MAX1575

White LED 1x/1.5x Charge Pump for Main and Sub-Displays

First 85% Efficient, Fractional, White-LED Charge Pump with Dual, Single-Wire Dimming Control for Main and Sub-Displays


Description

The MAX1575 charge pump drives up to four white LEDs in the main display and up to two white LEDs in the sub-display with regulated constant current for uniform intensity. By utilizing adaptive 1x/1.5x charge-pump modes and very-low-dropout current regulators, it achieves high efficiency over the full 1-cell lithium-battery input voltage range. A 1MHz fixed-frequency switching allows for tiny external components, and the regulation scheme is optimized to ensure low EMI and low input ripple.

The MAX1575 uses an external resistor to set the full-scale 100% LED current. Two enable inputs, ENM and ENS, are used for simple on/off controls for the main and sub-displays, respectively. By repeatedly pulsing either enable input, the LEDs can be dimmed in multiple steps down to 5%. Once the desired brightness is set, the MAX1575 maintains that brightness setting as long as the enable input is kept high. If an enable input is kept low for more than 2ms, the LED current for the respective display is set to zero. If both enable inputs are kept low for more than 2ms, the MAX1575 enters shutdown.

The MAX1575 is available in a 16-pin 4mm x 4mm thin QFN package (0.8mm max height).
MAX1575: Typical Operating Circuit MAX1575: Typical Operating Circuit Enlarge+

Key Features

  • Powers Main and Sub-Display LEDs
  • 85% Average Efficiency (PLED / PBATT) Over Li+ Battery Discharge
  • 2% LED Current Matching
  • Up to 30mA/LED Drive Capability
  • Adaptive 1x/1.5x Mode Switchover
  • Low Input Ripple and EMI
  • Individual 5% to 100% Dimming Through Single-Wire Serial Pulse Interface
  • Low 0.1µA Shutdown Current
  • 2.7V to 5.5V Supply Voltage Range
  • Soft-Start Limits Inrush Current
  • Output-Overvoltage Protection
  • Thermal-Shutdown Protection
  • 16-Pin Thin QFN 4mm x 4mm Package

Applications/Uses

  • Cell Phones with Main and Sub-Displays
  • PDAs/Smartphones with Up to Six White LEDs
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
MAX1575  1-Cell Li+ Charge Pump 6 6 Parallel 0.03 20 Serial Pulse 0.75 2.7 5.5 2 5 1000 $1.93 @1k
See All LED Drivers (75)
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.


MAX1575EVKIT: Evaluation Kit for the MAX1575

Technical Documents

Reference Schematic 1804 Driving LEDs in Battery-Operated Applications: Controlling Brightness Power Efficiently

Quality and Environmental Data

Request Reliability Report for: MAX1575 
Lead-Free Package Tin (Sn) Whisker Reports
 

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