+5V, Fail-Safe, 40Mbps, Profibus RS-485/

RS-422 Transceivers

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11

Applications Information

128 Transceivers on the Bus

The standard RS-485 receiver input impedance is 12k

Ω

(one unit load), and the standard driver can drive up to

32 unit loads. The MAX3465–MAX3469 family of trans-

ceivers has a 1/4-unit-load receiver input impedance

(48k

Ω), allowing up to 128 transceivers to be connect-

ed in parallel on one communication line. Any combina-

tion of these devices and/or other RS-485 transceivers

with a total of 32 unit loads or less can be connected to

the line.

Low-Power Shutdown Mode

(Except MAX3467)

Low-power shutdown mode is initiated by bringing

SHDN high (MAX3465/MAX3466), or both RE high and

DE low. In shutdown, the devices typically draw only

1µA of supply current. RE and DE can be driven simul-

taneously; the devices are guaranteed not to enter shut-

down if RE is high and DE is low for less than 50ns. If

the inputs are in this state for at least 800ns, the devices

are guaranteed to enter shutdown.

Driver Output Protection

Two mechanisms prevent excessive output current and

power dissipation caused by faults or by bus con-

tention. The first, a foldback current limit on the output

stage, provides immediate protection against short cir-

cuits over the whole common-mode voltage range (see

the Typical Operating Characteristics). The second, a

thermal-shutdown circuit, forces the driver outputs into

a high-impedance state if the die temperature exceeds

+140°C.

Propagation Delay

Many digital encoding schemes depend on the difference

between the driver and receiver propagation delay times.

Typical propagation delays are shown in the Typical

Operating Characteristics. The difference in receiver delay

Typical Applications

The MAX3465–MAX3469 transceivers are designed for

bidirectional data communications on multipoint bus

transmission lines. Figures 13 and 14 show typical net-

work applications circuits. To minimize reflections, the

line should be terminated at both ends in its character-

istic impedance, and stub lengths off the main line

should be kept as short as possible.

Profibus Termination

The MAX3465–MAX3469 are designed for driving

Profibus termination networks. With a worst-case load-

ing of two termination networks with 220

Ω termination

impedance and 390

Ω pullups and pulldowns, the dri-

Chip Information

TRANSISTOR COUNT: 610

PROCESS: BiCMOS

ATE

RECEIVER

OUTPUT

B

A

R

Figure 12. Receiver Propagation Delay Test Circuit

Ordering Information (continued)

PART

TEMP RANGE

PIN-PACKAGE

MAX3466CSD

0°C to +70°C

14 SO

MAX3466CPD

0°C to +70°C

14 Plastic DIP

MAX3466ESD

-40°C to +85°C

14 SO

MAX3466EPD

-40°C to +85°C

14 Plastic DIP

MAX3467CSA

0°C to +70°C

8 SO

MAX3467CPA

0°C to +70°C

8 Plastic DIP

MAX3467ESA

-40°C to +85°C

8 SO

MAX3467EPA

-40°C to +85°C

8 Plastic DIP

MAX3468CSA

0°C to +70°C

8 SO

MAX3468CPA

0°C to +70°C

8 Plastic DIP

MAX3468ESA

-40°C to +85°C

8 SO

MAX3468EPA

-40°C to +85°C

8 Plastic DIP

MAX3469CSA

0°C to +70°C

8 SO

MAX3469CPA

0°C to +70°C

8 Plastic DIP

MAX3469ESA

-40°C to +85°C

8 SO

MAX3469EPA

-40°C to +85°C

8 Plastic DIP