MAX749ESA Maxim Integrated Products, MAX749ESA Datasheet

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MAX749ESA

Manufacturer Part Number
MAX749ESA
Description
Display Drivers Digitally Adjustable able LCD Bias Supply
Manufacturer
Maxim Integrated Products
Datasheet

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The MAX749 generates negative LCD-bias contrast
voltages from 2V to 6V inputs. Full-scale output voltage
can be scaled to -100V or greater, and is digitally
adjustable in 64 equal steps by an internal digital-to-
analog converter (DAC). Only seven small surface-
mount components are required to build a complete
supply. The output voltage can also be adjusted using
a PWM signal or a potentiometer.
A unique current-limited control scheme reduces supply
current and maximizes efficiency, while a high switching
frequency (up to 500kHz) minimizes the size of external
components. Quiescent current is only 60µA max and is
reduced to under 15µA in shutdown mode. While shut
down, the MAX749 retains the voltage set point, simpli-
fying software control. The MAX749 drives either an
external P-channel MOSFET or a PNP transistor.
________________________Applications
19-0143; Rev 1; 2/95
Call toll free 1-800-998-8800 for free samples or literature.
__________Typical Operating Circuit
_______________General Description
0.1 F
V
DIGITAL
ADJUST
IN
ON/OFF
+5V
Notebook Computers
Laptop Computers
Palmtop Computers
Personal Digital Assistants
Communicating Computers
Portable Data-Collection Terminals
1
2
3
4
ADJ
CTRL
FB
V+
MAX749
C
_______________________________________________________________ Maxim Integrated Products
COMP
R
FB
DLOW
GND
DHI
CS
Digitally Adjustable LCD Bias Supply
5
8
7
6
R
SENSE
-V
OUT
____________________________Features
* Contact factory for dice specifications.
__________________Pin Configuration
MAX749CPA
MAX749CSA
MAX749C/D
MAX749EPA
MAX749ESA
______________Ordering Information
+2.0V to +6.0V Input Voltage Range
Flexible Control of Output Voltage:
Output Voltage Range Set by One Resistor
Low, 60µA Max Quiescent Current
15µA Max Shutdown Mode
Small Size – 8-Pin SO and Plastic DIP Packages
TOP VIEW
Digital Control
Potentiometer Adjustment
PWM Control
PART
CTRL
ADJ
V+
FB
-40°C to +85°C
-40°C to +85°C
1
2
3
4
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
MAX749
DIP/SO
8
7
6
5
CS
DHI
DLOW
GND
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
PIN-PACKAGE
1

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MAX749ESA Summary of contents

Page 1

... Output Voltage Range Set by One Resistor Low, 60µA Max Quiescent Current 15µA Max Shutdown Mode Small Size – 8-Pin SO and Plastic DIP Packages ______________Ordering Information PART MAX749CPA MAX749CSA MAX749C/D MAX749EPA MAX749ESA * Contact factory for dice specifications. __________________Pin Configuration TOP VIEW R SENSE ADJ -V OUT CTRL TEMP ...

Page 2

Digitally Adjustable LCD Bias Supply ABSOLUTE MAXIMUM RATINGS V+ ................................................................................-0.3V, +7V CTRL, ADJ, FB, DLOW, DHI, CS.....................-0.3V, (V+ + 0.3V) Continuous Power Dissipation (T = +70°C) A Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW SO (derate 5.88mW/°C above +70°C) .........................471mW ...

Page 3

Digitally Adjustable LCD Bias Supply __________________________________________Typical Operating Characteristics (T = +25° 47µH, unless otherwise noted.) A EFFICIENCY vs. OUTPUT CURRENT – PNP 85 80 -12V -24V - 470 BASE R = 0.25 ...

Page 4

Digitally Adjustable LCD Bias Supply ____________________________Typical Operating Characteristics (continued +25° 47µH, unless otherwise noted.) A LOAD-TRANSIENT RESPONSE OUTPUT VOLTAGE LOAD CURRENT V = -15V OUT TRANSISTOR = ZTX750 50 s/div V = -15V OUT TRANSISTOR = ...

Page 5

Digitally Adjustable LCD Bias Supply +2V TO +6V INPUT RESET 6-BIT POWER-ON COUNTER RESET CTRL LOGIC INCREMENT ADJ ON/OFF BIAS MAX749 Figure 1. Block Diagram, Showing External Circuitry Using a PNP Transistor _______________Detailed Description The MAX749 is a negative-output inverting ...

Page 6

Digitally Adjustable LCD Bias Supply Q TRIG MINIMUM OFF-TIME ONE-SHOT FLIP-FLOP S R MAXIMUM ON-TIME ONE-SHOT TRIG Q REF MAX749 Figure 2. Switch-Mode Power-Supply Section Block Diagram Once turned off, a one-shot holds the switch off for a minimum of ...

Page 7

Digitally Adjustable LCD Bias Supply ADJ CTRL SHUTDOWN RESET Figure 3. Shutdown-Reset-On-Shutdown Sequence of Operation. The device is not shut down during reset. ADJ CTRL Figure 4. Count-Up Operation ADJ CTRL t RS ...

Page 8

Digitally Adjustable LCD Bias Supply +4.5V to +6V 0 INPUT V+ CS MAX749 DHI CTRL DLOW ADJ R2 R1 GND C COMP V = -R1(13.33 A) OUT(MIN -(R1+R2)(13.33 A) OUT(MAX) Figure 8. ...

Page 9

Digitally Adjustable LCD Bias Supply Choosing an Inductor Practical inductor values range from 22µH to 100µH, and 47µH is normally a good choice. Inductors with a ferrite core or equivalent are recommended. The induc- tor’s saturation current rating – the ...

Page 10

Digitally Adjustable LCD Bias Supply The Sumida CD54-470N (47µH, 720mA, 370mΩ) is suit- able for a wide range of applications, and the larger CD105-470N (47µH, 1.17A, 170mΩ) permits higher cur- rent levels and efficiencies. Diode Selection The MAX749’s high switching ...

Page 11

Digitally Adjustable LCD Bias Supply Output Filter Capacitor A 22µF, 30V surface-mount (SMT) tantalum output filter capacitor typically maintains 100mVp-p output ripple when generating -24V at 40mA from a 5V input. Smaller capacitors, down to 10µF, may be used for ...

Page 12

Digitally Adjustable LCD Bias Supply _______________________________________________________Package Information ______________________________________________________________________________________ 0° - 15° Plastic DIP PKG. PLASTIC P P ...

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