19-2638; Rev 0; 10/02
Quintuple/Triple-Output TFT LCD Power Supplies
with Fault Protection and VCOM Buffer
General Description
The MAX1997/MAX1998 provide the voltages required for
active-matrix, thin-film transistor liquid-crystal displays
(TFT LCDs). Both combine a high-performance step-up
regulator with two linear-regulator controllers, input pro-
tection switch control, and flexible sequence program-
ming. The MAX1997 contains two additional linear-
regulator controllers and a VCOM buffer. The MAX1997/
MAX1998 can operate from input supplies of 2.7V to 5.5V
and feature multiple levels of protection circuitry, making
them complete power-supply systems for displays.
The main DC-DC converter provides the regulated supply
voltage for the display’s source-driver ICs. The converter
is a high-frequency (up to 1.5MHz) step-up regulator with
an integrated 14V N-channel MOSFET that allows the use
of ultra-small inductors and ceramic capacitors while
achieving efficiencies over 85%. Its current-mode control
architecture provides fast transient response to pulsed
loads. Internal soft-start and cycle-by-cycle current limit
help prevent input surge currents.
The positive and negative linear-regulator controllers
postregulate charge-pump outputs for TFT gate-on and
gate-off supplies. Both linear-regulator controllers, as well
as the step-up regulator, have supply-sequencing control
inputs. The three outputs can be sequenced in any order
by selecting the appropriate external components.
The MAX1997 features a high-current backplane driver
(VCOM). This buffer provides peak currents exceeding
300mA (typ) and requires only a 0.47µF output filter
capacitor. The MAX1997’s two additional linear-regulator
controllers can be used to build the gamma reference
voltage and a logic supply.
The MAX1997/MAX1998 have a unique input switch con-
trol that can replace the typical input supply fuse. When a
fault is detected, the regulator is disconnected from the
input supply. The fault detector monitors all the regulated
output voltages and the current from the input supply. In
addition, the MAX1997/MAX1998 enter shutdown when
the internal over-temperature threshold is reached.
The MAX1997 is available in a 32-pin thin QFN package
and the MAX1998 is available in a 20-pin thin QFN pack-
age. Both packages have a maximum thickness of
0.8mm suitable for ultra-thin LCD panels.
o
2.7V to 5.5V Input Supply Range
o
Adjustable (Up to +13V) Output Voltage for
Source-Driver ICs
o
Integrated High-Efficiency Power MOSFET
o
Linear-Regulator Controllers for TFT Gate-On and
Gate-Off Supplies
o
High-Current VCOM Buffer (MAX1997 Only)
o
Two Additional Linear-Regulator Controllers
(MAX1997 Only)
o
Programmable Power-Up Sequencing
o
Multiple Overload Protection with Thermal
Shutdown
o
1µA Shutdown Current
o
32-Pin/20-Pin Thin QFN Packages
Features
MAX1997/MAX1998
Ordering Information
PART
MAX1997ETJ
MAX1998ETP
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
32 Thin QFN 5mm x 5mm
20 Thin QFN 5mm x 5mm
Pin Configurations
FREQ
GATE
OCP
20
19
IN
18
17
PGND
CT
ONN
ONP
ON2
1
2
3
4
5
10
6
7
8
9
16
15
14
OCN
TOP VIEW
TGNDA
LX
DRVP
FBP
FB
MAX1998
13
12
11
DRVN
FBN
DRVA
REF
Notebook Computer Displays
LCD Monitors
Car Navigation Displays
THIN QFN 5mm
×
5mm
Pin Configurations continued at end of data sheet.
________________________________________________________________
Maxim Integrated Products
GND
Applications
1
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.
Quintuple/Triple-Output TFT LCD Power Supplies
with Fault Protection and VCOM Buffer
MAX1997/MAX1998
ABSOLUTE MAXIMUM RATINGS
IN,
SHDN,
FB, FBP, FBN, FB1, FB2, ONDC,
ONP, ONN, ON2,
TGNDA, TGNDB to GND.............-0.3V to +6V
PGND to GND .....................................................................±0.3V
LX, V
DDB
to GND....................................................-0.3V to +14V
DRVP, DRV1, DRV2, DRVA to GND .......................-0.3V to +30V
REF, FREQ, GATE, OCN, OCP, CT,
PFLT to GND ..................................................-0.3V to V
IN
+ 0.3V
DRVN to GND ..........................................V
IN
- 28V to V
IN
+ 0.3V
FBPB, FBNB, OUTB to GND.......................-0.3V to V
DDB
+ 0.3V
OUTB Continuous Output Current ..................................±100mA
MAX1997 Continuous Power Dissipation (T
A
= +70°C)
32-Pin Thin QFN
(derate 21.2mW/°C above +70°C) ............................1702mW
MAX1998 Continuous Power Dissipation (T
A
= +70°C)
20-Pin Thin QFN
(derate 20mW/°C above +70°C) ...............................1600mW
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
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.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= 3V, V
DDB
= 10V,
SHDN
= ONDC = FREQ = IN, C
REF
= 0.22µF, PGND = GND,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
IN Supply Range
IN Undervoltage Lockout Threshold
350mV (typ)
hysteresis
V
IN
rising
V
IN
falling
CONDITIONS
MIN
2.7
2.5
2.2
2.7
2.35
0.54
0.476
0.1
1.231
1.225
1.250
1.250
160
V
OCN
= V
OCP
= 1.5V to 0.8V
×
V
IN
V
OCN
= V
OCP
= 0.8V
×
V
IN
-5
-50
1.5
+5
+50
0.8
×
V
IN
21.8
43.6
87.2
5
10
15
200
200
V
IN
FREQ = IN
Operating Frequency
FREQ unconnected
FREQ = GND
0.637
1.5
0.75
0.375
0.863
MHz
13
µA
Ω
Ω
V
ms
TYP
MAX
5.5
2.9
2.5
1.25
1
1
1.269
1.275
µA
V
°C
mV
nA
V
UNITS
V
V
IN Quiescent Current (Note 1)
IN Shutdown Current
REF Output Voltage
Thermal Shutdown
OVERCURRENT COMPARATOR
Input Offset Voltage
Input Bias Current
OCN, OCP Input Common-Mode Range
FAULT TIMER
V
FB
= V
FBP
= V
FB1
= V
FB2
= 1.5V, V
FBN
= 0
(MAX1997 only)
V
FB
= V
FBP
= 1.5V, V
FBN
= 0 (MAX1998 only)
V
SHDN
= 0, V
IN
= 5.5V
-2µA < I
REF
< 50µA
-2µA < I
REF
< 75µA
mA
PFLT = GND (MAX1997 only)
Fault Timer Period
GATE Output Sink Current During Slew
GATE Output Pulldown Resistance
GATE Output Pullup Resistance
MAIN STEP-UP REGULATOR
Output Voltage Range
PFLT unconnected (MAX1997 only)
PFLT = IN, or MAX1998
V
GATE
= 1.5V during turn-on transition
V
GATE
< 0.5V
2
_______________________________________________________________________________________
Quintuple/Triple-Output TFT LCD Power Supplies
with Fault Protection and VCOM Buffer
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 3V, V
DDB
= 10V,
SHDN
= ONDC = FREQ = IN, C
REF
= 0.22µF, PGND = GND,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
Oscillator Maximum Duty Cycle
FB Regulation Voltage
FB Fault Trip Level
FB Load Regulation
FB Line Regulation
FB Input Bias Current
LX On-Resistance
LX Leakage Current
LX Current Limit
LX RMS Current Rating
Soft-Start Period
Soft-Start Step Size
POSITIVE LINEAR-REGULATOR CONTROLLERS (REG P, REG 1, AND REG 2)
I
DRVP
= 100µA
FB_ Regulation Voltage
FB_ Fault Trip Level
FB_ Input Bias Current
I
DRV1
= 1350µA (MAX1997 only)
I
DRV2
= 335µA (MAX1997 only)
V
FB
_ falling
V
FB
_ = 1.25V
V
DRVP
= 10V, I
DRVP
= 0.05mA to 1mA
FB_ Effective Load Regulation Error
(Transconductance)
V
DRV1
= 10V, I
DRV1
= 0.5mA to 5mA
(MAX1997 only)
V
DRV2
= 10V, I
DRV2
= 0.1mA to 2mA
(MAX1997 only)
I
DRVP
= 100µA, 2.7V < V
IN
< 5.5V
FB_ Line (IN) Regulation Error
I
DRV1
= 1350µA, 2.7V < V
IN
< 5.5V
(MAX1997 only)
I
DRV2
= 335µA, 2.7V < V
IN
< 5.5V
(MAX1997 only)
Bandwidth
DRVP Sink Current
DRV1 Sink Current (MAX1997 only)
DRV2 Sink Current (MAX1997 only)
DRV_ Leakage Current
Soft-Start Period
Soft-Start Step Size
NEGATIVE LINEAR-REGULATOR CONTROLLER (REG N)
FBN Regulation Voltage
FBN Fault Trip Level
FBN Input Bias Current
I
DRVN
= 100µA
V
FBN
rising
V
FBN
= 0V
95
325
-200
125
370
155
475
+200
mV
mV
nA
V
FB
_ = 1.5V, V
DRV
_ = 28V
V
FB
_ = 1.1V, V
DRV
_ = 10V
(Note 2)
1000
2
5
5
3.3
18
15
0.1
4096/f
OSC
V
REF
/32
10
µA
s
V
mA
kHz
1
mV
-1.5
-2
%
0.96
-250
1.00
1.04
+250
V
nA
1.225
1.250
1.275
V
(Note 2)
4096/f
OSC
V
REF
/32
V
LX
= 13V
1.6
I
LX
= 200mA
V
FB
falling
I
MAIN
= 0 to full load
V
IN
= 2.7V to 5.5V
V
FB
= 1.5V
-100
250
0.01
2.1
CONDITIONS
MIN
80
1.229
0.96
TYP
85
1.242
1.00
-1.6
0.2
0.4
+100
450
20
2.8
1.4
MAX
90
1.254
1.04
UNITS
%
V
V
%
%/V
nA
mΩ
µA
A
A
s
V
MAX1997/MAX1998
_______________________________________________________________________________________
3
Quintuple/Triple-Output TFT LCD Power Supplies
with Fault Protection and VCOM Buffer
MAX1997/MAX1998
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 3V, V
DDB
= 10V,
SHDN
= ONDC = FREQ = IN, C
REF
= 0.22µF, PGND = GND,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
FBN Effective Load Regulation Error
(Transconductance)
FBN Line (IN) Regulation Error
Bandwidth
DRVN Source Current
DRVN Leakage Current
Soft-Start Period
Soft-Start Step Size
VCOM BUFFER (MAX1997 only)
V
DDB
Supply Range
V
DDB
Supply Current
V
DDB
Shutdown Current
Input Offset Voltage
Input Bias Current
Input Offset Current
Input Common-Mode Range
Power-Supply Rejection Ratio
Common-Mode Rejection Ratio
Gain-Bandwidth Product
Load-Transient Settling Time
Transconductance
Output Current Drive
LOGIC SIGNALS (SHDN, ONDC)
Input Low Voltage
Input High Voltage
Input Current
CONTROL INPUTS AND OUTPUTS
ONN, ONP, ON2
Comparator Offset
DRVA Sink Current
DRVA Off-Leakage
CT Source Current
CT Discharge Resistance
FREQ, PFLT Input Low Voltage
FREQ, PFLT Input Middle Voltage
FREQ, PFLT Input High Voltage
FREQ, PFLT Input Current
FREQ, PFLT = GND or IN
V
IN
- 1
-50
+50
V
IN
/2
V
µA
V
ON _
- V
CT
, V
CT
= 1.25V ±50mV
V
DRVA
= 10V, V
CT
= 1.25V, V
ON2
= 2V
V
DRVA
= 28V, V
CT
= 1.25V, V
ON2
= 1V
V
CT
= 1V
V
CT
= 1V
2.5
-50
5
11
0.1
5
15
10
7.5
100
1
+50
mV
mA
µA
µA
Ω
V
100mV typ hysteresis
1.6
0.01
1
0.4
V
V
µA
V
FBPB
= V
FBNB
= 5V, V
DDB
= 9V
V
DDB
= 13V,
SHDN
= ONDC = GND
V
FBPB
= 2.5V, no load
V
FBPB
= V
FBNB
= 1.2V to V
DDB
- 1.2V
V
FBPB
= V
FBNB
= 1.2V to V
DDB
- 1.2V
V
DDB
= 4.5V to 13V
V
DDB
= 4.5V to 13V, V
FBPB
= 2.25V
V
FBPB
= V
FBNB
= 1.2V to V
DDB
- 1.2V
Small signal
R
L
= 25Ω, C
L
= 10nF, V
DRIVE
= 9V, settle to within
10mV (Note 4)
Small signal (±1mV overdrive)
Large signal (±30mV overdrive)
±100mV
overdrive, V
OUTB
= 3V or 7V
±150
-100
1.2
70
70
1/6πC
L
5
0.3
7.2
±300
-5
4.5
367
3.5
13
900
13
+5
1
+100
V
DDB
-
1.2
V
µA
µA
mV
µA
nA
V
dB
dB
Hz
µs
µS
mA
CONDITIONS
V
DRVN
= -10V, I
DRVN
= 50µA to 1mA
I
DRVN
= 100µA, 2.7V < V
IN
< 5.5V
(Note 2)
V
FBN
= 200mV, V
DRVN
= -10V
V
FBN
= -0.1V, V
DRVN
= -20V
1000
2
4.2
0.1
4096/f
OSC
V
REF
/32
10
MIN
TYP
18
1
MAX
25
UNITS
mV
mV
kHz
mA
µA
s
V
4
_______________________________________________________________________________________
Quintuple/Triple-Output TFT LCD Power Supplies
with Fault Protection and VCOM Buffer
ELECTRICAL CHARACTERISTICS
(V
IN
= 3V, V
DDB
= 10V,
SHDN
= ONDC = FREQ = IN, C
REF
= 0.22µF, PGND = GND,
T
A
= -40°C to +85°C,
unless otherwise noted.)
(Note 3)
PARAMETER
IN Supply Range
IN Undervoltage Lockout Threshold
350mV typ
hysteresis
V
IN
rising
V
IN
falling
CONDITIONS
MIN
2.7
2.5
2.2
TYP
MAX
5.5
2.9
2.5
1.25
1
1.223
1.218
-5
-50
1.5
1.270
1.280
+5
+50
0.8
×
V
IN
13
2
0.937
0.50
92
1.260
1.04
+100
450
1.6
I
DRVP
= 100µA
FB_ Regulation Voltage
FB_ Fault Trip Level
I
DRV1
= 1350µA (MAX1997 only)
I
DRV2
= 335µA (MAX1997 only)
V
FB
_ falling
V
DRVP
= 10V, I
DRVP
= 0.05mA to 1mA
FB_ Effective Load Regulation Error
(Transconductance)
V
DRV1
= 10V, I
DRV1
= 0.5mA to 5mA
(MAX1997 only)
V
DRV2
= 10V, I
DRV2
= 0.1mA to 2mA
(MAX1997 only)
DRVP Sink Current
DRV1 Sink Current (MAX1997 Only)
DRV2 Sink Current (MAX1997 Only)
V
FB
_ = 1.1V, V
DRV
_ = 10V
1
5
5
mA
-2.5
%
0.96
1.04
V
1.213
1.288
V
2.8
%
V
V
nA
mΩ
A
MHz
V
UNITS
V
V
MAX1997/MAX1998
IN Quiescent Current (Note 1)
V
FB
= V
FBP
= V
FB1
= V
FB2
= 1.5V, V
FBN
= 0
(MAX1997 only)
V
FB
= V
FBP
= 1.5V, V
FBN
= 0 (MAX1998 only)
-2µA < I
REF
< 50µA
-2µA < I
REF
< 75µA
V
OCN
= V
OCP
= 1.5V to 0.8V
×
V
IN
V
OCN
= V
OCP
= 0.8V
×
V
IN
mA
REF Output Voltage
OVERCURRENT COMPARATOR
Input Offset Voltage
Input Bias Current
OCN, OCP Input Common-Mode Range
MAIN STEP-UP REGULATOR
Output Voltage Range
mV
nA
V
V
IN
FREQ = IN
1
0.563
0.25
78
I
LX
= 200mA
V
FB
falling
V
FB
= 1.5V
1.215
0.96
-100
FREQ unconnected
FREQ = GND
V
Operating Frequency
Oscillator Maximum Duty Cycle
FB Regulation Voltage
FB Fault Trip Level
FB Input Bias Current
LX On-Resistance
LX Current Limit
POSITIVE LINEAR-REGULATOR CONTROLLERS (REG P, REG 1, AND REG 2)
_______________________________________________________________________________________
5
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