Typical Application Circuit Features ■ 87% Peak LED Drive Efficiency ■ 0.2% Current Matching between Current Sinks ■ Drives 6 LEDs with up to 30mA per LED in two distinct groups, for backlighting two displays (main LCD and sub LCD) ■ Dedicated Keypad LED Driver with up to 80mA of drive current ■ Independent Resistor-Programmable Current Settings ■ I 2C Compatible Brightness Control Interface ■ Adaptive 1×- 3/2× Charge Pump ■ Extended Li-Ion Input: 2.7V to 5.5V ■ Small low profile industry standard leadless package, LLP 24 : (4mm x 4mm x 0. The LM27964 is available in National's small 24-pin Leadless Leadframe Package (LLP-24). The proper gain for maintaining current regulation is chosen, based on LED forward voltage, so that efficiency is maximized over the input voltage range. The device provides excellent efficiency without the use of an inductor by operating the charge pump in a gain of 3/2, or in Pass-Mode. The LM27964 works off an extended Li-Ion input voltage range (2.7V to 5.5V). The LM27964 has an I 2C compatible interface that allows the user to independently control the brightness on each bank of LEDs. A single Keypad LED driver can power up to 16 keypad LEDs with a current of 5mA each. The primary group (4 LEDs) can be used to backlight the main phone display and the second group (2 LEDs) can be used to backlight a secondary display. The LED driver current sources are split into two independently controlled groups. Regulated internal current sources deliver excellent current matching in all LEDs. The LM27964 can drive up to 6 LEDs in parallel along with multiple keypad LEDs, with a total output current up to 180mA. The supply voltage range is between 3 V and 5.5 V.August 2007 LM27964 White LED Driver System with I2C Compatible Brightness Control General Description The LM27964 is a charge-pump-based white-LED driver that is ideal for mobile phone display backlighting. A selectable gradual output delay reduces the inrush current, whereas the selectable SDO synchronization feature works when the device is used in daisy-chain configuration. Drive high LED count very easily Individual brightness control of each. The high clock frequency is up to 30 MHz and it makes the device suitable for high data rate transmission. The AS1115 is single chip solution including a LED driver for 64LEDs and 16 Keys. Thermal management includes an overtemperature data alert and output thermal shutdown (170 ☌). The auto power-shutdown and auto power-on features (selectable) allow the device to save power without external intervention. Open/short error detection mode is available in the ALED1642GW. Programmable turn-on and turn-off time (four different values available) improves the low noise generation performance of the system.

The brightness can be adjusted separately for each channel through 12/16-bit grayscale control. The preferred technique for brightness control is through pulse width modulation (PWM). The current is programmed through an external resistor and can be adjusted by a 7-bit current gain register in two subranges. In the output stage, sixteen regulated current sources provide from 3 mA to 40 mA constant current to drive the LEDs. The ALED1642GW guarantees 20 V output driving capability allowing the user to connect several LEDs in series. The ALED1642GW is a monolithic, low voltage, low current power 16-bit shift register designed for LED panel displays.

Led driver with brightness control