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General Description

The MAX17062 is a high-performance step-up DC-DC

converter that provides a regulated supply voltage for

active-matrix thin-film transistor (TFT) liquid-crystal dis-

plays (LCDs). The MAX17062 incorporates current-

mode, fixed-frequency, pulse-width modulation (PWM)

circuitry with a built-in n-channel power MOSFET to

achieve high efficiency and fast-transient response.

Users can select 640kHz or 1.2MHz operation using a

logic input pin (FREQ). The high switching frequencies

allow the use of ultra-small inductors and low-ESR

ceramic capacitors. The current-mode architecture pro-

vides fast transient response to pulsed loads. A com-

pensation pin (COMP) gives users flexibility in adjusting

loop dynamics. The 22V internal MOSFET can generate

output voltages up to 20V from an input voltage

between 2.6V and 5.5V. Soft-start slowly ramps the input

current and is programmed with an external capacitor.

The MAX17062 is available in a 10-pin TDFN package.

Applications

Notebook Computer Displays

LCD Monitor Panels

LCD TV Panels

Features

o 90% Efficiency

o Adjustable Output from V

to 20V

o 2.6V to 5.5V Input Supply Range

o Input Supply Undervoltage Lockout

o Pin-Programmable 640kHz/1.2MHz Switching

Frequency

o Programmable Soft-Start

o Improved EMI

o FB Regulation Voltage Tolerance < 1%

o Small 10-Pin TDFN Package

o Thermal-Overload Protection

MAX17062

TFT-LCD Step-Up DC-DC Converter

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-1042; Rev 0; 10/07

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

MAX17062ETB+T -40°C to +85°C

10 TDFN-EP*

(3mm x 3mm)

T1033-2

COMP

12345

10 9 8 7 6

PGND

SHDN

FREQ

MAX17062

TOP VIEW

TDFN

(3mm x 3mm)

*EP = EXPOSED PAD.

*EP

Pin Configuration

LX LX

PGND

AGND

FREQ

COMP

OUT

2.6V TO 5.5V

SHDN

MAX17062

Minimal Operating Circuit

Denotes a lead-free package.

EP = Exposed pad.

T = Tape and reel.

Summary of content (14 pages)

PAGE 1
9-1042; Rev 0; 10/07 KIT ATION EVALU E L B AVAILA TFT-LCD Step-Up DC-DC Converter The MAX17062 is a high-performance step-up DC-DC converter that provides a regulated supply voltage for active-matrix thin-film transistor (TFT) liquid-crystal displays (LCDs). The MAX17062 incorporates currentmode, fixed-frequency, pulse-width modulation (PWM) circuitry with a built-in n-channel power MOSFET to achieve high efficiency and fast-transient response. Users can select 640kHz or 1.
PAGE 2
MAX17062 TFT-LCD Step-Up DC-DC Converter ABSOLUTE MAXIMUM RATINGS LX to AGND ............................................................-0.3V to +22V IN, SHDN, FREQ, FB to AGND..............................-0.3V to +7.5V COMP, SS to AGND ....................................-0.3V to (VIN + 0.3V) PGND to AGND .....................................................-0.3V to +0.3V LX Switch Maximum Continuous RMS Current .....................3.2A Continuous Power Dissipation (TA = +70°C) 10-Pin TDFN (derate 24.
PAGE 3
TFT-LCD Step-Up DC-DC Converter (VIN = V SHDN = 3V, FREQ = 3V, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS 0.3 VIN V CONTROL INPUTS SHDN, FREQ Input Low Voltage VIN = 2.6V to 5.5V SHDN, FREQ Input High Voltage VIN = 2.6V to 5.5V SHDN, FREQ Input Hysteresis VIN = 2.6V to 5.5V 0.7 VIN 0.
PAGE 4
ELECTRICAL CHARACTERISTICS (continued) (VIN = V SHDN = 3V, FREQ = 3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS 0.3 VIN V CONTROL INPUTS SHDN, FREQ Input Low Voltage VIN = 2.6V to 5.5V SHDN, FREQ Input High Voltage VIN = 2.6V to 5.5V 0.7 VIN V Note 1: Limits are 100% tested at TA = +25°C. Maximum and minimum limits over temperature are guaranteed by design. Typical Operating Characteristics (Circuit of Figure 1.
PAGE 5
TFT-LCD Step-Up DC-DC Converter SOFT-START (RLOAD = 30Ω) LOAD-TRANSIENT RESPONSE (ILOAD = 50mA TO 550mA) MAX17062 toc06 MAX17062 toc07 15V VOUT 500mV/div AC-COUPLED 0V VOUT 5V/div IOUT 500mA/div 50mA OV INDUCTOR CURRENT 1A/div INDUCTOR CURRENT 2A/div OA 0A 2ms/div 100μs/div L = 2.7μH RCOMP = 47kΩ CCOMP1 = 560pF PULSED LOAD-TRANSIENT RESPONSE (ILOAD = 100mA TO 1.1A) SWITCHING WAVEFORMS (ILOAD = 600mA) MAX17062 toc08 MAX17062 toc09 15V VOUT 200mV/div AC-COUPLED LX 10V/div 0V IOUT 1A/div 0.
PAGE 6
TFT-LCD Step-Up DC-DC Converter MAX17062 Pin Description PIN NAME 1 COMP 2 FB FUNCTION Compensation Pin for Error Amplifier. Connect a series RC from COMP to ground. See the Loop Compensation section for component selection guidelines. Feedback Pin. The FB regulation voltage is 1.24V nominal. Connect an external resistive voltage-divider between the step-up regulator’s output (VOUT) and AGND, with the center tap connected to FB.
PAGE 7
TFT-LCD Step-Up DC-DC Converter 4μA MAX17062 SKIP COMPARATOR SHDN IN BIAS SOFTSTART SKIP COMP ERROR AMPLIFIER SS ERROR COMPARATOR FB ∞ LX CONTROL AND DRIVER LOGIC 1.24V N CLOCK PGND OSCILLATOR FREQ SLOPE COMPENSATION Σ CURRENT SENSE 6μA MAX17062 Figure 2. MAX17062 Functional Diagram Detailed Description The MAX17062 is a highly efficient power supply that employs a current-mode, fixed-frequency, PWM architecture for fast-transient response and low-noise operation.
PAGE 8
MAX17062 TFT-LCD Step-Up DC-DC Converter Soft-Start The MAX17062 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 0.4V. Then the capacitor is charged at a constant current of 4μA (typ). During this time, the SS voltage directly controls the peak inductor current, allowing 0A at VSS = 0.4V to the full current limit at VSS = 1.5V.
PAGE 9
TFT-LCD Step-Up DC-DC Converter ⎛ V ⎞ L = ⎜ IN ⎟ ⎝ VMAIN ⎠ 2⎛ ⎞ ⎛η ⎞ VMAIN − VIN ⎜ ⎟ ⎜ TYP ⎟ ⎜I ⎟ ⎝ MAIN(MAX) × fOSC ⎠ ⎝ LIR ⎠ The inductor’s saturation current rating and the MAX17062’s LX current limit (I LIM ) should exceed I PEAK , and the inductor’s DC current rating should exceed IIN(DC,MAX). For good efficiency, choose an inductor with less than 0.1Ω series resistance.
PAGE 10
MAX17062 TFT-LCD Step-Up DC-DC Converter Input Capacitor Selection The input capacitor (CIN) reduces the current peaks drawn from the input supply and reduces noise injection into the IC. Two 4.7μF ceramic capacitors are used in the Typical Operating Circuit (Figure 1) because of the high source impedance seen in typical lab setups. Actual applications usually have much lower source impedance since the step-up regulator often runs directly from the output of another regulated supply.
PAGE 11
TFT-LCD Step-Up DC-DC Converter C11 0.22μF C12 0.1μF 3 C1 4.7μF 10V C2 4.7μF 10V 2 C15 0.22μF 3 2 R5 10Ω 8 C3 1μF VGON +29V 1 L1 2.7μH VIN 4.5V TO 5.5V D3 C14 0.1μF MAX17062 D2 1 VGOFF -15V U1 IN D1 VOUT +15V/600mA C7 10μF 25V 6 LX 7 LX C8 10μF 25V MAX17062 PGND 5 3 R1 100kΩ 9 10 SHDN PGND FREQ FB SS COMP C4 33nF AGND 4 R4 221kΩ 2 EP R3 20kΩ 1 R2 47kΩ C6 OPEN C5 560pF Figure 3.
PAGE 12
MAX17062 TFT-LCD Step-Up DC-DC Converter 3) Place the feedback voltage-divider-resistors as close to the FB pin as possible. The divider’s center trace should be kept short. Placing the resistors far away causes the FB trace to become an antenna that can pick up switching noise. Avoid running the feedback trace near LX. 4) Place the IN pin bypass capacitor as close to the device as possible. The ground connection of the IN bypass capacitor should be connected directly to AGND pins with a wide trace.
PAGE 13
TFT-LCD Step-Up DC-DC Converter 6, 8, &10L, DFN THIN.EPS ______________________________________________________________________________________ 13 MAX17062 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.
PAGE 14
MAX17062 TFT-LCD Step-Up DC-DC Converter Package Information (continued) (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.) COMMON DIMENSIONS PACKAGE VARIATIONS SYMBOL MIN. MAX. PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-1] x e A 0.70 0.80 T633-2 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF D 2.90 3.10 T833-2 8 1.50±0.10 2.30±0.10 0.