ZXLD1350_07 Datasheet, PDF (1/24 Pages) Zetex Semiconductors – 350mA LED driver with internal switch

ZXLD1350
350mA LED driver with internal switch
Description
The ZXLD1350 is a continuous mode
inductive step-down converter, designed for
driving single or multiple series connected
LEDs efficiently from a voltage source higher
than the LED voltage. The device operates
from an input supply between 7V and 30V and
provides an externally adjustable output
current of up to 350mA. Depending upon
supply voltage and external components, this
can provide up to 8 watts of output power.
The ZXLD1350 includes the output switch and
a high-side output current sensing circuit,
which uses an external resistor to set the
nominal average output current.
Output current can be adjusted above, or
below the set value, by applying an external
control signal to the 'ADJ' pin.
The ADJ pin will accept either a DC voltage or a
PWM waveform. Depending upon the control
frequency, this will provide either a continuous
or a gated output current. The PWM filter
components are contained within the chip.
The PWM filter provides a soft-start feature by
controlling the rise of input/output current. The
soft-start time can be increased using an
external capacitor from the ADJ pin to ground.
Applying a voltage of 0.2V or lower to the ADJ
pin turns the output off and switches the device
into a low current standby state.
The device is assembled in a TSOT23-5 pin
package.
Features
Applications
• Simple low parts count
• Low voltage halogen replacement LEDs
• Internal 30V NDMOS switch
• Automotive lighting
• 350mA output current
• Low voltage industrial lighting
• Single pin on/off and brightness control • LED back-up lighting
using DC voltage or PWM
• Internal PWM filter
• Illuminated signs
• Soft-start
• High efficiency (up to 95%^(*))
• Wide input voltage range: 7V to 30V
• 40V transient capability
• Output shutdown
• Up to 1MHz switching frequency
• Inherent open-circuit LED protection
• Typical 4% output current accuracy
(*) Using standard external components as specified under electrical characteristics. Efficiency is dependent upon the
number of LEDs driven and on external component types and values.
Pin connections
Typical application circuit
LX ¹
5 V_IN
VIN (12V - 30V)
Rs
0.33
GND ²
ADJ 3
4 I_SENSE
TSOT23-5
Top view
C1 1␮F
D1
ZLLS1000
L1 47␮H
VIN
N/C
ADJ
GND
ISENSE
LX
ZXLD1350
GND
Issue 6 - April 2007
1
© Zetex Semiconductors plc 2007
www.zetex.com