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MAX13485

General Description The MAX13485E/MAX13486E +5V, half-duplex, ±15kV ESD-protected RS-485 transceivers feature one driver and one receiver. These devices include fail-safe circuitry, guaranteeing a logic-high receiver output when receiver inputs are open or shorted. The receiver outputs a logic-high if all transmitters on a terminated bus are disabled (high impedance). The MAX13485E/MAX13486E include a hot-swap capability to eliminate false transitions on the bus during power-up or live-insertion.

The MAX13485E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free trans-mission up to 500kbps. The MAX13486E driver slew rate is not limited, allowing transmit speeds up to 16Mbps.

The MAX13485E/MAX13486E feature a 1/4-unit load receiver input impedance, allowing up to 128 transceivers on the bus. These devices are intended for half-duplex communications. All driver outputs are protected to ±15kV ESD using the Human Body Model. The MAX13485E/ MAX13486E are available in 8-pin SO and space-saving 8-pin μDFN packages. The devices operate over the extended -40°C to +85°C temperature range.

Applications Utility Meters

Industrial Controls

Industrial Motor Drives

Automated HVAC Systems

Features

o+5V Operation

o True Fail-Safe Receiver While Maintaining

EIA/TIA-485 Compatibility

o Hot-Swappable for Telecom Applications

o Enhanced Slew-Rate Limiting Facilitates Error-Free Data Transmission (MAX13485E)

o High-Speed Version (MAX13488E) Allows for Transmission Speeds Up to 16Mbps

o Extended ESD Protection for RS-485/RS-422 I/O Pins ±15kV Using Human Body Model

o1/4 Unit Load, Allowing Up to 128 Transceivers on the Bus

o Available in Space-Saving 8-Pin μDFN or Industry Standard 8-Pin SO Packages MAX13485E/MAX13486E

Half-Duplex RS-485/RS-422 Transceivers in μDFN 19-0742; Rev 0; 1/07

Ordering Information/

Selector Guide

+Denotes a lead-free package.

Note: All devices are specified over the -40°C to +85°C operating

temperature range.

Pin Configurations

M A X 13485E /M A X 13486E

ABSOLUTE MAXIMUM RATINGS

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.

(All voltages referenced to GND.)

V CC ........................................................................................+6V DE, RE , DI.................................................................-0.3V to +6V A, B..............................................................................-8V to 13V Short-Circuit Duration (RO, A, B) to GND..................Continuous Continuous Power Dissipation (T A = +70°C)

8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW 8-Pin μDFN (derate 4.8mW/°C above +70°C)..........380.6mW

Operating Temperature Range ...........................-40°C to +85°C Junction Temperature......................................................+150°C Storage Temperature Range.............................-65°C to +150°C Lead Temperature (soldering, 10s).................................+300°C

ELECTRICAL CHARACTERISTICS

(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.) (Notes 1, 2)

MAX13485E/MAX13486E

ELECTRICAL CHARACTERISTICS (continued)

(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.) (Notes 1, 2)

(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.) (Note 1)

M A X 13485E /M A X 13486E

SWITCHING CHARACTERISTICS —MAX13485E (continued)

(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.) (Note 1)

SWITCHING CHARACTERISTICS —MAX13486E

MAX13485E/MAX13486E

SWITCHING CHARACTERISTICS —MAX13486E (continued)

(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.) (Note 1)

unless otherwise noted.

Note 3:?V OD and ?V OC are the changes in V

OD and V OC when the DI input changes states.

Note 4:The short-circuit output current applied to peak current just prior to foldback current limiting. The short-circuit foldback

output current applies during current limiting to allow a recovery from bus contention.

Typical Operating Characteristics

(V CC = +5V, T A = +25°C, unless otherwise noted.)

3.03.2

3.6

3.4

3.8

4.0

-40

-15

SUPPLY CURRENT vs. TEMPERATURE

TEMPERATURE (°C)

S U P P L

Y C U R R E N T (m A )

OUTPUT CURRENT vs. RECEIVER

OUTPUT HIGH VOLTAGE

OUTPUT HIGH VOLTAGE (V)

O U T P U T C U R R E N T (m A )

201040305060021345

OUTPUT CURRENT vs. RECEIVER

OUTPUT LOW VOLTAGE

M A X 13485-86E t o c 03

OUTPUT LOW VOLTAGE (V)

O U T P U T C U R R E N T (m A )

M A X 13485E /M A X 13486E

Typical Operating Characteristics (continued)

(V CC = +5V, T A = +25°C, unless otherwise noted.)

4.04.44.24.84.6

5.25.05.4-40

-15

RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE

TEMPERATURE (°C)

O U T P U T H I G H V O L T A G E (V )

0.1

0.3

0.2

0.4

0.5-40

-15

RECEIVER OUTPUT LOW VOLTAGE vs. TEMPERATURE

TEMPERATURE (°C)

O U T P U T L O W V O L T A G E (V )

DIFFERENTIAL OUPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE

M A X 13485-86E t o c 06

OUTPUT VOLTAGE (V)

O U T P U T C U R R E N T (m A )

01.00.52.01.52.53.0-40

-15

6085DRIVER-DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE

TEMPERATURE (°C)D I F F E R E N T I A L O U T P U T V O L T A G E (V )

40208060100120

-7-5-4-3-6-20-112345OUTPUT CURRENT vs. TRANSMITTER

OUTPUT HIGH VOLTAGE

OUTPUT HIGH VOLTAGE (V)O U T P U T C U R R E N T (m A )

402080

60100120046281012

OUTPUT CURRENT vs. TRANSMITTER

OUTPUT LOW VOLTAGE

OUTPUT LOW VOLTAGE (V)

O U T P U T C U R R E N T (m A )

032145678910-40

-15

85SHUTDOWN CURRENT vs. TEMPERATURE

M A X 13485-86E t o c 10

TEMPERATURE (°C)S H U T D O W N C U R R E N T (μA )

300

400350500450550600-4010-153560

85DRIVER PROPAGATION

vs. TEMPERATURE (MAX13485E)

TEMPERATURE (°C)D R I V E R P R O P A G A T I O N D E L A Y (n s )

105

20152530-4010-15356085

DRIVER PROPAGATION DELAY vs. TEMPERATURE (MAX13486E)

TEMPERATURE (°C)

D R I V

E R P R O P A G A T I O N D E L A Y (n s )

MAX13485E/MAX13486E

Typical Operating Characteristics (continued)

(V CC = +5V, T A = +25°C, unless otherwise noted.)

RECEIVER PROPAGATION vs. TEMPERATURE (MAX13485E)

TEMPERATURE (°C)

P R O P A G A T I O N D E L A Y (n s )

-15

800-40

RECEIVER PROPAGATION vs. TEMPERATURE (MAX13486E)

TEMPERATURE (°C)

R E C E I V E R P R O P A G A T I O N (n s )

-15

0-40

400ns/div

DRIVER PROPAGATION (500kbps)

(MAX13485E)

DI 2V/div

MAX13485/86E toc15

A-B 5V/div

10ns/div DRIVER PROPAGATION (16Mbps)

(MAX13486E)

DI 2V/div

MAX13485/86E toc16

A-B 5V/div 10ns/div

RECEIVER PROPAGATION (16Mbps)

(MAX13486E)

B 2V/div

MAX13485/86E toc17

RO 2V/div

A 2V/div

M A X 13485E /M A X 13486E

Figure 1. Driver DC Test Load Figure 2. Driver Timing Test Circuit

Figure 3. Driver Propagation Delays

Test Circuits and Waveforms

MAX13485E/MAX13486E

Figure 4. Driver Enable and Disable Times

Figure 6. Receiver Propagation Delay Test Circuit

Figure 5. Driver-Enable and -Disable-Timing Test Load Figure 7. Receiver Propagation Delays

Test Circuits and Waveforms (continued)

M A X 13485E /M A X 13486E

Pin Description

Function Tables

Test Circuits and Waveforms (continued)

MAX13485E/MAX13486E

Figure 8. Receiver Enable and Disable Times

M A X 13485E /M A X 13486E

Detailed Description

The MAX13485E/MAX13486E half-duplex, high-speed transceivers for RS-485/RS-422 communication contain one driver and one receiver. These devices feature fail-safe circuitry that guarantees a logic-high receiver out-put when receiver inputs are open or shorted, or when they are connected to a terminated transmission line with all drivers disabled (see the Fail-Safe section). The MAX13485E/MAX13486E also feature a hot-swap capa-bility allowing line insertion without erroneous data transfer (see the Hot-Swap Capability section). The MAX13485E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free trans-mission up to 500kbps. The MAX13486E driver slew rate is not limited, making transmit speeds up to 16Mbps possible.

Fail-Safe

The MAX13485E/MAX13486E guarantee a logic-high receiver output when the receiver inputs are shorted or open, or when they are connected to a terminated transmission line with all drivers disabled. This is done by setting the receiver input threshold between -50mV and -200mV. If the differential receiver input voltage (A - B) is greater than or equal to -50mV, RO is logic-high. If (A - B)is less than or equal to -200mV, RO is logic-low. In the case of a terminated bus with all transmitters disabled,the receiver ’s differential input voltage is pulled to 0V by the termination. With the receiver thresholds of the MAX13485E/MAX13486E, this results is a logic-high with a 50mV minimum noise margin. Unlike previous fail-safe devices, the -50mV to -200mV threshold complies with the ±200mV EIA/TIA-485 standard.

Hot-Swap Capability

Hot-Swap Inputs

When circuit boards are inserted into a hot or powered backplane, differential disturbances to the data bus can lead to data errors. Upon initial circuit-board inser-tion, the data communication processor undergoes its own power-up sequence. During this period, the processor ’s logic-output drivers are high impedance and are unable to drive the DE and RE inputs of these devices to a defined logic level. Leakage currents up to ±10μA from the high impedance state of the proces-sor ’s logic drivers could cause standard CMOS enable inputs of a transceiver to drift to an incorrect logic level.Additionally, parasitic circuit-board capacitance could cause coupling of V CC or GND to the enable inputs.Without the hot-swap capability, these factors could improperly enable the transceiver ’s driver or receiver.

When V CC rises, an internal pulldown circuit holds DE low and RE high. After the initial power-up sequence,the pulldown circuit becomes transparent, resetting the hot-swap tolerable input.

Hot-Swap Input Circuitry

The enable inputs feature hot-swap capability. At the input there are two nMOS devices, M1 and M2 (Figure 9). When V CC ramps from zero, an internal 7μs timer turns on M2 and sets the SR latch, which also turns on M1. Transistors M2, a 1.5mA current sink, and M1, a 500μA current sink, pull DE to GND through a 5k ?resistor. M2 is designed to pull DE to the disabled state against an external parasitic capacitance up to 100pF that can drive DE high. After 7μs, the timer deactivates M2 while M1 remains on, holding DE low against tri-state leakages that can drive DE high. M1 remains on until an external source overcomes the required input current. At this time, the SR latch resets and M1 turns off. When M1 turns off, DE reverts to a standard high-impedance CMOS input. Whenever V CC drops below 1V, the hot-swap input is reset.

For RE there is a complementary circuit employing two pMOS devices pulling RE to V CC .

Figure 9. Simplified Structure of the Driver Enable Pin (DE)

+15V ESD Protection

As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against electro-static discharges encountered during handling and assembly. The driver outputs and receiver inputs of the MAX13485E/MAX13486E have extra protection against static electricity. Maxim ’s engineers have developed state-of-the-art structures to protect these pins against ESD of ±15kV without damage. The ESD structures withstand high ESD in all states: normal operation, shut-down, and powered down. After an ESD event, the MAX13485E/MAX13486E keep working without latchup or damage.

ESD protection can be tested in various ways. The trans-mitter outputs and receiver inputs of the MAX13485E/MAX13486E are characterized for protection to the follow-ing limits:

?±15kV using the Human Body Model

?±15kV using the Air Gap Discharge Method specified in IEC 61000-4-2 (MAX13485E only)

ESD Test Conditions

ESD performance depends on a variety of conditions.Contact Maxim for a reliability report that documents test setup, test methodology, and test results.

Human Body Model

Figure 10a shows the Human Body Model, and Figure 10b shows the current waveform it generates when dis-charged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of inter-est, which is then discharged into the test device through a 1.5k ?resistor.

IEC 61000-4-2

The IEC 61000-4-2 standard covers ESD testing and performance of finished equipment. H owever, it does not specifically refer to integrated circuits. The MAX13485E/MAX13486E help equipment designs to meet IEC 61000-4-2, without the need for additional ESD-protection components.

The major difference between tests done using the Human Body Model and IEC 61000-4-2 is higher peak current in IEC 61000-4-2 because series resistance is lower in the IEC 61000-4-2 model. H ence, the ESD

MAX13485E/MAX13486E

Figure 10a. Human Body ESD Test Model

Figure 10b. Human Body Current Waveform

Figure 10c. ICE 61000-4-2 ESD Test Model

Figure 10d. IEC 61000-4-2 ESD Generator Current Waveform

M A X 13485E /M A X 13486E

withstand voltage measured to IEC 61000-4-2 is gener-ally lower than that measured using the H uman Body Model. Figure 10c shows the IEC 61000-4-2 model,and Figure 10d shows the current waveform for the IEC 61000-4-2 ESD Contact Discharge test.

Machine Model

The machine model for ESD tests all pins using a 200pF storage capacitor and zero discharge resistance.

The objective is to emulate the stress caused when I/O pins are contacted by handling equipment during test and assembly. Of course, all pins require this protec-tion, not just RS-485 inputs and outputs.

The air-gap test involves approaching the device with a charged probe. The contact-discharge method connects the probe to the device before the probe is energized.

Applications Information

128 Transceivers on the Bus

The standard RS-485 receiver input impedance is 12k ?(1-unit load), and the standard driver can drive up to 32-unit loads. The MAX13485E/MAX13486E have a 1/4-unit load receiver input impedance (48k ?), allowing up to 128 transceivers to be connected in parallel on one communication line. Any combination of these devices,as well as other RS-485 transceivers with a total of 32-unit loads or fewer, can be connected to the line.

Reduced EMI and Reflections

The MAX13485E features reduced slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 500kbps.

Low-Power Shutdown Mode

Low-power shutdown mode is initiated by bringing both RE high and DE low. In shutdown, the devices draw a maximum of 10μA of supply current.

RE and DE can be driven simultaneously. The devices are guaranteed not to enter shutdown if RE is high and DE is low for less than 50ns. If the inputs are in this state for at least 700ns, the devices are guaranteed to enter shutdown.

Enable times t ZH and t ZL (see the Switching Character-istics ) assume the devices were not in a low-power shut-down state. Enable times t ZH(SHDN)and t ZL(SHDN)assume the devices were in shutdown state. It takes dri-vers and receivers longer to become enabled from low-power shutdown mode (t ZH(SHDN), t ZL(SHDN)) than from driver-/receiver-disable mode (t ZH , t ZL ).

Line Length

The RS-485/RS-422 standard covers line lengths up to 4000ft.

Typical Applications

The MAX13485E/MAX13486E transceivers are designed for half-duplex, bidirectional data communi-cations on multipoint bus transmission lines. Figure 11shows typical network applications circuits. To mini-mize reflections, terminate the line at both ends in its characteristic impedance, and keep stub lengths off the main line as short as possible. The slew-rate-limited MAX13485E is more tolerant of imperfect termination.

Chip Information

PROCESS: BiCMOS

Figure 11. Typical Half-Duplex RS-485 Network

MAX13485E/MAX13486E Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,

go to https://www.wendangku.net/doc/e45026792.html,/packages.)

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,go to https://www.wendangku.net/doc/e45026792.html,/packages .)

M A X 13485E /M A X 13486E

M axim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a M axim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

16____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600