MAX8879

Charge Pump for Backlight/Flash/RGB LEDs with Safety Timer

High-Efficiency Backlight and Flash Driver with Up to 400mA Flash Capability/Safety Timer and 3 RGB Drivers
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Active: In Production.

Description

The MAX8879 provides complete light management for main display backlight, subdisplay backlight (or RGB indicator), and white LED camera flash with regulated constant current up to 610mA total. By utilizing adaptive 1x/1.5x/2x charge-pump modes and very-low-dropout current regulators, it achieves high efficiency over the full 1-cell Li+ battery input voltage range. The 1MHz fixed-frequency switching allows for tiny external components while the regulation scheme is optimized to ensure low EMI and low input ripple. An integrated derating function protects the LEDs from overheating during high ambient temperatures.

The MAX8879 features an internally trimmed reference to set the maximum LED current. An I²C serial port is used for on/off control and setting the LED currents in 32 linear steps for main, sub/RGB, and movie. When using the RGB indicator, the I²C port provides 32k colors and programmable ramp-up/down rates. The camera flash for flash-mode operation is enabled by an active-low signal on the active-low FSH pin. A safety timer is activated on the falling edge of active-low FSH, which has an I²C-adjustable (programmable) period of no timer, 0.5s, 1.0s, or 2.0s (default). If the safety timer period expires, both flash and movie modes are disabled.

Data Sheet

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Key Features

  • Guaranteed 610mA Continuous Drive Capability
    • 4 LEDs at 30mA Each for Main Display
    • 3 LEDs at 30mA Each for Sub or RGB
    • 400mA Total for Flash
  • 2-Wire I²C Serial Port
    • 5-Bit (32-Step) Linear Dimming
    • 32k Colors
    • Ramp-Up/Down Rates
  • 92% Peak/83% Avg Efficiency (PLED/PBATT)
  • Adaptive 1x/1.5x/2x Mode Switchover
  • 0.3% (typ) LED Current Accuracy and Matching
  • Low Input Ripple and EMI
  • Low 0.1µA Shutdown Current
  • Output Overvoltage Protection
  • I²C Programmable Flash Safety Timer
  • Thermal Derating Function Protects LEDs
  • 24-Pin, 4mm x 4mm Thin QFN Package
 

Applications/Uses

  • Cell Phones and Smartphones
  • Displays with Up to 11 LEDs
  • PDAs, Digital Cameras, Camcorders
   

Key Specifications:

LED Drivers
Part Number Battery Input Regulation Topology Max. No. of LEDs LED Channels LED Configuration ILED per Channel
(A)
Dimming Ratio Dimming Control POUT
(W)
VIN
(V)
VIN
(V)
ICC
(mA)
LED String Volt.
(V)
Oper. Freq.
(kHz)
Budgetary
Price
max max min max max max See Notes
MAX8879  1-Cell Li+ Charge Pump 11 11 Parallel 0.1 32
Digital
I2C Serial
2.5 2.7 5.5 6.5 5 1000 $2.45 @1k
See All LED Drivers (80)

Pricing Notes:

This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.



Diagram

MAX8879: Typical Operating Circuit
Typical Operating Circuit

More Information

Please contact factory directly for MAX8879EVKIT ordering information.

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Document Ref.: 19-4266 Rev 0; 2008-10-10
This page last modified: 2010-03-05