Analog Devices ADP8870
The ADP8870 combines a programmable backlight LED charge pump driver with automatic phototransistor control of the brightness (LED Current) and a PWM input to control the scale of the output current. This combination allows for significant power savings because it automatically changes the current intensity based on the sensed ambient lighting levels and the display image content. It performs this function automatically and so removes the need for a processor to be monitoring the phototransistor. The light intensity thresholds are fully programmable via the I2C interface.
The ADP8870 allows up to six LEDs to be independently driven up to 30 mA (maximum). An additional seventh LED can be driven to 60 mA (maximum). All LEDs are individually programmable for minimum/maximum current and fade in/out times through an I2C interface. These LEDs can also be combined into groups to reduce the processor instructions during fade in/out.
Driving all of this is a two capacitor charge pump with gains of 1×, 1.5×, and 2×. This setup is capable of driving a maximum IOUT of 240 mA from a supply of 2.5 V to 5.5 V. A full suite of safety features including short-circuit, overvoltage, and overtemperature protection allow easy implementation of a safe and robust design. Additionally, input inrush currents are limited via an integrated soft start combined with controlled input to output isolation.
- Charge pump with automatic gain selection of 1x, 1.5x, and 2x for maximum efficiency.
- Two high accuracy (±5%) phototransistor inputs for automated ambient light sensing (ALS)
- 5 programmable ambient light-sensing zones for optimal backlight power savings
- PWM input can be used for Content Adaptive Brightness Control (CABC) of any, or all, of the LEDs
- Independent ALS control of D7, for automated response of keypad lighting to ambient light levels
- PWM input can be used for content adaptive brightness control (CABC) of any, or all, of the LEDs; PWM input scales the LED output current
- Seven independent and programmable LED drivers: Six drivers capable of 30 mA (max); One additional driver capable of 60 mA (max)
- Programmable maximum current limit (128 levels)
- Standby mode for <1 μA current consumption
- 16 programmable fade in and fade out times (0.1 s to 5.5 s) with choice of square or cubic rates.
- Fading override
- I2C compatible interface for all programming
- Dedicated reset pin and built-in power on reset (POR).
- Short circuit, over voltage, and over temperature protection.
- Internal soft start to limit inrush currents
- Input to output isolation during faults or shutdown
- Operates down to Vin = 2.5 V, with undervoltage lockout (UVLO) at 2.0 V.
- Small wafer level chip scale package (WLCSP) or lead frame chip scale package (LFCSP)
- Product Description: Parallel 7 WLED Driver with ALS & cABC
- LED #: 7
- LED Configuration: Parallel
- Topology: Capacitive
- Application: Backlighting
- I2C Support: Yes
- Max Iout (mA): 60mA
- Brightness Control: I2C
- Peak Efficiency (%): 89%
- Switching Frequency (MHz): 1.2MHz
- Vout (V): 4.3 to 5.5