The ISL97671/2/3/4 series LED drivers are designed to maintain dimming linearity at low LED PWM duty cycles by using an adaptive boost control circuit that regulates the output voltage even when the LEDs are off for most of the PWM cycle.
It responds to very low PWM duty cycles and provides dimming down to just 0.007% of full brightness with a 200Hz PWM frequency.
Dimming may be controlled by direct PWM dimming or by using 8-bit digital dimming via an I2C/SMBus interface.
The devices incorporate a proprietary dynamic headroom control circuit to detect the highest voltage LED string, and then regulate the boost output to the minimum required voltage.
The devices drive up to six 40mA strings of LEDs from a 4.5V to 26V input.
An LED current matching circuit achieves ±0.7% current matching between LED strings.
The ISL97671/2/3/4 series also includes an integrated boost converter to step-up the input voltage to support LED stack voltages up to 45V.
The devices’ phase shift capability can turn LED strings on at a specified phase, reducing peak input current by distributing channel currents within the dimming period.
For more information, see http://www.intersil.com
Micron-Electronic