3 to decouple the pin The value of C3 will determine the soft start time setting Please see the datasheet for calculation of the capacitor value Follow the ZXLD1350EV2 Power Up sequence Switching the output current off ee Switch off the power supply Solder a link across R1 pads Follow the ZXLD1350EV2 Power Up sequence Connect the ADJ pin to GND to turn off the output current Follow the ZXLD1350EV2 Power Up sequence The ZXLD1350 internal switch remains switched off output current off whilst the ADJ pin is pulled to GND Changing the LED current 1 2 3 4 Switch off the power supply Remove Rs Calculate and fit a new sense resistor Rs the value of which is based on the required LED current without dimming Rs can be calculated using following equation
3. for a single 1 watt LED With a 12V supply the switching frequency is typically 160kHz for three series connected 1 watt LEDs and 280kHz for a single 1 watt LED The detailed performance information for the device can be found in the datasheets Efficiency vs Vin Rsense 0 33 Ohms L 100uH NIC NPIS53D101MTRF 95 90 Eff g 1 LED A 2 LED x 3 LED 85 80 75 Figure 6 Efficiency vs supply voltage ZXLD1350EV2 User Guide Iss 5 10 04 07 EZETEX ZXLD1350EV2 SEMICONDUCTORS 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 users 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
4. 0 33R 0805 NCST10FR330FTRF NIC a 1 200ppm E R1 R2 Not fitted 0805 Notfitted C1 C2 1uF 50V 1206 a 1206 X7R erereOw oS Not fitted 0805 Notfited L1 100uH EFT RF MTRF we ee 5A rms components Inductor 40V 1 16A SOT23 ZLLS1000 Schottky diode ZXLD1350 TSOT23 5 ZXLD1350E5TA DC DC converter D1 D2 D3 1W LED sim J LXHL PWO1 1W power LED JP3 jumper pin strips ADJ LED a LED k A a d e e connector The slugs of the 1 watt LEDs are connected to isolated copper floods both on the top and bottom layers with thermal inter connection between the layers The slugs are electrically isolated from other circuits and pads on the evaluation board Warning At a nominal 24V_operation with 300mA output the board temperature rises b around 30C from ambient after 30 minutes of operation ZXLD1350EV2 EVALUATION BOARD k BZETEX T SEMICONDUCTORS a JP1 _ JP2 In partnership with FUTURE Lighting Solutions Bare board ZDB308R3 Copyright Zetex Plc 2006 Figure 3 Component layout ZXLD1350EV2 User Guide Iss 5 10 04 07 HZETEX ZXLD1 350 EV2 SEMICONDUCTORS EZETEX SEMICONDUCTORS Figure 4 Top View Figure 5 Bottom View ZXLD1350EV2 Connection Point Definition Name Description _ gt gt Positive supply voltage Connect a 24V positive supply to this pin Supply Ground OV Connect supply ground to this pin ADJ Internal vo
5. 1 pads Fit a 10nF capacitor at C3 to decouple the pin Drive the ADJ pin on the board with a DC voltage in the range 0 3V to 1 25V Do not exceed 1 25V as this represents 100 of the LED current set by Rs The current will increase in proportion to this voltage For example if 2 5V is applied the current will increase to 200 That is the current will be twice the 1 25V rating For such over drive of the ADJ pin the LED and ZXLD1350 are likely to be damaged The nominal LED current output current lout is given by hs EN lout 0 08 Vap Rs where lour the nominal LED current Vans the DC dimming voltage at ADJ pin resistor 0 08 is the multiplier for the reference voltage on ADJ pin Rs the sense resistor value in ohms Do not use a resistor value lower than 0 27Q 6 The dimming ratio is around 6 1 Note as the voltage approaches 0 2V on the ADJ pin the ZXLD1350 will shut down 7 Follow the ZXLD1350EV2 Power Up sequence High Frequency PWM Dimming Switch off the power supply Solder a link across R1 pads Ensure C3 is not fitted Connect a PWM signal to the ADJ pin via an open collector NPN transistor or an open drain N channel MOSFET Alternatively drive the ADJ pin directly with a PWM signal However make sure the PWM signal voltage levels do not violate the ADJ pin voltage rating Driving the ADJ pin above 1 25V will exceed the maximum set current for the value of Rs and may damage the device or LED
6. 6 Set the PWM frequency to between 10KHz and 50KHz The cut off frequency of the internal filter is 4kHz and exceeding the 50KHz may cause modulation with the switching regulator 7 The dimming ratio will be about 6 1 similar to the DC dimming The nominal LED current output current lout is given by aan dl aa pi lout 0 1 D Rs where lout the nominal LED current Rs the sense resistor value in ohms Do not use a resistor value lower than 0 270 D the duty cycle of the PWM dimming frequency 0 1V is the nominal sense voltage with ADJ open circuit or set to 1 25V Note The ADJ pin is internally referenced to 1 25V This pin should be left floating for normal operation without dimming Please refer to the datasheet for PWM frequency 8 Follow the ZXLD1350EV2 Power Up sequence ZXLD1350EV2 User Guide Iss 5 10 04 07 aZETEX SEMICONDUCTORS Low Frequency PWM Dimming a g1 8 Switch off the power supply Solder a link across R1 pads Make sure C3 is not fitted Connect a PWM signal to the ADJ pin via an open collector NPN transistor or an open drain N channel MOSFET Alternatively drive the ADJ pin directly with a PWM signal However make sure the PWM signal voltage levels do not violate the ADJ pin voltage rating Driving the ADJ pin above 1 25V will exceed the maximum set current for the value of Rs and may damage the device or LED The PWM frequency can be low around 100Hz or up to 1kHz The
7. HZETEX ZXLD1350EV2 SEMICONDUCTORS ZXLD1350EV2 EVALUATION BOARD USER GUIDE DESCRIPTION The ZXLD1350EV2 Figure 1 is an evaluation board for evaluating the ZXLD1350 350mA LED driver with internal switch The evaluation board can be used to drive 1 2 or 3 one watt LEDs or an external choice of LEDs The number of external connected LEDs depends on the forward voltage of the LEDs connected A connector J1 is provided which is compatible with the modular evaluation system used by Future Electronics Ltd The LEDs fitted on this evaluation board are from the LUXEON range distributed by Future Lighting Solutions www FutureLightingSolutions com The operating voltage is nominally 24V For three 1W series connected LEDs the voltage can be from 12V minimum to 30V maximum The 100UH inductor used in the circuit is based on a nominal 24V supply which should be connected across VIN and GND pins Note The evaluation board does not have reverse battery protection The nominal current for the evaluation board is set at 300mA with a 0 33 sense resistor Rs Jumpers J1 J2 and J3 allow the selection of the number of LEDs to be connected in series Jumper on at J1 bypasses LED D1 Jumper on at J3 bypasses LED D3 Removing jumper J2 disconnects all the on board LEDs from the current flow path Jumper 2 also doubles as a connection point for an ammeter to measure the LED current Before connecting external LEDs across test pins LED and LED or acro
8. V2 ZXLD1350 Operation In normal operation when voltage is applied at VIN the ZXLD13350 internal NDMOS switch is turned on Current starts to flow through sense resistor Rs inductor L1 and the LEDs The current ramps up linearly and the ramp rate is determined by the input voltage VIN and the inductor L1 This rising current produces a voltage ramp across Rs The internal circuit of the ZXLD1350 senses the voltage across Rs and applies a proportional voltage to the input of the internal comparator When this voltage reaches an internally set upper threshold the NDMOS switch is turned off The inductor current continues to flow through Rs L1 the LEDs the schottky diode SD1 and back to the supply rail but it decays with the rate of decay determined by the forward voltage drop of the LEDs and the schottky diode This decaying current produces a falling voltage at Rs which is sensed by the ZXLD1350 A voltage proportional to the sense voltage across Rs is applied at the input of the internal comparator When this voltage falls to the internally set lower threshold the NDMOS switch is turned on again This switch on and off cycle continues to provide the average LED current set by the sense resistor Rs Please refer to the datasheets for the threshold limits ZXLD1350 internal circuits electrical characteristics and parameters ZXLD1350EV2 User Guide Iss 5 10 04 07 EH ZETEX ZXLD1 350 EV2 SEMICONDUCTORS ZXLD1350EV2 Evaluation Board Rs
9. cted in series Jumper on at J1 bypasses LED D1 Jumper on at J3 bypasses LED D3 Removing jumper J2 disconnects all the 1 watt LEDs from the current flow path Jumper 2 also doubles as a connection point for an ammeter to measure the LED current Both DC and PWM dimming can be achieved by driving the ADJ pin For DC dimming the ADJ pin may be driven between 0 3V and 1 25V Driving the ADJ pin below 0 2V will shutdown the output current For PWM dimming an external open collector NPN transistor or open drain N channel MOSFET can be used to drive the ADJ pin The PWM frequency can be low around 100HZz to 1kHz or high between 10kHz to 50kHz C3 should not be fitted on the evaluation board when using the PWM dimming feature Shorting R1 will connect the test pin ADJ to device pin ADJ The capacitor C3 should be around 10nF to decouple high frequency noise at the ADJ pin for DC dimming The soft start time will be nominally 0 5ms without capacitor C3 Adding C3 will increase the soft start time by approximately 0 5ms nF For other reference designs or further applications information please refer to the ZXLD1350 datasheet Schematic Diagram Figure 2 shows the schematic for the ZXLD1350EV2 evaluation board RS Vin OR33 LED K Emi SD1 a a 1uF 50V ZLLS1000 sense 6 5 4 R2 3 not fitted 2 1 a R1 ZXLD1350 2 O L1 100uH C3 not fitted GND Figure 2 Schematic for the evaluation board ZXLD1350E
10. 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 th
11. e 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 b
12. een 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 Europe Americas Asia Pacific Corporate Headquarters Zetex GmbH Zetex Inc Zetex Asia Ltd Zetex Semiconductors plc Kustermann park 700 Veterans Memorial Highway 3701 04 Metroplaza Tower 1 Zetex Technology Park Chadderto
13. in of NDMOS switch GND GND Ground 0V ADJ Internal voltage ref pin 1 25V Leave floating for normal operation Connect to GND to turn off output current Drive with DC voltage 0 3V to 1 25V or with PWM signal to adjust output current or Connect a capacitor from this pin to ground to set soft start time ISENSE 4 Connect a sense resistor Rs from the ADJ pin to VIN to sense the nominal output current Nominal lout 0 1 Rs 5 Input voltage 7V to 30V Decouple to ground with a 1uF or higher ceramic capacitor ORDERING INFORMATION EVALBOARD ORDER NUMBER DEVICE ORDER NUMBER ZXLD1350EV2 ZXLD1350E5TA Please note Evaluation boards are subject to availability and qualified leads ZXLD1350EV2 User Guide Iss 5 10 04 07 EZETEX ZXLD1350EV2 SEMICONDUCTORS ZXLD1350EV2 EVALUATION BOARD REFERENCE DESIGN The ZXLD1350EV2 is configured to the reference design in Figure 2 The target application is a driver for one or more series connected 1W white LEDs for torches and other high powered LED driving applications The operating voltage is a nominal 24V For three 1W series connected LEDs the voltage can be from 12V minimum to 30V maximum The nominal current is set at 300mA with a 0 33Q sense resistor Rs For three series connected 1 watt LEDs with a nominal supply of 24V the ZXLD1350 runs in continuous mode at 545kHz with a 100uH inductor Jumpers J1 J2 and J3 allow selection of the number of LEDs to be conne
14. ltage ref pin 1 25 This pin can be used to achieve dimming and soft start and for switching the output current off e Leave floating for normal operation e See Other Features section to achieve dimming and soft start and for switching the output current off point Disconnect the jumper JP2 when driving an external load LED k LED k_ connects to the CATHODE of LED D1 and is the external LED cathode connection point Disconnect the jumper JP2 when driving external LEDs Pins 1 amp 2 LED a Pins 5 amp 6 LED k ZXDL1350EV2 OPERATION ZXLD1350EV2 Power Up 1 Connect VIN to 24V of the power supply unit PSU Connect GND to the power supply ground OV Warning The board does not feature reverse battery supply protection 2 Set the PSU to 24V 24V at VIN pin with ref to the GND pin 3 Turn on the PSU Warning Do not stare at the LEDs directly 4 Ensure jumper J2 is fitted With JP1 and JP3 disconnected jumper off all three LEDs should illuminate and will be regulated nominally at 300mA 5 To change the number of LEDs connected in series use jumper JP1 and JP3 to bypass LEDs D1 and D3 respectively Warning The LEDs may be hot ZXLD1350EV2 User Guide Iss 5 10 04 07 EH ZETEX ZXLD1 350 EV2 SEMICONDUCTORS OTHER FEATURES Dimming The ZXLD1350 provides three dimming options DC high frequency PWM and low frequency PWM dimming DC Voltage Dimming Switch off the power supply Solder a link across R
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16. ss J1 remove jumper J2 Jumpers J1 and J2 can be on or off Test point ADJ provides a connection point for DC or PWM dimming and shutdown Warning At 24V nominal operation with 300mA output the LEDs and the PCB may be hot and the LEDs will be ver bright ZXLD1350EV2 EVALUATION BOARD HZETEX i s miconDuctorns LED k l JP2 in partnership with lt v4 Lighting Solutions Bare board ZDB308R3 Copyright Zetex Pic 2006 Figure 1 ZXLD1350EV2 evaluation board ZXLD1350EV2 User Guide Iss 5 10 04 07 EZETEX ZXLD1350EV2 SEMICONDUCTORS ZXLD1350 DEVICE DESCRIPTION The ZXLD1350 is a continuous mode inductive driver in a TSOT23 5 package for driving one or more series connected LEDs efficiently from a voltage source higher than the LED voltage The device includes the output switch and a current sense circuit which requires an external sense resistor to set the nominal current up to 350mA ZXLD1350 DEVICE FEATURES DEVICE APPLICATIONS e Drives one or more series connected 1W white e LED flashlights LEDs up to 350mA High Power LED driving Internal 30V switch Low voltage halogen replacement LEDs Wide input voltage 7V to 30V Automotive lighting Inherent open circuit LED protection Illuminated signs Brightness control using DC or PWM Internal PWM filter ZXLD1350 Device Packages Pin and Definitions ZXLD1350 T SENSE 4 TSOT23 5 pack ZXLD1350 Device Pin Definition Description Name Dra
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