19-1979; Rev 0a; 3/01
Quad-Output TFT LCD DC-DC
Converters with Buffer
General Description
The MAX1778/MAX1880–MAX1885 multiple-output
DC-DC converters provide the regulated voltages
required by active matrix thin-film transistor (TFT) liquid
crystal displays (LCD) in a low-profile TSSOP package.
One high-power step-up converter and two low-power
charge pumps convert the 2.7V to 5.5V input voltage
into three independent output voltages. A built-in linear
regulator and VCOM buffer complete the power-supply
requirements.
The main step-up converter accurately generates an
externally set output voltage up to 13V that can supply
the display’s row/column drivers. The converter’s high
switching frequency and current-mode PWM architec-
ture provide fast transient response and allow the use
of small low-profile inductors and ceramic capacitors.
The low-power BiCMOS control circuitry and internal
14V switch (0.35Ω N-channel MOSFET) enable efficien-
cies up to 91%.
The dual low-power charge pumps (MAX1778/
MAX1880/MAX1881/MAX1882 only) independently reg-
ulate one positive output (V
POS
) and one negative out-
put (V
NEG
). These low-power outputs use external
diode and capacitor stages (as many stages as
required) to regulate output voltages up to +40V and
-40V. A unique control scheme minimizes output ripple
as well as capacitor sizes for both charge pumps.
A resistor-programmable, 40mA, low-dropout linear
regulator (MAX1778/MAX1881/MAX1883/MAX1884
only) provides preregulation or postregulation for any of
the supplies. For higher current applications, an exter-
nal transistor can be added. Additionally, the VCOM
buffer provides a high current output that is ideal for
driving the capacitive backplane of TFT LCD panels.
The VCOM buffer’s output voltage is preset with an
internal 50% resistive-divider or can be externally
adjusted for other voltages.
The MAX1778/MAX1880–MAX1885 are protected
against output undervoltage and thermal overload con-
ditions by a latched fault detection circuit that shuts
down the device. All devices are available in the ultra-
thin TSSOP package (1.1mm max height).
Features
o
500kHz/1MHz Current-Mode PWM Step-Up
Regulator
Up to +13V Main High-Power Output
±1% Accurate
High Efficiency (91%)
o
Dual Regulated Charge-Pump Outputs
(MAX1778/MAX1880/MAX1881/MAX1882 only)
Up to +40V Positive Charge-Pump Output
Up to -40V Negative Charge-Pump Output
o
Low-Dropout 40mA Linear Regulator
(MAX1778/MAX1881/MAX1883/MAX1884 only)
Up to +15V LDO Input
o
Optional Higher Current with External Transistor
o
2.7V to 5.5V Input Supply
o
Internal Supply Sequencing and Soft-Start
o
Power-Ready Output
o
Adjustable Fault-Detection Latch
o
Thermal Protection (+160°C)
o
0.1µA Shutdown Current
o
0.7mA IN Quiescent Current
o
Ultra-Small External Components
o
Thin TSSOP Package (1.1mm max height)
MAX1778/MAX1880–MAX1885
Ordering Information
PART
MAX1778EUG
MAX1880EUG
MAX1881EUG
MAX1882EUG
MAX1883EUP
MAX1884EUP
MAX1885EUP
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 TSSOP
24 TSSOP
24 TSSOP
24 TSSOP
20 TSSOP
20 TSSOP
20 TSSOP
Applications
TFT LCD Notebook Displays
TFT LCD Desktop Monitor Panels
Typical Operating Circuit appears at end of data sheet.
Pin Configurations and Selector Guide appear at end of
data sheet.
________________________________________________________________
Maxim Integrated Products
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.
Quad-Output TFT LCD DC-DC
Converters with Buffer
MAX1778/MAX1880–MAX1885
ABSOLUTE MAXIMUM RATINGS
IN,
SHDN,
TGND, FLTSET 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,
SUPB to GND ................................................-0.3V to +14V
LX, SUPP, SUPN to PGND .....................................-0.3V to +14V
SUPL to GND..........................................................-0.3V to +18V
LDOOUT to GND ....................................-0.3V to (V
SUPL
+ 0.3V)
INTG, REF, FB, FBN, FBP to GND ...............-0.3V to (V
IN
+ 0.3V)
FBL to GND .............-0.3V to the lower of (V
SUPL
+ 0.3V) or +6V
BUFOUT, BUF+, BUF- to GND ...............-0.3V to (V
SUPB
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
20-Pin TSSOP (derate 10.9mW/°C above +70°C) ......879mW
24-Pin TSSOP (derate 12.2mW/°C above +70°C) ......975mW
Operating Temperature Range
MAX1778EUG, MAX1883EUP ........................-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
= V
SUPB
= V
SUPL
= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =
PGND = GND, C
REF
= 0.22µF, C
BUF
= 1µF,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
Input Supply Range
Input Undervoltage Threshold
SYMBOL
V
IN
V
UVLO
V
IN
rising, 40mV hysteresis (typ)
MAX1778/MAX1880/
MAX1883 (f
OSC
= 1MHz)
MAX1881/MAX1882/
MAX1884/MAX1885
(f
OSC
= 500kHz)
MAX1778/MAX1880
(f
OSC
= 1MHz)
MAX1881/MAX1882
(f
OSC
= 500kHz)
MAX1778/MAX1880
(f
OSC
= 1MHz)
MAX1881/MAX1882
(f
OSC
= 500kHz)
CONDITIONS
MIN
2.7
2.2
2.4
0.7
TYP
MAX
5.5
2.6
1
mA
0.6
1
UNITS
V
V
IN Quiescent Supply Current
I
IN
V
FB
= V
FBP
= 1.5V, V
FBN
= -0.2V
0.4
0.3
0.4
0.3
0.1
0.1
0.1
0.1
6
0.7
mA
0.5
0.7
mA
0.5
10
10
10
10
13
µA
µA
µA
µA
µA
SUPP Quiescent Current
I
SUPP
V
FBP
= 1.5V
SUPN Quiescent Current
I
SUPN
V
FBN
= -0.2V
IN Shutdown Current
SUPP Shutdown Current
SUPN Shutdown Current
SUPL Shutdown Current
SUPB Shutdown Current
V
SHDN
= 0, V
IN
= 5V
V
SHDN
= 0, V
SUPP
= 13V,
MAX1778/MAX1880/MAX1881/MAX1882
V
SHDN
= 0, V
SUPN
= 13V,
MAX1778/MAX1880/MAX1881/MAX1882
V
SHDN
= 0, V
SUPL
= 13V
MAX1778/MAX1881/MAX1883/MAX1884
V
SHDN
= 0, V
SUPB
= 13V
2
_______________________________________________________________________________________
Quad-Output TFT LCD DC-DC
Converters with Buffer
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +3.0V,
SHDN
= IN, V
SUPP
= V
SUPN
= V
SUPB
= V
SUPL
= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =
PGND = GND, C
REF
= 0.22µF, C
BUF
= 1µF,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
MAIN STEP-UP CONVERTER
Main Output Voltage Range
FB Regulation Voltage
FB Input Bias Current
Operating Frequency
Oscillator Maximum Duty
Cycle
Integrator enabled,
C
INTG
= 1000pF
Integrator disabled
(INTG = REF)
V
MAIN
V
FB
I
FB
f
OSC
Integrator enabled, C
INTG
= 1000pF
Integrator disabled (INTG = REF)
V
FB
= 1.25V, INTG = GND
MAX1778/MAX1880/MAX1883
MAX1881/MAX1882/MAX1884/MAX1885
V
IN
1.234
1.220
-50
0.85
425
80
1
500
85
0.01
%
0.2
0.1
317
R
LX(ON)
I
LX
I
LX
= 100mA
V
LX
= 13V
Phase I = soft-start (1024/f
OSC
)
LX Current Limit
I
LIM
Phase II = soft-start (1024/f
OSC
)
Phase III = soft-start (1024/f
OSC
)
Phase IV = fully-on (after 3072/f
OSC
)
Maximum RMS LX Current
Soft-Start Period
FB Fault Trip Level
t
SS
Power-up to the end of Phase III
Falling edge, FLTSET = GND
Falling edge, FLTSET = 1V
1.07
0.955
2.7
0.5 x f
OSC
1.2
V
FBP
= 1.5V
V
FBP
= 1.2V
V
FBP
= 1.3V
Rising edge
Falling edge, FLTSET = GND
Falling edge, FLTSET = 1V
20
0.1
1.09
1.08
0.955
1.125
1.11
0.99
1.16
1.16
1.025
-50
5
2
1.25
1.3
+50
10
4
1.15
0.275
0.35
0.01
0.38
0.75
1.12
1.5
1
3072 / f
OSC
1.1
0.99
1.14
1.025
13
1.85
A
s
V
0.7
20
0.5
A
%/V
µs
Ω
µA
1.247
13
1.260
1.280
+50
1.15
575
91
V
V
nA
MHz
kHz
%
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1778/MAX1880–MAX1885
Load Regulation
I
LX
= 0 to 200mA,
V
MAIN
= 10V
Line Regulation
Integrator Transconductance
LX Switch On-Resistance
LX Leakage Current
POSITIVE CHARGE PUMP (MAX1778/MAX1880/MAX1881/MAX1882 ONLY)
V
SUPP
SUPP Input Supply Range
Operating Frequency
FBP Regulation Voltage
FBP Input Bias Current
DRVP PCH On-Resistance
DRVP NCH On-Resistance
Maximum RMS DRVP Current
FBP Power-Ready Trip Level
FBP Fault Trip Level
f
CHP
V
FBP
I
FBP
R
PCH(ON)
R
NCH(ON)
V
Hz
V
nA
Ω
Ω
kΩ
A
V
V
_______________________________________________________________________________________
3
Quad-Output TFT LCD DC-DC
Converters with Buffer
MAX1778/MAX1880–MAX1885
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +3.0V,
SHDN
= IN, V
SUPP
= V
SUPN
= V
SUPB
= V
SUPL
= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =
PGND = GND, C
REF
= 0.22µF, C
BUF
= 1µF,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
SUPN Input Supply Range
Operating Frequency
FBN Regulation Voltage
FBN Input Bias Current
DRVN PCH On-Resistance
DRVN NCH On-Resistance
Maximum RMS DRVN Current
FBN Power-Ready Trip Level
FBN Fault Trip Level
SUPL Input Supply Range
SUPL Undervoltage Lockout
SUPL Quiescent Current
Dropout Voltage (Note 1)
FBL Regulation Voltage
LDO Load Regulation
LDO Line Regulation
FBL Input Bias Current
LDO Current Limit
VCOM BUFFER
SUPB Input Supply Range
SUPB Quiescent Current
BUFOUT Leakage Current
Power-Supply Rejection Ratio
Input Common-Mode Voltage
Range
Common-Mode Rejection Ratio
Input Bias Current
Input Offset Current
Gain Bandwidth Product
PSRR
V
CM
CMRR
I
BIAS
I
OS
GBW
V
SUPB
= 4.5V to 13V, V
CM
= 2.25V
|V
OS
| < 10mV
V
CM
= 1.2V to 8.8V
V
CM
= 5V
V
CM
= 5V
C
BUF
= 1µF
V
SUPB
I
SUPB
V
SUPB
= 13V
-10
85
1.2
75
-100
-100
13
-10
+100
+100
98
8.8
4.5
420
13
850
+10
V
µA
µA
dB
V
dB
nA
nA
kHz
I
FBL
I
LDOLIM
I
SUPL
V
DROP
V
FBL
V
SUPL
Rising edge, 50mV hysteresis (typ)
I
LDO
= 100µA
LDO is set to
regulate at 9V
I
LDO
= 40mA
I
LDO
= 5mA
1.235
Falling edge
Rising edge
80
80
4.5
3.8
4
120
130
70
1.25
1.265
1.2
0.02
-0.8
40
130
+0.8
220
SYMBOL
V
SUPN
f
CHP
V
FBN
I
FBN
R
PCH(ON)
R
NCH(ON)
V
FBN
= +50mV
V
FBN
= -50mV
20
0.1
125
140
165
190
15
4.3
220
300
V
FBN
= 0
-50
-50
5
2
CONDITIONS
MIN
2.7
0.5 x f
OSC
0
+50
+50
10
4
TYP
MAX
13
UNITS
V
Hz
mV
nA
Ω
Ω
kΩ
A
mV
mV
V
V
µA
mV
V
%
%/V
µA
mA
NEGATIVE CHARGE PUMP (MAX1778/MAX1880/MAX1881/MAX1882 ONLY)
LOW-DROPOUT LINEAR REGULATOR (MAX1778/MAX1881/MAX1883/MAX1884 ONLY)
V
SUPL
= 10V, LDO regulating at 9V,
I
LDO
= 15mA
V
SUPL
= 10V, LDO regulating at 9V,
I
LDO
= 100µA to 40mA
V
SUPL
= 4.5V to 15V, FBL = LDOOUT,
I
LDO
= 15mA
V
FBL
= 1.25V
V
SUPL
= 10V, V
LDOOUT
= 9V, V
FBL
= 1.2V
4
_______________________________________________________________________________________
Quad-Output TFT LCD DC-DC
Converters with Buffer
MAX1778/MAX1880–MAX1885
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +3.0V,
SHDN
= IN, V
SUPP
= V
SUPN
= V
SUPB
= V
SUPL
= 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =
PGND = GND, C
REF
= 0.22µF, C
BUF
= 1µF,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
Output Voltage
SYMBOL
V
BUFOUT
BUF+ = GND
CONDITIONS
I
BUFOUT
= 0
I
BUFOUT
=
±5mA
I
BUFOUT
=
±45mA
Input Offset Voltage
Output Voltage Swing High
Output Voltage Swing Low
Peak Buffer Output Current
BUF+ Dual Mode™ Threshold
Voltage
REFERENCE
Reference Voltage
Reference Undervoltage
Threshold
LOGIC SIGNALS
SHDN
Input Low Voltage
SHDN
Input High Voltage
SHDN
Input Current
FLTSET Input Voltage Range
FLTSET Threshold Voltage
FLTSET Input Current
RDY
Output Low Voltage
RDY
Output High Leakage
Thermal Shutdown
Rising edge, 25mV hysteresis (typ)
V
FLTSET
= 1V
I
SINK
= 2mA
V
RDY
= 13V
Rising temperature
I
SHDN
0.67 x
V
REF
80
125
0.1
0.25
0.01
160
2.1
0.01
1
0.85 x
V
REF
170
50
0.5
1
0.9
V
V
µA
V
mV
nA
V
µA
°C
V
REF
-2µA < I
REF
< 50µA
1.231
0.9
1.25
1.05
1.269
1.2
V
V
Falling edge, 20mV hysteresis (typ)
80
V
OS
V
OH
V
OL
V
SUPB
= 4.5V to 13V,
V
CM
= 1.2V to
(V
SUPB
–1.2V)
I
BUFOUT
=
±5mA
I
BUFOUT
=
±45mA
MIN
4.99
4.97
4.93
-30
-70
9
9.6
0.4
±150
125
170
1
TYP
MAX
5.01
5.03
5.07
30
mV
70
V
V
mA
mV
V
UNITS
I
BUFOUT
= -45mA,
∆V
OS
= 1V
I
BUFOUT
= +45mA,
∆V
OS
= 1V
Dual Mode is a registered trademark of Maxim Integrated Products, Inc.
_______________________________________________________________________________________
5
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