Detailed Description

The MAX3280E/MAX3281E/MAX3283E/MAX3284E are

single, true fail-safe receivers designed to operate at

data rates up to 52Mbps. The fail-safe architecture guar-

antees a high output signal if both input terminals are

open or shorted together. See the True Fail-Safe section.

This feature assures a stable and predictable output

logic state with any transmitter driving the line. These

receivers function with a 3.3V or 5V supply voltage and

feature excellent propagation delay times (15ns).

The MAX3280E is a single receiver available in a 5-pin

SOT23 package. The MAX3281E (EN, active high) and

MAX3283E (EN, active low) are single receivers that

also contain an enable pin. Both the MAX3281E and

MAX3283E are available in a 6-pin SOT23 package.

pin, which allows communication with low-level logic

included in digital FPGAs. The MAX3284E is available

in a 6-pin SOT23 package.

The MAX3284E’s low-level logic application allows

users to set the logic levels. A logic high level of 1.65V

will limit the maximum data rate to 20Mbps.

±15kV ESD Protection

ESD-protection structures are incorporated on the

receiver input pins to protect against ESD encountered

during handling and assembly. The MAX3280E/

MAX3281E/MAX3283E/MAX3284E receiver inputs (A,

B) have extra protection against static electricity found

in normal operation. Maxim’s engineers developed

state-of-the-art structures to protect these pins against

±15kV ESD without damage. After an ESD event, this

family of parts continues working without latchup.

ESD protection can be tested in several ways. The

receiver inputs are characterized for protection to the

following:

• ±15kV using the Human Body Model

• ±6kV using the Contact Discharge method specified

in IEC 1000-4-2 (formerly IEC 801-2)

• ±12kV using the Air-Gap Discharge method speci-

fied in IEC 1000-4-2 (formerly IEC 801-2)

ESD Test Conditions

ESD performance depends on a number of conditions.

Contact Maxim for a reliability report that documents

test setup, methodology, and results.

Human Body Model

Figure 3a shows the Human Body Model, and Figure

3b 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 device through a

1.5k

Ω resistor.

IEC 1000-4-2

Since January 1996, all equipment manufactured

and/or sold in the European community has been

required to meet the stringent IEC 1000-4-2 specifica-

tion. The IEC 1000-4-2 standard covers ESD testing

and performance of finished equipment; it does not

specifically refer to integrated circuits. The

MAX3280E/MAX3281E/MAX3283E/MAX3284E help

±15kV ESD-Protected 52Mbps, 3V to 5.5V, SOT23

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

_______________________________________________________________________________________

5

Pin Description

PIN

MAX3280E

MAX3281E

MAX3283E

MAX3284E

NAME

FUNCTION

111

1

Positive Supply: 3V

capacitor to GND.

2

2

2

2

GND

Ground

333

3

RO

Receiver Output. RO will be high if (A–B)

≥ -50mV. RO will be

low if (A–B)

≤ -200mV.

4

4

4

4

B

Inverting Receiver Input

——

5

—

EN

Receiver Output Enable. Drive EN low to enable RO. When EN

is high, RO is high impedance.

—

5

——

EN

Receiver Output Enable. Drive EN high to enable RO. When

EN is low, RO is high impedance.

———

5

6

6

6

A

Noninverting Receiver Input