White LED
Charge Pump With LDO
FEATURES
- Powers Up to 5 LEDs for
BackLight & One Adjustable LDO Supply.
- Up to 25mA/LED Drive
for Backlight
- Up to 100mA Total Drive
for LDO
- Single-Wire 8-Step
Brightness/Voltage 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 BL250 is a low noise charge pump LED driver with regulated
constant current sink for uniform intensity. It is designed to drive five LEDs (LED1-LED5) at up to 25mA per
LED for backlighting application, and one
adjustable LDO voltage supply (VLDO) for general-purpose application, which can supply up
to 100mA of DC power. The BL250 requires
only four small ceramic capacitors and one current set resistor for a complete
LED power supply or add one capacitor and one resistor for LDO application.
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. The Backlight
full-scale current setting is set by an
external resistor on RB pin. The LDO supply full-scale voltage setting is done
through a resistor between RL and VLDO pins.
Shutdown mode and current output levels for the LED
drivers are selected via logic input ENB pin. ENB is toggled to adjust the LED
currents via internal counters and DACs. The part is shut down when ENB is Low
for >10µs.
The charge pump optimizes efficiency based on the
voltage across the LED current sources. The BL250 is available in a 3mm × 3mm
16-lead QFN package.
