SLK2701

OC48/24/12/3 SONET/SDH MULTIRATE TRANSCEIVER

SLLS518 − DECEMBER 2001

10

POST OFFICE BOX 655303

jitter tolerance (continued)

f0

f1

f2

f3

f4

Frequency − Hz

A3

A2

A1

Slope = −20 dB / Decade

Slope = −20 dB / Decade

OC-N/STS-N

LEVEL

f0

(Hz)

F1

(Hz)

F2

(Hz)

F3

(kHz)

F4

(kHz)

A1

(Ulpp)

A2

(Ulpp)

A3

(Ulpp)

3

10

30

300

6.5

65

0.15

1.5

15

12

10

30

300

25

250

0.15

1.5

15

24

Not specified

48

10

600

6000

100

1000

0.15

1.5

15

Figure 3. Input Jitter Tolerance

jitter generation

no jitter is presented to the inputs. The measurement bandwidth for intrinsic jitter is 12 kHz to 20 MHz.

loop timing mode

When LOOPTIME is high, the clock synthesizer used to serialize the transmit data is bypassed and the timing

is provided by the recovered clock. However, REFCLK is still needed for the recovery loop operation.

loss-of-lock indicator

The SLK2701 device has a lock detection circuit to monitor the integrity of the data input. When the clock

recovery loop is locked to the input serial data stream, the LOL signal goes high. If the recovered clock frequency

deviates from the reference clock frequency by more than 100 ppm, LOL goes low. If the data stream clock rate

deviates by more than 170 ppm, loss of lock occurs. If the data streams clock rate deviates more than 500 ppm

from the local reference clock, the LOL output status might be unstable. Upon power up, the LOL goes low until

the PLL is close to phase lock with the local reference clock.

loss of signal

The loss-of-signal (LOS) alarm is set high when no transitions appear in the input data path for more than 2.3

µs.

The LOS signal becomes active when the above condition occurs. If the serial inputs of the device are

ac-coupled to its source, the ac-coupling capacitor needs to be big enough to maintain a signal level above the

threshold of the receiver for the 2.3-

µs no transition period. Once activated, the LOS alarm pin is latched high

until the receiver detects an A1A2 pattern. The recovered clock (RXCLK) is automatically locked to the local

reference when LOS occurs. The parallel data (RXDATAx) may still be processed even when LOS is activated.