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xr-t7295 ...the analog plus company tm ds3/sonet sts-1 integrated line receiver rev. 1.05 1992 exar corporation, 48720 kato road, fremont, ca 94538 (510) 668-7000 fax (510) 668-7017 1 june 1997-3 features fully integrated receive interface for ds3 and sts-1 rate signals integrated equalization (optional) and timing recovery loss-of-signal and loss-of-lock alarms variable input sensitivity control 5v power supply pin compatible with xr-t7295e companion device to t7296 transmitter applications interface to ds-3 networks digital cross-connect systems csu/dsu equipment pcm test equipment fiber optic terminals general description the xr-t7295 ds3/sonet sts-1 integrated line receiver is a fully integrated receive interface that terminates a bipolar ds3 (44.736mbps) or sonet sts-1 (51.84mbps) signal transmitted over coaxial cable. (see figure 13 ). the device also provides the functions of receive equalization (optional), automatic-gain control (agc), clock-recovery and data retiming, loss-of-signal and loss-of-frequency-lock detection. the digital system interface is dual-rail, with received positive and negative 1s appearing as unipolar digital signals on separate output leads. the on-chip equalizer is designed for cable distances of 0 to 450ft. from the cross-connect frame to the device. the receive input has a variable input sensitivity control, providing three different sensitivity settings, to adapt longer cables. high input sensitivity allows for significant amounts of flat loss within the system. figure 1 shows the block diagram of the device. the xr-t7295 device is manufactured using linear cmos technology. the xr-t7295 is available in either a 20-pin plastic dip or 20-pin plastic soj package for surface mounting. two versions of the chip are available, one is for either ds3 or sts-1 operation (the xr-t7295, this data sheet), and the other is for e3 operation (the xr-t7295e, refer to the xr-t7295e data sheet). both versions are pin compatible. for either ds3 or sts-1, an input reference clock at 44.736mhz or 51.84mhz provides the frequency reference for the device. ordering information part no. package operating temperature range xr-t7295ip 20 lead 300 mil pdip -40 c to + 85 c xr-t7295iw 20 lead 300 mil jedec soj -40 c to + 85 c
xr-t7295 2 rev. 1.05 block diagram figure 1. block diagram ????? ????? ????? ??? ??? ??? ??? ??? ??? ??? ??? ??? ????? ????? ????? ????? ????? ?????? ?????? ?????? ??? ??? ??? ??? ??? ?? ?? ?? ??? ??? ??? ??? ??? ??? ?? ?? ?? ?? ?? ?? ? ? ? ? ?? ?? ? ? ? ? ?? ?? ? ? ? ? ? ?? ?? ?? ?? ? ? ?? ?? ?? ?? ? ? ?? attenuator agc peak detector slicers phase detector loop filter vco digital los detector analog los frequency phase aquisition circuit equalizer tuning ckt. analog los gain & equalizer 2 r in 18 45 20 1 11 9 12 10 16 15 7 19 17 3 6 13 8 14 reqb losthr ict tmc1 tmc2 exclk rlol rlos rndata rpdata rclk lpf1 lpf2 v dd a gnda v dd d gndd v dd c gndc retimer
xr-t7295 3 rev. 1.05 pin configuration v dd a losthr reqb ict rpdata rndata rclk exclk gnda r in tmc1 lpf1 lpf2 tmc2 rlos rlol v dd c gndd v dd d gndc 20 lead pdip (0.300o) 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 v dd a losthr reqb ict gnda r in tmc1 lpf1 rpdata rndata rclk exclk lpf2 tmc2 rlos rlol v dd c gndd v dd d gndc 20 lead soj (jedec, 0.300o) 20 1 11 10 2 3 4 5 6 7 15 14 13 12 17 16 8 9 19 18 pin description pin # symbol type description 1 gnda analog ground. 2 r in i receive input. analog receive input. this pin is internally biased at about 1.5v in series with 50 k w . 3,6 tmc1-tmc2 i test mode control 1 and 2 . internal test modes are enabled within the device by using tmc1 and tmc2. users must tie these pins to the ground plane. 4,5 lpf1-lpf2 i pll filter 1 and 2 . an external capacitor (0.1 m f 20%) is connected between these pins. 7 rlos o receive loss-of-signal. this pin us set high on loss of the data signal at the receive input. (see table 7 ) 8 rlol o receive pll loss-of-lock. this pin is set high on loss of pll frequency lock. 9 gndd digital ground for pll clock . ground lead for all circuitry running synchronously with pll clock. 10 gndc digital ground for exclk . ground lead for all circuitry running synchronously with exclk. 11 v dd d 5v digital supply ( 10%) for pll clock. power for all circuitry running synchronously with pll clock. 12 v dd c 5v digital supply ( 10%) for exclk . power for all circuitry running synchronously with exclk. 13 exclk i external reference clock . a valid ds3 (44.736mhz 100ppm) or sts-1 (51.84mhz + 100ppm) clock must be provided at this input. the duty cycle of exclk, referenced to v dd /2 levels, must be within 40% - 60% with a minimum rise and fall time (10% to 90%) of 5ns. 14 rclk o receive clock . recovered clock signal to the terminal equipment. 15 rndata o receive negative data . negative pulse data output to the terminal equipment. (see figure 11. ) 16 rpdata o receive positive data . positive pulse data output to the terminal equipment. (see figure 11 ) 17 ict i in-circuit test control (active-low) . if ict is forced low, all digital output pins (rclk, rpdata, rndata, rlos, rlol) are placed in a high-impedance state to allow for in-cir- cuit testing. there is an internal pull-up on this pin. 18 reqb i receive equalization bypass . a high on this pin bypasses the internal equalizer. a low places the equalizer in the data path. 19 losthr i loss-of-signal threshold control . the voltage forced on this pin controls the input loss- of-signal threshold. three settings are provided by forcing gnd, v dd /2, or v dd . this pin must be set to the desired level upon power-up and should not be changed during opera- tion. 20 v dd a 5v analog supply ( 10%).
xr-t7295 4 rev. 1.05 electrical characteristics test conditions: t a = -40 c to +85 c, v dd = 5v 10% typical values are for v dd = 5.0 v, 25 c, and random data. maximum values are for v dd = 5.5v all 1s data. symbol parameter min. typ. max. unit condition electrical characteristics i dd power supply current ds3 reqb = 0 82 106 ma reqb = 1 79 103 ma sts-1 reqb = 0 87 111 ma reqb = 1 83 108 ma logic interface characteristics input voltage v il low gndd 0.5 v v ih high v dd d- 0.5 v dd d v output voltage v ol low gndd 0.4 v -5.0ma v oh high v dd d- 0.5 v dd d v 5.0ma c i input capacitance 10 pf c l load capacitance 10 pf i l input leakage -10 10 m a -0.5 to v dd + 0.5v (all input pins except 2 and 17) 20 500 m a 0 v (pin 17) 10 100 m a v dd (pin 2) -50 -5 m a gndd (pin 2) specifications are subject to change without notice absolute maximum ratings power supply -0.5v to +6.5v . . . . . . . . . . . . . . . . . . . . . storage temperature -40 c to +125 c . . . . . . . . . . . . power dissipation 700 mw . . . . . . . . . . . . . . . . . . . . . . .
xr-t7295 5 rev. 1.05 ? ???? ???? ???? ????? ????? ????? ? ???? ???? ???? ???? ???? xr-t7296 transmitter cross connect frame dsx-3 or stsx-1 type 728a coaxial cable 0-450 ft. 0-450 ft. system a xr-t7295 system b figure 2. application diagram receiver system description receive path configurations in the receive signal path (see figure 1 ), the internal equalizer can be included by setting reqb = 0 or bypassed by setting reqb = 1. the equalizer bypass option allows easy interfacing of the xr-t7295 device into systems already containing external equalizers. figure 3 illustrates the receive path options. in case 1 of figure 3 , the signal from the dsx-3 cross-connect feeds directly into r in . in this mode, the user should set reqb = 0, engaging the equalizer in the data path. table 1 and the following sections describe the receive signal requirements. in case 2 of figure 3 , external line build-out (lbo) and equalizer networks precede the xr-t7295 device. in this mode, the signal at r in is already equalized, and the on-chip filters should be bypassed by setting reqb=1. the signal at r in must meet the amplitude limits described in table 1 in applications where the xr-t7295 device is used to monitor ds3 transmitter outputs directly, the receive equalizer should be bypassed. again, the signal at r in must meet the amplitude limits described in table 1. minimum signals are for soj devices. due to increased package parasitics, add 3db to all table values for dip devices. maximum input amplitude under all conditions is 850mv pk. although system designers typically use power in dbm to describe input levels, the xr-t7295 responds to peak input signal amplitude. therefore, the xr-t7295 input signal limits are given in mv pk. conversion factors are as follows: at dsx3: 390mv pk 0 dbm at dsx3 + 450 ft. of cable: 310 mv pk 0 dbm data rate reqb losthr minimum signal unit ds3 0 0 80 mv pk v dd /2 60 mv pk v dd 40 mv pk 1 0 80 mv pk v dd /2 80 mv pk v dd 80 mv pk sts-1 0 0 110 mv pk v dd /2 80 mv pk v dd 60 mv pk 1 0 110 mv pk v dd /2 110 mv pk v dd 110 mv pk table 1. receive input signal amplitude requirements
xr-t7295 6 rev. 1.05 figure 3. receiver configurations ??? ??? ??? ??? ??? ???? ???? ???? ???? ???? ???? ???? ?????? ?????? ?????? ?????? ?????? ??? ??? ??? ??? ??? ??? ??? ??? ?????? ?????? ?????? ?????? ?????? ??? ??? ??? existing off-chip networks 0-450 ft. case 2: d s x 225 ft. lbo closed for 225-450 ft. of cable 75 0.01 m f 0.1 m f r in reqb lpf1 lpf2 xr-t7295 case 1: 0-450 ft. r in xr-t7295 reqb d s x 0.01 m f 75 0.1 m f lpf1 lpf2 1 0 fixed equalizer ???? ???? ???? ???? ???? ???? ????
xr-t7295 7 rev. 1.05 ds3 signal requirements at the dsx pulse characteristics are specified at the dsx-3, which is an interconnection and test point referred to as the cross-connect (see figure 2. ) the cross-connect exists at the point where the transmitted signal reaches the distribution frame jack. table 2 lists the signal requirements. currently, two isolated pulse template requirements exist: the accunet t45 pulse template (see table 3 and figure 4 ) and the g.703 pulse template (see table 4 and figure 5 ). table 3 and table 5 give the associated boundary equations for the templates. the xr-t7295 correctly decodes any transmitted signal that meets one of these templates at the cross-connect. parameter specification line rate 44.736 mbps 20 ppm line code bipolar with three-0 substitution (b3zs) test load 75 w 5% pulse shape an isolated pulse must fit the template in figure 4 or figure 5 . 1 the pulse amplitude may be scaled by a constant factor to fit the template. the pulse amplitude must be between 0.36vpk and 0.85vpk, measured at the center of the pulse. power levels for and all 1s transmitted pattern, the power at 22.368 0.002mhz must be -1.8 to +5.7dbm, and the power at 44.736 0.002mhz must be -21.8dbm to -14.3dbm. 2, 3 notes 1 the pulse template proposed by g.703 standards is shown in figure 5 and specified in table 4. the proposed g.703 standards further state that the voltage in a time slot containing a 0 must not exceed 5% of the peak pulse amplitude, except for the residue of preceding pulses. 2 the power levels specified by the proposed g.703 standards are identical except that the power is to be measured in 3khz bands . 3 the all 1s pattern must be a pure all 1s signal, without framing or other control bits. table 2. dsx-3 interconnection specification lower curve upper curve time equation time equation t -0.36 0 t -0.68 0 -0.36 t +0.28 0.5 1+sin p /2 [ 1+t/0.18 ] -0.68 t +0.36 0.5 1+sin p /2 [ 1+t/0.34 ] 0.28 t 0.11e -3.42(t-0.3) 0.36 t 0.05 + 0.407e -1.84(t-0.36) table 3. dsx-3 pulse template boundaries for accunet t45 standards (see figure 4. )
xr-t7295 8 rev. 1.05 figure 4. dsx-3 isolated pulse template for accunet t45 standards ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? 1.0 0.8 0.6 0.4 0.2 0 -1.0 -0.5 0 0.5 1.0 1.5 2.0 time slots - normalized to peak location ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? normalized amplitude lower curve upper curve time function time function t -0.36 0 t -0.65 0 -0.36 t +0.28 0.5 1+sin p /2 [ 1+t/0.18 ] -0.65 t 0 1.05 1-e -4.6(t+0.65) 0.28 t 0.11e -3.42(t-0.3) 0 t 0.36 0.5 1+sin p /2 [ 1+t/0.34 ] 0.36 t 0.05+0.407e -1.84(t-0.36) table 4. dsx-3 pulse template boundaries for g.703 standards (see figure 5 ) figure 5. dsx-3 isolated pulse template for g.703 standards ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? 1.0 0.8 0.6 0.4 0.2 0 -1.0 -0.5 0 0.5 1.0 1.5 2.0 time slots - normalized to peak location ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? normalized amplitude
xr-t7295 9 rev. 1.05 sts-1 signal requirements at the stsx for sts-1 operation, the cross-connect is referred at the stsx-1. table 5 lists the signal requirements at the stsx-1. instead of the ds3 isolated pulse template, an eye diagram mask is specified for sts-1 operation (ta-tsy-000253). the xr-t7295 correctly decodes any transmitted signal that meets the mask shown in figure 6 at the stsx-1. parameter specification line rate 51.84 mbps line code bipolar with three-0 substitution (b3zs) test load 75 w 5% power levels a wide-band power level measurement at the stsx-1 interface using a low-pass filter with a 3db cutoff frequency of at least 200mhz is within -2.7 dbm and 4.7 dbm. table 5. stsx-1 interconnection specification figure 6. stsx-1 isolated pulse template for bellcore ta-tsy-000253 ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? ??????????????? 1.0 0.8 0.6 0.4 0.2 0 -1.0 -0.5 0 0.5 1.0 1.5 2.0 time slots - normalized to peak location ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ?????????????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? ??????? normalized amplitude line termination and input capacitance the recommended receive termination is shown in figure 3 the 75 w resistor terminates the coaxial cable with its characteristic impedance. the 0.01 m f capacitor to r in couples the signal into the receive input without disturbing the internally generated dc bias level present on r in . the input capacitance at the r in pin is 2.8pf typical (soj package) and 3.6pf typical (dip package). loss limits from the dsx-3 to the receive input the signal at the cross-connect may travel through a distribution frame, coaxial cable, connector, splitters, and back planes before reaching the xr-t7295 device. this section defines the maximum distribution frame and cable loss from the cross-connect to the xr-t7295 input. the distribution frame jack may introduce 0.6 0.55 db of loss. this loss may be any combination of flat or shaped (cable) loss. the maximum cable distance between the point where the transmitted signal exits the distribution frame jack and the xr-t7295 device is 450 ft. (see figure 2. ) the coaxial cable (type 728a) used for specifying this distance limitation has the loss and phase characteristics shown in figure 7 and figure 8 . other cable types also may be acceptable if distances are scaled to maintain cable loss equivalent to type 728a cable loss. timing recovery external loop filter capacitor figure 3 shows the connection to an external 0.1 m f capacitor at the lpf1/lpf2 pins. this capacitor is part of the pll filter. a non-polarized, low-leakage capacitor should be used. a ceramic capacitor with the value 0.1 m f 20% is acceptable.
xr-t7295 10 rev. 1.05 output jitter the total jitter appearing on the rclk output during normal operation consists of two components. first, some jitter appears on rclk because of jitter on the incoming signal. (the next section discusses the jitter transfer characteristic, which describes the relationship between input and output jitter.) second, noise sources within the xr-t7295 device and noise sources that are coupled into the device through the power supplies and data pattern dependent jitter due to misequalization of the input signal, all create jitter on rclk. the magnitude of this internally generated jitter is a function of the pll bandwidth, which in turn is a function of the input 1s density. for higher 1s density, the amount of generated jitter decreases. generated jitter also depends on the quality of the power supply bypassing networks used. figure 12 shows the suggested bypassing network, and table 6 lists the typical generated jitter performance. figure 7. loss characteristic of 728a coaxial cable (450 ft.) figure 8. phase characteristic of 728a coaxial cable (450 ft.) ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? 12 10 8 6 4 2 0 1.0 2.0 5.0 10 20 50 100 frequency (mhz) ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? ????????????? 100 80 60 40 20 0 1.0 2.0 5.0 10 20 50 100 frequency (mhz) loss (db) phase (degree) jitter transfer characteristic the jitter transfer characteristic indicates the fraction of input jitter that reaches the rclk output as a function of input jitter frequency. table 6 shows important jitter transfer characteristic parameters. figure 9 also shows a typical characteristic, with the operating conditions as described in table 6. although existing standards do not specify jitter transfer characteristic requirements, the xr-t7295 information is provided here to assist in evaluation of the device. parameter typ max unit generated jitter 1 all 1s pattern 1.0 ns peak-to-peak repetitive a100o pattern 1.5 ns peak-to-peak jitter transfer characteristic 2 characteristic peaking 0.05 0.1 db f 3db 005 205 0 d khz notes 1 repetitive input data pattern at nominal dsx-3 level with v dd = 5v t a = 25 c. 2 repetitive a100 o input at nominal dsx-3 level with v dd = 5v, t a = 25 c. table 6. generated jitter and jitter transfer characteristics
xr-t7295 11 rev. 1.05 jitter accommodation under all allowable operating conditions, the jitter accommodation of the xr-t7295 device exceeds all system requirements for error-free operation (ber<1e -9 ). the typical (v dd = 5v, t = 25 c, dsx-3 nominal signal level) jitter accommodation for the xr-t7295 is shown in figure 10. false-lock immunity false-lock is defined as the condition where a pll recovered clock obtains stable phase-lock at a frequency not equal to the incoming data rate. the xr-t7295 device uses a combination frequency/phase-lock architecture to prevent false-lock. an on-chip frequency comparator continuously compares the exclk reference to the pll clock. if the frequency difference between the exclk and pll clock exceeds approximately 0.5%, correction circuitry forces re-acquisition of the proper frequency and phase. acquisition time if a valid input signal is assumed to be already present at r in , the maximum time between the application of device power and error-free operation is 20ms. if power has already been applied, the interval between the application of valid data (or the action of valid data following a loss of signal) and error-free operation is 4ms. loss-of-lock detection as stated above, the pll acquisition aid circuitry monitors the pll clock frequency relative to the exclk frequency. the rlol alarm is activated if the difference between the pll clock and the exclk frequency exceeds approximately 0.5%. this will not occur until at least 250 bit periods after loss of input data. figure 9. typical pll jitter transfer characteristic ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ???????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? 1 0 -5 -4 -3 -2 -1 100 500 1k 5k 10k 50k100k 500k peak = 0.05db f3db = 205khz frequency (hz) magnitude response (db) ?????????????????????? ?????????????????????? ?????????????????????? ?????????????????????? ?????????????????????? ?????????????????????? ?????????????????????? ?????????????????????? ?????????????????????? ?????????????????????? ?????????????????????? 1 10 100 1k 10k 100k 1000k 40 10 1.0 0.1 ????? ????? xr-t7295 typical pub 54014 g.824 ???? ???? tr-tsy-000499 category 1 ???? ???? tr-tsy-000499 category 2 ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? 5k 10 10k 5 60k 1 300k 0.5 1m 0.4 xr-t7295 typical sinewave jitter frequency (hz) figure 10. input jitter tolerance at dsx-3 level jitter frequency (hz) jitter amplitude (u.i.) peak-peak sinewave jitter (u.i.)
xr-t7295 12 rev. 1.05 a high rlol output indicates that the acquisition circuit is working to bring the pll into proper frequency lock. rlol remains high until frequency lock has occurred; however, the minimum rlol pulse width is 32 clock cycles. phase hits in response to a phase hit in the input data, the xr-t7295 returns to error free operation in less than 2ms. during the requisition time, rlos may temporarily be indicated. loss-of-signal detection figure 1 shows that analog and digital methods of loss-of-signal (los) detection are combined to create the rlos alarm output. rlos is set if either the analog or digital detection circuitry indicates los has occurred. analog detection the analog los detector monitors the peak input signal amplitude. rlos makes a high-to-low transition (input signal regained) when the input signal amplitude exceeds the loss-of signal threshold defined in table 7. the rlos low-to-high transition (input signal loss) occurs at a level typically 1.0 db below the high-to-low transition level. the hysteresis prevents rlos chattering. once set, the rlos alarm remains high for at least 32 clock cycles, allowing for system detection of a los condition without the use of an external latch. to allow for varying levels of noise and crosstalk in different applications, three loss-of-signal threshold settings are available using the losthr pin. setting losthr = v dd provides the lowest loss-of-signal threshold; losthr = v dd /2 (can be produced using two 50 k w 10% resistors as a voltage divider between v dd d and gndd) provides an intermediate threshold; and losthr = gnd provides the highest threshold. the losthr pin must be set to its desired value at power-up and must not be changed during operation. digital detection in addition to the signal amplitude monitoring of the analog los detector, the digital los detector monitors the recovered data 1s density. the rlos alarm goes high if 160 32 or more consecutive 0s occur in the receive data stream. the alarm goes low when at least ten 1s occur in a string of 32 consecutive bits. this hysteresis prevents rlos chattering and guarantees a minimum rlos pulse width of 32 clock cycles. note, however, that rlos chatter can still occur. when reqb=1, input signal levels above the analog rlos threshold can still be low enough to result in a high bit error rate. the resultant data stream (containing) errors can temporarily activate the digital los detector, and rlos chatter can occur. therefore, rlos should not be used as a bit error rate monitor. rlos chatter can also occur when rlol is activated (high).
xr-t7295 13 rev. 1.05 data rate reqb losthr min. threshold max. threshold unit ds3 0 0 60 220 mv pk v dd /2 40 145 mv pk v dd 25 90 mv pk 1 0 45 175 mv pk v dd /2 30 115 mv pk v dd 20 70 mv pk sts-1 0 0 75 275 mv pk v dd /2 50 185 mv pk v dd 30 115 mv pk 1 0 55 220 mv pk v dd /2 35 145 mv pk v dd 25 90 mv pk notes - lower threshold is 1.5 db below upper threshold. - the rlos alarm is an indication of the presence of an input signal, not a bit error rate indication. table 1 gives the minim um input amplitude needed for error free operation (ber < 1e- 9 ) independent of the rlos state, the device will attempt to recover correct timing data. the rlos low-to-high transition typically occurs 1db below the high to low transition. table 7. analog loss-of-signal thresholds recovered clock and data timing table 8 and figure 11 summarize the timing relationships between the logic signals rclk, rpdata, and rndata. the duty cycle is referenced to v dd /2 threshold level. rpdata and rndata change on the rising edge of rclk and are valid during the falling edge of rclk. a positive pulse at r in creates a high level on rpdata and a low level on rndata. a negative pulse at the input creates a high level on rndata and a low level on rpdata, and a received zero produces low levels on both rpdata and rndata. in-circuit test capability when pulled low, the ict pin forces all digital output buffers (rclk, rpdata, rndata, rlos, rlol pins) to be placed in a high output impedance state. this feature allows in-circuit testing to be done on neighboring devices without concern for xr-t7295 device buffer damage. an internal pull-up device (nominally 50k w ) is provided on this pin therefore, users can leave this pin unconnected for normal operation. test equipment can pull ict low during in-circuit testing without damaging the device. this is the only pin for which internal pull-up/pull-down is provided.
xr-t7295 14 rev. 1.05 timing characteristics test conditions: all timing characteristics are measrured with 10pf loading, -40 c t a +85 c, v dd = 5v 10% symbol parameter min typ max unit trch1rch2 clock rise time (10% - 90%) 3.5 ns trcl2rcl1 clock fall time (10% - 90%) 2.5 ns trdvrcl receive data set-up time 5.0 ns trclrdx receive data hold time 8.5 ns trchrdv receive propagation delay 1 0.6 3.7 ns clock duty cycle 45 50 55 % note s 1 the total delay from r in to the digital outputs rpdata and rndata is three and a half rclk clocks. table 8. system interface timing characteristics figure 11. timing diagram for system interface rclk rpdata or rndata (rc) (rd) trchrdv trcl2rcl1 trch1rch2 trclrdx trdvrcl board layout considerations power supply bypassing figure 12 illustrates the recommended power supply bypassing network. a 0.1 m f capacitor bypasses the digital supplies. the analog supply v dd a is bypassed by using a 0.1 m f capacitor and a shield bead that removes significant amounts of high-frequency noise generated by the system and by the device logic. good quality, high-frequency (low lead inductance) capacitors should be used. finally, it is most important that all ground connections be made to a low-impedance ground plane. receive input the connections to the receive input pin, r in , must be carefully considered. noise-coupling must be minimized along the path from the signal entering the board to the input pin. any noise coupled into the xr-t7295 input directly degrades the signal-to-noise ratio of the input signal and may degrade sensitivity. pll filter capacitor the pll filter capacitor between pins lpf1 and lpf2 must be placed as close to the chip as possible. the lpf1 and lpf2 pins are adjacent, allowing for short lead lengths with no crossovers to the external capacitor. noise-coupling into the lpf1 and lpf2 pins may degrade pll performance. handling precautions although protection circuitry has been designed into this device, proper precautions should be taken to avoid exposure to electrostatic discharge (esd) during handling and mounting.
xr-t7295 15 rev. 1.05 c4 sensitive node shield bead 1 +5v c6 gnda v dd a gndd gndc v dd c v dd d 0.1 m f xr-t7295 0.1 m f figure 12. recommended power supply bypassing network notes 1 recommended shield beads are the fair-rite 2643000101 or the fair-rite 2743019446 (surface mount). compliance specifications compliance with at&t publication 54014, aaccu- net t45 service description and interface spec- ifications,o june 1987. compliance with ansi standard t1.102- 1989, adigital hierarchy - electrical interfaces, o 1989. compliance with compatibility bulletin 119, ainterconnection specification for digital cross-connects,o october 1979. compliance with ccitt recommendations g.703 and g.824, 1988. compliance with tr-tsy-000499, atransport sys- tems generic requirements (tsgr): common re- quirements,o december 1988. compliance with ta-tsy-000253, asynchronous optical network (sonet) transport system gener- ic criteria,o february 1990.
xr-t7295 16 rev. 1.05 1 5 1 6 1 4 1 3 1 2 1 1 1 0 9 2134 5678 r22 22k v cc v cc l o s t h r 1 2 3 4 5 6 7 8 r21 22k 1 2 3 4 8 6 5 s1 sw dip-4 rlos tp rlol tp receiver monitor outputs rlol 8 rlos 7 r in 2 exclk 13 v d d a 20 v d d c 1 2 v d d d 1 1 gndd 9 gndc 10 gnda 1 reqb 18 14 rndata 15 rpdata 16 tmc1 3 tmc2 6 lpf1 4 lpf2 5 losthr 19 ict/ 17 c2 0.01 m f r2 75 r6 75 input signal external clock b1 b2 r1 50 r5 50 r8 39 r10 39 r7 39 b5 tclk p2 gnd v d d a v d d d 6 lloop 3 rloop 2 ds3,sts-1/e3/ 4 taos 5 ict/ 26 txlev 25 encodis 11 decodis 12 rclk rndata 28 rpdata 27 dmo 18 bpv 13 tndata 8 tclk 9 tpdata 7 gnda 21 gndd 10 mtip 20 mring 19 ttip 23 tring 22 rclko 17 rpos 16 rneg 15 rnrz 14 u2 xr-t7296 rneg rclko rpos lloop rloop t3/e3 taos txlev ict encodis decodis receiver 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 s2 sw dip-8 outputs r3 36 r4 36 t1 pe65966 b6 tring ttip r15 270 r16 270 rnrz b4 tndata b3 tpdata c6 0.1 m f c3 0.1 m f c4 0.1 m f bt1 ferrite bead ferrite bead # fair rite 2643000101 c7 0.1 m f e1 22 m f p1 v cc rx transmiter monitor outputs dmo bpv c9 0.1 m f e2 22 m f c8 0.1 m f transformer # pulse engineering bt2 ferrite bead c5 0.1 m f pe 65966 pe 65967 in surface mount v cc tx u1 xr-t7295 7 rclk p3 r e q b i c t + + 1 24 figure 13. typical application schematic
xr-t7295 17 rev. 1.05 20 lead plastic dual-in-line (300 mil pdip) rev. 1.00 20 1 11 10 d e a 1 e 1 e a l seating plane symbol min max min max inches a 0.145 0.210 3.68 5.33 a 1 0.015 0.070 0.38 1.78 a 2 0.115 0.195 2.92 4.95 b 0.014 0.024 0.36 0.56 b 1 0.030 0.070 0.76 1.78 c 0.008 0.014 0.20 0.38 d 0.925 1.060 23.50 26.92 e 0.300 0.325 7.62 8.26 e 1 0.240 0.280 6.10 7.11 e 0.100 bsc 2.54 bsc e a 0.300 bsc 7.62 bsc e b 0.310 0.430 7.87 10.92 l 0.115 0.160 2.92 4.06 a 0 15 0 15 millimeters a a 2 b 1 b c note: the control dimension is the inch column e b e a
xr-t7295 18 rev. 1.05 symbol min max min max a 0.145 0.200 3.60 5.08 a 1 0.025 --- 0.64 --- a 2 0.120 0.140 3.05 3.56 b 0.014 0.020 0.36 0.51 c 0.008 0.013 0.20 0.30 d 0.496 0.512 12.60 13.00 e 0.292 0.300 7.42 7.62 e 1 0.262 0.272 6.65 6.91 e 0.050 bsc 1.27 bsc h 0.335 0.347 8.51 8.81 r 0.030 0.040 0.76 1.02 inches millimeters e 20 11 20 lead small outline j lead (300 mil jedec soj) rev. 1.00 10 d e h b a 1 seating plane note: the control dimension is the inch column 1 a 2 a c r e 1
xr-t7295 19 rev. 1.05 notes
xr-t7295 20 rev. 1.05 notice exar corporation reserves the right to make changes to the products contained in this publication in order to im- prove design, performance or reliability. exar corporation assumes no responsibility for the use of any circuits de- scribed herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. charts and schedules contained here in are only for illustration purposes and may vary depending upon a user's specific application. while the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. exar corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. products are not authorized for use in such applications unless exar corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of exar corporation is adequately protected under the circum- stances. copyright 1992 exar corporation datasheet june 1997 reproduction, in part or whole, without the prior written consent of exar corporation is prohibited.

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