Datasheet

Dual Serial UART with 128-Word FIFOs
MAX3109
65Maxim Integrated
Figure 31. RS-485 Half-Duplex Application
Typical Application Circuit
Figure 31 shows the MAX3109 being used in a half-
duplex RS-485 application. The microcontroller, the
RS-485 transceiver, and the MAX3109 are powered by a
single 3.3V supply. SPI is used as the controller’s com-
munication interface. The microcontroller provides an
external clock source to clock the UART.
The MAX14840 receiver is always enabled, so echoing
occurs. Enable auto echo suppression in the MAX3109
by setting the MODE2[7]: EchoSuprs bit high.
Set the MODE1[4]: TranscvCtrl bit high to enable auto
transceiver direction control in order to automatically
control the DE input of the transceiver.
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character,
but the drawing pertains to the package regardless of RoHS
status.
MAX14840E
A1
B1
DI
RO
RE
DE
MAX3109
TX0
RX0
AGND DGNDV
18
V
CC
V
EXT
V
L
IRQ
SPI/I2C
LDOEN
XOUT
RST
XIN
SPI
3.3V
MICROCONTROLLER
RTS0
MAX14840E
A2
B2
DI
RO
RE
DE
TX1
RX1
RTS1
10kΩ
1µF
0.1
µF
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
32 TQFN-EP T3255+1
21-0180 90-0012