Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsLinear ICsMAX3140CEI+

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 Transceivers for EMI-

Local Area Networks 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

MAX3140

SPI/MICROWIRE-Compatible UART with Integrated

True Fail-Safe RS-485/RS-422 Transceivers

________________________________________________________________

Maxim Integrated Products

19-1453; Rev 1; 9/10

PART

MAX3140CEI+

MAX3140EEI+ -40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

28 QSOP

Ordering Information

SPI/QSPI are trademarks of Motorola, Inc.

MICROWIRE is a trademark of National Semiconductor Corp.

Pin Configuration appears at end of data sheet.

Typical Application Circuit

SCLK

SPI/

MICRO-

WIRE

DIN

DOUT

µP

UART

IRQ

H/F SRL

HALF/FULL-DUPLEX

RS-485/RS-422

TXP

CONTROL

LOGIC

RS-485

RS-422

RXP

MAX3140

Denotes a lead(Pb)-free/RoHS-compliant package.

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.

Summary of content (36 pages)

PAGE 1
9-1453; Rev 1; 9/10 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers The MAX3140 is a complete universal asynchronous receiver-transmitter (UART) and a true fail-safe RS485/RS-422 transceiver combined in a single 28-pin QSOP package for space-, cost-, and power-constrained applications. The MAX3140 saves additional board space as well as microcontroller (µC) I/O pins by featuring an SPI™/QSPI™/MICROWIRE™-compatible serial interface.
PAGE 2
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers ABSOLUTE MAXIMUM RATINGS X2, DOUT, IRQ Short-Circuit Duration (to VCC or GND) ......................................................Continuous Continuous Power Dissipation (TA = +70°C) 28-pin QSOP (derate 10.8mW/°C above +70°C)..........860mW Operating Temperature Ranges MAX3140CEI .......................................................0°C to +70°C MAX3140EEI ....................................................
PAGE 3
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers (VCC = +5V ±5%, DE = VCC, RE = GND, SHDN = VCC, fXTL = 1.8432MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are measured with VCC = +5V, UART configured for 9600 baud, TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.
PAGE 4
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers UART SWITCHING CHARACTERISTICS (VCC = +5V ±5%, fXTL = 1.8432MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are measured with VCC = +5V, UART configured for 9600 baud, TA = +25°C.
PAGE 5
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers MAX3140 SWITCHING CHARACTERISTICS—SRL = Unconnected (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.
PAGE 6
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers SWITCHING CHARACTERISTICS—SRL = VCC (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.
PAGE 7
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers MAX3140 SWITCHING CHARACTERISTICS—SRL = GND (VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER Driver Input to Output SYMBOL tDPLH tDPHL CONDITIONS MIN Figures 3 and 5, RDIFF = 54Ω, CL1 = CL2 = 100pF TYP MAX 34 60 34 60 UNITS ns Driver Output Skew | tDPLH - tDPHL | tDSKEW Figures 3 and 5, RDIFF = 54Ω, CL1 = CL2 = 100pF -2.
PAGE 8
Typical Operating Characteristics (VCC = +5V, TA = +25°C, unless otherwise noted.) UART SHUTDOWN CURRENT vs. TEMPERATURE 700 600 500 400 300 350 7 6 5 4 3 2 100 1 -20 0 20 40 60 80 300 STANDBY 250 200 150 50 -40 100 -20 0 20 40 60 80 1000 100 100 10k 100k 1M TEMPERATURE (°C) BAUD RATE (bps) UART SUPPLY CURRENT vs. EXTERNAL CLOCK FREQUENCY TX, RTS, DOUT OUTPUT CURRENT vs. OUTPUT LOW VOLTAGE RS-485 TRANSCEIVER NO-LOAD SUPPLY CURRENT vs.
PAGE 9
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers IRO = 8mA 0.40 0.35 0.30 0.25 0.20 4.3 4.2 4.1 4.0 3.8 -60 -40 -20 0 20 40 60 80 -20 0 20 40 60 80 125 100 -60 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) RS-485 RECEIVER PROPAGATION DELAY (10Mbps MODE) vs. TEMPERATURE RS-485 DRIVER PROPAGATION DELAY (115kbps MODE) vs. TEMPERATURE RS-485 DRIVER PROPAGATION DELAY (500kbps MODE) vs.
PAGE 10
Typical Operating Characteristics (continued) (VCC = +5V, TA = +25°C, unless otherwise noted.) OUTPUT CURRENT vs. RS-485 DRIVER OUTPUT LOW VOLTAGE MAX3140-21 -100 MAX3140-20 120 RS-485 RECEIVER PROPAGATION DELAY (SRL = GND) OUTPUT CURRENT vs.
PAGE 11
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers PIN FULL DUPLEX HALF DUPLEX NAME FUNCTION 1 1 X2 UART Crystal Connection. Leave X2 unconnected for external clock. See the Crystals, Oscillators, and Ceramic Resonators section. 2 2 X1 UART Crystal Connection. X1 also serves as an external clock input. See the Crystals, Oscillators, and Ceramic Resonators section. 3 3 CTS UART Clear-to-Send Active-Low Input. Read via the CTS bit.
PAGE 12
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Pin Description (continued) PIN FULL DUPLEX HALF DUPLEX NAME FUNCTION 21 21 RXP RS-485 Receiver Phase. Connect RXP to GND or leave it unconnected for normal receiver phase/polarity. Connect RXP to VCC to invert the receiver phase/polarity. 22 22 VCC Positive Supply (4.75V to 5.25V) 23 23 DIN UART SPI/MICROWIRE Serial-Data Input. Schmitt-trigger input.
PAGE 13
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers MAX3140 Y R RECEIVER OUTPUT VOD 1k TEST POINT VCC S1 CL 15pF R 1k VOC S2 Z Figure 1. Driver DC Test Load Figure 2. Receiver Enable/Disable Timing Test Load VCC DE DI CL1 Y S1 500Ω RDIFF OUTPUT UNDER TEST VID Z CL CL2 S2 Figure 4. Driver Enable/Disable Timing Test Load Figure 3. Driver Timing Test Circuit 3V 3V DI 1.5V DE 1.5V 0 tPLH 1.5V tZL(SHDN), tZL tLZ Y, Z VO Y VO 0 -VO 1.
PAGE 14
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers 3V RE RO VOL 1V A -1V B 1.5V 1.5V 0 VOH 1.5V 1.5V OUTPUT tPHL tZL(SHDN), tZL tPLH tLZ VCC RO 1.5V OUTPUT NORMALLY LOW RO 1.5V VOL + 0.5V INPUT OUTPUT NORMALLY HIGH VOH - 0.5V 0 tZH(SHDN), tZH tHZ Figure 8. Receiver Enable and Disable Times Figure 7. Receiver Propagation Delays B ATE VID RR RECEIVER OUTPUT A Figure 9.
PAGE 15
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers SPI Interface The MAX3140 is compatible with SPI, QSPI (CPOL = 0, CPHA = 0), and MICROWIRE serial-interface standards (Figure 11). The MAX3140 has a unique full-duplex architecture that expects a 16-bit word for DIN and simultaneously produces a 16-bit word for DOUT regardless of which read/write register used.
PAGE 16
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers clearing of internal registers, are executed only on CS’s rising edge. Every time CS goes low, a new 16-bit stream is expected. Figure 13 shows an example of using the WRITE CONFIGURATION register. Table 1 describes the bits located in the WRITE CONFIGURATION, READ CONFIGURATION, WRITE DATA, and READ DATA registers.
PAGE 17
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers BIT NAME BIT TYPE POR STATE B0–B3 write 0000 Baud-Rate Divisor Select Bits. Sets the baud clock’s value (Table 6). B0–B3 read 0000 Baud-Rate Divisor Select Bits. Reads the 4-bit baud clock value assigned to these registers. CTS read No change D0t–D7t write XXXXXXXX Transmit-Buffer Register. Eight data bits written into the transmit-buffer register. D7t is ignored when L = 1.
PAGE 18
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Table 1. Bit Descriptions (continued) BIT NAME RA/FE SHDNi BIT TYPE read write POR STATE DESCRIPTION 0 Receiver-Activity/Framing-Error Bit. In shutdown mode, this is the RA bit. In normal operation, this is the FE bit. In shutdown mode, a transition on RX sets RA = 1. In normal mode, a framing error sets FE = 1. A framing error occurs if a zero is received when the first stop bit is expected.
PAGE 19
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Setting the WRITE CONFIGURATION register clears the receive FIFO and the R, T, RA/FE, D0r–D7r, D0t–D7t, Pr, and Pt registers. Bits RTS and CTS remain unchanged. The new configuration is valid on CS’s rising edge if the transmit buffer is empty (T = 1) and transmission is over. If the latest transmission has not been completed (T = 0), the registers are updated when the transmission is over.
PAGE 20
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers READ CONFIGURATION Register (D15, D14 = 0, 1) Use the READ CONFIGURATION register to read back the last configuration written to the UART. In this mode, bits 15 and 14 of the DIN configuration word are required to be 0 and 1, respectively, to enable the READ CONFIGURATION mode. Clear bits 13–1 of the DIN word. Bit 0 is the test bit to put the UART in test mode (see the Test Mode section).
PAGE 21
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers that is being received from the RX FIFO. Table 4 shows the bit assignment for the WRITE DATA register. To change the RTS pin’s output state without transmitting data, set the TE bit high. If performing a WRITE DATA operation, the R bit clears on the falling edge of SCLK’s 16th clock pulse if no new data is available. READ DATA Register (D15, D14 = 0, 0) Use the READ DATA register for receiving data from the RX FIFO.
PAGE 22
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Table 5.
PAGE 23
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers BIT NAME MASK BIT MEANING WHEN SET DESCRIPTION Pr PM Received parity bit = 1 The Pr bit reflects the value in the word currently in the receive-buffer register (oldest data available). The Pr bit is set when parity is enabled (PE = 1) and the received parity bit is 1. The Pr bit is cleared either when parity is not enabled (PE = 0), or when parity is enabled and the received bit is 0.
PAGE 24
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Example 2: Setting up only the data-available (or databeing-read) interrupt. Send the 16-bit word below into DIN of the MAX3140 using the WRITE CONFIGURATION register. This 16-bit word configures the MAX3140 for 9600bps, 8-bit words, no parity, and one stop bit with a 1.8432MHz crystal.
PAGE 25
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Phase Control Circuitry Occasionally, twisted-pair lines are connected backward from normal orientation. The MAX3140 has two pins that invert the phase of the driver and the receiver to correct for this problem. For normal operation, drive TXP and RXP low, connect them to ground, or leave them unconnected (internal pull-down). To invert the driver phase, drive TXP high or connect it to VCC.
PAGE 26
9-Bit Networks SIR IrDA Mode The MAX3140 supports a common multidrop communication technique referred to as 9-bit mode. In this mode, the parity bit is set to indicate a message that contains a header with a destination address. Set the MAX3140’s parity mask to generate interrupts for this condition. Operating a network in this mode reduces the processing overhead of all nodes by enabling the slave controllers to ignore most message traffic. This relieves the remote processor to handle more useful tasks.
PAGE 27
MAX3140 FIG19 A 20dB/div MAX3140 MAX3140 FIG18 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers A 20dB/div O 100kHz/div 1MHz O 100kHz/div 1MHz Figure 18. Driver Output Waveform and FFT Plot of MAX3140 with SRL = VCC, Transmitting a 20kHz Signal Figure 19. Driver Output Waveform and FFT Plot of MAX3140 with SRL = Unconnected, Transmitting a 20kHz Signal sis of a 20kHz signal transmitted with SRL = GND.
PAGE 28
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Typical Applications The MAX3140 is designed for bidirectional data communications on multipoint bus transmission lines. The RS-485 transceiver can be used in any RS-485 application due to its numerous features and its programmability. A typical half-duplex circuit for the MAX3140 is shown in Figure 24, and a corresponding half-duplex MAX3140 (FULL DUPLEX) network is shown in Figure 25.
PAGE 29
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers MAX3140 VCC 10k VCC H/F SHDN +5V IRQ DIN DOUT SCLK CS CTS UART RTS TX RX VCC μP X1 MAX3140 100k X2 RO DI R Z Y HALF-DUPLEX RS-485 I/O D DE RXP RE* SRL TXP *NOTE: TO SHUT DOWN THE RS-485 TRANSCEIVER, DRIVE RE SEPARATELY. Figure 24. Typical Half-Duplex Operating Circuit 120Ω 120Ω DE B Z DI D D DI DE RO RE Y B A B A A R R RO RE R R D D MAX3140 DI DE RO RE DI DE RO RE Figure 25.
PAGE 30
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers VCC 10k VCC IRQ DIN DOUT SCLK CS SHDN H/F UART CTS X1 RTS TX RX MAX3140 RO DI μP X2 A R B FULL-DUPLEX RS-422 I/O Y D Z DE RE* RXP TXP SRL *NOTE: TO SHUT DOWN THE RS-485 TRANSCEIVER, DRIVE RE SEPARATELY WITH AN I/O OF A μP. Figure 26.
PAGE 31
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers MAX3140 VCC 10k VCC +5V MAX3120 H/F IRQ DIN DOUT SCLK CS μP UART IN IrDA MODE MAX3140 VCC 100k SOFTWARE NON-IrDA UART TX X1 X2 RO R RX TX RTS UNCONNECTED IrDA I/O RX DI Z Y HALF-DUPLEX RS-485 I/O D DE RXP RE* SRL TXP *NOTE: TO SHUT DOWN THE RS-485 TRANSCEIVER, DRIVE RE SEPARATELY. Figure 28.
PAGE 32
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Software Driver Listing 1 is a C-language outline of an interrupt-driven software driver that interfaces to a MAX3140, providing an intermediate layer between the bit-manipulation subroutine and the familiar PutChar/GetChar subroutines. The user must supply code for managing the transmit and receive queues, as well as the low-level hardware interface itself.
PAGE 33
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers MAX3140 Listing 1.
PAGE 34
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Listing 1.
PAGE 35
SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers TOP VIEW + X2 1 28 SHDN X1 2 27 IRQ CTS 3 26 CS RTS 4 25 SCLK PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 28 QSOP E28M+1 21-0055 90-0173 24 DOUT RX 5 TX 6 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only.
PAGE 36
MAX3140 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers Revision History PAGES CHANGED REVISION NUMBER REVISION DATE 0 6/99 Initial release — 1 9/10 Changed the maximum value of the “Driver Rise or Fall Time” parameter in the Switching Characteristics—SRL = VCC table 6 DESCRIPTION Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.