Rainbow Electronics MAX1885 - Manual (Page 17)

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
1 1 1 1 FB
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).
2 2 2 2 INTG
Main Step-Up Integrator Output. When using the integrator,
connect 1000pF to analog ground (GND). To disable the
integrator, connect INTG to REF.
3 3 3 3 IN
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.
4 4 4 4 BUF+
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).
5 5 5 5 BUF-
VCOM Buffer (Operational Transconductance Amplifier) Negative
Feedback Input
6 6 6 6 SUPB
VCOM Buffer (Operational Transconductance Amplifier) Supply
Voltage
7 7 7 7 BUFOUT VCOM Buffer (Operational Transconductance Amplifier) Output
8 8 8 8 GND
Analog Ground. Connect to power ground (PGND) underneath the
IC.
9 9 9 9 REF
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.