Crystal-less Long-Haul Solutions LXT310/360 Universal Line Interf

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Crystal-less Long-Haul Solutions LXT310/360 Universal Line Interf

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Crystal-less Long-Haul Solutions
LXT310/360 Universal Line Interface Unit Design Guide
Introduction
This note describes applications crystal-less LXT360 transceiver newer generation network access equipment. this application note guide when upgrading designs using LXT360. Before designing circuit using this device, refer data sheets both devices complete information. LXT360 provides several advanced features. While LXT360 provides both (1.544 Mbps) (2.044 Mbps) operation, this application note focuses only hardware-controlled, designs. Additional application notes detail migration paths design using other LXT360 features.
Identifying Major LXT360 Design Improvements
Jitter Attenuation Circuitry LXT310 device requires pullable 6.176 crystal provide selectable jitter attenuation. jitter attenuation circuitry either transmit receive path, depending application. LXT360 requires only MCLK signal provide same selectable jitter attenuation functions since uses digital circuitry. needs crystal high-frequency external clock jitter attenuation. External Clock Requirements MCLK input signal LXT310 optional. used, clock must have accuracy ±100 ppm. MCLK input signal LXT360 mandatory. clock must stand alone reference with accuracy better 1.544 applications. Applications LXT310 long-haul transceiver only. LXT360 operates either short- long-haul transceiver applications. Available Line Coding Schemes LXT310 allows B8ZS encoding either Unipolar Bipolar mode. LXT360 transceiver offers B8ZS line encoding only Unipolar Mode. Reset Operation Reset LXT310 occurs when both LLOOP RLOOP inputs pulled High while TAOS pulled least Reset LXT360 occurs when LLOOP, RLOOP TAOS pulled High simultaneously least Output Control LXT310 provides high-impedance state option TTIP/TRING outputs only when TCLK grounded. LXT360 provides high-impedance state limited TTIP/TRING outputs when TCLK pulled High. additional high-impedance state option available output pins when TRSTE pulled High. Line Attenuation Indication LXT310 provides Line Attenuation Indication (LATN) both Hardware Host Modes. LXT360 provides LATN Software Mode only. NLOOP Detection LXT310 transceiver, holding RLOOP, LLOOP TAOS High simultaneously then pulling three enables NLOOP detection function. Alternatively, tying RCLK RLOOP also enables NLOOP. Resetting device disables NLOOP detection. LXT360 setting RLOOP input ±0.2 ("Midrange") enables NLOOP detection. Setting RLOOP High disables NLOOP detection. Loss Signal Detection Clear Criteria LXT310 device declares Loss Signal (LOS) condition when detects consecutive spaces. clears condition when receiver detects 12.5% mark density (i.e., marks within 32-bit period) with more than consecutive LXT360 transceiver also declares condition when detects consecutive spaces. clears condition when receiver detects 12.5% mark density (determined marks sliding 128-bit period) with fewer than consecutive
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DIAGNOSTIC FUNCTIONS
LXT360 provides several diagnostic features provided LXT310 transceiver. These Dual Loopback function, Error Insertion Detection, Condition Monitoring Elastic Store Pointer Monitoring. LXT360 data sheet details these functions. addition, LXT360 provides both Quasi-Random Signal Source Detector diagnostic procedures.
these applications. Table lists transformers that Level Communications specifications when tested with LXT360 device.
Table Transmit Return Loss (1.544 Mbit/s-Long- Short-Haul)
EC4-1 Refer LXT360 Data Sheet Xfrmr/ 1:2/ Xmission Line Twisted Pair Twisted Pair (pF) Return Loss
Three-State Input Pins
LXT310 uses two-state (High Low) configuration inputs some LXT360 control inputs recognize three states. Typical values these states are: High Midrange floating).
1:1.151/
1:1.15 transmit transformer keeps total transceiver power dissipation level, 0.47 blocking capacitor must placed TTIP TRING.
control three-state inputs standard tristate buffer. Figure shows typical driver circuit these inputs. Setting output buffer high-impedance state places three-state input into Midrange state. Application designers must take into account current drawn internal resistors (part each three-state input) before choosing buffer drive these inputs their High states.
Table Recommended Transformers LXT360/LXT361
Turns Ratio 1:1.15 Part Number PE-65388 PE-65770 PE-65351 PE-65771 Manufacturer Pulse Engineering
Figure Typical Circuit LXT360 Three-State Inputs
LXT360 buffer with tri-state output Typical 3State Input
0553-5006-IC 66Z-1308 671-5832 67127370 67130850 TD61-1205G TD67-1205G 8006-155 671-5792
Bell-Fuse Fil-Mag Midcom Schott Corp
HALO (combination set) Fil-Mag Midcom Pulse Engineering
Line Interface Considerations
improve transmit return loss, capacitor transmit side shown Figures through This capacitor typically vary depending resistor transformer values, board layout parasitics protection diodes. Table shows combinations transformers, resistors capacitors needed transmit side shown
PE-64936 PE-65778 67130840 67109510 TD61-1205G TD67-1205G
Schott Corp
HALO (combination set)
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Bipolar Mode with Line Coding (without Zero Suppression)
Most pins LXT360 have same names functions those LXT310, although some differ. section describes modifications needed change from LXT310 LXT360 Hardware Control Mode. LXT360 pins included this discussion have same connections signal level requirements those LXT310. Table summary pins whose functions change when movi from LXT310 LXT360. 6.176 crystal requi LXT310 must deleted when migrati LXT360. functi pins LXT310 change locati LXT360 transceiver. particular attention locations these signals. Figure shows connection differences between transceivers this configuration. LXT360 requi independent, external clock called MCLK. MCLK input signal must have nominal rate 1.544 accuracy better. LXT310 uses same nominal frequency, requires better accuracy than ±100 ppm. LXT310, called MODE. This High Low, tied RCLK pin. RCLK signal MODE enables B8ZS encoders decoders. LXT360, MODE three-state input pin: High, Midrange. Setting drange enables B8ZS encoders decoders LXT360 applications (and forces transceiver into unipolar operation).
LXT360, called TRSTE. threestate input. With TRSTE LXT360 devi output pins into high-impedance state. conj uncti with MODE (pin this also sets operational mode transceiver. enable Long-Haul, Bipolar, Hardware Control Mode, TRSTE must pulled Low. data sheet complete description operating modes. This XTALOUT nput LXT310. Leave this connected LXT360. Move LXT310 signal (EGL) LXT360. LXT60, must pulled enable Long-Haul operation. LXT310 signal (NLOOP) appears LXT360. LATN signal which LXT310, available Hardware Mode LXT360. However, binary encoded equivalent LATN provided LXT360 Software Mode. signal, which appears LXT310 appears LXT360 (EC1). NLOOP signal, which appears LXT310, available LXT360. Pins These pins retain their functions from LXT310, names signal change. LXT310, LBO1 LBO2. LXT360 uses names (pin (pin 25). functions connecti remain same. LXT360 Data Sheet detai
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Crystal-less Long-Haul Solutions Figure Bipolar Mode Using Line Coding (without Zero Suppression)
LXT310
MCLK MODE 6.176 XTALOUT TTIP 12.5 TRING LATN LBO1 LBO1 XTALIN
LXT360 1.544 Clock
MCLK MODE
TRSTE
TTIP
12.5
NLOOP
NLOOP
TRING
NLOOP
LBO2
LBO2
(EGL)
NOTE:
Pins shown this figure have same function both LXT310 T360. They require modification proper functioning.
Table Bipolar Mode using Line Coding (without Zero Suppression)
LXT310 Pin# Name MCLK1 MODE XTALIN LATN NLOOP LBO1 LBO2 Function/State 1.544 MHz/GND Name MCLK MODE LXT360 Function/ State 1.544 Comments Mandatory LXT360 applications MODE TRSTE operation mode Crystal used LXT360 function assigned pin. long-haul operation. LATN supported LXT360 Hardware Control Mode. NLOOP changes location. Refer Table LXT360 Data Sheet.
6.176 Crystal TRSTE Input-Low Input Output Output select Xmit line build outs.
XTALOUT 6.176 Crystal
NLOOP Output select Xmit line buildouts, including EC4,
MCLK optional LXT310 applications. With LXT310, MCLK supplied, must grounded.
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Using B8ZS Encoding/Decoding
LXT310 supports B8ZS encoding/decoding both Unipolar polar Modes. LXT360 configures itself polar mode (i.e., TPOS becomes TDATA TNEG becomes INSBPV) when B8ZS enabled. enable B8ZS encoders decoders, MODE Midrange. Other connecti same line coding. Figure shows changes needed connections LXT310 LXT360. Table summary modifi cations needed adapt LXT310 application LXT360.
Figure Unipolar Mode (with B8ZS Zero Suppression)1
LXT310
MCLK RCLK RCLK
LXT360 1.544 Clock
MCLK MODE Midrange
6.176
XTALIN
MODE
TRSTE
XTALOUT TTIP 12.5
TTIP
TRING
12.5
NLOOP
NLOOP
TRING
INSBPV
LATN
LBO1
LBO1
NLOOP
LBO2
LBO2
(EGL)
NOTE:
Pins shown this figure have same function both LXT310 LXT360. They require modification proper functioning.
Table Unipolar Mode (B8ZS Zero Suppression Enabled)
LXT310 Name MCLK1 MODE XTALIN XTALOUT LATN NLOOP LBO1 LBO2 Function/State 1.544 MHz/GND RCLK High 8.152 Crystal 8.152 Crystal Input Output Output Outs. Name MCLK MODE INSBPV TRSTE NLOOP LXT360 Function/State 1.544 Midrange Input-Low Output select Xmit Line Outs receiver range. long-haul operation.
Comments Mandatory LXT360 applications MODE TRSTE operation mode Refer Data Sheet Crystal used LXT360
LATN supported LXT360 Hardware Control Mode. NLOOP changes location. Refer Table LXT360 Data Sheet.
MCLK optional LXT310 applications. MCLK supplied LXT310, must grounded. "Midrange" means leave unconnected
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Enabling NLOOP Detection
Tying RCLK output RLOOP input enables Network Loop detecti (NLOOP) LXT310 transcei ver. NLOOP detection also enabled holding RLOOP, LLOOP TAOS High simultaneously then bringing them Low. enable NLOOP detection LXT360 transcei ver, RLOOP input Midrange Figure
Figure Bipolar Mode (with NLOOP Detection Enabled)
LXT310
MCLK MODE RCLK
LXT360 1.544 Clock
MCLK MODE RCLK TRSTE RLOOP RCLK Midrange
6.176
RCLK XTALIN RLOOP
XTALOUT 12.5 NLOOP LBO1 LBO2 TTIP 12.5
TTIP
TRING LATN LBO1
NLOOP
TRING
NLOOP
LBO2
(EGL)
NOTE:
Pins shown this figure have same function both LXT310 LXT360. They require modification proper functioning.
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Crystal-less Long-Haul Solutions LXT310/360 Universal Line Interf

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