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General Description

The MAX17067 boost converter incorporates high-

performance (at 1.2MHz), current-mode, fixed-frequency,

pulse-width modulation (PWM) circuitry with a built-in

0.15Ω n-channel MOSFET to provide a highly efficient

regulator with fast response.

High switching frequency (640kHz or 1.2MHz selectable)

allows for easy filtering and faster loop performance. An

external compensation pin provides the user flexibility in

determining loop dynamics, allowing the use of small,

low equivalent-series-resistance (ESR) ceramic output

capacitors. The device can produce an output voltage

as high as 18V.

Soft-start is programmed with an external capacitor, which

sets the input-current ramp rate. The MAX17067 is avail-

able in a space-saving 8-pin μMAX

package. The ultra-

small package and high switching frequency allow the

total solution to be less than 1.1mm high.

Application

LCD Displays

Features

o 90% Efficiency

o Adjustable Output from V

to 18V

o 2.4A, 0.15Ω, 22V Power MOSFET

o +2.6V to +4.0V Input Range

o Pin-Selectable 640kHz or 1.2MHz Switching

Frequency

o Programmable Soft-Start

o Small 8-Pin µMAX Package

o Integrated Input Voltage Clamp Circuit

MAX17067

Low-Noise Step-Up DC-DC Converter

________________________________________________________________

Maxim Integrated Products

LXGND

FREQFB

COMP

μMAX

TOP VIEW

MAX17067

SHDN

2.6V TO 4V

GND

FREQ

OUT

COMP

SHDN

MAX17067

ON/OFF

Typical Operating Circuit

19-3106; Rev 0; 1/08

Pin Configuration

Ordering Information

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE

PIN-

PACKAGE

PKG

CODE

MAX17067EUA+ -40°C to +85°C 8 μMAX

U8+1

μMAX is a registered trademark of Maxim Integrated Products, Inc.

Denotes a lead-free package.

Summary of content (13 pages)

PAGE 1
9-3106; Rev 0; 1/08 KIT ATION EVALU E L B AVAILA Low-Noise Step-Up DC-DC Converter The MAX17067 boost converter incorporates highperformance (at 1.2MHz), current-mode, fixed-frequency, pulse-width modulation (PWM) circuitry with a built-in 0.15Ω n-channel MOSFET to provide a highly efficient regulator with fast response. High switching frequency (640kHz or 1.2MHz selectable) allows for easy filtering and faster loop performance.
PAGE 2
MAX17067 Low-Noise Step-Up DC-DC Converter ABSOLUTE MAXIMUM RATINGS LX to GND ..............................................................-0.3V to +22V SHDN, FREQ to GND ............................................-0.3V to +7.5V IN to GND (Note 1) ...................................................-0.3V to +6V SS, COMP, FB to GND ................................-0.3V to (VIN + 0.3V) RMS LX Pin Current ..............................................................1.
PAGE 3
Low-Noise Step-Up DC-DC Converter (VIN = SHDN = 3V, FREQ = 3V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.3 x VIN V CONTROL INPUTS Input Low Voltage VIL SHDN, FREQ, VIN = 2.6V to 4.0V Input High Voltage VIH SHDN, FREQ, VIN = 2.6V to 4.0V 0.7 x VIN 0.
PAGE 4
ELECTRICAL CHARACTERISTICS (continued) (VIN = SHDN = 3V, FREQ = 3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 1.8 3.4 A 275 0.19 0.40 V/A n-CHANNEL SWITCH Current Limit ILIM VFB = 1V, duty cycle = 68% (Note 4) On-Resistance R ON VIN = 3V Current-Sense Transresistance RCS SOFT-START 100 6.5 μA 0.3 x VIN V Reset Switch Resistance Charge Current VSS = 1.2V 2.
PAGE 5
Low-Noise Step-Up DC-DC Converter SOFT-START (RLOAD = 18Ω) SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX17067 toc05 MAX17067 toc04 4.0 SUPPLY CURRENT (mA) 3.5 VOUT 5V/div 3.0 2.5 SWITCHING 2.0 0V 1.5 INDUCTOR CURRENT 1A/div 0A 1.0 NONSWITCHING 0.5 0 2.5 2.7 2.9 3.1 3.3 3.5 3.7 2ms/div 3.9 SUPPLY VOLTAGE (V) LOAD-TRANSIENT RESPONSE (ILOAD = 10mA TO 200mA) PULSED LOAD-TRANSIENT RESPONSE (ILOAD = 40mA TO 1.1A) MAX17067 toc06 MAX17067 toc07 IOUT 1A/div 0.
PAGE 6
Low-Noise Step-Up DC-DC Converter MAX17067 Pin Description PIN NAME 1 COMP 2 FB 3 SHDN Active-Low Shutdown Control Input. Drive SHDN low to turn off the MAX17067. 4 GND Ground 5 LX Switch Pin. Connect the inductor/catch diode to LX and minimize the trace area for lowest EMI. 6 IN Supply Pin. Bypass IN with at least a 1μF ceramic capacitor directly to GND. 7 FREQ 8 FUNCTION Compensation Pin for Error Amplifier. Connect a series RC from COMP to ground.
PAGE 7
Low-Noise Step-Up DC-DC Converter 4μA MAX17067 SKIP COMPARATOR SHDN IN BIAS SKIP COMP ERROR AMPLIFIER SOFTSTART SS ERROR COMPARATOR FB ∞ LX CONTROL AND DRIVER LOGIC 1.24V N CLOCK GND OSCILLATOR FREQ SLOPE COMPENSATION CURRENT SENSE Σ 5μA MAX17067 Figure 2. Functional Diagram IN Supply Clamp Circuit The MAX17067 features an internal clamp to allow applications where there is overvoltage stress on the supply line.
PAGE 8
MAX17067 Low-Noise Step-Up DC-DC Converter Soft-Start Thermal-Overload Protection The MAX17067 can be programmed for soft-start upon power-up with an external capacitor. When the shutdown pin is taken high, the soft-start capacitor (CSS) is immediately charged to 0.5V. Then the capacitor is charged at a constant current of 4.5μA (typ). During this time, the SS voltage directly controls the peak inductor current, allowing 0A at VSS = 0.5V to the full current limit at VSS = 1.5V.
PAGE 9
Low-Noise Step-Up DC-DC Converter Calculate the approximate inductor value using the typical input voltage (VIN), the maximum output current (IMAIN(MAX)), the expected efficiency (ηTYP) taken from an appropriate curve in the Typical Operating Characteristics, and an estimate of LIR based on the above discussion: 2 ⎞⎛ η ⎛ VIN ⎞ ⎛ VMAIN − VIN TYP ⎞ L=⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎝ VMAIN ⎠ ⎝ IMAIN(MAX) × fOSC ⎠ ⎝ LIR ⎠ Choose an available inductor value from an appropriate inductor family.
PAGE 10
MAX17067 Low-Noise Step-Up DC-DC Converter Diode Selection The output diode should be rated to handle the output voltage and the peak switch current. Make sure that the diode’s peak current rating is at least IPK and that its breakdown voltage exceeds VOUT. Schottky diodes are recommended. Input and Output Capacitor Selection Low-ESR capacitors are recommended for input bypassing and output filtering. Low-ESR tantalum capacitors are a good compromise between cost and performance.
PAGE 11
Low-Noise Step-Up DC-DC Converter VIN 2.6V TO 4.0V Figure 3 shows the MAX17067 in a single-ended primary inductance converter (SEPIC) topology. This topology is useful when the input voltage can be either higher or lower than the output voltage, such as when converting a single lithium-ion (Li+) cell to a 3.3V output. L1A and L1B are two windings on a single inductor.
PAGE 12
MAX17067 Low-Noise Step-Up DC-DC Converter Layout Procedure Good PCB layout and routing are required in high-frequency switching power supplies to achieve good regulation, high efficiency, and stability. It is strongly recommended that the evaluation kit PCB layouts be followed as closely as possible. Place power components as close together as possible, keeping their traces short, direct, and wide. Avoid interconnecting the ground pins of the power components using vias through an internal ground plane.
PAGE 13
Package Information 4X S 8 8 INCHES DIM A A1 A2 b E Ø0.50±0.1 H c D e E H 0.6±0.1 L 1 1 α 0.6±0.1 S BOTTOM VIEW D MIN 0.002 0.030 MAX 0.043 0.006 0.037 0.010 0.014 0.005 0.007 0.116 0.120 0.0256 BSC 0.116 0.120 0.188 0.198 0.016 0.026 6° 0° 0.0207 BSC 8LUMAXD.EPS (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.) MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95 0.25 0.