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

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Overview

Powers Main and Sub-Display LEDs
85% Average Efficiency (P_LED / P_BATT) 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

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).

Applications

Cell Phones with Main and Sub-Displays
PDAs/Smartphones with Up to Six White LEDs

Documentation

Data Sheet 1

MAX1575: White LED 1x/1.5x Charge Pump for Main and Sub-Displays Data Sheet (Rev.2) 09/14/2005

Technical Articles 2

Charge-Pump and Step-Up DC-DC Converter Solutions for Powering White LEDs in Series or Parallel Connections 04/23/2002

Driving LEDs in Battery-Operated Applications: Controlling Brightness Power Efficiently 03/03/2023

This is the most up-to-date revision of the Data Sheet.

Software Resources

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Hardware Ecosystem

Parts	Product Life Cycle	Description
Charge Pumps 1
MAX1595	PRODUCTION	Regulated 3.3V/5.0V Step-Up/Step-Down Charge Pump
LED Drivers 12
MAX1570	PRODUCTION	White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump
MAX1910	PRODUCTION	1.5x/2x High-Efficiency White LED Charge Pumps
MAX1912		1.5x/2x High-Efficiency White LED Charge Pumps

MAX1573	PRODUCTION	White LED 1x/1.5x Charge Pump in UCSP and Thin QFN
MAX1574	PRODUCTION	180mA, 1x/2x, White LED Charge Pump in 3mm x 3mm TDFN
MAX1582		High-Efficiency Step-Up Converters for White LED Main and Subdisplay Backlighting
MAX1848	PRODUCTION	White LED Step-Up Converter in SOT23
MAX1561	PRODUCTION	High-Efficiency, 26V Step-Up Converters for Two to Six White LEDs
MAX1599	PRODUCTION	High-Efficiency, 26V Step-Up Converters for Two to Six White LEDs
MAX1553	PRODUCTION	High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs
MAX1554	PRODUCTION	High-Efficiency, 40V Step-Up Converters for 2 to 10 White LEDs
MAX1698	PRODUCTION	High-Efficiency Step-Up Current Regulator for LEDs

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