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Ultra-Efficient Negative Charge-Pump LED Driver with Dual LDOs in 3mm x 3mm Thin QFN

Independent Adaptive Voltage Supply for Four WLEDs with Two 200mA Low-Noise/High PSRR LDOs for Display Backlighting

Product Details

Key Features

Parametric specs for LED Drivers
VIN (V) (min) 2.7
VIN (V) (max) 5.5
Max. No. of LEDs 4
# LED Channels 4
Regulation Topology Charge Pump
Battery Input 1-Cell Li+
LED Configuration Parallel
ILED per Channel (A) (max) 0.024
Dimming Ratio (max) 240
Dimming Control Serial Pulse
POUT (W) 0.4
ICC (mA) (max) 1.4
LED String Volt. (V) (max) 5.5
Switching Frequency (kHz) 1000
Package/Pins TQFN/16
Budgetary
Price (See Notes)
2.12
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Simplified Block Diagram

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Parameters

Parametric specs for LED Drivers
VIN (V) (min) 2.7
VIN (V) (max) 5.5
Max. No. of LEDs 4
# LED Channels 4
Regulation Topology Charge Pump
Battery Input 1-Cell Li+
LED Configuration Parallel
ILED per Channel (A) (max) 0.024
Dimming Ratio (max) 240
Dimming Control Serial Pulse
POUT (W) 0.4
ICC (mA) (max) 1.4
LED String Volt. (V) (max) 5.5
Switching Frequency (kHz) 1000
Package/Pins TQFN/16
Budgetary
Price (See Notes)
2.12

Key Features

  • High-Efficiency Charge Pump for Up to Four White LEDs
    • Independent Adaptive Voltage Supply for Each LED
    • 24mA to 0.1mA Dimming Range
    • 1% (typ) Current Accuracy and 0.3% Current Matching
    • Low 65µA (typ) Quiescent Current
  • Dual 200mA Low-Noise, High PSRR LDOs
    • 16 Different Output Voltage Combinations Up to 3.3V
    • High 60dB PSRR at 10kHz
  • Flexible Single-Wire Control for Dimming and LDO Output Voltage
  • Low 0.5µA (typ) Shutdown Mode
  • Soft-Start Limits Inrush Current
  • Thermal Shutdown and Open- and Short-Circuit Protection
  • Tiny 16-Pin, 3mm x 3mm Thin QFN Package (0.8mm max Height) with Exposed Paddle

Applications/Uses

  • Cell Phones and Smartphones
  • White LED Backlighting

Description

The MAX8822 drives up to four white light-emitting diodes (LEDs) with regulated constant current for display backlighting in cell phones, digital cameras, PDAs, and other handheld devices. By utilizing a proprietary negative 0.5x inverting charge pump and innovative independent low-dropout (LDO) adaptive current regulators, very high efficiency is achieved over the full 1-cell Li+ battery voltage range, even with large LED VF mismatch. The 1MHz fixed-frequency switching allows for tiny external components. The regulation scheme is optimized to ensure low EMI and low input ripple. Two 200mA, low-noise, high power-supply-rejection-ratio (PSRR) LDOs with programmable output voltages are included on-chip to provide power to camera modules or other devices.

The MAX8822 features a single-wire, serial-pulse control-logic interface that programs LED current and the output voltages of the LDOs. The LED dimming range is pseudo-logarithmic from 24mA to 0.1mA in 31 steps. LDO output voltages are programmable in 16 different combinations to meet various camera module requirements.

The MAX8822 includes soft-start, thermal shutdown, open- and short-circuit protection.

Simplified Block Diagram

MAX8822: Typical Operating Circuit MAX8822: Typical Operating Circuit Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .