19-1453; Rev 1; 9/10
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
General Description
The MAX3140 is a complete universal asynchronous
receiver-transmitter (UART) and a true fail-safe RS-
485/RS-422 transceiver combined in a single 28-pin
QSOP package for space-, cost-, and power-con-
strained applications. The MAX3140 saves additional
board space as well as microcontroller (µC) I/O pins by
featuring an SPI™/QSPI™/MICROWIRE™-compatible
serial interface. It is pin-programmable for configuration
in all RS-485/RS-422 networks.
The MAX3140 includes a single RS-485/RS-422 driver
and receiver featuring true fail-safe circuitry, which
guarantees a logic-high receiver output when the
receiver inputs are open or shorted. This feature pro-
vides immunity to faults without requiring complex ter-
mination. The MAX3140 provides software-selectable
control of half- or full-duplex operation, data rate, slew
rate, and transmitter and receiver phase. The RS-485
driver slew rate is programmable to minimize EMI and
results in maximum data rates of 115kbps, 500kbps,
and 10Mbps. Independent transmitter/receiver phase
control enables software correction of twisted-pair
polarity reversal. A 1/8-unit-load receiver input imped-
ance allows up to 256 transceivers on the bus.
The MAX3140’s UART includes an oscillator circuit
derived from an external crystal, and a baud-rate gen-
erator with software-programmable divider ratios for all
common baud rates from 300 baud to 230k baud. The
UART features an 8-word-deep receive FIFO that mini-
mizes processor overhead and provides a flexible inter-
rupt with four maskable sources, including address
recognition on 9-bit networks. Two control lines are
included for hardware handshaking—one input and
one output.
The MAX3140 operates from a single +5V supply and
typically consumes only 645µA with the receiver active.
Hardware-invoked shutdown reduces supply current to
only 20µA. The UART and RS-485/RS-422 functions can
be used together or independently since the two func-
tions share only supply and ground connections (the
MAX3140 is hardware- and software-compatible with the
MAX3100 and MAX3089).
Features
o
Integrated UART and RS-485/RS-422 Transceiver
in a Single 28-Pin QSOP
o
SPI/MICROWIRE-Compatible Interface Saves µC
I/O Pins
o
True Fail-Safe Receiver Output Eliminates
Complex Network Termination
o
Pin-Programmable RS-485/RS-422 Features
Half/Full-Duplex Operation
Slew-Rate Limiting for Reduced EMI
115kbps/500kbps/10Mbps Data Rates
Receiver/Transmitter Phase for Twisted-Pair
Polarity Reversal
o
Full-Featured UART
Programmable Up to 230k baud with a
3.6864MHz Crystal
8-Word Receive FIFO Minimizes Processor
Overhead
9-Bit Address-Recognition Interrupt
o
Allows Up to 256 Transceivers on the Bus
o
Low 20µA Hardware Shutdown Mode
o
Hardware/Software-Compatible with MAX3100
and MAX3089
MAX3140
Ordering Information
PART
MAX3140CEI+
MAX3140EEI+
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
28 QSOP
+Denotes
a lead(Pb)-free/RoHS-compliant package.
Typical Application Circuit
MAX3140
SPI/
MICRO-
WIRE
CS
SCLK
DIN
DOUT
IRQ
R
t
CONTROL
LOGIC
RS-485
RS-422
R
t
UART
Applications
Industrial-Control
Local Area Networks
HVAC and Building Control
Point-of-Sale Devices
Transceivers for EMI-
Sensitive Applications
Embedded Systems
Intelligent Instrumentation
µP
SPI/QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
Pin Configuration appears at end of data sheet.
H/F SRL TXP RXP
HALF/FULL-DUPLEX
RS-485/RS-422
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
MAX3140
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..........................................................................+6V
Input Voltage to GND (CS,
SHDN,
X1,
CTS,
RX, DIN, SCLK,
RE,
DE, H/F, SRL, TXP, RXP, Dl) .............-0.3V to (V
CC
+ 0.3V)
Output Voltage to GND
DOUT,
RTS,
TX, X2, RO...........................-0.3V to (V
CC
+ 0.3V)
IRQ
........................................................................-0.3V to +6V
Driver Output Voltage (Y, Z) ...............................................±13V
Receiver Input Voltage, Half Duplex (Y, Z)......................... ±13V
Receiver Input Voltage, Full Duplex (A, B) .........................±25V
TX,
RTS
Output Current ...................................................100mA
X2, DOUT,
IRQ
Short-Circuit Duration
(to V
CC
or GND) ......................................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
28-pin QSOP (derate 10.8mW/°C above +70°C)..........860mW
Operating Temperature Ranges
MAX3140CEI .......................................................0°C to +70°C
MAX3140EEI ....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
Soldering Temperature (reflow) .......................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= +5V ±5%, DE = V
CC
,
RE
= GND,
SHDN
= V
CC
, f
XTL
= 1.8432MHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values
are measured with V
CC
= +5V, UART configured for 9600 baud, T
A
= +25°C.) (Note 1)
PARAMETER
POWER SUPPLY
Supply Voltage
V
CC
SHDN
= V
CC
;
SHDNi bit = 0,
no load
SRL = V
CC
SRL = GND
or open
DE = V
CC
DE = GND
DE = V
CC
DE = GND
4.75
0.7
0.64
0.74
0.69
0.47
5.25
1.9
1.6
2
1.8
1
mA
mA
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Current
I
CC
Supply Current with Only UART I
CC
SHDN
Shut Down
UART
Supply Current with Both
RS-485 Transceiver and UART
Shut Down
Input High Voltage
Input Low Voltage
Input Current
Input Capacitance
Input High Voltage
Input Low Voltage
Input Hysteresis
Input Leakage Current
Input Capacitance
UART OUTPUTS (DOUT, TX,
RTS)
Output High Voltage
Output Low Voltage
Output Leakage
Output Capacitance
2
V
OH1
V
OL1
I
LKG2
C
OUT1
I
CC
SHDN
(FULL)
SHDN
= GND or SHDNi bit = 1
SHDN
= GND or SHDNi bit = 1;
DE = GND;
RE
= V
CC
20
µA
UART OSCILLATOR INPUT (X1)
V
IH1
V
IL1
I
IN1
C
IN1
V
IH2
V
IL2
V
HYST2
I
LKG1
C
IN2
I
SOURCE
= 5mA; DOUT,
RTS
I
SOURCE
= 10mA; TX only
I
SINK
= 4mA; DOUT,
RTS
I
SINK
= 25mA; TX only
CS
= V
CC
; D
OUT
only
5
V
CC
- 0.5
V
CC
- 0.5
0.4
0.9
±1
5
250
±1
0.7V
CC
0.3V
CC
V
X1
= 0 or V
CC
SHDNi bit = 0
SHDNi bit = 1
5
0.7V
CC
0.2V
CC
25
2
V
V
µA
pF
V
V
mV
µA
pF
UART LOGIC INPUTS (DIN, SCLK,
CS, SHDN, CTS,
RX)
V
V
µA
pF
_______________________________________________________________________________________
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +5V ±5%, DE = V
CC
,
RE
= GND,
SHDN
= V
CC
, f
XTL
= 1.8432MHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values
are measured with V
CC
= +5V, UART configured for 9600 baud, T
A
= +25°C.) (Note 1)
PARAMETER
Output Low Voltage
Output Leakage
Output Capacitance
RS-485 DRIVER
V
OD1
Differential Output Voltage
Change in Magnitude of
Differential Output Voltage
Common-Mode Output
Voltage
Change In Magnitude of
Common-Mode Voltage
Input High Voltage
Input Low Voltage
DI Input Hysteresis
Input Current
SRL Input High Voltage
SRL Input Middle Voltage
SRL Input Low Voltage
SRL Input Current
Full-Duplex Input Current
(A and B)
Full-Duplex Output Leakage
(Y and Z)
Short-Circuit Output Current
RS-485 RECEIVER
Differential Threshold Voltage
Input Hysteresis
Output High Voltage
Output Low Voltage
Three-State Output Current
Input Resistance
Output Short-Circuit Current
V
TH
ΔV
TH
V
OH
V
OL
I
OZR
R
IN
I
OSR
I
SOURCE
= 4mA, V
ID
= -50mV
I
SINK
= 4mA, V
ID
= -200mV
0.4V
≤
V
O
≤
2.4V
-7V
≤
V
CM
≤
12V
0
≤
V
RO
≤
V
CC
96
±7
±95
V
CC
- 1.5
0.4
±1
-7V
≤
V
CM
≤
+12V
-200
-125
25
-50
mV
mV
V
V
µA
kΩ
mA
3
V
OD2
ΔV
OD
V
OC
ΔV
OC
V
IH1
V
IL1
V
HYS
I
IN1
I
IN2
V
IH2
V
IM2
V
IL2
I
IN3
I
IN4
I
O
SRL = V
CC
SRL = GND (Note 3)
DE = GND
V
CC
= GND or 5.25V
DE = GND
V
CC
= GND or 5.25V
(Note 4)
V
IN
= 12V
V
IN
= -7V
V
IN
= 12V
V
IN
= -7V
-7V
≤
V
OUT
≤
V
CC
I
OSD
0
≤
V
OUT
≤
12V
0
≤
V
OUT
≤
V
CC
±25
-100
-250
250
mA
-75
125
-75
125
(Note 3)
No load, Figure 1
R = 50Ω (RS-422), Figure 1
R = 27Ω (RS-422), Figure 1
R = 50Ω or R = 27Ω, Figure 1 (Note 2)
R = 50Ω or R = 27Ω, Figure 1
R = 50Ω or R = 27Ω, Figure 1 (Note 2)
DE, Dl,
RE
H/F, TXP, RXP
DE, Dl, RE, H/F, TXP, RXP
SRL = V
CC
or unconnected
DE, DI,
RE
H/F, TXP, RXP, internal pull-down
10
V
CC
- 0.8
0.4
·
V
CC
0.6
·
V
CC
0.8
75
100
±2
40
2.0
2.4
0.8
2.0
1.5
0.2
3
0.2
V
V
V
V
V
mV
µA
V
V
V
µA
µA
µA
5
V
SYMBOL
V
OL2
I
LKG3
C
OUT2
I
SINK
= 4mA
V
IRQ
= V
CC
5
CONDITIONS
MIN
TYP
MAX
0.4
±1
UNITS
V
µA
pF
UART
IRQ
OUTPUT
(Open Drain)
MAX3140
_______________________________________________________________________________________
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
MAX3140
UART SWITCHING CHARACTERISTICS
(V
CC
= +5V ±5%, f
XTL
= 1.8432MHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are measured with V
CC
= +5V,
UART configured for 9600 baud, T
A
= +25°C.) (Note 1)
PARAMETER
UART AC TIMING
(Figure 1)
CS
Low to DOUT Valid
CS
High to DOUT Tri-State
CS
to SCLK Setup Time
CS
to SCLK Hold Time
SCLK Fall to DOUT Valid
DIN to SCLK Setup Time
DIN to SCLK Hold Time
SCLK Period
SCLK High Time
SCLK Low Time
SCLK Rising Edge to
CS
FaIling
CS
Rising Edge to SCLK
Rising
CS
High Pulse Width
Output Rise Time
Output Fall Time
t
DV
t
TR
t
CSS
t
CSH
t
DO
t
DS
t
DH
t
CP
t
CH
t
CL
t
CS0
t
CS1
t
CSW
tr
tf
TX,
RTS,
DOUT; C
LOAD
= 100pF
TX,
RTS,
DOUT,
IRQ;
C
LOAD
= 100pF
C
LOAD
= 100pF
100
0
238
100
100
100
200
200
10
10
C
LOAD
= 100pF
C
LOAD
= 100pF, R
CS
= 10kΩ
100
0
100
100
100
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
SWITCHING CHARACTERISTICS—SRL = Unconnected
(V
CC
= +5V ±5%, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC
= +5V and T
A
= +25°C.)
PARAMETER
Driver Input to Output
Driver Output Skew
|
t
DPLH
- t
DPHL
|
Driver Rise or Fall Time
Maximum Data Rate
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
Receiver Input to Output
SYMBOL
t
DPLH
t
DPHL
t
DSKEW
t
DR
, t
DF
f
MAX
t
DZH
t
DZL
t
DLZ
t
DHZ
t
RPLH
,
t
RPHL
t
RSKD
t
RZL
t
RZH
t
RLZ
t
RHZ
t
SHDN
t
DZH(SHDN)
t
DZL(SHDN)
t
RZH(SHDN)
t
RZL(SHDN)
Figures 4 and 6, C
L
= 100pF, S2 closed
Figures 4 and 6, C
L
= 100pF, S1 closed
Figures 4 and 6, C
L
= 15pF, S1 closed
Figures 4 and 6, C
L
= 15pF, S2 closed
Figures 7 and 9,
|
V
ID
|
≥
2.0V,
rise and fall time of V
ID
≤
15ns
Figures 7 and 9,
|
V
ID
|
≥
2.0V,
rise and fall time of V
ID
≤
15ns
Figures 2 and 8, C
L
= 100pF, S1 closed
Figures 2 and 8, C
L
= 100pF, S2 closed
Figures 2 and 8, C
L
= 100pF, S1 closed
Figures 2 and 8, C
L
= 100pF, S2 closed
(Note 5)
Figures 4 and 6, C
L
= 15pF, S2 closed
Figures 4 and 6, C
L
= 15pF, S1 closed
Figures 2 and 8, C
L
= 100pF, S2 closed
Figures 2 and 8, C
L
= 100pF, S1 closed
50
127
3
20
20
20
20
200
CONDITIONS
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
667
115
3500
3500
100
100
200
±30
50
50
50
50
600
6000
6000
3500
3500
MIN
500
500
TYP
2030
2030
-3
1320
MAX
2600
2600
±200
2500
UNITS
ns
ns
ns
kbps
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
MAX3140
|
t
RPLH
- t
RPHL
|
Differential
Receiver Skew
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable Time from Low
Receiver Disable Time from
High
Time to Shutdown
Driver Enable from Shutdown to
Output High
Driver Enable from Shutdown to
Output Low
Receiver Enable from Shutdown
to Output High
Receiver Enable from Shutdown
to Output Low
_______________________________________________________________________________________
5
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