Datasheet

AD9557 Data Sheet
Rev. B | Page 8 of 92
REFERENCE MONITORS
Table 8.
Parameter Min Typ Max Unit Test Conditions/Comments
REFERENCE MONITORS
Reference Monitor
Loss of Reference Detection Time 1.1 DPLL PFD
period
Nominal phase detector period = R/f
REF
0F0F
1
Frequency Out-of Range Limits <2 10
5
Δf/f
REF
(ppm)
Programmable (lower bound is subject to quality
of the system clock (SYSCLK)); SYSCLK accuracy
must be better than the lower bound
Validation Timer
0.001 65.535 sec Programmable in 1 ms increments
1
f
REF
is the frequency of the active reference; R is the frequency division factor determined by the R divider.
REFERENCE SWITCHOVER SPECIFICATIONS
Table 9.
Parameter Min Typ Max Unit Test Conditions/Comments
REFERENCE SWITCHOVER SPECIFICATIONS
Maximum Output Phase Perturbation
(Phase Build-Out Switchover)
Assumes a jitter-free reference; satisfies
Telcordia GR-1244-CORE requirements; select
high PM base loop filter bit (Register 0x070E, Bit 0)
is set to 1 for all active references
50 Hz DPLL Loop Bandwidth Valid for automatic and manual reference
switching
Peak
0
±100
ps
Steady State 0 ±100 ps
2 kHz DPLL Loop Bandwidth
Valid for automatic and manual reference
switching
Peak 0 ±250 ps
Steady State 0 ±100 ps
Time Required to Switch to a New Reference
Phase Build-Out Switchover 1.1 DPLL PFD
period
Calculated using the nominal phase detector
period (NPDP = R/f
REF
); the total time required is
equal to the time plus the reference validation
time and the time required to lock to the new
reference