1 Features

1• High-Efficiency DC-DC Boost Converter With 28-V

Integrated Power MOSFET

• 2.7-V to 5.5-V VDD Range for Supporting Single-

Cell Li-Ion Battery Applications

• Six 25-mA High-Precision LED Current Sinks

• Adaptive Boost Voltage and LED Current Sink

Headroom Controls for Maximum System

Efficiency

• LED String Count Auto-Detect for Maximum

Design Flexibility

• Smart Phase Shift PWM Mode for Reduced

Audible Noise

• PWM Input Duty Cycle Brightness Control, PWM

Output Frequency Selectable Independent of

Input Frequency

• Hybrid PWM Plus Current Dimming for Higher

LED Drive Optical Efficiency

• Switching Frequency, PWM Output Frequency,

and LED Current can be set Through Resistors or

I2C Interface

• Programmable Boost SW Slew Rate Control and

Spread Spectrum Scheme for Reduced Switching

Noise and Improved EMI Performance

• UVLO, TSD, BST_OVP, BST_OCP, BST_UV,

LED OPEN* and LED Short Fault Coverage

• Minimum Number of External Components

2 Applications

Tablet LCD Display LED Backlight

3 Description

The LP8557 and LP8557I are high-efficiency LED

drivers each featuring an integrated DC-DC inductive

boost converter and six high-precision current sinks.

LP8557 is intended for applications that exclusively

use a pulse width modulated (PWM) signal for

controlling the brightness while LP8557I is intended

for applications that can utilize an I2C master as well.

The boost converter has adaptive output voltage

control. This feature minimizes the power

consumption by adjusting the voltage to the lowest

sufficient level under all conditions.

The adaptive current sink headroom voltage control

scales the headroom voltage with the LED current for

optimal system efficiency.

The LED string auto-detect function enables use of

the same device in systems with 1 to 6 LED strings

for the maximum design flexibility.

Proprietary hybrid PWM plus current mode dimming

enables additional system power savings. Phase-shift

PWM allows reduced audible noise and smaller boost

output capacitors.

Flexible CABC support combines brightness level

selections based on the PWM input and I2C

commands.