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Date: 03/28/05

SP3070E - SP3078E Family, ±15kV ESD-Protected, Failsafe RS-485/RS422 Transceivers

© Copyright 2005 Sipex Corporation

eration, shutdown, and powered down. After

an ESD event, the SP3070E - SP3078E keep

working without latchup or damage.

ESD protection can be tested in various ways.

The transmitter outputs and receiver inputs of

the SP3070E - SP3078E are characterized

for protection to the following limits:

■ ±15kV using the Human Body Model

■ ±8kV using the Contact Discharge

method specified in IEC 1000-4-2

■ ±15kV Airgap

ESD TEST CONDITIONS

ESD performance depends on a variety of

conditions. Contact Sipex for a reliability

report that documents test setup, method-

ology and results.

IEC 1000-4-2

The IEC 1000-4-2 standard covers ESD

testing and performance of finished equip-

ment. However, it does not specifically refer

to integrated circuits. The SP3070E family

of devices helps you design equipment to

meet IEC 1000-4-2, without the need for

additional ESD-protection components.

The major difference between tests done

using the Human Body Model and IEC 1000-

4-2 is higher peak current in IEC 1000-4-2,

because series resistance is lower in the

IEC 1000-4-2 model. Hence, the ESD with-

stand voltage measured to EC 1000-4-2 is

generally lower than that measured using

the human body model.

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.

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.

DETAILED DESCRIPTION

256 TRANSCEIVERS ON THE BUS

The standard RS-485 receiver input imped-

ance is 12kΩ (1 unit load), and the standard

driver can drive up to 32 unit loads. The

SP3070E family of transceivers has a 1/8-

unit load receiver input impedance (96Ω),

allowing up to 256 transceivers to be con-

nected 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 con-

nected to the line.

REDUCED EMI AND REFLECTIONS

The SP3070E, SP3071E and SP3072E fea-

ture reduced slew-rate drivers that minimize

EMI and reduce reflections caused by im-

properly terminated cables, allowing error-

free data transmission up to 250kbps. The

SP3073, SP3074 and SP3075 offer higher

driver output slew-rate limits, allowing trans-

mit speeds up to 500kbps.

LOW POWER SHUTDOWN MODE

Low-power shutdown mode is initiated by

bringing both RE high and DE low. In shut-

down, the devices typically draw only 50nA

of supply current.

RE and DE can be driven simultaneously;

the parts 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

600ns, the parts are guaranteed to enter

shutdown.

Enable times t

was not in a low-power shutdown state.

Enable times t

the parts were shut down. It takes drivers

and receivers longer to become enabled

from low-power shutdown mode t

ZH(SHDN)

and t

able mode (t