Cirrus Logic CS61884 - Manual (Page 53)

CS61884
DS485F3 53
18.1 Transformer specifications
Recommended transformer specifications are
shown in
Table 12 . Any transformer used with the
CS61884 should meet or exceed these specifica-
tions.
18.2 Crystal Oscillator Specifications
When a reference clock signal is not available, a
CMOS crystal oscillator may be used as the refer-
ence clock signal. The oscillator must have a mini-
mum symmetry of 40-60% and minimum stability
of + 100ppm for both E1 and T1/J1 applications.
18.3 Designing for AT&T 62411
For information on requirements of the AT&T
62411 and the design of the appropriate system
synchronizer, refer to Application Note AN012
“AT&T 62411 Design Considerations - Jitter and
Synchronization” and Application Note AN011
“Jitter Testing Procedures for Compliance with
AT&T 62411”.
18.4 Line Protection
Secondary protection components can be added to
the line interface circuitry to provide lightning
surge and AC power-cross immunity. For addition-
al information on the different electrical safety
standards and specific applications circuit recom-
mendations, refer to Application Note AN034
“Secondary Line Protection for T1 and E1 Cards”.
Table 12. Transformer Specifications
Descriptions Specifications
Turns Ratio Receive/Trans-
mit 1:2
Primary Inductance 1.5mH min. @ 772 kHz
Primary Leakage Induc-
tance 0.3
μH max @ 772 kHz
Secondary leakage Induc-
tance 0.4
μH max @ 772 kHz
Inter winding Capacitance 18pF max, primary to
secondary
ET-Constant 16V -
μs min.