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MAX8740ETB+T

P1-P3P4-P6P7-P9P10-P12
General Description
The MAX8740 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 MAX8740 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 30V internal MOSFET can generate
output voltages up to 28V from a 2.6V and 5.5V input
voltage range. Soft-start slowly ramps the input current
and is programmed with an external capacitor.
The MAX8740 is available in a 10-pin thin DFN package.
Applications
Notebook Computer Displays
LCD Monitor Panels
Features
♦ 90% Efficiency
♦ Adjustable Output from V
IN
to 28V
♦ 2.6V to 5.5V Input Supply Range
♦ Input Supply Undervoltage Lockout
♦ Pin-Programmable 640kHz/1.2MHz Switching
Frequency
♦ Programmable Soft-Start
♦ 0.1µA Shutdown Current
♦ Small, 10-Pin Thin DFN Package
MAX8740
TFT-LCD Step-Up DC-DC Converter
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-3698; Rev 0; 5/05
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.
EVALUATION KIT
AVAILABLE
PART
TEMP RANGE
PIN-PACKAGE
MAX8740ETB
-40°C to +85°C
10 TDFN 3mm x 3mm
COMP
1
FB
2 3
GND
4
GND
5
10 9 8 7 6
SHDN
SS
FREQ
LX
LX
IN
MAX8740
TOP VIEW
THIN DFN
3mm x 3mm
Pin Configuration
LX LX
FB
GND
GND
FREQ
IN
COMP
SS
1
4
5
2
3
9
8
67
10
V
OUT
V
IN
2.6V TO 5.5V
SHDN
MAX8740
Minimal Operating Circuit
MAX8740
TFT-LCD Step-Up DC-DC Converter
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
IN
= V
SHDN
= 3V, T
A
= 0°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.)
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.
LX to GND ..............................................................-0.3V to +30V
IN, SHDN, FREQ, FB to GND ...................................-0.3V to +6V
COMP, SS to GND.......................................-0.3V to (V
IN
+ 0.3V)
LX Switch Maximum Continuous RMS Current .....................2.4A
Continuous Power Dissipation (T
A
= +70°C)
10-Pin TDFN (derate 24.1mW/°C above +70°C) .......1481.5mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER CONDITIONS
MIN TYP MAX
UNITS
V
OUT
< 18V 2.6 5.5
Input Voltage Range
18V < V
OUT
< 24V 4.0 5.5
V
Output Voltage Range 28 V
IN Undervoltage-Lockout
Threshold
V
IN
rising, typical hysteresis is 50mV; LX remains off
below this level
2.20 2.38 2.57
V
V
FB
= 1.3V, not switching
0.22 0.44
IN Quiescent Current
V
FB
= 1.0V, switching, FREQ = GND 2 5
mA
IN Shutdown Current SHDN = GND 0.1
10.0
µA
ERROR AMPLIFIER
FB Regulation Voltage Level to produce V
COMP
= 1.24V
1.22 1.24 1.26
V
FB Input Bias Current V
FB
= 1.24V 50
125
250 nA
FB Line Regulation Level to produce V
COMP
= 1.24V, V
IN
= 2.6V to 5.5V
0.05 0.15
%/V
Transconductance
100 200
315 µS
Voltage Gain
2400
V/V
OSCILLATOR
FREQ = GND
540 640
740
Frequency
FREQ = IN
1000 1220 1500
kHz
Maximum Duty Cycle 88 91 94 %
n-CHANNEL MOSFET
Current Limit V
FB
= 1V, 71% duty cycle 3.9 4.6 5.3 A
V
IN
= 3V (typ value at T
A
= +25°C)
0.11 0.17
On-Resistance
V
IN
= 5V (typ value at T
A
= +25°C)
0.095 0.15
Ω
Leakage Current V
LX
= 28V 30 55 µA
Current-Sense Transresistance
0.09 0.15 0.25
V/A
SOFT-START
Reset Switch Resistance 100 Ω
Charge Current V
SS
= 1.2V 2.5 4.5 7.5 µA
MAX8740
TFT-LCD Step-Up DC-DC Converter
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
SHDN
= 3V, T
A
= 0°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER CONDITIONS
MIN
MAX
UNITS
CONTROL INPUTS
SHDN, FREQ Input Low Voltage V
IN
= 2.6V to 5.5V
0.3 x
V
IN
V
SHDN, FREQ Input High Voltage
V
IN
= 2.6V to 5.5V
0.7 x
V
IN
V
SHDN, FREQ Input Hysteresis V
IN
= 2.6V to 5.5V
0.1 x
V
IN
V
FREQ Pulldown Current 2.3 6.0 9.5 µA
SHDN Input Current SHDN = GND
0.001
1µA
ELECTRICAL CHARACTERISTICS
(V
IN
= V
SHDN
= 3V, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER CONDITIONS
MIN TYP MAX
UNITS
V
OUT
< 18V 2.6 5.5
Input Voltage Range
18V < V
OUT
< 28V 4.0 5.5
V
Output Voltage Range 28 V
V
FB
= 1.3V, not switching
0.44
IN Quiescent Current
V
FB
= 1.0V, switching, FREQ = GND 5
mA
IN Shutdown Current SHDN = GND 10 µA
ERROR AMPLIFIER
FB Regulation Voltage Level to produce V
COMP
= 1.24V
1.215 1.260
V
FB Line Regulation Level to produce V
COMP
= 1.24V, V
IN
= 2.6V to 5.5V
0.15
%/V
Transconductance
100 330
µS
OSCILLATOR
FREQ = GND
490 770
Frequency
FREQ = IN
900 1600
kHz
n-CHANNEL MOSFET
Current Limit V
FB
= 1V, 71% duty cycle 3.9 5.3 A
Current-Sense Transresistance
0.09 0.25
V/A
CONTROL INPUTS
SHDN, FREQ Input Low Voltage V
IN
= 2.6V to 5.5V
0.3 x
V
IN
V
SHDN, FREQ Input High Voltage
V
IN
= 2.6V to 5.5V
0.7 x
V
IN
V
Note 1: -40°C specifications are guaranteed by design, not production tested.
P1-P3P4-P6P7-P9P10-P12

MAX8740ETB+T

Mfr. #:
Buy MAX8740ETB+T
Manufacturer:
Maxim Integrated
Description:
LCD Drivers TFT-LCD Step-Up DC/DC Converter
Lifecycle:
New from this manufacturer.
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