MAX1778/MAX1880–MAX1885
Quad-Output TFT LCD DC-DC
Converters with Buffer
______________________________________________________________________________________ 17
Pin Description
PIN
MAX1778
MAX1881
MAX1880
MAX1882
MAX1883
MAX1884
MAX1885 NAME FUNCTION
1111FB
Main Step-Up Regulator Feedback Input. Regulates to 1.25V
nominal. Connect a resistive divider from the output (V
MAIN
) to FB
to analog ground (GND).
2222INTG
Main Step-Up Integrator Output. When using the integrator,
connect 1000pF to analog ground (GND). To disable the
integrator, connect INTG to REF.
3333IN
Main Supply Voltage. The supply voltage powers the control
circuitry for all of the regulators and may range from 2.7V to 5.5V.
Bypass with a 0.1µF capacitor between IN and GND, as close to
the pins as possible.
4444BUF+
VCOM Buffer (Operational Transconductance Amplifier) Positive
Feedback Input. Connect to GND to select the internal resistive
divider that sets the positive input to half the amplifier’s supply
voltage (V
BUF+
= V
SUPB
/2).
5555BUF-
VCOM Buffer (Operational Transconductance Amplifier) Negative
Feedback Input
6666SUPB
VCOM Buffer (Operational Transconductance Amplifier) Supply
Voltage
7777BUFOUT VCOM Buffer (Operational Transconductance Amplifier) Output
8888GND
Analog Ground. Connect to power ground (PGND) underneath the
IC.
9999REF
Internal Reference Bypass Terminal. Connect a 0.22µF ceramic
capacitor from REF to analog ground (GND). External load
capability up to 50µA.
10 10 −−FBP
Positive Charge-Pump Regulator Feedback Input. Regulates to
1.25V nominal. Connect a resistive divider from the positive
charge-pump output (V
POS
) to FBP to analog ground (GND).
11 11 −−FBN
Negative Charge-Pump Regulator Feedback Input. Regulates to
0V nominal. Connect a resistive divider from the negative charge-
pump output (V
NEG
) to FBN to the reference (REF).
12 12 10 10 SHDN
Active-Low Shutdown Control Input. Pull SHDN low to force the
controller into shutdown. If unused, connect SHDN to IN for normal
operation. A rising edge on SHDN clears the fault latch.
13 − 11 − SUPL
Low-Dropout Linear Regulator Input Voltage. Can range from 4.5V
to 15V. Bypass with a 1µF capacitor to GND (see Capacitor
Selection and Regulator Stability). Connect both input pins
together externally.
(9 Seiten)
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