19-2485; Rev 1; 10/02
Triple-Output TFT LCD Power Supply
with Fault Protection
General Description
The MAX1889 provides the three regulated output volt-
ages required for active matrix, thin-film transistor liquid
crystal displays (TFT LCDs). It combines a high-perfor-
mance step-up regulator with two linear-regulator con-
trollers and multiple levels of protection circuitry for a
complete power-supply system.
The main DC-DC converter is a high-frequency
(500kHz/1MHz), current-mode step-up regulator with
an integrated N-channel power MOSFET that allows the
use of ultra-small inductors and ceramic capacitors.
With its high closed-loop bandwidth performance, the
MAX1889 provides fast transient response to pulsed
loads while operating with efficiencies over 85%. The
positive and negative linear-regulator controllers post-
regulate charge-pump outputs for TFT gate-on and
gate-off supplies.
The MAX1889 has a unique input switch control that
can replace the typical input fuse by disconnecting the
load from the input supply when a fault is detected.
The fault detector monitors all three regulated output
voltages and can monitor current from the input supply
as well. Additionally, the MAX1889 enters thermal shut-
down when its overtemperature threshold is reached.
The MAX1889 undervoltage lockout is set at 2.5V (max)
to allow the input supply to droop under pulsed load
conditions while avoiding any unexpected behavior
when its input voltage dips momentarily. Also, the built-
in soft-start and cycle-by-cycle current limiting prevent
input surge currents during power-up.
The MAX1889 is available in a 16-pin thin QFN pack-
age with a maximum thickness of 0.8mm for ultra-thin
LCD panel design.
Features
o
High-Performance Step-Up Regulator
Fast Transient Response
Current-Mode Control Architecture
Built-In High-Efficiency N-Channel Power
MOSFET
Current-Limit Comparator
>85% Efficiency
Selectable Switching Frequency
(500kHz/1MHz)
Internal Soft-Start
o
Positive Linear-Regulator Controller
o
Negative Linear-Regulator Controller
o
Triple-Level Protection Against Smoke or Fire
Input Switch Replaces Input Fuse
Output Overload Detection with Timer Latch
Thermal Shutdown
o
2.7V to 5.5V Input Operating Range
o
Ultra-Small External Components
o
1µA Shutdown Current (max)
o
1mA Quiescent Current (max)
o
Ultra-Thin 16-Pin QFN Package
(0.8mm Maximum Thickness)
MAX1889
Ordering Information
PART
MAX1889ETE
MAX1889EGE*
TEMP RANGE PIN-PACKAGE
-40°C to +85°C
-40°C to +85°C
16 Thin QFN (5mm
✕
5mm)
16 QFN (5mm
✕
5mm)
*
Future product—Contact factory for availability.
Applications
LCD Monitors
Car Navigation Displays
SHDN
PGND
GND
REF
1
2
16
IN
Pin Configuration
OCN
13
12 TGND
11 LX
10 FREQ
9
5
FB
6
FBN
7
DRVN
8
DRVP
FBP
OCP
14
TOP VIEW
15
MAX1889
3
4
THIN QFN
(5mm x 5mm)
________________________________________________________________
Maxim Integrated Products
GATE
Notebook Computer Displays
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.
Triple-Output TFT LCD Power Supply
with Fault Protection
MAX1889
ABSOLUTE MAXIMUM RATINGS
IN,
SHDN,
OCN, OCP,
FB, FBP, FBN, FREQ to GND ...............................-0.3V to +6V
PGND to GND.....................................................................±0.3V
LX to PGND ............................................................-0.3V to +14V
DRVP to GND .........................................................-0.3V to +30V
REF, GATE, TGND to GND ..........................-0.3V to (V
IN
+ 0.3V)
DRVN to GND .....................................(V
IN
- 28V) to (V
IN
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QFN (derate 19.2mW/°C above +70°C) .........1538mW
Operating Temperature Range
MAX1889EGE ..................................................-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
(V
IN
= 3V,
SHDN
= 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
(UVLO) Threshold
IN Quiescent Current
IN Shutdown Current
REF Output Voltage
Thermal Shutdown
MAIN STEP-UP REGULATOR
Main Output Voltage Range
Operating Frequency
Oscillator Maximum Duty Cycle
FB Regulation Voltage
FB Fault Trip Level
Load Regulation
Line Regulation
FB Input Bias Current
LX Switch On-Resistance
LX Leakage Current
LX Current Limit
LX RMS Current Rating
Soft-Start Period
Soft-Start Step Size
POSITIVE LINEAR-REGULATOR CONTROLLER
FBP Regulation Voltage
FBP Fault Trip Level
FBP Input Bias Current
FBP Effective Transconductance
I
FBP
V
FBP
I
DRVP
= 0.2mA
V
FBP
falling
V
FBP
= 1.25V
V
DRVP
= 10V, I
DRVP
= 0.1mA to 2mA
1.213
0.96
-50
75
1.25
1.0
1.288
1.04
+50
V
V
nA
mS
t
SS
I
FB
R
LX(ON)
I
LX
I
LIM
Not tested
4096 /
f
OSC
V
REF
/32
V
LX
= 13V
1.6
V
FB
I
LX
= 200mA, slope = 0 (Note 2)
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
V
MAIN
f
OSC
V
FREQ
= V
IN
V
FREQ
= 0V
80
1.229
0.95
V
IN
0.85
1
500
85
1.242
1.0
-1.6
0.2
+100
450
20
2.8
1.4
90
1.254
1.05
13
1.15
V
MHz
kHz
%
V
V
%
%/V
nA
mΩ
µA
A
A
s
V
V
REF
SYMBOL
V
IN
V
UVLO
I
IN
350mV typical
hysteresis
V
SHDN
= 0, V
IN
= 5V
-2µA < I
REF
< 50µA
1.231
V
IN
rising
V
IN
falling
CONDITIONS
MIN
2.7
2.55
2.2
2.7
2.35
0.1
1.250
160
TYP
MAX
5.5
2.85
2.5
1.0
1.0
1.269
UNITS
V
V
mA
µA
V
°C
V
FB
= V
FBP
= 1.5V, V
FBN
= 0V (Note 1)
2
_______________________________________________________________________________________
Triple-Output TFT LCD Power Supply
with Fault Protection
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 3V,
SHDN
= 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
FBP Line Regulation
Bandwidth
DRVP Sink Current
DRVP Off-Leakage Current
FBN Regulation Voltage
FBN Fault Trip Level
FBN Input Bias Current
FBN Effective Transconductance
FBN Line Regulation
Bandwidth
DRVN Sink Current
DRVN Off-Leakage Current
LOGIC SIGNAL (SHDN)
Input Low Voltage
Input High Voltage
Input Current
LOGIC SIGNAL (FREQ)
Input Low Voltage
Input High Voltage
Input Current
OVERCURRENT COMPARATOR
Input Offset Voltage
Input Bias Current
OCN, OCP Input
Common-Mode Range
FAULT TIMER AND GATE DRIVER
Fault Timer Period
GATE Output Sink Current
During Slew
GATE Output
Pulldown Resistance
GATE Output Pullup Resistance
t
FAULT
I
GATE
V
FREQ
= 0V, 32768/f
OSC
V
FREQ
= V
IN
, 65536/f
OSC
V
GATE
= 1.5V, during turn-on transition
V
GATE
< 0.5V
6
64
64
12
18
200
200
ms
µA
Ω
Ω
I
OCN
,
I
OCP
V
OCN
= V
OCP
= V
IN
-5
-50
1.5
+5
+50
0.8 x
V
IN
mV
nA
V
I
FREQ
0.15 x V
IN
typical hysteresis
0.7 x
V
IN
0.01
1
0.3 x
V
IN
V
V
µA
I
SHDN
100mV typical hysteresis, V
IN
= 2.7V to 5.5V
V
IN
= 2.7V to 5.5V
1.6
0.01
1
0.4
V
V
µA
I
DRVN
I
FBN
V
FBN
I
DRVP
SYMBOL
(Note 3)
V
FBP
= 1.1V, V
DRVP
= 10V
V
FBP
= 1.1V, V
DRVP
= 28V
I
DRVN
= 0.2mA
V
FBN
rising
V
FBN
= 0V
V
DRVN
= -10V, I
DRVN
= 0.1mA to 2mA
I
DRVN
= 0.2mA, V
IN
= 2.7V to 5.5V
(Note 2)
V
FBN
= 200mV, V
DRVN
= -10V
V
FBP
= -0.1V, V
DRVN
= -20V
200
5
0.1
10
95
325
-50
75
1
CONDITIONS
I
DRVP
= 0.2mA, V
IN
= 2.7V to 5.5V
200
5
0.1
125
400
10
155
475
+50
MIN
TYP
1
MAX
UNITS
mV
kHz
mA
µA
mV
mV
nA
mS
mV
kHz
mA
µA
MAX1889
NEGATIVE LINEAR-REGULATOR CONTROLLER
_______________________________________________________________________________________
3
Triple-Output TFT LCD Power Supply
with Fault Protection
MAX1889
ELECTRICAL CHARACTERISTICS
(V
IN
= 3V,
SHDN
= IN, C
REF
= 0.22µF, PGND = GND,
T
A
= -40°C to +85°C.)
(Note 4)
PARAMETER
IN Supply Range
IN ULVO Threshold
IN Quiescent Current
IN Shutdown Current
REF Output Voltage
MAIN STEP-UP REGULATOR
Main Output Voltage Range
Operating Frequency
Oscillator Maximum Duty Cycle
FB Regulation Voltage
FB Fault Trip Level
Line Regulation
FB Input Bias Current
LX Switch On-Resistance
LX Current Limit
FBP Regulation Voltage
FBP Fault Trip Level
FBP Input Bias Current
FBP Effective Transconductance
Bandwidth
DRVP Sink Current
FBN Regulation Voltage
FBN Fault Trip Level
FBN Input Bias Current
FBN Effective Transconductance
Bandwidth
DRVN Sink Current
LOGIC SIGNAL (SHDN)
Input Low Voltage
Input High Voltage
Input Current
I
SHDN
100mV typical hysteresis
1.6
1
0.4
V
V
µA
I
DRVN
I
FBN
I
DRVP
V
FBN
I
FBP
I
FB
R
LX(ON)
I
LIM
V
FBP
I
DRVP
= 0.2mA
V
FBP
falling
V
FBP
= 1.25V
V
DRVP
= 10V, I
DRVP
= 0.1mA to 2mA
(Note 2)
V
FBP
= 1.1V, V
DRVP
= 10V
I
DRVN
= 0.2mA
V
FBN
rising
V
FBN
= 0V
V
DRVN
= -10V, I
DRVN
= 0.1mA to 2mA
(Note 2)
V
FBN
= 200mV, V
DRVN
= -10V
1.6
1.213
0.96
-50
60
200
5
95
325
-50
60
200
5
155
475
+50
V
FB
I
LX
= 200mA, slope = 0 (Note 2)
V
FB
falling
V
IN
= 2.7V to 5.5V
V
FB
= 1.5V
-100
V
MAIN
f
OSC
V
FREQ
= V
IN
V
IN
0.75
78
1.215
0.96
13
1.25
92
1.260
1.04
0.45
+100
450
2.8
1.288
1.04
+50
V
MHz
%
V
V
%/V
nA
mΩ
A
V
V
nA
mS
kHz
mA
mV
mV
nA
mS
kHz
mA
V
REF
SYMBOL
V
IN
V
UVLO
I
IN
V
IN
rising
V
IN
falling
V
FB
= V
FBP
= 1.5V, V
FBN
= 0V (Note 1)
V
SHDN
= 0, V
IN
= 5V
-2µA < I
REF
< 50µA
1.231
CONDITIONS
MIN
2.7
2.55
2.2
MAX
5.5
2.85
2.5
1.0
1.0
1.269
UNITS
V
V
mA
µA
V
POSITIVE LINEAR-REGULATOR CONTROLLER
NEGATIVE LINEAR-REGULATOR CONTROLLER
4
_______________________________________________________________________________________
Triple-Output TFT LCD Power Supply
with Fault Protection
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 3V,
SHDN
= IN, C
REF
= 0.22µF, PGND = GND,
T
A
= -40°C to +85°C.)
(Note 4)
PARAMETER
LOGIC SIGNAL (FREQ)
Input Low Voltage
Input High Voltage
Input Current
OVERCURRENT COMPARATOR
Input Offset Voltage
Input Bias Current
OCN, OCP Input
Common-Mode Range
FAULT TIMER AND GATE DRIVER
GATE Output Sink Current
GATE Output
Pulldown Resistance
GATE Output Pullup Resistance
I
GATE
V
GATE
= 1.5V, during turn-on transition
V
GATE
< 0.5V
6
18
200
200
µA
Ω
Ω
I
OCN
,
I
OCP
V
OCN
= V
OCP
= V
IN
-5
-50
1.5
+5
+50
0.8 x
V
IN
mV
nA
V
I
FREQ
0.15 x V
IN
typical hysteresis
0.7 x V
IN
1
0.3 x V
IN
V
V
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1889
Note 1:
Quiescent current does not include switching losses.
Note 2:
FB regulation voltage is tested with no slope compensation ramp. Slope compensation needs to be included when selecting
resisitors for setting the output voltage (see
Main Step-Up Regulator
and
Output Voltage Selection
sections).
Note 3:
Guaranteed by design. Not production tested.
Note 4:
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= +3.3V, V
MAIN
= +9V, V
PL
= +20V, V
NL
= -7V,
SHDN
= FREQ = IN, PGND = GND, T
A
= +25°C, unless
otherwise noted.)
STEP-UP REGULATOR EFFICENCY
vs. LOAD CURRENT (V
MAIN
= 9V)
MAX1889 toc01
STEP-UP REGULATOR OUTPUT VOLTAGE
vs. LOAD CURRENT (V
MAIN
= 9V)
MAX1889 toc02
STEP-UP REGULATOR EFFICIENCY
vs. LOAD CURRENT (V
MAIN
= 13V)
MAX1889 toc03
100
9.1
9.0
OUTPUT VOLTAGE (V)
8.9
8.8
8.7
8.6
8.5
V
IN
= 2.7V
V
IN
= 3.3V
V
IN
= 5.5V
100
90
EFFICIENCY (%)
90
EFFICIENCY (%)
80
A
B
C
80
A
70
B
C
A: V
IN
= 2.7V
B: V
IN
= 3.3V
C: V
IN
= 5.5V
1
10
100
1000
70
60
A: V
IN
= 2.7V
B: V
IN
= 3.3V
C: V
IN
= 5.5V
1
10
100
1000
60
50
LOAD CURRENT (mA)
50
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
_______________________________________________________________________________________
5
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