White LED
Charge Pump With 8 Drivers
FEATURES
- Powers Up to 2 sets of
4 LEDs Each For Backlight Application.
- Up to 25mA/LED Drive
for Backlight
- Single-Wire 8-Step
Brightness Control
- Over temperature Over
Voltage, Output Short Protection
- Soft Start with Low
Input Ripple and EMI
- Maximized Efficiency
- 2.7V to 5.5V Supply
Voltage Range
- 3mmx4mm 20-Pin QFN
Package
DESCRIPTION
The BL144 is a low noise charge pump LED driver with regulated
constant current sink for uniform intensity. It is designed to drive 2 sets of four LEDs (LED1-4, LED5-8) at up to 25mA per
LED for backlighting application. The
BL144 requires only four small ceramic capacitors and two current set resistors
for a complete LED power supply and current controller.
Built-in soft-start circuitry prevents excessive
inrush current during start-ups. The 1MHz fixed-frequency switching allows for
tiny external components, and the regulation scheme is optimized to ensure low
EMI and low input ripple. Two independent
full-scale current settings are set by two external resistors on RB1 and RB2
pins.
Shutdown mode and current output levels are selected
via two logic inputs ENB1 and ENB2 pins. ENB1 and ENB2 are toggled to adjust
the LED currents via internal counters and DACs. The part is shut down when both
ENB1 and ENB2 are low for >10µs.
The charge pump optimizes efficiency based on the
voltage across the LED current sources. The BL144 is available in a 3mm × 4mm
20-lead QFN package.
