White LED
Charge Pump With Flash Drive
FEATURES
- Powers Up to 4 LEDs for
BackLight & 1 High Current LED for Camera Flash Application.
- Up to 25mA/LED Drive
for Backlight
- Up to 200mA Total Drive
for Flash
- 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
- 3mmx3mm 16-Pin QFN
Package
DESCRIPTION
The BL241 is a low noise charge pump LED driver with regulated
constant current sink for uniform intensity. It is designed to drive four LEDs (LED1-4) at up to 25mA per
LED for backlighting application and one
LED (LEDF) for camera flash lighting which can be driven up to 200mA. The BL241 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. Independent
Backlight and Flash full-scale current settings are set by two external
resistors on RB and RF pins.
Shutdown mode and current output levels are selected
via two logic inputs ENB and ENF pins. ENB and ENF are toggled to adjust the
LED currents via internal counters and DACs. The part is shut down when both
ENB and ENF are Low for >10µs.
The charge pump optimizes efficiency based on the
voltage across the LED current sources. The BL241 is available in a 3mm × 3mm
16-lead QFN package.
