LED Driver/Monitor AD8240
FEATURES FUNCTIONAL BLOCK DIAGRAM
VPLUS SHUNT
5 6 BASE VO 7 8 RSENSE
VSENSE 1 10kΩ 5V
2
REFERENCE PWM R1
350kΩ
LATCH-OFF
DRIVER 3 R2
250kΩ AD8240 GENERAL DESCRIPTION 4 GND The AD8240 LED driver/monitor, in combination with an
external transistor, supplies a constant 12 V to drive LED
lamps. This allows cost-effective LED lamp monitoring and
short-circuit protection. The output is regulated at 12 V when
the supply voltage is between 12.5 V and 27 V.
A CMOS compatible, level-dependent, digital input can be used
for PWM control of the LED brightness. VO is turned on when
the PWM input is high and turned off when the input is low.
The AD8240 is designed to work with a PWM frequency up
to 500 Hz, and a typical PWM range from 5% to 95%.
Open LED detection is accomplished by measuring the change
in LED lamp current caused by an open LED(s) through the use
of an internal high-side current-sense amplifier that amplifies …