±15kV ESD-Protected, Fail-Safe, 20Mbps, Slew-Rate-

Limited RS-485/RS-422 Transceivers in a SOT

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Detailed Description

The MAX3060E/MAX3061E/MAX3062E high-speed trans-

ceivers for RS-485/RS-422 communication contain one

driver and one receiver. These devices feature fail-safe

circuitry, which guarantees a logic-high receiver output

when the 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). All devices

have a hot-swap input structure that prevents distur-

bances on the differential signal lines when a circuit

board is plugged into a hot backplane (see the Hot-Swap

Capability section). The MAX3060E features a reduced

slew-rate driver that minimizes EMI and reduces reflec-

tions caused by improperly terminated cables, allowing

error-free data transmission up to 115kbps (see the

Reduced EMI and Reflections section). The MAX3061E is

also slew-rate limited, transmitting up to 500kbps. The

MAX3062E driver is not slew-rate limited, allowing trans-

mit speeds up to 20Mbps. The MAX3060E/MAX3061E/

MAX3062E are half-duplex transceivers.

All of these parts operate from a single +5V supply.

Drivers are output short-circuit current limited. Thermal-

shutdown circuitry protects drivers against excessive

power dissipation. When activated, the thermal-shut-

down circuitry places the driver outputs into a high-

impedance state.

Receiver Input Filtering

The receivers of the MAX3060E and MAX3061E incorpo-

rate input filtering in addition to input hysteresis. This fil-

tering enhances noise immunity with differential signals

that have very slow rise and fall times. Receiver propa-

gation delay increases by 2ns due to this filtering.

Fail-Safe

The MAX3060E family of devices guarantee a logic-high

receiver output when the receiver inputs are shorted or

open, or when they are connected to a terminated trans-

mission line with all drivers disabled. This is done by set-

ting the receiver 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 dis-

abled, the receiver’s differential input voltage is pulled to

0V by the termination. In the case of an unterminated bus

with all transmitters disabled, the receiver’s differential

input voltage is pulled to 0V by the receiver’s input resis-

tors. With the receiver thresholds of the MAX3060E fami-

ly, this results in a logic high output with a 50mV

minimum input noise margin. Unlike previous fail-safe

devices, the -50mV to -200mV threshold complies with

the ±200mV EIA/TIA-485 standard.

PIN

NAME

FUNCTION

1RO

Receiver Output. When RE is low and when A - B

≥ -50mV, RO is high; if A - B ≤ -200mV, RO is low. RO

is high impedance when RE is high.

2

RE

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. RE is a hot-swap input and reverts to a standard

CMOS input after the first low transition.

3DE

Driver Output Enable. Drive DE high to enable driver outputs. Driver outputs are high impedance when

DE is low. Drive RE high and DE low to enter low-power shutdown mode. DE is a hot-swap input and

reverts to a standard CMOS input after the first high transition.

4DI

Driver Input. With DE high, a low on DI forces the noninverting output low and the inverting output high.

Similarly, a high on DI forces the noninverting output high and the inverting output low.

5

GND

Ground

6

A

Noninverting Receiver Input and Noninverting Driver Output

7

B

Inverting Receiver Input and Inverting Driver Output

Positive Supply. Bypass with a 0.1µF capacitor to GND.

Pin Description