Datasheet

MAX3140
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
12 ______________________________________________________________________________________
Pin Description (continued)
Transceiver Function Tables
21
22 Positive Supply (4.75V to 5.25V)V
CC
22
23
24
UART SPI/MICROWIRE Serial-Data Output. High impedance when CS is high.
DOUT24
UART SPI/MICROWIRE Serial-Data Input. Schmitt-trigger input.DIN23
25
26
UART Active-Low Chip-Select Input. DOUT goes high impedance when CS is high. IRQ, TX,
and RTS are always active. Schmitt-trigger input.
CS
26
27
28
UART Hardware Shutdown Input. When shut down (SHDN = 0), the UART oscillator turns off
immediately without waiting for the current transmission to end, reducing the supply current
to just leakage currents.
SHDN
28
UART Active-Low Interrupt Output. Open-drain interrupt output to microprocessor.
IRQ
27
UART SPI/MICROWIRE Serial-Clock Input. Schmitt-trigger input.SCLK25
RS-485 Receiver Phase. Connect RXP to GND or leave it unconnected for normal receiver
phase/polarity. Connect RXP to V
CC
to invert the receiver phase/polarity.
RXP21
FULL
DUPLEX
HALF
DUPLEX
PIN
NAME FUNCTION
* In half-duplex mode, the driver outputs serve as receiver inputs. The full-duplex receiver inputs ( A and B) still have a 1/8-unit load, but
do not affect the receiver output.
RE
DETXP
TRANSMITTING
Z YDI
0 11X 10
1 00X 10
1 01X 11
0 10X 11
High-Z High-ZX0 0X
Shutdown (High-Z)X1 0X
0
0
0
0
1
1
H/F
OUTPUTSINPUTS
0
0
1
1
0
0
RXP
X
X
X
X
X
X
DE
0
0
0
0
0
0
RE
≥ -0.05V
≤ -0.2V
≥ -0.05V
≤ -0.2V
X
X
A-B
1
0
0
1
1
0
RO
X
X
X
X
≥ -0.05V
≤ -0.2V
Y-Z
1
1
0
0
1
1
X
X
X
X
X
X
1 0
0
0
1
0
0
0
0
X
X
Open/
Shorted
X1
Open/
Shorted
X
0
0
1
1
1
0
1 0
≥ -0.05V
≤ -0.2V
X
Open/
Shorted
X
Open/
Shorted
X
X
1
0
1
1
X
X
X High-Z
X
Shutdown
(High-Z)
X
X
OUTPUTS
RECEIVING
INPUTS