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PDF MAX1885 Data sheet ( Hoja de datos )
| Número de pieza | MAX1885 | |
| Descripción | Quad-Output TFT LCD DC/DC Converters | |
| Fabricantes | Maxim Integrated | |
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MAX1778/MAX1880–MAX1885
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 switch-
ing frequency and current-mode PWM architecture 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 efficiencies up to 91%.
The dual low-power charge pumps (MAX1778/MAX1880/
MAX1881/MAX1882 only) independently regulate one
positive output (VPOS) and one negative output (VNEG).
These low-power outputs use external diode and capaci-
tor 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 external
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 conditions by a
latched fault detection circuit that shuts down the device.
All devices are available in the ultrathin TSSOP package
(1.1mm max height).
Applications
●● TFT LCD Notebook Displays
●● TFT LCD Desktop Monitor Panels
Features
●● 500kHz/1MHz Current-Mode PWM Step-Up
Regulator
• Up to +13V Main High-Power Output
±1% Accurate
• High Efficiency (91%)
●● Dual Regulated Charge-Pump Outputs (MAX1778/
MAX1880–MAX1882 only)
• Up to +40V Positive Charge-Pump Output
• Up to -40V Negative Charge-Pump Output
●● Low-Dropout 40mA Linear Regulator (MAX1778/
MAX1881/MAX1883/MAX1884 only)
• Up to +15V LDO Input
●● Optional Higher Current with External Transistor
●● 2.7V to 5.5V Input Supply
●● Internal Supply Sequencing and Soft-Start
●● Power-Ready Output
●● Adjustable Fault-Detection Latch
●● Thermal Protection (+160°C)
●● 0.1μA Shutdown Current
●● 0.7mA IN Quiescent Current
●● Ultra-Small External Components
●● Thin TSSOP Package (1.1mm max height)
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX1778EUG
-40°C to +85°C 24 TSSOP
MAX1778EUG+
-40°C to +85°C 24 TSSOP
MAX1880EUG
-40°C to +85°C 24 TSSOP
MAX1881EUG
-40°C to +85°C 24 TSSOP
MAX1882EUG
-40°C to +85°C 24 TSSOP
MAX1883EUP
-40°C to +85°C 20 TSSOP
MAX1884EUP
-40°C to +85°C 20 TSSOP
MAX1885EUP
-40°C to +85°C 20 TSSOP
+Denotes lead(Pb)-free/RoHS-compliant package.
Typical operating Circuit appears at end of data sheet.
Pin Configurations and Selector Guide appear at end of
data sheet.
19-1979; Rev 3; 4/15
1 page  
MAX1778/MAX1880–MAX1885
Quad-Output TFT LCD DC/DC
Converters with Buffer
Electrical Characteristics (continued)
(VIN = +3.0V, SHDN = IN, VSUPP = VSUPN = VSUPB = VSUPL = 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =
PGND = GND, CREF = 0.22μF, CBUF = 1μF, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
Output Voltage
SYMBOL
VBUFOUT
CONDITIONS
IBUFOUT = 0
BUF+ = GND
IBUFOUT = ±5mA
IBUFOUT = ±45mA
MIN
4.99
4.97
4.93
TYP
MAX
5.01
5.03
5.07
UNITS
V
Input Offset Voltage
VOS
VSUPB = 4.5V to
13V, VCM = 1.2V to
(VSUPB - 1.2V)
IBUFOUT = ±5mA
IBUFOUT = ±45mA
-30
-70
+30
mV
+70
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
VOH
VOL
IBUFOUT = -45mA, ∆VOS = 1V
IBUFOUT = +45mA, ∆VOS = 1V
Falling edge, 20mV hysteresis (typ)
VREF
-2µA < IREF < 50µA
ISHDN
Rising edge, 25mV hysteresis (typ)
VFLTSET = 1V
ISINK = 2mA
VRDY = 13V
Rising temperature
9 9.6
0.4 1
±150
80 125 170
V
V
mA
mV
1.231
0.9
1.25
1.05
1.269
1.2
V
V
2.1
0.67 x
VREF
80
0.01
125
0.1
0.25
0.01
160
0.9
1
0.85 x
VREF
170
50
0.5
1
V
V
µA
V
mV
nA
V
µA
°C
Dual Mode is a trademark of Maxim Integrated Products, Inc.
www.maximintegrated.com
Maxim Integrated │ 5
5 Page 
MAX1778/MAX1880–MAX1885
Quad-Output TFT LCD DC/DC
Converters with Buffer
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +3.3V, SHDN = IN, VMAIN = VSUPP = VSUPN = VSUPB = VSUPL = 8V, BUF- = BUFOUT, BUF+ = FLTSET =
TGND = PGND = GND, TA = +25°C.)
RIPPLE VOLTAGE WAVEFORMS
MAX1778 toc16
8V A
-5V B
20V
C
STEP-UP CONVERTER
SOFT-START (LIGHT LOAD)
MAX1778 toc17
2V
A
0
8V
6V B
4V
0.5A
C
0
1µs/div
A. VMAIN = 8V, IMAIN = 200mA, 10mV/div
B. VNEG = -5V, INEG = 10mA, 20mV/div
C. VPOS = 20V, IPOS = 5mA, 20mV/div
1ms/div
A. VSHDN = O TO 2V, 2V/div
B. VMAIN = 8V, 2V/div
C. INDUCTOR CURRENT, 500mA/div
RLOAD = 400Ω
POWER-UP SEQUENCE
MAX1778 toc19
POWER-UP SEQUENCE
(CIRCUIT OF FIGURE 10)
4V MAX1778 toc20
2V 2V A
A
00
5V 20V B
0 B 10V C
20V C 0
10V D 0 D
0 -5V
E
-10V
2ms/div
A. VSHDN = O TO 2V, 2V/div
B. RDY, 5V/div
C. POSITIVE CHARGE PUMP = VPOS = 20V, RLOAD = 4kΩ, 10V/div
D. STEP-UP CONVERTER: VMAIN = 8V, RLOAD = 40Ω, 10V/div
E. NEGATIVE CHARGE PUMP: VNEG = -5V, RLOAD = 500Ω, 10V/div
1ms/div
A. RDY, 2V/div
B. POSITIVE CHARGE PUMP, VPOS(SYS) = 20V, 10V/div
C. STEP-UP CONVERTER: VMAIN(SYS) = 8V, 10V/div
D. NEGATIVE CHARGE PUMP, VNEG = -5V, -5V/div
STEP-UP CONVERTER
SOFT-START (HEAVY LOAD)
MAX1778 toc18
2V
0
8V
6V
4V
1.0A
0.5A
0
1ms/div
A. VSHDN = O TO 2V, 2V/div
B. VMAIN = 8V, 2V/div
C. INDUCTOR CURRENT, 500mA/div
RLOAD = 20Ω
A
B
C
POWER-UP INTO SHORT-CIRCUIT
(CIRCUIT OF FIGURE 10)
MAX1778 toc21
4V
2V A
0
5V
0B
10V
5V C
0
100µs/div
A. RDY, 2V/div
B. GATE OF N-CH MOSFET, 5V/div
C. STEP-UP CONVERTER, VMAIN(START) = 8V, 5V/div
VMAIN(SYS) = GND
www.maximintegrated.com
Maxim Integrated │ 11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet MAX1885.PDF ] | |
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