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MAX8798AETX+-MAX8798ETX+-MAX8798ETX+T
Internal-Switch Boost Regulator with Integrated 3-Channel Scan Driver for TFT LCDs
General DescriptionThe MAX8798 includes a high-performance, step-up
regulator; a high-speed operational amplifier; a digitally
adjustable VCOM calibration device with nonvolatile
memory; an I2C interface; and a high-voltage, level-shift-
ing scan driver. The device is optimized for thin-film
transistor (TFT) liquid-crystal display (LCD) applications.
The step-up DC-DC converter provides the regulated
supply voltage for panel source driver ICs. The high
switching frequency allows the use of ultra-small induc-
tors and ceramic capacitors. The current-mode control
architecture provides fast transient response to pulsed
loads typical of source driver loads. The step-up regu-
lator features soft-start and current limit.
The high-current operational amplifier is designed to
drive the LCD backplane (VCOM). The amplifier fea-
tures high output current (±150mA), fast slew rate
(45V/µs), wide bandwidth (20MHz), and rail-to-rail
inputs and outputs.
The programmable VCOM calibrator is externally
attached to the VCOM amplifier’s resistive voltage-divider
and sinks a programmable current to adjust the VCOM
output-voltage level. An internal 7-bit digital-to-analog
converter (DAC) controls the sink current. The DAC is
ratiometric relative to BOOST and is guaranteed to be
monotonic over all operating conditions. The calibrator IC
includes an EEPROM to store the desired VCOM voltage
level. The 2-wire I2C interface between the LCD panel
and the programming circuit minimizes panel connector
lead count and simplifies production equipment.
The high-voltage, level-shifting scan driver is designed
to drive the TFT panel gate drivers. Its three outputs
swing 65V (maximum) between +45V (maximum) and
-25V (minimum) and can swiftly drive capacitive loads.
To save power, the two complementary outputs are
designed to allow charge sharing during state changes.
The MAX8798 is available in a 36-pin, thin QFN pack-
age with a maximum thickness of 0.8mm for ultra-thin
LCD panels.
ApplicationsNotebook Computer Displays
LCD Monitor Panels
Features1.8V to 5.5V IN Supply Voltage Range1.8V to 4.0V VDDInput Voltage Range1.2MHz Current-Mode Step-Up Regulator
Fast Transient Response
Built-In 20V, 1.9A, 150mΩMOSFETHigh-Speed (20MHz) Operational Amplifier
±150mA Output CurrentHigh-Voltage Drivers with Scan Logic
+45V to -25V Outputs
65V (maximum) Swing
Output Charge SharingProgrammable VCOM Calibrator
7-Bit Adjustable Current-Sink Output2C Interface
EEPROM Setting MemoryThermal-Overload Protection
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
Ordering InformationSCAN DRIVER
LOGIC
AND
GATE DRIVERS
VMAIN
VINVP
TO VCOM
BACKPLANE
SDA
COMP
PGND
BGND
VCOM
POS
NEG
SCL
BOOST
GON
SET
STVP
GOFF
CKVBCS
CKV
SHDN
OECON
STV
CPV
WPN
CKVCS
CKVB
WPPSCLS
VDD
OUT
I2C
BUS
VIN
SYSTEM
PANEL3.3V
LINEAR
REG
VCOM CALIBRATORGND
AGND
1.9A
STEP-UP
REG
DISH
1kΩ
50kΩ
Simplified Operating Circuit19-0971; Rev 1; 6/08
EVALUATION KITAVAILABLE
PARTTEMP RANGEPIN-
PACKAGE
PKG
CODE MAX8798ETX+ -40°C to +85°C 36 Thin QFN
6mm x 6mm T-3666M-1
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VIN = VDD= VSHDN= +3V, circuit of Figure 2, VBOOST= 8V, VGON= 23V, VGOFF= -12V, VPOS= 0, VNEG= 1.5V, VOE= VCPV=
VSTV= VOECON= 0, TA
= 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)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.
IN, VL, SHDNto AGND.........................................-0.3V to +7.5V
VDD, SDA, SCL, SCLS, WPN, WPP, SET to GND...-0.3V to +4.0V
OECON, CPV, OE, STV to AGND..........................-0.3V to +4.0V
COMP, FB to AGND......................................-0.3V to (VL + 0.3V)
DISH to GND............................................................-6V to+2.0V
LX to PGND............................................................-0.3V to +20V
OUT, VCOM, NEG, POS to BGND........-0.3V to (BOOST + 0.3V)
PGND, BGND, AGND to GND...............................-0.3V to +0.3V
GON to AGND........................................................-0.3V to +50V
GOFF to AGND.............................................-30V to(VIN + 0.3V)
GON to GOFF......................................................................+70V
BOOST to BGND....................................................-0.3V to +20V
CKV, CKVB, STVP, CKVCS,
CKVBCS to AGND..................(GOFF - 0.3V) to (GON + 0.3V)
LX, PGND RMS Current Rating.............................................2.4A
Continuous Power Dissipation (TA= +70°C)
NiPd Lead Frame with Nonconductive Epoxy
36-Pin, 6mm x 6mm Thin QFN
(derate 27.2mW/°C above +70°C).........................2179.8mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
PARAMETERCONDITIONSMINTYPMAXUNITS VDD Input Voltage Range 1.8 4.0 V
VDD Quiescent Current VDD = 3V 4 10 μA
VDD Undervoltage Lockout VDD rising; typical hysteresis 100mV 1.3 1.75 V
IN Input Voltage Range (Note 1) 1.8 6.0 V
IN Quiescent Current VIN = 3V, VFB = 1.5V, not switching 0.04 0.1 mA
IN Undervoltage Lockout IN rising; typical hysteresis 100mV 1.4 1.75 V
Thermal Shutdown Rising edge, hysteresis = 15 oC 160 oC
BOOTSTRAP LINEAR REGULATOR (VL)VL Output Voltage IVL = 100μA 3.15 3.3 3.45 V
VL Undervoltage Lockout VL rising, typical hysteresis 200mV 2.4 2.7 3.0 V
VL Maximum Output Current VFB = 1.1V 10 mA
MAIN DC-DC CONVERTERLX not switching, no load on VL 1.5 2 BOOST Supply Current LX switching, no load on VL 3 4 mA
Operating Frequency 990 1170 1350 kHz
Oscillator Maximum Duty Cycle 88 92 96 %
FB Regulation Voltage 1.216 1.235 1.254 V
FB Load Regulation 0 < ILOAD < 200mA, transient only -1 %
FB Line Regulation VIN= 1.8V to 5.5V, FB to COMP -0.15 -0.08 +0.15 %/V
FB Input Bias Current VFB = 1.25V 50 125 200 nA
FB Transconductance I = 5μA at COMP 70 160 280 μS
FB Voltage Gain FB to COMP 2400 V/V
FB Fault Timer Trip Threshold Falling edge 0.96 1 1.04 V
LX On-Resistance ILX = 1.2A 150 300 m
LX Leakage Current VLX = 18V 0.01 20 μA
LX Current Limit Duty cycle = 65% 1.6 1.9 2.2 A
Current-Sense Transresistance 0.25 0.42 0.55 V/A
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
PARAMETERCONDITIONSMINTYPMAXUNITS
OPERATIONAL AMPLIFIER BOOST Supply Range 5 18 V
BOOST Overvoltage
Fault Threshold (Note 2) 18.1 19 19.9 V
BOOST Undervoltage
Fault Threshold (Note 3) 1.0 1.4 V
Large-Signal Voltage Gain 1V < (VNEG, VPOS) < (VBOOST - 1V) 120 dB
Common-Mode Rejection Ratio 1V < (VNEG, VPOS) < (VBOOST - 1V) 75 dB
1V < (VNEG, VPOS) < (VBOOST - 1V) -25 -5 +25 Input Offset Voltage VBOOST/2 -15 -2.5 +12 mV
Input Bias Current 1V < (VNEG, VPOS) < (VBOOST - 1V) -50 +50 nA
Input Common-Mode
Voltage Range 1V < (VNEG, VPOS) < (VBOOST - 1V) 0 VBOOST V
VCOM Output Voltage
Swing High IVCOM = 5mA VBOOST
- 100
VBOOST
- 50 mV
VCOM Output Voltage Swing Low IVCOM = -5mA 50 100 mV
VCOM Output-Current High VVCOM = VBOOST - 1V -75 mA
VCOM Output-Current Low VVCOM = 1V +75 mA
Slew Rate 1V < (VNEG, VPOS) < (VBOOST - 1V) 40 V/μs
-3dB Bandwidth 1V < (VNEG, VPOS) < (VBOOST - 1V) 20 MHz
Short to VBOOST/2, sourcing 50 150 VCOM Short-Circuit Current Short to VBOOST/2, sinking 50 150 mA
PROGRAMMABLE VCOM CALIBRATORGON Input Range 16.1 45.0 V
GON Threshold to Enable Program Rising edge, 60mV hysteresis 15.6 16.0 V
SET Voltage Resolution 7 Bits
SET Differential Nonlinearity Monotonic overtemperature -2 +2 LSB
SET Zero-Scale Error -1 +1 +2 LSB
SET Full-Scale Error -3 +3 LSB
SET Current 120 μA
To GND, VBOOST = 18V 8.5 170.0 SET External Resistance
(Note 4) To GND, VBOOST = 6V 2.5 50.0 k
VSET/VBOOST Voltage Ratio DAC full scale 0.05 V/V
OUT Leakage Current When OUT is off 1 nA
OUT Settling Time To ±0.5 LSB error band 20 μs
OUT Voltage Range VSET +
0.5V 18 V
EEPROM Write Cycles (Note 5) 1000 —
ELECTRICAL CHARACTERISTICS (continued)(VIN = VDD= VSHDN= +3V, circuit of Figure 2, VBOOST= 8V, VGON= 23V, VGOFF= -12V, VPOS= 0, VNEG= 1.5V, VOE= VCPV=
VSTV= VOECON= 0, TA
= 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
PARAMETERCONDITIONSMINTYPMAXUNITS
2-WIRE INTERFACE
Logic-Input Low Voltage (VIL) SDA, SCL, WPN, VDD = 3V 0.3 x
VDDV
Logic-Input High Voltage (VIH) SDA, SCL, WPN, VDD = 3V 0.7 x
VDD V
WPP Logic-Output Low Voltage IWPP = 1mA +0.1 V
WPP Logic-Output High Voltage IWPP = 1mA VDD -
0.1 V
SDA Logic-Output Low Sink Current SDA forced to 3.3V 6 mA
Logic Input Current SDA, SCL, SCL_S,WPN to VDD or GND -1 +1 μA
Input Capacitance SDA, SCL, SCL_S 5 pF
SCL Frequency (fCLK) DC 500 kHz
SCL High Time (tCLH) 600 ns
SCL Low Time (tCLL) 1300 ns
SDA, SCL, SCLS Rise Time (tR) CBUS = total capacitance of bus line in pF 20 + 10
x CBUS 300 ns
SDA, SCL, SCLS Fall Time (tF) CBUS = total capacitance of bus line in pF 20 + 10
x CBUS 300 ns
START Condition Hold Time
(tHDSTT)10% of SDA to 90% of SCL 600 ns
START Condition Setup Time
(tSVSTT) 600 ns
Data Input Hold Time (tHDDAT) 0 ns
Data Input Setup Time (tSUDAT) 150 ns
STOP Condition Setup Time
(tSVSTP) 600 ns
Bus Free Time (tUF) 1300 ns
Input Filter Spike Suppression (tSP) SDA, SCL (Note 5) 250 ns
WPN = GND 1 MSCL-SCLS Switch Resistance WPN = VDD 20 50
HIGH-VOLTAGE SCAN DRIVER
GON Input Voltage Range 12 45 V
GOFF Input Voltage Range -25 -2 V
GON to GOFF VGON - VGOFF 65 V
GON Supply Current STV, CPV, OE, OECON = AGND 250 350 μA
GOFF Supply Current STV, CPV, OE, OECON = AGND 100 200 μA
Output-Voltage Low CKV, CKVB, STVP,
-5mA output current
VGOFF
+ 0.2
VGOFF
+ 0.05 V
Output-Voltage High CKV, CKVB, STVP,
5mA output current
VGON
- 0.05
VGON
- 0.2 V
Propagation Delay Between OE VCPV = 0, VSTV = 0, CLOAD = 4.7nF, 50 250 450 ns
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VDD= VSHDN= +3V, circuit of Figure 2, VBOOST= 8V, VGON= 23V, VGOFF= -12V, VPOS= 0, VNEG= 1.5V, VOE= VCPV=
VSTV= VOECON= 0, TA
= 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
PARAMETERCONDITIONSMINTYPMAXUNITS
Output Slew Rate CKV, CKVB Without charge sharing,
STV = VDD, CLOAD = 4.7nF, 5020 40 V/μs
Propagation Delay Between
STV and STVP CLOAD = 4.7nF 250 450 ns
STVP Output Slew Rate CLOAD = 4.7nF, 50 20 40 V/μs
Charge-Sharing Discharge
Path Resistance
CKV to CKVCS and
CKVB to CKVBCS 250 400
DISH Turn-On Threshold Dish falling -1.8 V
STV, CPV, OE Input Low Voltage 0.8 V
STV, CPV, OE Input High Voltage 1.6 V
OECON Input Low Voltage 1.5 V
OECON Input High Voltage 2.0 V
OECON Sink Current VOECON = 5V = VDD 0.4 0.8 mA
STV, CPV, OE
Input Current
VSTV = VDD or GND,
VCPV = VDD or GND,
VOE = VDD or GND,
VOECON = VDD or GND
-1 +1 μA
CKV, CKVB, STVP Output
High-Impedance Current
VCKV = GON or GOFF, high impedance
VCKVB = GON or GOFF, high impedance
VCKVCS = GON or GOFF, high impedance
VCKVBCS = GON or GOFF, high impedance
VSTVP = GON or GOFF, high impedance
-1 +1 μA
CONTROL INPUTS
Input Low Voltage SHDN 0.6 V
SHDN, 1.8V < VIN< 3.0V 1.8 Input High Voltage SHDN, 3.0V < VIN< 5.5V 2.0 V
SHDN Input Current VSHDN = 0 or 3V -1 +1 μA
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VDD= VSHDN= +3V, circuit of Figure 2, VBOOST= 8V, VGON= 23V, VGOFF= -12V, VPOS= 0, VNEG= 1.5V, VOE= VCPV=
VSTV= VOECON= 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
ELECTRICAL CHARACTERISTICS
(VIN = VDD= VSHDN= +3V, circuit of Figure 2, VBOOST= 8V, VGON= 23V, VGOFF= -12V, VPOS= 0, VNEG= 1.5V, VOE= VCPV=
VSTV= VOECON= 0, TA= -40°C to +85°C, unless otherwise noted.) (Note 6)
PARAMETERCONDITIONSMINTYPMAXUNITS
VDD Input Voltage Range 1.8 4.0 V
VDD Quiescent Current VDD = 3V 10 μA
VDD Undervoltage Lockout VDD rising; typical hysteresis 100mV 1.75 V
IN Input Voltage Range (Note 1) 1.8 6.0 V
IN Quiescent Current VIN = 3V, VFB = 1.5V, not switching 0.1 mA
IN Undervoltage Lockout VIN rising; typical hysteresis 100mV 1.75 V
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VDD= VSHDN= +3V, circuit of Figure 2, VBOOST= 8V, VGON= 23V, VGOFF= -12V, VPOS= 0, VNEG= 1.5V, VOE= VCPV=
VSTV= VOECON= 0, TA= -40°C to +85°C, unless otherwise noted.) (Note 6)
PARAMETERCONDITIONSMINTYPMAXUNITS
BOOTSTRAP LINEAR REGULATOR (VL)
VL Output Voltage IVL = 100μA 3.15 3.45 V
VL Undervoltage Lockout VVL rising, typical hysteresis 100mV 2.4 3.0 V
MAIN DC-DC CONVERTER
LX not switching, no load on VL 2 BOOST Supply Current LX switching, no load on VL 4 mA
Operating Frequency 990 1350 kHz
Oscillator Maximum Duty Cycle 88 96 %
FB Regulation Voltage 1.216 1.254 V
FB Line Regulation VIN= 1.8V to 5.5V, FB to COMP -0.15 +0.15 %/V
FB Transconductance I = 5μA at COMP 70 280 μS
FB Fault-Timer Trip Threshold Falling edge 0.96 1.04 V
LX On-Resistance ILX = 1.2A 300 m
LX Current Limit Duty cycle = 65% 1.6 2.2 A
OPERATIONAL AMPLIFIER
BOOST Supply Range 5 18 V
BOOST Overvoltage Fault Threshold (Note 2) 18.1 19.9 V
BOOST Undervoltage Fault Threshold (Note 3) 1.4 V
Input Offset Voltage 1V < (VNEG, VPOS) < (VBOOST - 1V) -25 +25 mV
Input Common-Mode Voltage Range 1V < (VNEG, VPOS) < (VBOOST - 1V) 0 VBOOST V
VCOM Output-Voltage Swing High IVCOM = 5mA VBOOST
- 100 mV
VCOM Output-Voltage Swing Low IVCOM = -5mA 100 mV
Short to VBOOST/2, sourcing 50 VCOM Short-Circuit Current Short to VBOOST/2, sinking 50 mA
PROGRAMMABLE VCOM CALIBRATOR
GON Input Range 16.1 45.0 V
GON Threshold to Enable Program Rising edge, 60mV hysteresis 16.0 V
SET Voltage Resolution 7 Bits
SET Differential Nonlinearity Monotonic overtemperature -2 +2 LSB
SET Zero-Scale Error -1 +2 LSB
SET Full-Scale Error -3 +3 LSB
SET Current 120 μA
To GND, VBOOST = 18V 8.5 170.0 SET External Resistance
(Note 4) To GND, VBOOST = 6V 2.5 50.0 k
OUT Voltage Range VSET +
0.5V 18 V
EEPROM Write Cycles (Note 5) 1000 —
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
PARAMETERCONDITIONSMINTYPMAXUNITS
2-WIRE INTERFACE
Logic-Input Low Voltage (VIL) SDA, SCL, WPN, VDD = 3V 0.3 x
VDDV
Logic-Input High Voltage (VIH) SDA, SCL, WPN, VDD = 3V 0.7 x
VDD V
WPP Logic-Output Low Voltage IWPP = 1mA +0.1 V
WPP Logic-Output High Voltage IWPP = -1mA VDD -
0.1 V
SDA Logic-Output Low Sink Current SDA forced to 3.3V 6 mA
SCL Frequency (fCLK) DC 500 kHz
SCL High Time (tCLH) 600 ns
SCL Low Time (tCLL) 1300 ns
SDA, SCLS, and SCL Rise Time (tR) CBUS = total capacitance of bus line in pF 20 + 10
x CBUS 300 ns
SDA, SCLS, and SCL Fall Time (tF) CBUS = total capacitance of bus line in pF 20 + 10
x CBUS 300 ns
START Condition Hold Time
(tHDSTT)10% of SDA to 90% of SCL 600 ns
START Condition Setup Time
(tSVSTT) 600 ns
Data Input Hold Time (tHDDAT) 0 ns
Data Input Setup Time (tSUDAT) 150 ns
STOP Condition Setup Time (tSVSTP) 600 ns
Bus Free Time (tUF) 1300 ns
Input Filter Spike Suppression (tSP) SDA, SCL (Note 5) 250 ns
WPN = GND 1 MSCL-SCLS Switch Resistance WPN = VDD 50
HIGH-VOLTAGE SCAN DRIVER
GON Input Voltage Range 12 45 V
GOFF Input Voltage Range -25 -2 V
GON to GOFF VGON - VGOFF 65 V
GON Supply Current STV, CPV, OE, OECON = AGND 350 μA
GOFF Supply Current STV, CPV, OE, OECON = AGND 200 μA
Output-Voltage Low CKV, CKVB, STVP,
-5mA output current
VGOFF
+ 0.2 V
Output-Voltage High CKV, CKVB, STVP,
5mA output current
VGON
- 0.2 V
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VDD= VSHDN= +3V, circuit of Figure 2, VBOOST= 8V, VGON= 23V, VGOFF= -12V, VPOS= 0, VNEG= 1.5V, VOE= VCPV=
VSTV= VOECON= 0, TA
= -40°C to +85°C, unless otherwise noted.) (Note 6)
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
PARAMETERCONDITIONSMINTYPMAXUNITS
Propagation Delay Between OE
Rising Edge and CKV/CKVB Edge VCPV = 0, VSTV = 0, CLOAD = 4.7nF, 50 450 ns
Output Slew Rate CKV, CKVB Without charge sharing,
STV = VDD, CLOAD = 4.7nF, 5020 V/μs
Propagation Delay Between STV
and STVP CLOAD = 4.7nF 450 ns
STVP Output Slew Rate CLOAD = 4.7nF, 50 20 V/μs
Charge-Sharing Discharge Path
Resistance
CKV to CKVCS and
CKVB to CKVBCS 400
DISH Turn-On Threshold Dish falling -1.8 V
STV, CPV, OE Input Low Voltage 0.8 V
STV, CPV, OE Input High Voltage 1.6 V
OECON Input Low Voltage 1.5 V
OECON Input High Voltage 2.0 V
OECON Sink Current OECON = STV = VDD 0.4 mA
CONTROL INPUTS
Input Low Voltage SHDN 0.6 V
SHDN, 1.8V < VIN< 3.0V 1.8 Input High Voltage SHDN, 3.0V < VIN< 5.5V 2.0 V
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VDD= VSHDN= +3V, circuit of Figure 2, VBOOST= 8V, VGON= 23V, VGOFF= -12V, VPOS= 0, VNEG= 1.5V, VOE= VCPV=
VSTV= VOECON= 0, TA= -40°C to +85°C, unless otherwise noted.) (Note 6)
Note 1:For 5.5V < VIN < 6.0V, use the MAX8798 for no longer than 1% of IC lifetime. For continuous operation, the input voltage
should not exceed 5.5V.
Note 2:Inhibits boost switching if VBOOSTexceeds the threshold This fault is not latched.
Note 3:Step-up regulator switching is not enabled until BOOST is above undervoltage threshold.
Note 4:SET external resistor range is verified at DAC full scale.
Note 5:Guaranteed by design, not production tested.
Note 6:-40°C specs are guaranteed by design, not production tested.
tCLL
tCLH
tHDDATtSUDATtSUSTPtBF
SDA
SCL
VIH
VIL
tHDSTT
Figure 1. Timing Definitions Used in the Electrical Characteristics
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
STEP-UP REGULATOR EFFICIENCY
vs. LOAD CURRENT
MAX17088 toc01
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN = 5.0V
VIN = 3.0V
VIN = 2.2V
STEP-UP REGULATOR OUTPUT
LOAD REGULATION vs. LOAD CURRENT
MAX17088 toc02
LOAD CURRENT (mA)
OUTPUT ERROR (%)
VIN = 5.0V
VIN = 3.0V
VIN = 2.2V
IN SUPPLY QUIESCENT CURRENT
vs. IN SUPPLY VOLTAGE
MAX17088 toc03
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
0.2A
NO LOAD
STEP-UP REGULATOR SUPPLY CURRENT
vs. TEMPERATURE
MAX17088 toc04
TEMPERATURE (°C)
BOOST SUPPLY CURRENT (mA)
IN SUPPLY CURRENT (60-1510
IIN
IBOOST
STEP-UP CONVERTER SWITCHING
FREQUENCY vs. INPUT VOLTAGE
MAX8798 toc05
INPUT VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
200mA LOAD
STEP-UP REGULATOR
HEAVY-LOAD SOFT-START
MAX8798 toc06
2ms/div
5V/div
VMAIN
5V/div
500mA/div
SHDN CONTROL
5V/div
STEP-UP REGULATOR LOAD TRANSIENT
RESPONSE (20mA TO 300mA)
MAX8798 toc07
100μs/div
VLX
10V/div1A/div
0mV
VMAIN (AC-COUPLED)
200mV/div
LOAD CURRENT
200mA/div
L = 3.6μH
RCOMP = 100kΩ
0mA
Typical Operating Characteristics
(Circuit of Figure 2, VIN= 3V, TA= +25°C, unless otherwise noted.)
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN= 3V, TA= +25°C, unless otherwise noted.)
STEP-UP REGULATOR PULSED LOAD
TRANSIENT RESPONSE (20mA TO 1A)
MAX17088 toc08
10μs/div
VLX10V/divL = 3.6μH
RCOMP = 100kΩ
CCOMP1 = 220pF0V
1A/div
0mV
VMAIN
AC-COUPLED
200mV/div
IMAIN
1A/div
TIMER-DELAY LATCH
RESPONSE TO OVERLOAD
MAX17088 toc09
10ms/div
VLX
10V/div
VMAIN
5V/div
2A/div
LOAD CURRENT
1A/div
BOOST SUPPLY CURRENT
vs. BOOST SUPPLY VOLTAGE
MAX17088 toc11
OUTPUT VOLTAGE (V)
INPUT CURRENT (mA)69
VIN = 3.3V
VIN = 5V
NO LOAD ON VMAIN
BOOST SUPPLY CURRENT
vs. TEMPERATURE
MAX17088 toc12
TEMPERATURE (°C)
BOOST CURRENT (mA)60-1510
VBOOST = 15V
VBOOST = 8V
OPERATIONAL AMPLIFIER
FREQUENCY RESPONSE
MAX17088 toc13
FREQUENCY (Hz)
GAIN (dB)
10k1k
100100k
NO LOAD
100pF LOAD
33pF LOAD
OPERATIONAL AMPLIFIER PSRR
vs. FREQUENCY
MAX17088 toc14
FREQUENCY (Hz)
GAIN (dB)
10k1k
100100k
OPERATIONAL AMPLIFIER RAIL-TO-RAIL
INPUT/OUTPUT WAVEFORMS
MAX17088 toc15
10μs/div
VPOS
5V/div
VVCOM
5V/div
POWER-UP SEQUENCE
OF ALL SUPPLY OUTPUTS
MAX17088 toc10
2ms/div
5V/div0V
VGON20V/div
VCOM
5V/div
VMAIN
5V/div
VIN
5V/div
VGOFF
20V/div
SHDN
5V/div
SHDN
CONTROL
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
OPERATIONAL AMPLIFIER
LOAD TRANSIENT RESPONSE
MAX8798 toc16
2μs/div
VVCOM
(AC-COUPLED)
200mV/div
0mV
0mA
IVCOM
100mA/div
OPERATIONAL AMPLIFIER
LARGE-SIGNAL STEP RESPONSE
MAX8798 toc17
200ns/div
VPOS
2V/div
VCOM
2V/div
OPERATIONAL AMPLIFIER
SMALL-SIGNAL STEP RESPONSE
MAX8798 toc18
200ns/div
VPOS
(AC-COUPLED)
100mV/div
0mV
0mV
VCOM
(AC-COUPLED)
100mV/div
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN= 3V, TA= +25°C, unless otherwise noted.)
STV/STVP INPUT/OUTPUT
WAVEFORMS WITH LOGIC INPUT
MAX8798 toc19
4μs/div
STV
5V/div
STVP
10V/div
CPV AND OE/CKV AND CKVB INPUT/OUTPUTWAVEFORMS WITH LOGIC INPUT
(STV = 0V, CLOAD = 5.0nF AND 50Ω, R1, R2 = 200Ω)
MAX8798 toc19_1
4μs/div
CPV5V/div
5V/div
CKV
20V/div
CKVB
20V/div
STV RISING EDGE
PROPAGATION DELAY
MAX8798 toc20
100ns/div
STV
5V/div
STVP
10V/div
OE/CKV RISING EDGE
PROPAGATION DELAY
MAX8798 toc20_1
100ns/div
5V/div
CKV
10V/div
STV FALLING EDGE
PROPAGATION DELAY
MAX8798 toc21
100ns/div
STV
5V/div
STVP10V/div
OE/CKV FALLING EDGE
PROPAGATION DELAY
MAX8798 toc21_1
100ns/div
5V/div
CKV
10V/div
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN= 3V, TA= +25°C, unless otherwise noted.)
CALIBRATOR SIGNAL LSB
DOWNWARD STEP RESPONSE
MAX8798 toc22
40μs/div
SCL
5V/div
SDA
5mV/div
0mV
0mV
VCOM
(AC-COUPLED)
10mV/div
VSET
(AC-COUPLED)
10mV/div
CALIBRATOR SIGNAL LSB
UPWARD STEP RESPONSE
MAX8798 toc23
40μs/div
SCL
5V/div
SDA
5V/div
0mV
0mV
VCOM
(AC-COUPLED)
10mV/div
VSET
(AC-COUPLED)
10mV/div
CALIBRATOR FULL-SCALE
UPWARD STEP RESPONSE
MAX8798 toc24
40μs/div
SCL5V/div
SDA5V/div
4.025V
2.422V
0mV
VCOM
2V/div
VSET
200mV/div
CALIBRATOR FULL-SCALE
DOWNWARD STEP RESPONSE
MAX8798 toc25
40μs/div
SCL
5V/div
SDA5V/div
4.025V
2.422V
0mV
VCOM
2V/div
VSET
200mV/div
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
Pin Description
PINNAMEFUNCTION
1 CKV
High-Voltage, Gate-Pulse Output. When enabled, CKV toggles between its high state (connected to
GON) and its low state (connected to GOFF) on each falling edge of the CPV input. Further, CKV is high
impedance whenever CPV and OE are both low or whenever CPV is low and OECON is high.
2 CKVCS CKV Charge-Sharing Connection. CKVCS connects to CKV whenever CKV is high impedance to allow
connection to CKVB, sharing charge between the capacitive loads on these two outputs.
3 CKVBCS CKVB Charge-Sharing Connection. CKVBCS connects to CKVB whenever CKVB is high impedance to
allow connection to CKV, sharing charge between the capacitive loads on these two outputs.
4 CKVB High-Voltage, Gate-Pulse Output. CKVB is the inverse of CKV during active states and is high
impedance whenever CKV is high impedance.
5 STVP
High-Voltage, Start-Pulse Output. STVP is low (connected to GOFF) whenever STV is low and is high
(connected to GON) only when STV is high and CPV and OE are both low. When STV is high and either
CPV or OE is high, STVP is high impedance.
6 STV Vertical Sync Input. The rising edge of STV begins a frame of data. The STV input is used to generate the
high-voltage STVP output.
7 OECON
Active-Low, Output-Enable Timing Input. OECON is driven by an RC-filtered version of the OE input signal. If
OE remains high long enough for the resistor to charge the capacitor up to the OECON threshold, the OE
signal is masked until OE goes low and the capacitor is discharged below the threshold through the resistor.
8 OE Active-High, Gate-Pulse Output Enable. CKV and CKVB leave the high-impedance charge-sharing state
on the rising edge of OE.
9 CPV Vertical Clock-Pulse Input. CPV controls the timing of the CKV and CKVB outputs that change state (by
first sharing charge) on its falling edge.
10 GND Logic Ground
11 DISH
GOFF Discharge Input. Pulling DISH below ground activates an internal connection between GOFF and
GND, rapidly discharging the GOFF supply. Typically, DISH is capacitively connected to IN, so that
when VIN falls GOFF is discharged.
12 VDDSupply Input. Logic supply input for the VCOM calibrator. Bypass to GND through a minimum 0.1μF
capacitor.
13 WPN Active-Low, Write-Protect Input. When WPN is low, I2C commands are ignored and the VCOM calibrator
settings cannot be modified.
14 SCLS Alternate I2C-Compatible Clock Input. When WPN is high, SCLS connects to SCL to drive SCL from an
alternate clock source.
15 SCL I2C-Compatible Clock Input and Output
16 SDA I2C-Compatible Serial Bidirectional Data Line
17 WPP Write-Protect Output. WPP is the inverse of WPN. It can be used to control active-high, write-protect
inputs on other devices.
18 SET Full-Scale, Sink-Current Adjustment Input. Connect a resistor, RSET, from SET to GND to set the full-
scale adjustable sink current that is VBOOST / (20 x RSET). IOUT is equal to the current through RSET.
19 VL
3.3V On-Chip Regulator Output. This regulator powers internal analog circuitry for the step-up regulator,
op amp, and VCOM calibrator. External loads up to 10mA can be powered. Bypass VL to GND with a
0.22μF or greater ceramic capacitor.
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
Pin Description (continued)
PINNAMEFUNCTION
20 BGND Amplifier Ground
21 BOOST Operational Amplifier Supply Input. Connect to VMAIN (Figure 2) and bypass to BGND with a 1μF or
greater ceramic capacitor.
22 OUT
Adjustable Sink-Current Output. OUT connects to the resistive voltage-divider at the op amp input POS
(between BOOST and GND) that determines the VCOM output voltage. IOUT lowers the divider voltage by
a programmable amount.
23 POS Operational Amplifier Noninverting Input
24 NEG Operational Amplifier Inverting Input
25 VCOM Operational Amplifier Output SHDNShutdown Control Input. Pull SHDN low to disable the step-up regulator. The VCOM calibrator, op amp,
and scan driver functions remain enabled.
27 IN Step-Up Regulator Supply Input. Bypass IN to AGND (pin 34) with a 1μF or greater ceramic capacitor.
28, 29 LX Switching Node. Connect inductor/catch diode here and minimize trace area for lowest EMI.
30, 31 PGND Power Ground. Source connection of the internal step-up regulator power switch.
32 FB Feedback Input. Reference voltage is 1.24V nominal. Connect external resistor-divider
midpoint here and minimize trace area. Set VOUT according to: VOUT = 1.24V (1 + R1/R2).
33 COMP Compensation Input for Error Amplifier. Connect a series RC from COMP to AGND. Typical values are
180k and 470pF.
34 AGND Ground
35 GOFF Gate-Off Supply. GOFF is the negative supply voltage for the CKV, CKVB, and STVP high-voltage driver
outputs. Bypass to PGND with a minimum of 0.1μF ceramic capacitor.
36 GON Gate-On Supply. GON is the positive supply voltage for the CKV, CKVB, and STVP high-voltage driver
outputs. Bypass to VMAIN or PGND with a minimum of 0.1μF ceramic capacitor.
— EP Exposed Backside Pad. Connect to the analog ground plane through multiple vias to enhance thermal
performance.
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
VMAIN
8V, 300mA
VIN
2.2V TO 3.6V
-12V, 20mA
20V, 20mA
TO VCOM
BACKPLANE
SDA
COMP
PGND
BGND
VCOM
POS
NEG
10μF10μF
0.1μF
RCOMP
100kΩ
CCOMP
220pF
SCL
BOOST
200kΩ
200kΩ
2.6μH
SET
GOFF
STVP
GON
CKVBCS
CKV
SHDN
OECON
STV
DISH
CPV
WPN
0.1μF
CKVCS
CKVB
WPPSCLS
VDD
OUT
I2C BUS
VIN
SYSTEM
20kΩ
3nF
PANEL
0.22μF
0.1μF
GND
AGND
1μF
10Ω
0.1μF
0.1μF
0.1μF
0.1μF0.1μF
0.1μF
0.1μF
200Ω
200Ω
20kΩ
20kΩ
RSET
25kΩ
200kΩ
34kΩ
MAX8798
Figure 2. MAX8798 Typical Operating Circuit
MAX8798
Internal-Switch Boost Regulator with
Integrated 3-Channel Scan Driver for TFT LCDs
SCAN DRIVER
LOGIC
AND
GATE DRIVERS
I2C
INTERFACE
VMAINVIN
1.8V TO 5.5VVP
TO VCOM
BACKPLANE
SDA
COMP
PGND
BGND
VCOM
POS
NEG
SCL
BOOST
GON
SET
STVP
GOFF
CKVBCS
CKV
SHDN
OECON
STV
DISH
500Ω
250kΩ
CPV
WPN
CKVCS
CKVB
WPPSCLS
VDD
OUT
I2C BUS
VIN
SYSTEM
PANELVL
DACGND
AGND
1.6A
min
STEP-UP
Figure 3. MAX8798 Functional Diagram
