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MAX8784ETL+

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24
General Description
The MAX8784 generates supply rails for the thin-film
transistor (TFT) liquid-crystal display (LCD) panels in TVs
and monitors. It includes a step-up regulator, a regulated
positive and a negative charge-pump, three high-current
operational amplifiers, and Dual Mode™, logic-con-
trolled, high-voltage switch control block. HVS mode
automatically increases the output voltages of the boost
regulator and the positive charge-pump to stress test
display panels during production. The MAX8784 can
operate from input voltages of 4V to 5.5V and is opti-
mized for LCD TV panel and LCD monitor applications.
The step-up DC-DC regulator provides a regulated sup-
ply voltage for TFT source drivers. The step-up regulator
is a high-frequency (1.2MHz), high-efficiency, current-
mode regulator. The step-up regulator has a built-in
110mΩ (typ) power MOSFET. The high-switching fre-
quency allows the use of ultra-small inductors and
ceramic capacitors. The current-mode architecture pro-
vides fast transient response and easy compensation.
The step-up regulator features output undervoltage pro-
tection, soft-start, internal current limit, and adjustable
output voltage by an external resistive divider.
The three operational amplifiers drive the LCD back-
plane and the gamma-correction-divider string. Each
operational amplifier has a fast slew rate (45V/µs), a
wide bandwidth (20MHz), and a high-output short-cir-
cuit current (200mA). Each op amp has rail-to-rail input
and rail-to-rail output operation.
The positive charge-pump regulator and the negative
charge-pump regulator provide regulated supply volt-
ages for the TFT gate drivers. The positive charge
pump is a two-stage charge pump, which requires no
external diodes. The output voltages of both charge
pumps are resistor adjustable. The logic-controlled
high-voltage switch allows the manipulation of the posi-
tive TFT gate-driver supply.
The MAX8784 is available in a small (5mm x 5mm), low-
profile (0.8mm), 40-pin TQFN package and operates
over the -40°C to +85°C temperature range.
Applications
LCD TVs and LCD Monitors
Features
o Step-Up Regulator Supply for LCD Panel Source
Driver
Fast Transient Response to Pulsed Load
Built-In 18V, 4A, 0.11Ω n-Channel Power
MOSFET with Lossless Current Sensing
Cycle-by-Cycle Current-Limit Comparator
90% Efficiency (5V In to 15V Out)
1.2MHz Switching Frequency
o Three High-Current 19V Operational Amplifiers
180mA Output Short-Circuit Current
45V/µs Slew Rate
20MHz Bandwidth
Rail-to-Rail Input and Output Operation
o Regulated Charge-Pump Tripler with Integrated
Diodes for TFT Gate-On Supply
o Regulated Charge Pump for TFT Gate-Off Supply
o Built-In Sequencing
Internal Digital Soft-Start
36V Gate-On Switch
Startup Timing Capacitors for AVDD and GON
o Undervoltage and Thermal Protection
o 4V to 5.5V Input Operating Range
MAX8784
Step-Up Regulator, Internal Charge Pumps, Switch
Control, and Operational Amplifier for TFT LCDs
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
SHDN
DRVN
FBN
REF
FB
AGND
COMP
VIN
VGOFF
STEP-UP
OUTPUT
STEP-UP
OUTPUT
V
CC
PGND
LX
ADEL
FBP
VGON
GDEL
SUP
POUT
C1N
C2P
C1P
DRN
CTL
TCON
C2N
RSET
OUT3
POS3
OUT2
OUT1
POS1
NEG1
POS2
NEG2
HVSVIN
PGND
STEP-UP
OUTPUT
STEP-UP
OUTPUT
TO
VCOM
TO
VCOM
TO
VCOM
ON/OFF
GON
MAX8784
Simplified Operating Circuit
19-0737; Rev 0; 1/07
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.
PART
TEMP RANGE
PIN-
PACKAGE
PKG CODE
MAX8784ETL+
-40°C to +85°C
40 TQFN
5mm x 5mm
T4055-1
Dual Mode is a trademark of Maxim Integrated Products, Inc.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
EVALUATION KIT
AVAILABLE
MAX8784
Step-Up Regulator, Internal Charge Pumps, Switch
Control, and Operational Amplifier for TFT LCDs
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
CC
= +5V, Circuit of Figure 1, AVDD = SUP = +14V, 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.
V
CC
, CTL, HVS, SHDN, ADEL, GDEL to AGND ....-0.3V to +7.5V
REF, COMP, FB, FBN, FBP to AGND.........-0.3V to (V
CC
+ 0.3V)
POS1, NEG1, POS2, NEG2, POS3, OUT1, OUT2,
OUT3 to AGND .......................................-0.3V to (V
SUP
+ 0.3)
PGND, BGND to AGND.........................................-0.3V to +0.3V
LX, RSET to PGND .................................................-0.3V to +22V
SUP to AGND .........................................................-0.3V to +22V
DRVN to AGND.........................................-0.3V to (V
SUP
+ 0.3V)
C1N, C2N to AGND ..................................-0.3V to (V
SUP
+ 0.3V)
C1P to AGND .........................................................-0.3V to +30V
POUT to C2P, C1P to C2P......................................-0.3V to +22V
C2P, POUT to AGND..............................................-0.3V to +40V
GON, DRN to AGND ..............................................-0.3V to +40V
DRN to GON............................................................-30V to +30V
REF Short Circuit to AGND.........................................Continuous
RMS V
CC
Current................................................................50mA
RMS DRVN Current...........................................................400mA
LX, PGND RMS Current Rating.............................................2.4A
Continuous Power Dissipation (T
A
= +70°C)
40-Pin TQFN (derate 35.7mW/°C above +70°C) .......2857mW
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
Soldering Temperature (reflow) .......................................+260°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
CC
Input Supply Range 4.0 5.5 V
V
CC
Undervoltage Lockout Threshold V
CC
rising, typical hysteresis = 50mV 2.4 2.6 2.8 V
V
FB
= 1.3V, not switching 1.0
V
FB
= 1.1V, switching, no load, V
SUP
disconnected,
V
FBP
= V
CC
, V
FBN
= 0V
46
V
CC
Quiescent Current
SHDN = GND 0.05
mA
SHDN Input Low Voltage 0.8 V
SHDN Input High Voltage 1.8 V
SHDN Input Current -1 +1 µA
REFERENCE
REF Output Voltage No external load 1.238 1.250 1.262 V
REF Load Regulation 0 < I
LOAD
< 50µA 10 mV
REF Sink Current In regulation 10 µA
REF Undervoltage Lockout Threshold Rising edge, typical hysteresis = 200mV 1.0 1.15 V
OSCILLATOR AND TIMING
Frequency 1000 1200 1400 kHz
Oscillator Maximum Duty Cycle 87 90 93 %
Duration to Trigger Fault Condition 47 55 65 ms
AD E L, G D E L C ap aci tor C har g e C ur r ent 4 5 6 µA
ADEL, GDEL Turn-On Threshold 1.25 1.32 V
STEP-UP REGULATOR
FB = COMP, C
COMP
= 1nF 1.235 1.246 1.256
FB Regulation Voltage
FB = COMP, C
COMP
= 1nF, +25°C to +85°C 1.238 1.246 1.256
V
FB Fault-Trip Level Falling edge 0.96 1.00 1.04 V
FB Load Regulation 0 < I
LOAD
< full -1 %
FB Line Regulation V
CC
= 4.5V to 5.5V 0.25 %/V
FB Input Bias Current V
FB
= 1.25V 100 200 nA
MAX8784
Step-Up Regulator, Internal Charge Pumps, Switch
Control, and Operational Amplifier for TFT LCDs
_______________________________________________________________________________________ 3
PARAMETER CONDITIONS MIN TYP MAX UNITS
FB Transconductance ∆I
COMP
= ±2.5µA, FB = COMP 75 160 280 µS
LX Current Limit V
FB
= 1.1V, duty cycle = 75% 3.5 4.0 4.6 A
LX On-Resistance I
LX
= 1.0A 0.10 0.19 Ω
Current-Sense Transresistance 0.10 0.20 0.26 V/A
Soft-Start Period 7-bit current ramp 3 ms
POSITIVE CHARGE-PUMP REGULATOR
V
SUP
Input Supply Range 619V
V
SUP
O ver vol tag e C har g e- P um p Inhi b i tV
SUP
= rising, typical hysteresis = 200mV 20 21 22 V
FBP Regulation Voltage 1.225 1.25 1.275 V
FBP Line Regulation Error V
SUP
= 10V ~ 19V, V
POUT
= 28V 0.1 %/V
FBP Input Bias Current V
FBP
= 1.5V -100 +100 nA
POUT Output-Voltage Range I
VGON
= 0mA 36 V
POUT Fixed Output Voltage HVS = V
CC
, I
POUT
= 0mA 29.1 30 30.9 V
POUT Output Current Limit Not in dropout, V
SUP
= 9V, V
POUT
= 24V 20 50 mA
C1N, C2N High-Side On-Resistance 9.0 Ω
C1N, C2N Low-Side On-Resistance 6.0 Ω
C1P Switch On-Resistance 15.0 Ω
C2P Switch On-Resistance 10.0 Ω
POUT Switch On-Resistance 10.0 Ω
FBP Fault-Trip Level Falling edge 0.96 1.00 1.04 V
Positive Charge-Pump Soft-Start Period 7-bit voltage ramp 3 ms
NEGATIVE CHARGE-PUMP REGULATOR
FBN Regulation Voltage V
REF
- V
FBN
0.985 1.00 1.015 V
FBN Input Bias Current V
FBN
= 250mV -50 +50 nA
FBN Line Regulation Error V
SUP
= 11V to 19V, VGOFF = -9V, I
VGOFF
= -20mA 0.1 %/V
DRVN PCH On-Resistance 10 Ω
DRVN NCH On-Resistance 6 Ω
FBN Fault-Trip Level Rising edge 450 mV
N eg ati ve C har g e- P um p S oft- S tar t P er i od 7-bit voltage ramp 3 ms
POSITIVE GATE-DRIVER TIMING AND CONTROL SWITCHES
CTL Input-Low Voltage 0.8 V
CTL Input-High Voltage 1.8 V
CTL Input Current CTL = 0V or V
CC
-1 +1 µA
CTL-to-GON Rising Propagation Delay 200 ns
CTL-to-GON Falling Propagation Delay 200 ns
GON-to-POUT Switch On-Resistance V
GDEL
= 1.5V, CTL = V
CC
10 20 Ω
GO N - to- P OU T S w i tch S atur ati on C ur r ent V
POUT
- V
GON
> 5V 180 mA
GON-to-DRN Switch On-Resistance V
GDEL
= 1.5V, CTL = 0V 60 Ω
GON-to-DRN Switch Saturation Current V
GON
- V
DRN
> 5V 35 mA
GON-to-PGND Switch On-Resistance V
GDEL
= 1.0V 100 kΩ
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +5V, Circuit of Figure 1, AVDD = SUP = +14V, T
A
= 0°C to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.)
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24

MAX8784ETL+

Mfr. #:
Buy MAX8784ETL+
Manufacturer:
Maxim Integrated
Description:
Display Drivers & Controllers Reg, CP, Op Amp for TFT LCDs
Lifecycle:
New from this manufacturer.
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