Datasheet

MAX3140
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
14 ______________________________________________________________________________________
V
OH
V
OL
A
B
1V
-1V
1.5V 1.5V
OUTPUT
INPUT
RO
t
PLH
t
PHL
Figure 7. Receiver Propagation Delays
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
3V
0
V
CC
RO
RO
0
1.5V 1.5V
V
OL
+ 0.5V
V
OH
- 0.5V
1.5V
1.5V
t
ZL(SHDN)
, t
ZL
t
LZ
t
ZH(SHDN)
, t
ZH
t
HZ
RE
Figure 8. Receiver Enable and Disable Times
R
B
RECEIVER
OUTPUT
ATE
A
V
ID
R
Figure 9. Receiver Propagation Delay Test Circuit
_______________Detailed Description
The MAX3140 combines an SPI/QSPI/MICROWIRE-
compatible UART (MAX3100) and an RS-485/RS-422
transceiver (MAX3089) in one package. The UART sup-
ports data rates up to 230k baud for both standard
UART bit streams as well as IrDA, and includes an
8-word receive FIFO. Also included is a parity-bit inter-
rupt useful in 9-bit address recognition.
The RS-485/RS-422 transceiver has a true fail-safe
receiver and allows up to 256 transceivers on the bus.
Other features include pin-selectable full/half-duplex
operation and a phase control to correct for twisted-
pair reversal. The slew rate of the RS-485/RS-422 trans-
ceiver is selectable, limiting the maximum data rate to
115kbps, 500kbps, or 10Mbps. The RS-485/RS-422 dri-
vers are output short-circuit current limited, and thermal
shutdown circuitry protects the RS-485/RS-422 drivers
against excessive power dissipation.
The UART and RS-485/RS422 functions can be used
together or independently since the two functions only
share supply and ground connections. This part oper-
ates from a single +5V supply.