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SEMICONDUCTORS
DESCRIPTION
The ZXLD1937 is a PFM inductive boost converter
designed for driving 2, 3 or 4 series connected white
LEDs from a Li-Ion cell and up to 8 LEDs from a 5V
supply. The device operates from an input supply of
between 2.5V and 5.5V and provides an adjustable
output current of up to 50mA.
The ZXLD1937 includes the output switch and peak
current sense resistor, and can operate with a
maximum output voltage of 28V.
Quiescent current is typically 60H9262A and a shutdown
function is provided to reduce this current to less than
500nA in the 'off' state.
ADVANCED FEATURES
• True Analog Dimming via PWM
FEATURES
• 1mm height profile TSOT23-5 pin package
• Internal PWM filter for flicker free output
• High efficiency (80% typ)
• Wide input voltage range: 2.5V to 5.5V
• Up to 50mA output current
• Low quiescent current: (60H9262A typ)
• 500nA maximum shutdown current
• Up to 1MHz switching frequency
• Low external component count
• Inherently matched LED currents
Output current can be adjusted by applying a PWM
control signal to the 'Enable' pin. Depending upon the
control frequency, this will provide either a continuous
or a 'chopped' output current. The PWM filter
components are contained within the chip.
The device is assembled in the TSOT23-5 pin package
with 1mm maximum height profile.
APPLICATIONS
• Mobile phones
• Digital cameras
• PDAs
• LCD modules
• Portable internet appliances
• Palmtop computers
ZXLD1937
ISSUE 1 - JULY 2004
ADJUSTABLE LED DRIVER WITH INTERNAL SWITCH IN TSOT23-5
PIN CONNECTIONS
TYPICAL APPLICATION CIRCUIT