MAX1778 Datasheet, PDF (1/38 Pages) Maxim Integrated Products – Quad-Output TFT LCD DC-DC Converters with Buffer

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).
Applications
TFT LCD Notebook Displays
TFT LCD Desktop Monitor Panels
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)
PART
MAX1778EUG
MAX1880EUG
MAX1881EUG
MAX1882EUG
MAX1883EUP
MAX1884EUP
MAX1885EUP
Ordering Information
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
Typical Operating Circuit appears at end of data sheet.
Pin Configurations and Selector Guide appear at end of
data sheet.
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