Zetex Semiconductors PLC ZXLD1362EV3 User Manual

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 to the Zetex ZXLD1360 and ZXLD1350 products for applications requiring
input voltages lower than 30V.
The nominal current for the evaluation board is set at 700mA with a
The 68uH inductor used in the circuit is based on a 30V nominal supply, which should be connected across +VIN and
GND pins.

Note: The evaluation board does not have reverse polarity protection. It is fitted with a 2.1mm DC power plug with
positive to the centre pole.

Test point ADJ provides a connection point for DC or PWM dimming and shutdown.

Warning: with 700mA output, the connected LED will be hot and very bright

Figure 1: ZXLD1362EV3 evaluation board

0.15Ω sense resistor, R1.

ZXLD1362EV3 User Guide issue 1 1/7 11-01-2008

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

• Drives one or more series-connected LEDs

• LEDs up to 1000mA.

• Internal 60V switch.

• Wide input voltage: 7V to 60V.

• Inherent open circuit LED protection.

• Brightness control using DC or PWM.

• Internal PWM filter.

ZXLD1362 Device Packages, Pin and Definitions

DEVICE APPLICATIONS

• LED flashlights.

• High Power LED driving.

• Low-voltage halogen replacement LEDs.

• Automotive lighting.

• Illuminated signs.

TSOT23-5 pack

ZXLD1362 Device Pin Definition
Name Pin No Description

LX 1 Drain of NDMOS switch.
GND 2 Ground (0V).
ADJ 3 Internal voltage ref. pin (1.25V) :

• Leave floating for normal operation.

• Connect to GND to turn off output current.

• Drive with a DC voltage (0.3V to 1.25V) or with a PWM signal to adjust

output current

• Connect a capacitor from this pin to ground to set the soft-start time.

ISENSE 4 Connect a sense resistor, Rs, from the ADJ pin to VIN to sense the nominal

output current. Nominal I

VIN 5 Input voltage: 7V to 60V. Decouple to ground with a 100nF and a 10uF or

higher ceramic capacitor depending on the input voltage[1].

= 0.1/ R1

out

ORDERING INFORMATION

EVALBOARD ORDER NUMBER

ZXLD1362EV3

DEVICE ORDER NUMBER

ZXLD1362E5TA

Please note: Evaluation boards are subject to
availability and qualified leads.

ZXLD1362EV3 User Guide issue 1 2/7 11-01-2008

K

A

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
device operates in continuous mode at approximately 150 kHz, with a 68uH inductor.

An accurate way of determining the current, avoiding the need to insert an ammeter in the current path, is to measure
the voltage on the sense resistor. A 10K resistor and a 1uF capacitor can be used to form a low pass filter and the
voltage across the capacitor represents a more stable dc reading of current. Using this method, 100mV represents

0.7 Amp when using a 0.15 sense resistor.

The ADJ pin connects to a low pass filter within the ZXLD1362 chip to provide some decoupling, but the external
capacitor C2 (100nF) is used to provide additional decoupling to reduce any high frequency noise as well as
enabling the soft start function.
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 shut down 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 100Hz to 1 kHz, or high between 10 kHz to 50 kHz.
For low frequency, PWM capacitor C2 should be removed on the evaluation board, to give a more accurate duty
cycle.
Shorting R2 will connect the test pin ADJ to device pin ADJ if needed.
The external capacitor C2 on the ADJ pin sets the soft start time. The amount of soft start time achievable is
approximately 0.2ms/nF.
For other reference designs or further applications information, please refer to the ZXLD1362 datasheet.

Schematic Diagram

Figure 2 shows the schematic for the ZXLD1362EV3 evaluation board.

Vin

R1

0.15Ω sense resistor R1. The

LED

ADJ

GND

R2

54

Vin V sense

3

ADJ LX

ZXLD1362

GND

1

C1

C4

C2

Figure 2: Schematic for the evaluation board ZXLD1362EV3

C3

D1

L1

LED

ZXLD1362EV3 User Guide issue 1 3/7 11-01-2008