Datasheet

Dual Serial UART with 128-Word FIFOs
MAX3109
64 Maxim Integrated
Power-Supply Sequencing
The device’s power supplies can be turned on in any
order. Each supply can be present over the entire speci-
fied range regardless of the presence or level of the
others. Ensure the presence of the interface supplies V
L
and V
EXT
before sending input signals to the controller
and transceiver interfaces.
Connector Sharing
The TX_ and RTS_ outputs can be programmed to be
high impedance. This feature is used in cases where the
MAX3109 shares a common connector with other com-
munications devices. Set the output of the MAX3109 to
high impedance when the other communication devices
are active. Set the MODE1[2]: TxHiZ bit high to set TX_
to a high-impedance state. Set the MODE1[3]: RTSHiZ
bit high to set RTS_
to a high-impedance state. Figure 29
shows an example of connector sharing with a USB
transceiver.
RS-232 5x3 Application
The four GPIOs can be used to implement the other flow
control signals defined in ITU V.24. Figure 30 shows how
the GPIOs create the DSR, DTR, DCD, and RI signals
found on some RS-232/V.28 interfaces.
Set the FlowCtrl[1:0] bits high to enable automatic hard-
ware RTS_/CTS_ flow control.
Figure 29. Connector Sharing with a USB Transceiver
Figure 30. RS-232 Application
MAX3109
TX_
RX_
MAX13481E
D+
D-
OE
TX/D+
RX/D-
SHARED
CONNECTOR
MAX3109
TX0
RX0
Tx
Rx
SPI/I
2
C
MAX3245
T1IN
R1OUT
MICROCONTROLLER
RST
LDOEN
IRQ
RTS0
CTS0
RTS
CTS
T2IN
R2OUT
GPIO0
GPIO1
DTR
DSR
T3IN
R3OUT
GPIO2
GPIO3
DCD
RI
R4OUT
R5OUT