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SY69952 IN AN OC-3 TRANSMISSION SYSTEM
Introduction
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.
APPLICATION NOTE AN-05
General Requirements
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
W T T Ref. Plane (Ground) W
Stripline
Dielectric Height H
Dielectric Height H Ref. Plane (Ground) 1/2 Place Conductor Center at H/2
Figure 2
Ref. Plane (Ground)
Figure 1
Requirements: W/(H-T)<0.35 AND T/H<0.25
87 Er + 1.41 Ln 5.98 H 0.8 W + T
60 Er
Ln
4H 0.536W + 0.67T
H is the height of the Dielectric to the Ground (Ref. Plane) W is the Trace Width (Design Variable) Er is the Dielectric Constant - Consult with your Board Fabrication House (4.4 Typical) T is the thickness of the run - Consult with your Board Fabrication House (Typically 0.0022 with Plating)
H is the height of the Dielectric to the Ground (Ref. Plane) W is the Trace Width (Design Variable) Er is the Dielectric Constant - Consult with your Board Fabrication House (4.4 Typical) T is the thickness of the run - Consult with your Board Fabrication House (Typically 0.0022 with Plating)
Rev.: C
Amendment: /0
1
Issue Date: June, 1998
Micrel
APPLICATION NOTE AN-05
PIN DEFINITIONS
Pin ROUT+ ROUT- RIN+ RIN- MODE VCC CD LOOP REFCLK- REFCLK+ TOUT- TOUT+ PLL1+ Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 Type Receive Receive Receive Receive Control Power Control Control Reference Reference Transmit Transmit Transmit 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) Route away from TX, & Digital Runs.(1) 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) LOW Frequency Switching. Routing should avoid noisy areas so run is not conduit. Use common mode choke to isolate.(2) No/LOW Frequency Switching. Routing should avoid noisy areas so run is not a conduit. Use common mode choke to isolate.(2) 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) 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. 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. 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) 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) LOW Frequency Switching. Routing should avoid noisy areas so run is not conduit. Use common mode choke to isolate.(2)
PLL1-
14
Transmit
PLL2-
15
Receive
PLL2+
16
Receive
TSER- TSER+ TCLK+ TCLK- VCC VEE (GND) VCC LFI
17 18 19 20 21 22 23 24
Transmit Transmit Transmit Transmit Power Ground Power Alarm
2
Micrel
APPLICATION NOTE AN-05
PIN DEFINITIONS (Continued)
Pin RSER+ RSER- RCLK+ RCLK- Pin No. 25 26 27 28 Type Receive Receive Receive Receive Description 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)
NOTES: 1. a) These runs are to be held to an impedance of 50. See Microstrip or Stripline above. Parallel Termination 130/82 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 Alarm/VCC/Ground
VCC/Control
Transmit Outputs to Optics or Cable Interface
Transmit Interface to UNI
Ground Transmit Filter (PLL1)
Guard Receive Filter (PLL2)
Figure 3
3
Micrel
APPLICATION NOTE AN-05
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
C1
control response to Lower and Mid Range Modulation Frequencies. And C2 (optional) controls the the response to High Range Modulation Frequencies.
C3
R1
Figure 4
Transmit Filter Recommended Values: PLL1+, Pin 13, C1 = 0.1F, PLL1-, Pin 14, R1 = 500, Optional PLL1+ and PLL1-, C2 = 47pF
Receive Filter Recommended Values: PLL2+, Pin 16, C1 = 0.1F, PLL2-, Pin 15, R1 = 120, 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) 0.1
R1, Then C1 -20db/decade Acceptable Range C2
-20
130kHz
Figure 5
Frequency
4
Micrel
NOTES:
1. For TTL Crystal Oscillator open SW1 and close SW2.
2. For PECL Crystal Oscillator close SW1 and open SW2.
3. Legend: F: Force S: Sense F
4. Resistor termination must be as close to the device as possible. S F
S ROUT+ RCLKRCLK+ RSERRSER+ LFI VCC 0.1 uF ROUT+ 5V RIN+ RIN83 Ohm VCC F CD LOOP REFCLKF TOUTS TOUT+ 125 Ohm 500 0.1 uF Transmit Filter GND PLL1PLL1+ REFCLK+ S MODE
+ 2V -
CONFIGURATION LAYOUT WITH SPLIT POWER SUPPLY
5
83 Ohm
SY69952
VEE VCC TCLKTCLK+ TSER+ TSERPLL2+ PLL2120 0.1 uF Receive Filter GND 0.1 uF
SW1
SW2
Crystal Oscillators
GND 125 Ohm
+ 3V or 1.3V -
Power Supply
APPLICATION NOTE AN-05
Micrel
APPLICATION NOTE AN-05
MICREL-SYNERGY
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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. (c) 2000 Micrel Incorporated
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