To meet this
specification, a PLL in holdover must meet the requirements in Table 7-1
(Table 15 in the G.8262 specification). The procedure for this test
is that the DUT obtains lock from IN0, which contains a valid input
clock. Then the input is switched to IN1, which contains no valid
input, thus entering holdover and remains in holdover for the
remainder of the test. The LMK5C33216 met this specification. The
TIE plot shown in Figure 7-2
demonstrates compliance to the standard in green.
Table 7-1 Transient
Response Specifications During Holdover | EEC Option 2 |
---|
Applies For | S > TBD(6) |
a1 (ns/s)(1) | 50 |
a2 (ns/s)(2) | 300 |
b (ns/s2)(3) | 4.63 × 10-4 |
c (ns)(4) | 1000 |
d (ns/s2)(5) | 4.63 × 10-4 |
(1) a1 represents an initial
frequency offset under constant temperature conditions (±1
K)
(2) a2 accounts for temperature
variations after the clock went into holdover. If there are
no temperature variations, the term
a2S should not contribute
to the phase error.
(3) b represents the average frequency drift
caused by aging. This value is derived from typical aging
characteristics after 60 days of continuous operation. It is
not intended to measure this value on a per day basis, as
the temperature effect will dominate.
(4) The phase offset c takes care of any
additional phase shift that may arise during the transition
at the entry of the holdover state.
(5) d represents the maximum temporary
frequency drift rate at constant temperature allowed during
holdover. However, it is not required that d and
b be equal.
(6) TBD: To be defined.