19-1740; Rev 0; 6/00
Triple-Output TFT LCD DC-DC Converter
General Description
The MAX1748 triple-output DC-DC converter in a low-
profile TSSOP package provides the regulated voltages
required by active matrix, thin-film transistor (TFT) liquid
crystal displays (LCDs). One high-power DC-DC con-
verter and two low-power charge pumps convert the
+3.3V to +5V input supply voltage into three independent
output voltages.
The primary high-power DC-DC converter generates a
boosted output voltage (V
MAIN
) up to 13V that is regu-
lated within ±1%. The low-power BiCMOS control cir-
cuitry and the low on-resistance (0.35Ω) of the
integrated power MOSFET allows efficiency up to 93%.
The 1MHz current-mode PWM architecture provides
fast transient response and allows the use of ultra-small
inductors and ceramic capacitors.
The dual charge pumps independently regulate one
positive output (V
POS
) and one negative output (V
NEG
).
These low-power outputs use external diode and
capacitor stages (as many stages as required) to regu-
late output voltages up to +40V and down to -40V. A
proprietary regulation algorithm minimizes output rip-
ple, as well as capacitor sizes for both charge pumps.
The MAX1748 is available in the ultra-thin TSSOP pack-
age (1.1mm max height).
Features
o
Three Integrated DC-DC Converters
o
1MHz Current-Mode PWM Boost Regulator
Up to +13V Main High-Power Output
±1% Accuracy
High Efficiency (93%)
o
Dual Charge-Pump Outputs
Up to +40V Positive Charge-Pump Output
Down to -40V Negative Charge-Pump Output
o
Internal Supply Sequencing
o
Internal Power MOSFETs
o
+2.7V to +5.5V Input Supply
o
0.1µA Shutdown Current
o
0.6mA Quiescent Current
o
Internal Soft-Start
o
Power-Ready Output
o
Ultra-Small External Components
o
Thin TSSOP Package (1.1mm max)
MAX1748
Ordering Information
PART
MAX1748EUE
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 TSSOP
________________________Applications
TFT Active Matrix LCD Displays
Passive Matrix LCD Displays
PDAs
Digital Still Cameras
Camcorders
TOP VIEW
RDY 1
FB 2
INTG 3
IN 4
GND 5
REF 6
FBP 7
FBN 8
Pin Configuration
16 TGND
15 LX
14 PGND
MAX1748
13 SUPP
12 DRVP
11 SUPN
10 DRVN
9
SHDN
TSSOP
Typical Operating Circuit appears at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
Triple-Output TFT LCD DC-DC Converter
MAX1748
ABSOLUTE MAXIMUM RATINGS
IN,
SHDN,
TGND to GND .........................................-0.3V to +6V
DRVN to GND .........................................-0.3V to (V
SUPN
+ 0.3V)
DRVP to GND..........................................-0.3V to (V
SUPP
+ 0.3V)
PGND to GND.....................................................................±0.3V
RDY
to GND ...........................................................-0.3V to +14V
LX, SUPP, SUPN to PGND .....................................-0.3V to +14V
INTG, REF, FB, FBN, FBP to GND ...............-0.3V to (V
IN
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
16-Pin TSSOP (derate 9.4mW/°C above +70°C) ..........755mW
Operating Temperature Range
MAX1748EUE .................................................-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
= +3.0V,
SHDN
= IN, V
SUPP
= V
SUPN
= 10V, TGND = PGND = GND, C
REF
= 0.22µF, C
INTG
= 470pF,
T
A
= 0°C to +85°C,
unless
otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Input Supply Range
Input Undervoltage Threshold
IN Quiescent Supply Current
SUPP Quiescent Current
SUPN Quiescent Current
IN Shutdown Current
SUPP Shutdown Current
SUPN Shutdown Current
MAIN BOOST CONVERTER
Output Voltage Range
FB Regulation Voltage
FB Input Bias Current
Operating Frequency
Oscillator Maximum Duty Cycle
Load Regulation
Line Regulation
Integrator Gm
LX Switch On-Resistance
LX Leakage Current
SYMBOL
V
IN
V
UVLO
I
IN
I
SUPP
I
SUPN
CONDITIONS
V
IN
rising, 40mV hysteresis (typ)
V
FB
= V
FBP
= 1.5V, V
FBN
= -0.2V
V
FBP
= 1.5V
V
FBN
= -0.1V
V
SHDN
= 0, V
IN
= 5V
V
SHDN
= 0, V
SUPP
= 13V
V
SHDN
= 0, V
SUPN
= 13V
MIN
2.7
2.2
TYP
2.4
0.6
0.4
0.4
0.1
0.1
0.1
MAX
5.5
2.6
1
0.8
0.8
10
10
10
13
UNITS
V
V
mA
mA
mA
µA
µA
µA
V
V
nA
MHz
%
%
%/V
µmho
V
MAIN
V
FB
I
FB
f
OSC
I
MAIN
= 0 to 200mA, V
MAIN
= 10V
T
A
= 0°C to +85°C
V
FB
= 1.25V, INTG = GND
V
IN
1.235
-50
0.85
78
1
85
0.2
0.1
320
1.248
1.261
50
1.15
90
R
LX(ON)
I
LX
I
LX
= 100mA
V
LX
= 13V
Phase I = soft-start (1.0ms)
0.275
Phase II = soft-start (1.0ms)
Phase III = soft-start (1.0ms)
Phase IV = fully on (after 3.0ms)
1.1
0.35
0.01
0.380
0.75
1.12
1.5
1
3072 /
f
OSC
1.07
1.1
0.7
20
0.500
Ω
µA
LX Current Limit
I
LX(MAX)
A
2.0
A
s
1.14
13
V
V
Maximum RMS LX Current
Soft-Start Period
FB Fault Trip Level
POSITIVE CHARGE PUMP
V
SUPP
Input Supply Range
2
t
SS
Power-up to the end of Phase III
V
SUPP
2.7
_______________________________________________________________________________________
Triple-Output TFT LCD DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +3.0V,
SHDN
= IN, V
SUPP
= V
SUPN
= 10V, TGND = PGND = GND, C
REF
= 0.22µF, C
INTG
= 470pF,
T
A
= 0°C to +85°C,
unless
otherwise noted. Typical values are at T
A
= +25°C.)
MAX1748
PARAMETER
Operating Frequency
FBP Regulation Voltage
FBP Input Bias Current
DRVP PCH On-Resistance
DRVP NCH On-Resistance
FBP Power-Ready Trip Level
FBP Fault Trip Level
Maximum RMS DRVP Current
NEGATIVE CHARGE PUMP
V
SUPN
Input Supply Range
Operating Frequency
FBN Regulation Voltage
FBN Input Bias Current
DRVN PCH On-Resistance
DRVN NCH On-Resistance
FBN Power-Ready Trip Level
FBN Fault Trip Level
Maximum RMS DRVN Current
REFERENCE
Reference Voltage
Reference Undervoltage
Threshold
LOGIC SIGNALS
SHDN
Input Low Voltage
SHDN
Input High Voltage
SHDN
Input Current
RDY
Output Low Voltage
RDY
Output High Voltage
SYMBOL
CONDITIONS
MIN
TYP
0.5
×
f
OSC
MAX
UNITS
Hz
V
FBP
I
FBP
V
FBP
= 1.5V
V
FBP
= 1.213V
V
FBP
= 1.275V
Rising edge
Falling edge
1.20
-50
1.25
3
1.5
1.30
50
10
4
1.159
V
nA
Ω
Ω
kΩ
V
V
A
20
1.091
1.125
1.11
0.1
V
SUPN
2.7
0.5
×
f
OSC
13
V
Hz
V
FBN
I
FBN
V
FBN
= -0.05V
V
FBN
= 0.035V
V
FBN
= -0.025V
Rising edge
Falling edge
-50
-50
0
3
1.5
50
50
10
4
165
mV
nA
Ω
Ω
kΩ
mV
mV
A
20
80
110
130
0.1
V
REF
-2µA < I
REF
< 50µA
V
REF
rising
1.231
0.9
1.25
1.05
1.269
1.2
V
V
0.4V hysteresis (typ)
2.1
I
SHDN
I
SINK
= 2mA
V
RDY
= 13V
0.01
0.25
0.01
0.9
1
0.5
1
V
V
µA
V
µA
_______________________________________________________________________________________
3
Triple-Output TFT LCD DC-DC Converter
MAX1748
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +3.0V,
SHDN
= IN, V
SUPP
= V
SUPN
= 10V, TGND = PGND = GND, C
REF
= 0.22µF, C
INTG
= 470pF,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
Input Supply Range
Input Undervoltage Threshold
IN Quiescent Supply Current
SUPP Quiescent Current
SUPN Quiescent Current
IN Shutdown Current
SUPP Shutdown Current
SUPN Shutdown Current
MAIN BOOST CONVERTER
Output Voltage Range
FB Regulation Voltage
FB Input Bias Current
Operating Frequency
Oscillator Maximum Duty Cycle
LX Switch On-Resistance
LX Leakage Current
LX Current Limit
FB Fault Trip Level
POSITIVE CHARGE PUMP
SUPP Input Supply Range
FBP Regulation Voltage
FBP Input Bias Current
DRVP PCH On-Resistance
DRVP NCH On-Resistance
FBP Power-Ready Trip Level
NEGATIVE CHARGE PUMP
SUPN Input Supply Range
FBN Regulation Voltage
FBN Input Bias Current
DRVN PCH On-Resistance
DRVN NCH On-Resistance
FBN Power-Ready Trip Level
REFERENCE
Reference Voltage
Reference Undervoltage
V
REF
-2µA < I
REF
< 50µA
V
REF
rising
1.223
0.9
1.269
1.2
V
V
V
FBN
= 0.035V
V
FBN
= -0.025V
Rising edge
20
80
165
V
SUPN
V
FBN
I
FBN
V
FBN
= -0.05V
2.7
-50
-50
13
50
50
10
4
V
mV
nA
Ω
Ω
kΩ
mV
V
FBP
= 1.213V
V
FBP
= 1.275V
Rising edge
20
1.091
1.159
V
SUPP
V
FBP
I
FBP
V
FBP
= 1.5V
2.7
1.20
-50
13
1.30
50
10
4
V
V
nA
Ω
Ω
kΩ
V
R
LX(ON)
I
LX
I
LX(MAX)
I
LX
= 100mA
V
LX
= 13V
Phase I = soft-start (1.0ms)
Phase IV = fully on (after 3.0ms)
0.275
1.1
1.07
V
MAIN
V
FB
I
FB
F
OSC
V
FB
= 1.25V, INTG = GND
V
IN
1.225
-50
0.75
78
13
1.271
50
1.25
90
0.7
20
0.500
2.0
1.14
V
V
nA
MHz
%
Ω
µA
A
V
SYMBOL
V
IN
V
UVLO
I
IN
I
SUPP
I
SUPN
V
IN
rising, 40mV hysteresis (typ)
V
FB
= V
FBP
= 1.5V, V
FBN
= -0.2V
V
FBP
= 1.5V
V
FBN
= -0.1V
V
SHDN
= 0, V
IN
= 5V
V
SHDN
= 0, V
SUPP
= 13V
V
SHDN
= 0, V
SUPN
= 13V
CONDITIONS
MIN
2.7
2.2
MAX
5.5
2.6
1
0.8
0.8
10
10
10
UNITS
V
V
mA
mA
mA
µA
µA
µA
4
_______________________________________________________________________________________
Triple-Output TFT LCD DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +3.0V,
SHDN
= IN, V
SUPP
= V
SUPN
= 10V, TGND = PGND = GND, C
REF
= 0.22µF, C
INTG
= 470pF,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
LOGIC SIGNALS
SHDN
Input Low Voltage
SHDN
Input High Voltage
SHDN
Input Current
RDY
Output Low Voltage
RDY
Output High Leakage
I
SHDN
I
SINK
= 2mA
V
RDY
= 13V
0.45V hysteresis (typ)
2.1
1
0.5
1
0.9
V
V
µA
V
µA
SYMBOL
CONDITIONS
MIN
MAX
UNITS
MAX1748
Note 1:
Specifications from 0°C to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 5, V
IN
= 3.3V, T
A
= +25°C, unless otherwise noted.)
MAIN OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1748 toc01
MAIN STEP-UP CONVERTER
EFFICIENCY vs. LOAD CURRENT
(BOOST ONLY)
MAX1748toc02
MAIN STEP-UP CONVERTER
EFFICIENCY vs. LOAD CURRENT
(BOOST ONLY)
V
MAIN
= 8V
V
IN
= 5.0V
95
90
EFFICIENCY (%)
85
V
IN
= 3.3V
80
75
70
65
60
MAX1748toc03
10.04
10.02
10.00
9.98
V
MAIN
(V)
9.96
9.94
9.92
9.90
9.88
9.86
9.84
0
100
200
300
I
MAIN
(mA)
400
500
V
IN
= 3.3V
V
IN
= 5.0V
100
95
90
EFFICIENCY (%)
85
V
MAIN
= 10V
V
IN
= 5.0V
100
V
IN
= 3.3V
80
75
70
65
60
600
0
100
200
300
I
MAIN
(mA)
400
500
600
0
100
200 300 400 500 600 700 800
I
MAIN
(mA)
EFFICIENCY vs. LOAD CURRENT
(BOOST CONVERTER AND CHARGE PUMPS)
MAX1748toc04
NEGATIVE CHARGE-PUMP OUTPUT
VOLTAGE vs. LOAD CURRENT
V
NEG
= -5V
MAX1748toc05
NEGATIVE CHARGE-PUMP EFFICIENCY
vs. LOAD CURRENT
V
SUPN
= 6V
70
EFFICIENCY (%)
60
50
40
30
20
V
NEG
= -5V
0
5
10
15
20
I
NEG
(mA)
25
30
35
40
V
SUPN
= 8V
MAX1748toc06
90
85
80
EFFICIENCY (%)
75
70
65
60
55
50
0
50
V
IN
= 3.3V
V
NEG
= -5V WITH I
NEG
= 10mA
V
POS
= 15V WITH I
POS
= 5mA
V
MAIN
= 10V
V
MAIN
= 8V
-4.60
-4.65
-4.70
-4.75
V
NEG
(V)
-4.80
-4.85
-4.90
-4.95
-5.00
-5.05
0
80
V
SUPN
= 6V
V
SUPN
= 10V
V
SUPN
= 8V
V
SUPN
= 10V
100 150 200 250 300 350 400
I
MAIN
(mA)
5
10
15
20
I
NEG
(mA)
25
30
35
40
_______________________________________________________________________________________
5
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