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.