73K224BL
V.22bis, V.22, V.21, Bell 212A, 103
Single-Chip Modem w/ Integrated Hybrid
DATA SHEET
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
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
AEA Electronics’ “Autotest I” modem test set and line
simulator, operating under computer control. All tests
were run full-duplex, using a Concord Data Systems
224 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.
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.
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© 2005, 2008 TERIDIAN Semiconductor Corporation
Rev 7.1
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