MAX3882 Maxim Integrated Products, MAX3882 Datasheet - Page 8

• Manufacturer Part Number: MAX3882
• Description: 2.488Gbps/2.67Gbps 1:4 Demultiplexer
• Manufacturer: Maxim Integrated Products

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The MAX3882 can operate at both OC-48 and OC-48
with FEC data rates. Select the data frequency using
the RATESET pin.
The fully integrated PLL has a second-order transfer
function, with a loop bandwidth (f
external capacitor between V
damping of the PLL. All jitter specifications are based
on the C
jitter transfer bandwidth does not change as the exter-
nal capacitor changes, but the jitter peaking, acquisi-
tion time, and loop stability are affected.
2.488Gbps/2.67Gbps 1:4 Demultiplexer with
Clock and Data Recovery and Limiting Amplifier
Figure 1. Definition of Input Voltage Swing
Figure 3. Definition of Clock-to-Q Delay
8
(PD+) - (PD-)
V
V
V
V
PCLK+
CC
CC
CC
CC
_______________________________________________________________________________________
+ 0.4V
- 0.4V
- 0.4V
- 0.8V
V
V
CC
CC
FIL
capacitor being 0.068µF. Note that the PLL
t
CK-Q
(b) DC-COUPLED SINGLE-ENDED INPUT
(a) AC-COUPLED SINGLE-ENDED INPUT
t
CK
Loop Filter and VCO
CC_
VCO Tuning Range
L
VCO and FIL sets the
800mV
800mV
) fixed at.1.7MHz. An
5mV
5mV
For an overdamped system (f
peaking (J
mated by:
The PLL zero frequency (f
capacitor (CFIL) and can be approximated according to:
Figures 6 and 7 show the open-loop and closed-loop
transfer functions. The PLL acquisition time is also
directly proportional to the external capacitor C
Figure 2. Relationship Between Control Voltage and Threshold
Voltage
Figure 4. LOL Assert Time and PLL Acquisition Time
Measurement
+188
+170
+152
-152
-170
-188
INPUT DATA
LOL OUTPUT
V
TH
(mV)
0.3
P
) of a second-order system can be approxi-
LOL ASSERT TIME
2.488Gbps PRBS 2
J
1.1
f
P
Z
= 20log(1 + f
= 1 / 2π(650)C
23
- 1
THRESHOLD-SETTING ACCURACY
(PART-TO-PART VARIATION OVER PROCESS)
Z
THRESHOLD-SETTING STABILITY
(OVER TEMPERATURE AND POWER SUPPLY)
) is a function of the external
1.3
Z
Z
/ f
/ f
FIL
L
L
) < 0.25, the jitter
2.1
)
2.488Gbps PRBS 2
ACQUISITION TIME
V
FIL
CTRL
23
.
(V)
- 1