参数资料
型号: SI5017-EVB
厂商: Silicon Laboratories Inc
文件页数: 2/12页
文件大小: 0K
描述: BOARD EVALUATION FOR SI5017
标准包装: 1
主要目的: 计时,时钟和数据恢复(CDR)
已用 IC / 零件: SI5017
已供物品:
其它名称: 336-1125
Si5017-EVB
Functional Description
The evaluation board simplifies characterization of the
Si5017 Clock and Data Recovery (CDR) device by
providing access to all of the Si5017 I/Os. Device
performance can be evaluated by following the “Test
Configuration” section. Specific performance metrics
include input sensitivity, jitter tolerance, jitter generation,
and jitter transfer.
Power Supply
The evaluation board requires one 3.3 V supply. Supply
When applied, REFCLK is used to center the frequency
of the DSPLL? so the device can lock to the data.
Ideally, the REFCLK frequency should be 1/128th,
1/32nd, or 1/16th the VCO frequency and must have a
frequency accuracy of ±100 ppm. Internally, the CDR
automatically recognizes the REFCLK frequency within
one of these three frequency ranges. Typical REFCLK
frequencies are given in Table 1. REFCLK is ac coupled
to the SMA jacks located on the top side of the
evaluation board.
Table 1. Typical REFCLK Frequencies
filtering is placed on the board to filter typical system
noise components; however, initial performance testing
should use a linear supply capable of supplying the
nominal voltage ±5% dc.
CAUTION : The evaluation board is designed so that the
body of the SMA jacks and GND are shorted. Care must
be taken when powering the PCB at potentials other
than GND at 0.0 V and VDD at 3.3 V relative to chassis
SONET/SDH
19.44 MHz
77.76 MHz
155.52 MHz
SONET/SDH
with
15/14 FEC
20.83 MHz
83.31 MHz
166.63 MHz
Ratio of
VCO to
REFCLK
128
32
16
V LOS = ---------------------------------------
GND.
Device Powerdown
The CDR can be powered down via the RESET/CAL
signal. When asserted, the evaluation board draws
minimal current. RESET/CAL is controlled via one
jumper located in the lower left-hand corner of the
evaluation board. RESET/CAL is wired to the signal
post adjacent to the VDD post. For a valid reset to occur
when using external reference clock mode, a proper
external reference clock frequency must be applied as
specified in Table 1. CLKOUT, DATAOUT, DATAIN
CLKOUT, DATAOUT, and DATAIN (all high-speed I/Os)
are wired to the board perimeter on 30 mil (0.030 inch)
50 ? microstrip lines to the end-launch SMA jacks as
labeled on the PCB. These I/Os are ac coupled to
simplify direct connection to a wide array of standard
test hardware. Because each of these signals are
differential, both the positive (+) and negative (–)
terminals must be terminated to 50 ? . Terminating only
one side will adversely degrade the performance of the
CDR. The inputs are terminated on the die with 50 ?
resistors.
Note: The 50 ? termination is for each terminal/side of a dif-
ferential signal, thus the differential termination is actu-
ally 50 ? + 50 ? = 100 ? .
REFCLK
REFCLK is optional for clock and data recovery within
the Si5017 device. If REFCLK is not used, jumper both
JP15 and JP16. These jumpers pull the REFCLK+ input
to VDD and REFCLK– input to GND, which configures
the device to operate without an external reference.
Loss-of-Lock (LOL)
Loss-of-lock (LOL) is an indicator of the relative
frequency between the data and the REFCLK. LOL
asserts when the frequency difference is greater than
±600 ppm. To prevent LOL from de-asserting
prematurely, there is hysterisis in returning from the out-
of-lock condition. LOL will be de-asserted when the
frequency difference is less than ±300 ppm.
LOL is wired to a test point which is located on the
upper right-hand side of the evaluation board.
Loss-of-Signal Alarm Threshold Control
The loss-of-signal alarm (LOS) is used to signal low
incoming data amplitude levels. The programmable
threshold control is set by applying a dc voltage level
from a low noise voltage source to the LOS_LVL pin.
The LOS_LVL is controllable through the BNC jack J10.
The mapping of the LOS_LVL voltage to input signal
alarm threshold level is shown in Figure 1. The LOS
Threshold to LOS Level is mapped as follows:
V LOS_LVL – 1.5
25
If this function is not used, install jumper to JP1 header.
2
Rev. 1.0
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