Zetex Semiconductors PLC ZXLD1362EV3 user manual

Summary of the content on the page No. 1

ZXLD1362EV3 USER GUIDE

DESCRIPTION
The ZXLD1362EV3, Figure 1, is a PCB constructed using an aluminium base for evaluating the ZXLD1362 LED
driver with internal switch [1]. The evaluation board can be used to drive an external choice of LEDs; the total forward
voltage across the LEDs depending on the number and type connected.

The operating voltage is nominally higher than 30V for the external LEDs, and can be raised to 60V maximum, which
will reduce the supply current. Please refer

Summary of the content on the page No. 2

ZXLD1362 DEVICE DESCRIPTION The ZXLD1362 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 1000mA. ZXLD1362 DEVICE FEATURES DEVICE APPLICATIONS • Drives one or more series-connected LEDs • LED flashlights. • LEDs up

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ZXLD1362EV3 EVALUATION BOARD REFERENCE DESIGN The ZXLD1362EV3 is configured to the reference design in Figure 2. The target application is a driver for one or more series-connected LEDs for luminaires in both commercial and automotive applications. The maximum operating voltage is 60V, and the nominal current is set at 700mA with a 0.15 Ω sense resistor R1. The device operates in continuous mode at approximately 150 kHz, with a 68uH inductor. An accurate way of determining the curr

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ZXLD1362 Operation In normal operation, when voltage is applied at +VIN, the ZXLD1362 internal NDMOS switch is turned on. Current starts to flow through sense resistor R1, 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 R1. The internal circuit of the ZXLD1362 senses the voltage across R1 and applies a proportional voltage to the input of the i

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ZXLD1362EV3 Connection Point Definition Name Description +VIN Positive supply voltage. GND Supply Ground (0V). ADJ Internal voltage ref. pin (1.25V). This pin can be used to achieve dimming and soft-start, and for switching the output current off. • Leave floating for normal operation. • See 'Circuit Features' section to achieve dimming, soft-start and for switching the output current off. LED A LED A connects to the external LED anode LED K LED K connects to the external

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PERFORMANCE The system efficiency depends on the sense resistor, supply voltage, switching inductor, and the number of LEDs. With a 60V supply and 15 LEDs, the switching frequency is typically 200 kHz and efficiency levels >90% are achievable. Visit our website www.zetex.com to find useful tools for circuit design and simulation. REFERENCE [1] ZXLD1362 Datasheet – www.zetex.com ZXLD1362EV3 User Guide issue 1 6/7 11-01-2008

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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 t