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PDF MAX3140 Data sheet ( Hoja de datos )
| Número de pieza | MAX3140 | |
| Descripción | SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-1453; Rev 0; 6/99
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).
Applications
Industrial-Control
Local Area Networks
Transceivers for EMI-
Sensitive Applications
HVAC and Building Control Embedded Systems
Point-of-Sale Devices
Intelligent Instrumentation
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
PART
MAX3140CEI
MAX3140EEI
Ordering Information
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
28 QSOP
Typical Application Circuit
SPI/
MICRO-
WIRE
CS
SCLK
µP DIN
DOUT
UART
IRQ
MAX3140
CONTROL
LOGIC
RS-485
RS-422
Rt
Rt
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 SRLTXP RXP
HALF/FULL-DUPLEX
RS-485/RS-422
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
1 page  
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
SWITCHING CHARACTERISTICS—SRL = Unconnected
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP
Driver Input to Output
Driver Output Skew
| tDPLH - tDPHL |
tDPLH
tDPHL
tDSKEW
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
500 2030
500 2030
-3
Driver Rise or Fall Time
tDR, tDF
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
667 1320
Maximum Data Rate
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
fMAX
tDZH
tDZL
tDLZ
tDHZ
Figures 4 and 6, CL = 100pF, S2 closed
Figures 4 and 6, CL = 100pF, S1 closed
Figures 4 and 6, CL = 15pF, S1 closed
Figures 4 and 6, CL = 15pF, S2 closed
115
Receiver Input to Output
| tRPLH - tRPHL | Differential
Receiver Skew
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable Time from Low
Receiver Disable Time from
High
tRPLH,
tRPHL
tRSKD
tRZL
tRZH
tRLZ
tRHZ
Figures 7 and 9, | VID | ≥ 2.0V,
rise and fall time of VID ≤ 15ns
Figures 7 and 9, | VID | ≥ 2.0V,
rise and fall time of VID ≤ 15ns
Figures 2 and 8, CL = 100pF, S1 closed
Figures 2 and 8, CL = 100pF, S2 closed
Figures 2 and 8, CL = 100pF, S1 closed
Figures 2 and 8, CL = 100pF, S2 closed
127
3
20
20
20
20
Time to Shutdown
tSHDN
(Note 5)
50 200
Driver Enable from Shutdown to
Output High
tDZH(SHDN)
Figures 4 and 6, CL = 15pF, S2 closed
Driver Enable from Shutdown to
Output Low
tDZL(SHDN)
Figures 4 and 6, CL = 15pF, S1 closed
Receiver Enable from Shutdown
to Output High
tRZH(SHDN)
Figures 2 and 8, CL = 100pF, S2 closed
Receiver Enable from Shutdown
to Output Low
tRZL(SHDN)
Figures 2 and 8, CL = 100pF, S1 closed
MAX
2600
2600
±200
2500
3500
3500
100
100
200
±30
50
50
50
50
600
6000
6000
3500
3500
UNITS
ns
ns
ns
kbps
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
_______________________________________________________________________________________ 5
5 Page 
SPI/MICROWIRE-Compatible UART with Integrated
True Fail-Safe RS-485/RS-422 Transceivers
Pin Description
PIN
FULL
HALF
DUPLEX DUPLEX
NAME
1 1 X2
2 2 X1
3 3 CTS
4 4 RTS
5 5 RX
6 6 TX
7 7 H/F
8 8 GND
9 9 RO
10 10 RE
11 11 DE
12 12 DI
13 13 SRL
14 14 N.C.
15 15 TXP
16 — Y
— 16 Y
17 17 N.C.
18 — Z
— 18 Z
19 — B
— 19 B
20 — A
— 20 A
FUNCTION
UART Crystal Connection. Leave X2 unconnected for external clock. See the Crystals,
Oscillators, and Ceramic Resonators section.
UART Crystal Connection. X1 also serves as an external clock input. See the Crystals,
Oscillators, and Ceramic Resonators section.
UART Clear-to-Send Active-Low Input. Read via the CTS bit.
UART Request-to-Send Active-Low Output. Controlled by the RTS bit. Use to control the dri-
ver enable in RS-485 networks.
UART Asynchronous Serial-Data (receiver) Input. The serial information received from the modem
or RS-232/RS-485 receiver. A transition on RX while in shutdown generates an interrupt (Table 1).
UART Asynchronous Serial-Data (transmitter) Output
RS-485 Half/Full-Duplex Selector Pin. Connect H/F to VCC for half-duplex mode; connect H/F
to GND or leave it unconnected for full-duplex mode.
Ground
RS-485 Receiver Output. When RE is low and if A - B ≥ -50mV, RO will be high; if A - B ≤
-200mV, RO will be low.
RS-485 Receiver Output Enable. Drive RE low to enable RO; RO is high impedance when RE
is high. Drive RE high and DE low to enter low-power shutdown mode.
RS-485 Driver Output Enable. Drive DE high to enable driver outputs. These outputs are high
impedance when DE is low. Drive RE high and DE low to enter low-power shutdown mode.
RS-485 Driver Input. With DE high, a low on DI forces noninverting output low and inverting
output high. Similarly, a high on DI forces noninverting output high and inverting output low.
RS-485 Transceiver Slew-Rate-Limit Selector Pin. Connect SRL to GND for a 10Mbps com-
munication rate, connect SRL to VCC for a 500kbps rate, or leave SRL unconnected for a
115kbps rate.
No Connection. Not internally connected.
RS-485 Transmitter Phase. Connect TXP to GND or leave it floating for normal transmitter
phase/polarity. Connect TXP to VCC to invert the transmitter phase/polarity.
RS-485 Noninverting Driver Output
RS-485 Noninverting Receiver Input and RS-485 Noninverting Driver Output*
No Connection. Not internally connected.
RS-485 Inverting Driver Output
RS-485 Inverting Receiver Input and RS-485 Inverting Driver Output*
RS-485 Inverting Receiver Input
RS-485 Receiver Input Resistors*
RS-485 Noninverting Receiver Input
RS-485 Receiver Input Resistors*
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet MAX3140.PDF ] | |
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