MAX1880EUG Maxim Integrated Products, MAX1880EUG Datasheet - Page 19

• Manufacturer Part Number: MAX1880EUG
• Description: DC/DC Switching Converters
• Manufacturer: Maxim Integrated Products

Specifications of MAX1880EUG

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The MAX1778/MAX1880–MAX1885 are highly efficient
multiple-output power supplies for thin-film transistor
(TFT) liquid crystal display (LCD) applications. The
devices contain one high-power step-up converter, two
low-power charge pumps, an operational transconduc-
tance amplifier (V
regulator. The primary step-up converter uses an inter-
nal N-channel MOSFET to provide maximum efficiency
and to minimize the number of external components.
The output voltage of the main step-up converter
(V
tors.
The dual charge pumps (MAX1778/MAX1880/
MAX1881/MAX1882 only) independently regulate a
positive output (V
These low-power outputs use external diode and
capacitor stages (as many stages as required) to regu-
late output voltages from -40V to +40V. A unique
Figure 1. Typical Application Circuit
MAIN
) can be set from V
V
IN
INPUT
= 3.3V
V
LDOOUT
COM
V
POS
NEGATIVE
______________________________________________________________________________________
NEG
4.7μF
C
= -5V
TO LOGIC
LDO
= 5V
IN
) and a negative output (V
Detailed Description
buffer), and a low-dropout linear
1.0μF
4.7μF
C
IN
LDO
C3
to 13V with external resis-
100kΩ
R
RDY
0.22μF
49.9kΩ
C
0.22μF
REF
MAIN
R8
(8V)
200kΩ
49.9kΩ
R5
C1
R6
0.1μF
R7
150kΩ
C2
Quad-Output TFT LCD DC-DC
IN
SHDN
RDY
SUPL
LDOOUT
FBL
DRVN
FBN
REF
INTG
FLTSET
PGND
NEG
MAX1778
).
6.8μH
L1
control scheme minimizes output ripple as well as
capacitor sizes for both charge pumps.
A resistor-programmable 40mA linear regulator
(MAX1778/MAX1881/MAX1883/MAX1884 only) can
provide preregulation or postregulation for any of the
supplies. For higher current applications, an external
transistor can be added.
Additionally, the V
output that is ideal for driving capacitive loads, such as
the backplane of a TFT LCD panel. The positive feed-
back input features dual mode operation, allowing this
input to be connected to an internal 50% resistive-
divider between the buffer’s supply voltage and
ground, or externally adjusted for other voltages.
Also included in the MAX1778/MAX1880–MAX1885 is a
precision 1.25V reference that sources up to 50µA,
logic shutdown, soft-start, power-up sequencing,
adjustable fault detection, thermal shutdown, and an
active-low, open-drain ready output.
BUFOUT
Converters with Buffer
SUPN
DRVP
TGND
SUPB
SUPP
BUF+
BUF-
GND
FBP
LX
FB
0.1μF
49.9kΩ
0.1μF
274kΩ
C4
C4
R4
49.9kΩ
R2
R2
750kΩ
R3
C
1.0μF
BUF
COM
buffer provides a high current
BUFFER OUTPUT
V
BUFOUT
C
(2) 4.7μF
C5
1.0μF
OUT
= V
SUPB
MAIN
V
MAIN
C7
1.0μF
/2
= 8V
POSITIVE
V
POS
= 20V
19