73K324BL
CCITT V.22bis,V.23,V.22,V.21, Bell 212A
Single-Chip Modem w/ Integrated Hybrid
DATA SHEET
To accomplish this, high speed digital devices should
be locally bypassed, and the telephone line interface
and K-Series device should be located close to each
other near the area of the board where the phone line
connection is accessed. To avoid problems, power
supply and ground traces should be routed separately
to the analog and digital functions on the board, and
digital signals should not be routed near low level or
high impedance analog traces. The analog and digital
grounds should only connect at one point near the K-
Series device ground pin to avoid ground loops. The
K-Series modem ICs should have both high frequency
and low frequency bypassing as close to the package
as possible.
BER VS. S/N
This test measures the ability of the modem to
operate over noisy lines with a minimum of data-
transfer errors. Since some noise is generated in
the best of dial-up lines, the modem must operate
with the lowest S/N ratio possible. Better modem
performance is indicated by test curves that are
closest to the BER axis. A narrow spread between
curves representing the four line parameters
indicates minimal variation in performance while
operating over a range of operating conditions.
Typically, a DPSK modem will exhibit better BER
performance test curves receiving in the low band
than in the high band.
MODEM PERFORMANCE
CHARACTERISTICS
BER VS. RECEIVE LEVEL
This test measures the dynamic range of the
modem. Because signal levels vary widely over
dial-up lines, the widest possible dynamic range is
desirable. The minimum Bell specification calls for
36 dB of dynamic range. S/N ratios are held
constant at the indicated values while the receive
level is lowered from a very high to very low signal
levels. The width of the “bowl” of these curves,
taken at the BER point, is the measure of dynamic
range.
The curves presented here define modem IC
performance under a variety of line conditions while
inducing disturbances that are typical of those
encountered during data transmission on public
service telephone lines. Test data was taken using an
TAS “1200” modem test set and line simulator,
operating under computer control. All tests were run
full-duplex, using a standard off-the-shelf modem as
the reference modem. A 511 pseudo-random-bit
pattern was used for each data point. Noise was C-
message weighted and all signal-to-noise (S/N) ratios
reflect total power measurements similar to the CCITT
V.56 measurement specification. The individual tests
are defined as follows.
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© 2005, 2008 TERIDIAN Semiconductor Corporation
Rev 6.1
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