ISL78171 is a 6-channel, 50mA, LED driver capable of very

high dynamic range dimming. It offers an integrated boost

converter, six high precision, adjustable current sinks and a

SMBus/I2C interface for digital programmability and extensive

diagnostics. These features provide the ISL78171 with the

necessary capabilities to design compact, highly versatile LED

backlight for a wide variety of ambient lighting conditions.

The integrated peak current mode PWM boost converter

operates with a constant frequency and can boost an input

voltage range of 4.5V - 26.5V to an output up to 40V and supply

six strings of LEDs with up to 50mA each. A dynamic headroom

control circuit detects and regulates the highest voltage string to

improve efficiency in multistring configurations.

The six high precision adjustable current sinks offer typical

current matching better than ±1 and a dimming ratio that is

capable of exceeding 60,000:1. The dimming ratio can be

adjusted with either or both the I2C/SMBus and an external

PWM signal. They also feature an optional channel phase shift

control which helps to reduce the input and output

capacitance and ripple, to improve efficiency and to prevent

audible noise.

The SMBus/I2C interface offers a wide range of

programmability that includes the boost FET slew rate control,

individual string enabling and converter switching frequency

selections. It offers a wide range of protection features and

diagnostics that cover all perceivable faults, enabling the

system to self-diagnose the functioning of the backlight and

react to such conditions as failed LEDs. The ISL78171 is offered

in a compact and thermally efficient 20 Ld QFN package with an

ambient temperature range of -40°C to +105°C.

Features

• 6 channels at 50mA maximum per channel

• Input voltage: 4.5V to 26.5V, output voltage: 40V max

• Bootstrap operation Input:3V to 21V output: 26.5V max

• PWM dimming with phase shift control

• SMBus/I2C controlled PWM or DC dimming

• Direct PWM dimming

• Internal PWM dimming mode linearity: 0.4 to 100,

dimming frequency <30kHz

• Direct PWM dimming duty cycle linearity: 0.007 to 100

at a dimming frequency of 200Hz

• Current matching ±0.7 typ

• 600kHz/800kHz/1.2MHz selectable switching frequency

• Dynamic headroom control

• Fault protection

- String open/short circuit, OVP, OTP and optional output

short circuit fault protection

• AEC-Q100 qualified

Applications

• Infotainment display LED backlighting

• LCD monitor LED backlighting

• Field sequential RGB LED backlighting