Datasheet

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General Description

The MAX1570 fractional charge pump drives up to five

white LEDs with regulated constant current for uniform

intensity. The MAX1570 maintains the highest possible

efficiency over the full 1-cell lithium-ion (Li+) battery

input voltage range by utilizing a 1x/1.5x fractional

charge pump and very-low-dropout current regulators.

The MAX1570 operates with 1MHz fixed-frequency

switching, allowing for tiny external components. The

regulation scheme is optimized to ensure low EMI and

low input ripple.

An external resistor sets the full-scale LED current,

while two digital inputs control on/off and select

between three levels of brightness. A pulse-width mod-

ulation (PWM) signal can also be used to modulate LED

brightness.

The MAX1570 is available in 16-pin 4mm ✕ 4mm Thin

QFN packaging (0.8mm max height).

Applications

White LED Backlighting

Cell Phones and Smart Phones

PDA and Palmtop Computers

Portable MP3 Players

Digital Cameras and Camcorders

Features

♦ Excellent 0.3% LED-to-LED Current Matching

♦ 30mA/LED Drive Capability

♦ Proprietary 1x/1.5x Modes for Ultra-High

Efficiency

♦ Low Input Ripple and EMI

♦ Eliminates Ballast Resistors

♦ Digital or PWM LED Dimming Control

♦ 0.1µA Shutdown Current

♦ 2.7V to 5.5V Supply Voltage Range

♦ Soft-Start Limits Inrush Current

♦ Thermal-Shutdown Protection

♦ No External Inductor, Schottky, or Zener Diode

Required

♦ Tiny 16-Pin 4mm

✕ 4mm Thin QFN Package

♦

MAX1570

White LED Current Regulator with 1x/1.5x

High-Efficiency Charge Pump

________________________________________________________________ Maxim Integrated Products 1

SET

EN1

PGND

C1N

LED5

GND

EN2

C1P

LED4

LED3

LED2

LED1

C2N

OUT

C2P

12 4

12 11 9

MAX1570

THIN QFN

4mm x 4mm

TOP VIEW

Pin Configuration

Ordering Information

LED1

LED2

LED3

LED4

LED5

4.7µF

PGNDGND

C1P C1N C2P C2N

1µF1µF

EN1

EN2

SET

1µF

2.7V TO 5.5V

ON/OFF

AND

DIMMING

1x/1.5x

REGULATING CHARGE PUMP

REFERENCE

AND

CONTROL

LOW-DROPOUT

CURRENT

REGULATORS

MAX1570

OUT

Typical Operating Circuit

19-2526; Rev 1; 4/05

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART TEMP RANGE PIN-PACKAGE

MAX1570ETE -40°C to +85°C 16 Thin QFN

Summary of content (11 pages)

PAGE 1
9-2526; Rev 1; 4/05 White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump The MAX1570 fractional charge pump drives up to five white LEDs with regulated constant current for uniform intensity. The MAX1570 maintains the highest possible efficiency over the full 1-cell lithium-ion (Li+) battery input voltage range by utilizing a 1x/1.5x fractional charge pump and very-low-dropout current regulators.
PAGE 2
MAX1570 White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump ABSOLUTE MAXIMUM RATINGS IN, OUT, EN1, EN2 to GND ......................................-0.3V to +6V SET, LED1, LED2, LED3, LED4, LED5 to GND ...........................................-0.3V to (VIN + 0.3V) PGND to GND..........................................................-0.3 to +0.3V C1N, C2N to GND ..........................................-0.3V to (VIN + 1V) C1P, C2P to GND ..........................................-0.
PAGE 3
White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump (VIN = 3.6V, GND = PGND = 0, EN1 = EN2 = IN, CIN = C1 = C2 = 1µF, COUT = 4.7µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS LED1 Dual Mode™ Threshold MIN TYP MAX UNITS 50 75 100 mV Thermal-Shutdown Threshold 160 °C Thermal-Shutdown Hysteresis 20 °C ELECTRICAL CHARACTERISTICS (VIN = 3.6V, GND = PGND = 0, EN1 = EN2 = IN, CIN = C1 = C2 = 1µF, COUT = 4.
PAGE 4
Typical Operating Characteristics (EN1 = EN2 = IN, CIN = 1µF, C1 = C2 = 1µF, COUT = 4.7µF, RSET = 9.09kΩ, TA = +25°C, unless otherwise noted.) 80 75 70 65 250 200 150 10mA/LED, EN1 = VIN, EN2 = GND 100 60 70 60 MAX1570 toc03 10mA/LED, EN1 = VIN, EN2 = GND 50 40 5mA/LED, EN1 = GND, EN2 = VIN 30 3.4 3.6 5mA/LED, EN1 = GND, EN2 = VIN 0 3.8 4.0 2.5 4.2 3.0 3.5 4.0 4.5 5.0 10 0 5.5 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) LED EFFICIENCY vs. SUPPLY VOLTAGE (5 LEDs) SUPPLY POWER vs.
PAGE 5
White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump LED CURRENT vs. TEMPERATURE (VIN = 3.3V, RSET = 7.5kΩ) 11.9 11.8 EN1 = EN2 = VIN LED CURRENT (mA) 14 12 EN1 = VIN, EN2 = GND 10 8 EN1 = GND, EN2 = VIN 6 25 11.7 LED CURRENT (mA) 16 LED CURRENT vs. RSET 30 MAX1570 toc11 18 LED CURRENT (mA) 12.0 MAX1570 toc10 20 11.6 11.5 11.4 11.3 11.0 0 2.5 3.0 3.5 4.0 4.5 5.0 -15 SUPPLY VOLTAGE (V) 10 35 TEMPERATURE (°C) 10 85 60 5.
PAGE 6
White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump MAX1570 Pin Description 6 PIN NAME FUNCTION 1 C1P Transfer Capacitor 1 Positive Connection 2 EN2 Enable, Dimming Control Input 2. EN2 and EN1 control shutdown, 1/3 current, 2/3 current, and full current (see Table1). 3 GND Analog Ground. Connect directly to the exposed paddle underneath the IC. 4 LED5 LED5 Cathode Connection. Current flowing into LED5 is 230 times the current flowing out of SET.
PAGE 7
White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump The MAX1570 is a complete charge-pump buck/boost converter requiring only four small ceramic capacitors. The MAX1570 utilizes a proprietary 1x/1.5x fractional charge-pump topology to drive up to five white LEDs with regulated constant current for uniform intensity. The MAX1570 operates with a 1MHz fixed frequency.
PAGE 8
MAX1570 White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump Table 1. Enable Input Modes EN_ INPUT LOGIC LEVELS MODE LED CURRENT EN1 = 0, EN2 = 0 Shutdown mode 0 EN1 = 0, EN2 = 1 On, VSET = 200mV, LED1 threshold = 200mV EN1 = 1, EN2 = 0 On, VSET = 400mV, LED1 threshold = 300mV 2/3 EN1 = 1, EN2 = 1 On, VSET = 600mV, LED1 threshold = 400mV Full 1/3 Table 2. Capacitor Selection OUTPUT (mA) CIN (µF) C1 (µF) C2 (µF) COUT (µF) 40 1 0.22 0.22 4.7 80 1 0.47 0.47 4.
PAGE 9
White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump Component Selection Typical external component values are shown in Table 2 and Table 3. PC Board Layout and Routing Maximum power dissipation occurs around 4.2V on IN and 4.0V at OUT with maximum load current. PD = [((1.5 × V ) IN At higher IN voltages this device switches to 1x mode and power dissipation is lowered. The MAX1570 is a high-frequency switched-capacitor voltage regulator.
PAGE 10
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 24L QFN THIN.EPS MAX1570 White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.
PAGE 11
White LED Current Regulator with 1x/1.5x High-Efficiency Charge Pump PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm 21-0139 D 2 2 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.