AN-05 [ETC]
SY69952 in an OC-3 Transmission System ; SY69952在OC- 3传输系统\n
| 型号： | AN-05 |
| 厂家： | 
ETC |
| 描述： | SY69952 in an OC-3 Transmission System
|
| 文件： | 总6页 (文件大小：63K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SY69952 IN AN OC-3
TRANSMISSION SYSTEM
APPLICATION NOTE
AN-05
Introduction
General Requirements
The SY69952 Serial Transceiver is used in SONET/SDH
and ATM applications to recover clock and data information
from a 155.52MHz or 51.84MHz NRZ (Non Return to Zero)
or NRZI (Non Return to Zero Invert on ones) serial data
stream. This device also provides a bit rate Transmit clock,
from a byte rate source through the use of a frequency
multiplier PLL, and differential data buffering for the Transmit
side of the system. This device is compliant with all relevant
SONET/SDH specifications including ANSI T1X1.6/91-022,
ANSI T1X1.3/93-006R1 Draft and ITU/CCITT G958.
For optimum performance of SY69952, loop filter networks
are required. The loop filter network can be achieved using
very few low cost external components. The purpose of the
loop filter network is to minimize jitter characteristics of the
device. In addition, proper power supply filtering techniques
can also minimize jitter and matched impedance techniques
should be used to maximize operating frequency and
minimize wave-form distortion.
FORMULAS FOR CALCULATION OF CONTROLLED IMPEDANCE RUNS
Microstrip Stripline
Ref. Plane
(Ground)
Dielectric
Height H
W
W
T
T
Dielectric
Height H
Ref. Plane (Ground)
Ref. Plane
(Ground)
1/2
Place Conductor
Center at H/2
Figure 1
Figure 2
Requirements: W/(H-T)<0.35 AND T/H<0.25
60
87
5.98 H
0.8 W + T
4H
Ln
Ln
0.536πW + 0.67πT
Er + 1.41
Er
H is the height of the Dielectric to the Ground (Ref. Plane)
W is the Trace Width (Design Variable)
H is the height of the Dielectric to the Ground (Ref. Plane)
W is the Trace Width (Design Variable)
Er is the Dielectric Constant –
Er is the Dielectric Constant –
Consult with your Board Fabrication House (4.4 Typical)
Consult with your Board Fabrication House (4.4 Typical)
T is the thickness of the run –
T is the thickness of the run –
Consult with your Board Fabrication House (Typically 0.0022 with
Plating)
Consult with your Board Fabrication House (Typically 0.0022 with
Plating)
Rev.: C
Amendment:/0
Issue Date: June, 1998
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APPLICATION NOTE
AN-05
Micrel
PIN DEFINITIONS
Pin
Pin No.
Type
Description
If Unused NC or VCC. Route away from TX, & Digital Runs.(1)
If Unused NC or VCC. Route away from TX, & Digital Runs.(1)
Route away from TX, & Digital Runs.(1)
ROUT+
ROUT–
RIN+
RIN–
1
2
3
4
5
6
Receive
Receive
Receive
Receive
Control
Power
Route away from TX, & Digital Runs.(1)
MODE
VCC
No/LOW Frequency Switching.
Isolation from system supply. Decouple with RF beads (or inductor or common mode
chokes), NPO/COG ceramic and tantalum caps.(2)
CD
7
8
Control
Control
LOW Frequency Switching. Routing should avoid noisy areas so run is not conduit. Use
common mode choke to isolate.(2)
LOOP
No/LOW Frequency Switching. Routing should avoid noisy areas so run is not a conduit.
Use common mode choke to isolate.(2)
REFCLK–
REFCLK+
TOUT–
9
Reference
Reference
Transmit
Transmit
Transmit
Route away from TX, & Digital Runs.(1)
Route away from TX, & Digital Runs.(1)
Route away from TX, & Digital Runs.(1)
Route away from TX, & Digital Runs.(1)
10
11
12
13
TOUT+
PLL1+
Place filter components next to IC. Do not route any signal near or beneath these pins or
the TX filter connected to them. Use a ground guard around the filter components to
collapse fields.
PLL1–
PLL2–
PLL2+
14
15
16
Transmit
Receive
Receive
Place filter components next to IC. Do not route any signal near or beneath these pins or
the TX filter connected to them. Use a ground guard around the filter components to
collapse fields.
Place filter components next to IC. Do not route any signal near or beneath these pins or
the TX filter connected to them. Use a ground guard around the filter components to
collapse fields.
Place filter components next to IC. Do not route any signal near or beneath these pins or
the TX filter connected to them. Use a ground guard around the filter components to
collapse fields.
TSER–
TSER+
TCLK+
TCLK–
VCC
17
18
19
20
21
Transmit
Transmit
Transmit
Transmit
Power
Route away from Receiver runs.(1)
Route away from Receiver runs.(1)
Route away from Receiver runs.(1)
Route away from Receiver runs.(1)
Isolation from system supply. Decouple with RF beads (or inductor or common mode
chokes), NPO/COG ceramic and tant caps.(2)
VEE (GND)
VCC
22
23
24
Ground
Power
Alarm
Tie to system ground. If the system GND is noisy then isolation from system GND with RF
bead (or inductor or common mode choke). Ensure adequate current capacity.(2)
Isolation from system supply. Decouple with RF beads (or inductor or common mode
chokes), NPO/COG ceramic and tant caps.(2)
LFI
LOW Frequency Switching. Routing should avoid noisy areas so run is not conduit. Use
common mode choke to isolate.(2)
2
APPLICATION NOTE
AN-05
Micrel
PIN DEFINITIONS (Continued)
Pin
Pin No.
25
Type
Description
Route away from TX, & Digital Runs.(1)
RSER+
RSER–
RCLK+
RCLK–
Receive
Receive
Receive
Receive
26
Route away from TX, & Digital Runs.(1)
Route away from TX, & Digital Runs.(1)
Route away from TX, & Digital Runs.(1)
27
28
NOTES:
1. a) These runs are to be held to an impedance of 50Ω. See Microstrip or Stripline above. Parallel Termination 130/82Ω shall be placed at their
destinations; b) Runs must be of equal length to their corresponding differential counterpart. For example: RSER+ is equal to RSER–, RCLK+ is equal
to RCLK–, etc.; c) These pairs must experience the same terrain of the PWB; d) Runs shall be constant distance to ground throughout their route. This
will reduce crosstalk; e) Transmit runs shall be separated from receive runs.
2. Effective use of Common Mode Chokes or RF Beads dictate the following rules: a) Single Ended Signals shall utilize one half and the other should be
connected to Grounds. This recommendation includes VCC. For this application ensure the Choke's )or RF Bead's) Max. Impedance is below the
Fundamental (First) Harmonic; b) Differential Signals would have the positive signal on one half and the negative signal on the other. For this application
ensure the Choke's max. Impedance is beyond the third harmonic. Failure to do so will result in sinusoidal waveforms instead of square waveforms. RF
Beads are NOT recommended for this application; c) Separation of Grounds would have noisy ground on both of the inputs and clean (Analog or Receive)
Ground on both of the outputs. For this application ensure the Choke's (or RF Bead's) Max. Impedance is below the Fundamental (First) Harmonic.
LAYOUT RECOMMENDATIONS (OPTIONAL)
The layout in figure 3 shows a typical configuration for very dense systems. The emphasis is on the loop filters PLL1
and PLL2 which are surrounded by a ground guard plane to reduce electromagnetic interference.
SY69952
Receiver Inputs
Receiver Outputs
to UNI
V
CC/Control
Alarm/VCC/Ground
Transmit
Outputs to Optics or
Cable Interface
Transmit Interface
to UNI
Ground
Guard
Transmit Filter
(PLL1)
Receive Filter
(PLL2)
Figure 3
3
APPLICATION NOTE
AN-05
Micrel
LOOP FILTER ADJUSTMENT
This section is ONLY applicable if initial values of external
loop filters need to be adjusted for tuning the SY69952 to a
layout or for customer's desired jitter response. R1 and C1
control response to Lower and Mid Range Modulation
Frequencies. And C2 (optional) controls the the response
to High Range Modulation Frequencies.
C1
C3
R1
Figure 4
Transmit Filter Recommended Values:
PLL1+, Pin 13, C1 = 0.1µF,
Receive Filter Recommended Values:
PLL2+, Pin 16, C1 = 0.1µF,
PLL1–, Pin 14, R1 = 500Ω,
PLL2–, Pin 15, R1 = 120Ω,
Optional PLL1+ and PLL1–, C2 = 47pF
Optional PLL2+ and PLL2–, C2 = 47pF
If Jitter Amplitude response adjustment is required the
following is an explanation of typical Loop Filter
characteristics.
Jitter
Gain
(dB)
C2
0.1
R1, Then C1
-20db/decade
Acceptable
Range
-20
130kHz
Frequency
Figure 5
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APPLICATION NOTE
AN-05
Micrel
CONFIGURATION LAYOUT WITH SPLIT POWER SUPPLY
5
APPLICATION NOTE
AN-05
Micrel
MICREL-SYNERGY 3250 SCOTT BOULEVARD SANTA CLARA CA 95054 USA
TEL + 1 (408) 980-9191 FAX + 1 (408) 914-7878 WEB http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 2000 Micrel Incorporated
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