Document
19-2731; Rev 1; 10/03
KIT ATION EVALU E L B A AVAIL
High-Efficiency, 26V Step-Up Converters for Two to Six White LEDs
General Description
The MAX1561/MAX1599 step-up converters drive up to six white LEDs with a constant current to provide backlight in cell phones, PDAs, and other hand-held devices. The step-up converter topology allows series connection of the white LEDs so the LED currents are identical for uniform brightness. This configuration eliminates the need for ballast resistors and expensive factory calibration. The MAX1561/MAX1599 include an internal, high-voltage, low-RDS(ON) N-channel MOSFET switch for high efficiency and maximum battery life. A single Dual Mode™ input provides a simple means of brightness adjustment and on/off control. Fast 1MHz (500kHz for the MAX1599) current-mode, pulse-width modulated (PWM) operation allows for small input and output capacitors and a small inductor while minimizing ripple on the input supply/battery. Programmable soft-start eliminates inrush current during startup. Both devices are available in a space-saving, 8-pin 3mm x 3mm thin DFN package with exposed paddle (EP).
Features
o Accurate Current Regulation for Uniform Illumination o High Efficiency Up to 87% o Flexible Analog or PWM Dimming Control o Up to 900mW Output Power with Internal 30V MOSFET Switch o Fast 1MHz (MAX1561) or 500kHz (MAX1599) PWM Operation o Small, Low-Profile External Components o 2.6V to 5.5V Input Range o 26V (max) Output with Overvoltage Protection o Optimized for Low 15mVP-P Input Ripple o Soft-Start with Zero Inrush Current o 0.3µA Shutdown Current o Tiny 8-Pin 3mm x 3mm Thin DFN Package
MAX1561/MAX1599
Ordering Information
PART MAX1561ETA MAX1599ETA TEMP RANGE -40°C to +85°C -40°C to +85°C PIN-PACKAGE 8 TDFN-EP* 8 TDFN-EP* TOP MARK ACS AHG
Applications
Cell Phones and Smart Phones PDAs, Palmtops, and Wireless Handhelds e-Books and Subnotebooks White LED Display Backlighting
*EP = Exposed paddle.
Typical Operating Circuit
INPUT 2.6V TO 5.5V OUTPUT UP TO 6 LEDs IN LX OUT
OUT 1
Pin Configuration
TOP VIEW
MAX1561 MAX1599 8 LX 7 PGND 6 GND 5 COMP
PWM OR ANALOG DIMMING
MAX1561 MAX1599 CTRL PGND
IN 2 CTRL 3 CS 4
COMP
GND
CS
3mm × 3mm THIN DFN
Dual Mode is a trademark of Maxim Integrated Products, Inc. ________________________________________________________________ Maxim Integrated Products 1
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.
High-Efficiency, 26V Step-Up Converters for Two to Six White LEDs MAX1561/MAX1599
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V PGND to GND .......................................................-0.3V to +0.3V LX, OUT to GND .....................................................-0.3V to +30V CTRL to GND...................-0.3V to the lower of +6V or (VIN + 2V) COMP, CS to GND.........................................-0.3 to (VIN + 0.3V) ILX.............................................................................................1A Continuous Power Dissipation (TA = +70°C) 3mm x 3mm 8-Pin TDFN (derate 24.4mW/°C above +70°C) .............................1950mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN = 3V, VOUT = 20V, COUT = 0.1µF, CCOMP = 0.15µF, RSENSE = 7.5Ω, VCTRL = 1.5V, Figure 1, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER Supply Voltage UVLO Threshold UVLO Hysteresis Quiescent Current Shutdown Supply Current OVLO Threshold OVLO Hysteresis OUT Input Bias Current Output Voltage Range ERROR AMPLIFIER CTRL to CS Regulation CS Input Bias Current CTRL Input Resistance CTRL Dual-Mode Threshold CTRL Dual-Mode Hysteresis CTRL Shutdown Enable Delay CS-to-COMP Transconductance OSCILLATOR Operating Frequency Minimum Duty Cycle Maximum Duty Cycle MAX1561 MAX1599 PWM mode Pulse skipping CTRL = IN, CS = GND 91 0.80 0.4 1.0 0.5 12 0 94 1.25 0.6 MHz % % (Note 2) VCOMP = 1.0V MAX1561 MAX1599 6.5 13.6 32 VCTRL = 1V, VIN = 2.6V to 5.5V VCS = VCTRL/10 VCTRL ≤ 1.0V TA = +25°C TA = +85°C 290 100 0.095 0.100 0.01 0.03 500 170 5 8.2 16.4 50 10.5 21.0 82 780 240 0.105 1 V µA kΩ mV mV ms µS VOUT = 26V, VCTRL > 0.24V VOUT = VIN, CTRL = GND (Note 1) (VIN - VD1) 10 No swit.