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