MAX8847Z

High-Performance Negative Charge Pump for 6 White LEDs in 3mm x 3mm Thin QFN

Achieves Industry's Highest Efficiency Using a Negative Charge Pump to Independently Drive 6 White LEDs

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Overview

Negative 1x/1.5x Charge Pump
Adaptive Current Regulators
Independent Voltage Supply for Each LED
24mA to 0.1mA Serial-Pulse Dimming (MAX8847Y)
24mA to 0mA PWM Dimming (MAX8847Z)
2% (max) LED Current Accuracy, 1% (typ) Matching
Low 120µA Quiescent Current
Low 0.4µA Shutdown Current
Inrush Current Limit
Temperature Derating Function
16-Pin, 3mm x 3mm Thin QFN Packages

The MAX8847Y/MAX8847Z negative charge pumps drive up to 6 white LEDs with regulated constant current for display backlight applications. By utilizing an inverting charge pump and extremely low-dropout adaptive current regulators, these ICs achieve very high efficiency over the full 1-cell Li+ battery voltage range even with large LED forward voltage mismatch. The 1MHz fixed-frequency switching allows for tiny external components. The regulation scheme is optimized to ensure low EMI and low input ripple. The MAX8847Y/MAX8847Z include thermal shutdown, open- and short-circuit protection.

The MAX8847Y/MAX8847Z support independent LED on/off and dimming control. The MAX8847Z has PWM dimming control for LED1–LED6. The MAX8847Y has PWM dimming control for LED1–LED4 and serial-pulse dimming control for LED5 and LED6. The serial-pulse dimming ranges are pseudo-logarithmic from 24mA to 0.1mA and off in 32 steps. All devices include a temperature derating function to safely allow bright 24mA full-scale output current while automatically reducing current gradually to protect LEDs at high ambient temperatures above +60°C.

The MAX8847Y/MAX8847Z are available in 16-pin, 3mm x 3mm thin QFN packages.

Applications