SSM2142

–6–

REV. B

THE CABLE PAIR

The SSM2142 is capable of driving a 10 V rms signal into

600

Ω and will remain stable despite cable capacitances of up to

0.16

µF in either balanced or single-ended configurations. Low

impedance shielded audio cable such as the standard Belden

8451 or similar is recommended, especially in applications

traversing considerable distances. The user is cautioned that the

so-called “audiophile” cables may incur four times the capac-

itance per unit length of the standard industrial-grade product.

In situations of extreme load and/or distance, adding a second

parallel cable allows the user to trade off half of the total line

resistance against a doubling in capacitive load.

SINGLE-ENDED OPERATION

The SSM2142 is designed to be compatible with existing

balanced-pair interface systems. Just as in transformer-based

circuits, identical but opposite currents are generated by the

output pair which can be ground-referenced if desired and

transmitted on a single wire. Single-ended operation requires

that the unused side of the output pair be grounded to a solid

return path in order to avoid voltage offset errors at the nearby

input common. The signal quality obtained in these systems is

directly dependent on the quality of the ground at each end of

the wire. Also note that in single-ended operation the gain

through the device is still 6 dB, and that the SSM2142 incurs

no significant degradation in signal distortion or output drive

capability, although the noise rejection inherent in balanced-

pair systems is lost.

POWER SUPPLY SEQUENCING

A problem occasionally encountered in the interface system en-

vironment involves irregular application of the supplies. The

user is cautioned that applying power erratically can inadvert-

ently bias parts of the circuit into a latch-up condition. The

small geometries of an integrated circuit are easily breached and

damaged by short-risetime spikes on a supply line, which usu-

ally demonstrate considerable overshoot. The questionable

practice of exchanging components or boards while under

power can create such an undesirable sequence as well. Possible

options which offer improved board-level device protection

include: additional bypass capacitors, high-current reverse-

biased steering diodes between both supplies and ground, vari-

ous transient surge suppression devices, and safety grounding

connectors.

Likewise, power should be applied to the device before the

output is connected to “live” systems which may carry voltages

of sufficient magnitude to turn on the output devices of the

SSM2142 and damage the device. In any case, of course, the

user must always observe the absolute maximum ratings shown

in the specifications.

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

8-Lead Plastic DIP

0.160 (4.06)

0.115 (2.92)

0.130

(3.30)

MIN

0.210

(5.33)

MAX

0.015

(0.381) TYP

0.430 (10.92)

0.348 (8.84)

0.280 (7.11)

0.240 (6.10)

4

5

8

1

0.070 (1.77)

0.045 (1.15)

0.022 (0.558)

0.014 (0.356)

0.325 (8.25)

0.300 (7.62)

0 - 15

0.100

(2.54)

BSC

0.015 (0.381)

0.008 (0.203)

SEATING

PLANE

8-Lead Cerdip

0.005 (0.13) MIN

0.055 (1.35) MAX

0.405 (10.29) MAX

0.150

(3.81)

MIN

0.200

(5.08)

MAX

0.310 (7.87)

0.220 (5.59)

0.070 (1.78)

0.030 (0.76)

0.200 (5.08)

0.125 (3.18)

0.023 (0.58)

0.014 (0.36)

0.320 (8.13)

0.290 (7.37)

0 - 15

0.015 (0.38)

0.008 (0.20)

0.100 (2.54)

BSC

SEATING PLANE

0.060 (1.52)

0.015 (0.38)

4

1

5

8

16-Lead Small Outline (SOIC)

SEATING

PLANE

0.2992 (7.60)

0.2914 (7.40)

0.4193 (10.65)

0.3937 (10.00)

0.1043 (2.65)

0.0926 (2.35)

0.0118 (0.30)

0.0040 (0.10)

0.4133 (10.50)

0.3977 (10.10)

0.0192 (0.49)

0.0138 (0.35)

0.0500

(1.27)

BSC

0.0500 (1.27)

0.0157 (0.40)

0 - 8

9

16

1

8

SEE

DETAIL

ABOVE

0.0125 (0.32)

0.0091 (0.23)

0.0291 (0.74)

0.0098 (0.25) x 45