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1 zarlink semiconductor inc. zarlink, zl and the zarlink semiconductor logo are trademarks of zarlink semiconductor inc. copyright 2003-2005, zarlink semiconductor inc. all rights reserved. features ? provides t1 clock at 1.544 mhz locked to an 8 khz reference clock (frame pulse) ? provides cept clock at 2.048 mhz and st-bus clock and timing signals locked to an internal or external 8 khz reference clock ? typical inherent output jitter (unfiltered)= 0.07 ui peak-to-peak ?typical jitter attenuation at: 10 hz=23 db,100 hz=43 db, 5 to 40 khz 64 db ? jitter-free ?free-run? mode ? uncommitted two-input nand gate ? low power cmos technology applications ? synchronization and timing control for t1 and cept digital trunk transmission links ? st- bus clock and frame pulse source description the MT8941B is a dual digital phase-locked loop providing the timing and sync hronization signals for the t1 or cept transmission links and the st-bus. the first pll provides the t1 clock (1.544 mhz) synchronized to the input frame pulse at 8 khz. the timing signals for the cept transmission link and the st-bus are provided by the second pll locked to an internal or an external 8 khz frame pulse signal. the MT8941B offers improved jitter performance over the mt8940. the two devices also have some functional differences, which are listed in the section on ?differences between MT8941B and mt8940?. february 2005 ordering information MT8941Be 24 pin pdip tubes MT8941Bp 28 pin plcc tubes MT8941Bpr 28 pin plcc tape & reel MT8941Bp1 28 pin plcc* tubes MT8941Bpr1 28 pin plcc* tape & reel *pb free matte tin -40 c to +85 c MT8941B advanced t1/cept digital trunk pll data sheet figure 1 - functional block diagram f0i c12i ms0 ms1 ms2 ms3 c8kb c16i ai bi yo v dd v ss rst cvb cv encv f0b c4b c4o enc4o c2o c2o enc2o 2:1 mux variable clock control mode selection logic dpll #2 input selector clock generator frame pulse control 4.096 mhz clock control 2.048 mhz clock control dpll #1
MT8941B data sheet 2 zarlink semiconductor inc. figure 2 - pin connections pin description pin # name description dip plcc 11en cv variable clock enable (ttl compatible input) - this input directly controls the three states of cv (pin 22) under all modes of operation. when high, enables cv and when low, puts it in high impedance condition. it also controls t he three states of cvb signal (pin 21) if ms1 is low. when encv is high, the pin cvb is an output and when low, it is in high impedance state. however, if ms1 is high, cvb is always an input. 22ms0 mode select ?0? input (ttl compatible) - this input in conjunction with ms1 (pin 4) selects the major mode of operation for both dplls. (refer to tables 1 and 2.) 33c12i 12.352 mhz clock input (ttl compatible) - master clock input for dpll #1. 46ms1 mode select-1 input (ttl compatible) - this input in conjunction with ms0 (pin 2) selects the major mode of operation for both dplls. (refer to tables 1 and 2.) 57 f0i frame pulse input (ttl compatible) - this is the frame pulse input at 8 khz. dpll #1 locks to the falling edge of this i nput to generate t1 (1.544 mhz) clock. 68 f0b frame pulse bidirectional (ttl compatible input and totem-pole output) - depending on the minor mode selected for dpll #2, it prov ides the 8 khz frame pulse output or acts as an input to an external frame pulse. 79ms2 mode select-2 input (ttl compatible) - this input in conjunction with ms3 (pin 17) selects the minor mode of operation for dpll #2. (refer to table 3.) 810c16i 16.384 mhz clock input (ttl compatible) - master clock input for dpll #2. 911en c4o enable 4.096 mhz clock (ttl compatible input) - this active high input enables c4o (pin 11) output. when low, the output c4 o is in high impedance condition. 10 12 c8kb clock 8 khz bidirectional (ttl compatible input and totem-pole output) - this is the 8 khz input signal on the falling edge of which the dpll #2 locks during its normal mode. when dpll #2 is in single clock mode, this pin outputs an 8 khz internal signal provided by dpll #1 which is also connected internally to dpll #2. 28 pin plcc 24 pin pdip 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 24 23 22 21 20 19 18 17 envc ms0 c12i ms1 f0i f0b ms2 c16i enc4o c8kb c4o vss vdd rst cv cvb yo bi ai ms3 enc2o c2o c2o c4b 4 5 6 7 8 9 10 11 25 24 23 22 21 20 19 ? n c nc cvb yo bi ai ms3 enc2o nc ms1 f0 i f0b ms2 c16i enc4o c 2 o 3 2 1 2 8 2 7 2 6 1 2 1 3 1 4 1 5 1 6 1 7 1 8 c 1 2 i m s 0 e n c v v d d r s t c v c 8 k b c 4 o v s s c 4 b c 2 o n c
MT8941B data sheet 3 zarlink semiconductor inc. 11 13 c4o clock 4.096 mhz (three state output) - this is the inverse of the signal appearing on pin 13 (c4b) at 4.096 mhz and has a rising edge in the frame pulse (f0b ) window. the high impedance state of this output is controlled by enc4o (pin 9). 12 14 v ss ground (0 volt) 13 15 c4b clock 4.096 mhz- bidirect ional (ttl compatible input and totem-pole output) - when the mode select bit ms3 (pin 17) is high, it provides the 4.096 mhz clock output with the falling edge in the frame pulse (f0b ) window. when pin 17 is low, c4b is an input to an external clock at 4.096 mhz. 14 16 c2o clock 2.048 mhz (three state output) - this is the divide by two output of c4b (pin 13) and has a falling edge in the frame pulse (f0b ) window. the high impedance state of this output is controlled by en c2o (pin 16). 15 17 c2o clock 2.048 mhz (three state output) - this is the divide by two output of c4b (pin 13) and has a rising edge in the frame pulse (f0b ) window. the high impedance state of this output is controlled by en c2o (pin 16). 16 19 en c2o enable 2.048 mhz clock (ttl compatible input) - this active high input enables both c2o and c2o outputs (pins 14 and 15). when low, these outputs are in high impedance condition. 17 20 ms3 mode select 3 input (ttl compatible) - this input in conjunction with ms2 (pin 7) selects the minor mode of operation for dpll #2. (refer to table 3.) 18, 19 21, 22 ai, bi inputs a and b (ttl compatible) - these are the two inputs of the uncommitted nand gate . 20 23 y o output y (totem pole output) - output of the uncommitted nand gate. 21 24 cvb variable clock bidirectional (ttl co mpatible input and totem-pole output) - when acting as an output (ms1-low) during the normal mode of dpll #1, this pin provides the 1.544 mhz clock locked to the input frame pulse f0i (pin 5). when ms1 is high, it is an input to an external clock at 1.544 mhz or 2.04 8 mhz to provide the internal signal at 8 khz to dpll #2. 22 26 cv variable clock (three state output) - this is the inverse output of the signal appearing on pin 21, the high impedance state of which is controlled by en cv (pin 1). 23 27 rst reset (schmitt trigger input) - this input (active low) puts the MT8941B in its reset state. to guarantee proper operat ion, the device must be reset afte r power-up. the time constant for a power-up reset circuit (see figures 9-13) mu st be a minimum of five times the rise time of the power supply. in normal operation, the rst pin must be held low for a minimum of 60 nsec to reset the device. 24 28 v dd v dd (+5 v) power supply. 4, 5, 18, 25 nc no connection. pin description (continued) pin # name description dip plcc
MT8941B data sheet 4 zarlink semiconductor inc. functional description the MT8941B is a dual digital phase-locked loop providing the timing and synchronizatio n signals to the interface circuits for t1 and cept (30+2) primary multiplex digi tal transmission links. as shown in the functional block diagram (see figure 1), the MT8941B has two digital phas e-locked loops (dplls), associated output controls and the mode selection logic circuits. the two dplls, although similar in principle, oper ate independently to provide t1 (1.544 mhz) and cept (2.048 mhz) transmi ssion clocks and st-bus timing signals. the principle of operation behind the tw o dplls is shown in figure 3. a mast er clock is divided down to 8 khz where it is compared with the 8 khz input, and depending on the output of the phase co mparison, the master clock frequency is corrected. figure 3 - dpll principle the MT8941B achieves the frequency correction in both directions by using three methods; speed-up, slow-down and no-correction. as shown in figure 4, the falling edge of the 8 khz input signal (c8kb for dpll #2 or f0i for dpll # 1) is used to sample the internally generated 8 khz clock and th e correction signal (cs) once in every frame (125 s). if the sampled cs is ?1?, then the dpll makes a speed-up or slow-down correction depending upon the sampled value of the internal 8 khz signal. a sampled ?0? or ?1? causes the frequency correction circui t to respectively stretch or shrink the master clock by half a period at one instant in the frame. if the sa mpled cs is ?0?, then the dpll makes no correction on the master clock input. note that since the internal 8 khz si gnal and the cs signal are derived from the master clock, a correction will ca use both clocks to stretch or shrink simultaneously by an amount equal to half the period of t he master clock. once in synchronization, the falling edge of the reference signal (c8kb or f0i ) will be aligned with either the falling or the rising edge of cs. it is aligned wi th the rising edge of cs when the refe rence signal is slower than the internal 8 khz signal. on the ot her hand, the fa lling edge of the reference si gnal will be aligned with the falling edge of cs if the reference signal is faster than the internal 8 khz signal. figure 4 - phase comparison master clock (12.352 mhz / 16.384 mhz) frequency correction 8 output (1.544 mhz / 2.048 mhz) input (8 khz) phase comparison 193 / 256 c8kb (dpll #2) or f0i (dpll #1) sampling edge interna l 8 khz correction correction cs speed-up region slow-down region t cs t csf no-correction f0b (dpll #2) dpll #1 : dpll #2: t csf = 766 t p16 where, t p12 is the 12.352 mhz master clock oscillator period for dpll #1 and t p16 is the 16.384 mhz master clock period for dpll #2. t cs = 4 t p12 0.5 t p12 t cs = 512 t p16 0.5 t p16
MT8941B data sheet 5 zarlink semiconductor inc. input-to-output phase relationship the no-correction window size is 324 ns for dpll #1 and 32 s for dpll #2. it is possible for the relative phase of the reference signal to swing inside the no-correction window depending on its jitter and the relative drift of the master clock. as a result, the phase relationship betw een the input signal and the outp ut clocks (and frame pulse in case of dpll #2) may vary up to a maximum of window size . this situation is illustra ted in figure 4. the maximum phase variation for dpll #1 is 324 ns and for dpll #2 it is 32 s. however, this phase difference can be absorbed by the input jitter buffer of zarlink?s t1/cept devices. the no-correction window acts as a filter for low frequen cy jitter and wander since the dpll does not track the reference signal inside it. the size of the no-correction window is less than or equal to the size of the input jitter buffer on the t1 and cept devices to guarantee that no slip will occur in the received t1/cept frame. the circuit will remain in synchronizati on as long as the input frequency is within the lock-in range of the dplls (refer to the section on ?jitter performance and lock-in range? for further details). the lock-in range is wide enough to meet the ccitt line rate specification (1.544 mhz 32 ppm and 2.048 mhz 50 ppm) for the high capacity terrestrial digital service. the phase sampling is done once in a frame (8 khz) for each dpll. the divisions are set at 8 and 193 for dpll #1, which locks to the falling edge of the input at 8 khz to ge nerate t1 (1.544 mhz) clock. for dpll #2, the divisions are set at 8 and 256 to provide the cept/st-bus clock at 2.048 mhz synchronized to the falling edge of the input signal (8 khz). the master clock source is specifie d to be 12.352 mhz for dpll #1 and 16.384 mhz for dpll #2 over the entire temperat ure range of operation. the inputs ms0 to ms3 are used to select the operating mode of the MT8941B, see tables 1 to 4. all the outputs are controlled to the high impedance condition by thei r respective enable controls. the uncommitted nand gate is available for use in applications involving zarlin k?s mt8976/ mh89760 (t1 interfaces) and mt8979/mh89790 (cept interfaces). modes of operation the operation of the MT8941B is categorized into major modes and minor modes. the major modes are defined for both dplls by the mode select pins ms0 and ms1. the minor modes are selected by pins ms2 and ms3 and are applicable only to dpll #2. there are no minor modes for dpll #1. major modes of dpll #1 dpll #1 can be operated in three major modes as select ed by ms0 and ms1 (table 1). when ms1 is low, it is in normal mode, which provides a t1 (1.544 mhz) clock si gnal locked to the falling edge of the input frame pulse f0i (8 khz). dpll #1 requires a master clock input of 12.352 mhz (c12i). in the second and third major modes (ms1 is high), dpll #1 is set to divide an external 1.544 mhz or 2.048 mhz signal applied at cvb (pin 21). the division can be set by ms0 to be either 193 (low) or 256 (high). in these modes, the 8 khz output at c8kb is connected internally to dpll #2, which operates in single clock mode. major modes of dpll #2 there are four major modes for dpll #2 selectable by ms0 and ms1, as shown in table 2. in all these modes dpll #2 provides the cept pcm30 timing, and the st-bus clock and framing signals. in normal mode, dpll #2 provides the cept/st-bus compat ible timing signals locked to the falling edge of the 8 khz input signal (c8kb). these signals are 4.096 mhz (c4o and c4b ) and 2.048 mhz (c2o and c2o ) clocks, and the 8 khz frame pulse (f0b ) derived from the 16.384 mhz master clock. this mode can be the same as the free- run mode if the c8kb pin is tied to v dd or v ss .
MT8941B data sheet 6 zarlink semiconductor inc. table 1 - major modes of dpll #1 table 2 - major modes of dpll #2 m s 0 m s 1 mode of operation function x 0 normal provides the t1 (1.544 mhz) clock synchronized to the falling edge of t he input frame pulse (f0i). 0 1 divide-1 dpll #1 divides the cvb input by 193. the divided output is connected to dpll #2. 1 1 divide-2 dpll #1 divides the cvb input by 256. the divided output is connected to dpll #2. note: x: indicates don?t care m s 0 m s 1 mode of operation function 0 0 normal provides cept/st-bus timing signals locked to the falling edge of the 8 khz input signal at c8kb. 1 0 free-run provides cept/st-bus timing and framing signals with no external inputs, except the master clock. 01single clock-1 provides cept/st-bus timing signals locked to the falling edge of the 8 khz internal signal provided by dpll #1. 11single clock-2 provides cept/st-bus timing signals locked to the falling edge of the 8 khz internal signal provided by dpll #1.
MT8941B data sheet 7 zarlink semiconductor inc. table 3 - minor modes of dpll #2 in free-run mode, dpll #2 generates the stand-alone ce pt and st-bus timing and framing signals with no external inputs except the master clock set at 16.384 mhz. the dpll makes no correction in this configuration and provides the timing signa ls without any jitter. the operation of dpll #2 in single clock-1 mode is i dentical to single clock-2 mode, providing the cept and st-bus compatible timing signals synchronized to the internal 8 khz signal ob tained from dpll#1 in divide mode. when single clock-1 mode is selected for dpll #2, it automatically selects the divide-1 mode for dpll #1, and thus, an external 1.544 mhz clock signal app lied at cvb (pin 21) is divided by dpll #1 to generate the internal signal at 8 khz on to which dpll #2 loc ks. similarly when single clock-2 mode is selected, dpll #1 is in divide-2 mode, with an exte rnal signal of 2.048 mhz pr oviding the internal 8 khz signal to dpll #2. in both these modes, this internal signal is available on c8kb (pin 10) and dpll #2 locks to the falling edge to provide the cept and st-bus compatible timing signals. this is in contrast to the normal mode where these timing signals are synchronized with the falling edge of the 8 khz signal on c8kb. minor modes of dpll #2 the minor modes for dpll #2 depends upon the status of the mode select bits ms2 and ms3 (pins 7 and 17). m s 2 m s 3 functional description 1 1 provides cept/st-bus 4.096 mhz and 2.048 mhz clocks and 8khz frame pulse depending on the major mode selected. 0 1 provides cept/st-bus 4.096 mhz & 2.048 mhz clocks depending on the major mode selected while f0b acts as an input. however, the input on f0b has no effect on the operation of dpll #2 unless it is in free-run mode. 0 0 overrides the major mode selected and accepts properly phase related external 4.096 mhz clock and 8 khz frame pulse to provide the st-bus compatible clock at 2.048 mhz. 1 0 overrides the major mode selected and accepts a 4.096 mhz external clock to provide the st -bus clock and frame pulse at 2.048 mhz and 8 khz, respectively.
MT8941B data sheet 8 zarlink semiconductor inc. table 4 - summary of modes of operation - dpll #1 and #2 when ms3 is high, dpll #2 operates in any of the major modes selected by ms0 and ms1. when ms3 is low, it overrides the major mode selected and dpll#2 a ccepts an external clock of 4.096 mhz on c4b (pin 13) to provide the 2.048 mhz clocks (c2o and c2o ) and the 8 khz frame pulse (f0b ) compatible with the st-bus format. the mode select bit ms2 controls the direction of the signal on f0b (pin 6). when ms2 is low, the f0b pin is an 8 khz frame pulse input. this input is effective only when ms3 is also low and pin c4b is fed by a 4.096 mhz clock, which has a proper phase relationship with the signal on f0b (refer figure 18). otherwise, the input on pin f0b will have no bearing on the operation of dpll #2, unless it is in free-run mode as selected by ms0 and ms1. in free-run mode, the input on f0b is treated the same way as the c8kb input is in normal mode. th e frequency of the signal on f0b should be 16 khz for dpll #2 to lock and generate the st-bus compatible clocks at 4.096 mhz and 2.048 mhz. mode # m s 0 m s 1 m s 2 m s 3 operating modes dpll #1 dpll #2 0 0000 normal mode: provides the t1 (1.544 mhz) clock synchronized to the falling edge of the input frame pulse (f0i ). properly phase related external 4.096 mhz clock and 8 khz frame pulse provide the st- bus clock at 2.048 mhz. 1 0001normal mode normal mode: f0b is an input but has no function in this mode. 2 0010 normal mode external 4.096 mhz provides the st-bus clock and frame pulse at 2.048 mhz and 8 khz, respectively. 3 0011 normal mode normal mode: provides the cept/st-bus compatible timing signals locked to the 8 khz input signal (c8kb). 4 0100divide-1 mode same as mode ?0?. 5 0101divide-1 mode single clock-1 mode f0b is an input but has no function in this mode. 6 0110divide-1 mode same as mode 2. 7 0111 divide-1 mode: divides the cvb input by 193. the divided output is connected to dpll #2. single clock-1 mode: provides the cept/st-bus compatible timing signals locked to the 8 khz internal signal provided by dpll #1. 8 1000normal mode same as mode ?0?. 9 1001 normal mode f0b is an input and dpll #2 locks on to it only if it is at 16 khz to provide the st-bus control signals. 10 1010normal mode same as mode 2. 11 1011 normal mode free-run mode: provides the st-bus timing signals with no external inputs except the master clock. 12 1100divide-2 mode same as mode ?0?. 13 1101 divide-2 mode single clock-2 mode: f0b is an input but has no function in this mode. 14 1110divide-2 mode same as mode 2. 15 1111 divide-2 mode: divides the cvb input by 256. the divided output is connected to dpll#2. single clock-2 mode: provides the cept/st-bus compatible timing signals locked to the 8 khz internal signal provided by dpll #1.
MT8941B data sheet 9 zarlink semiconductor inc. when ms2 is high, the f0b pin provides the frame pulse output compatible with the st-bus format and locked to the internal or external input signal as determined by the other mode select pins. table 4 summarizes the modes of the tw o dpll. it should be noted that each of the major modes selected for dpll #2 can have any of the minor modes, although some of the combinations are functionally similar. the required operation of both dpll #1 and dpll #2 must be considered when determining ms0-ms3. table 5 - functions of the bidirectional signals in each mode the direction and frequency of each of the bidirectional signals ar e listed in table 5 for each of the given modes in table 4. jitter performance and lock-in range the output jitter of a dpll is composed of the intrinsic jitter, measured when no jitter is present at the input, and the output jitter resulting from jitter on the input signal. the spectrum of the intrinsic jitter for both dplls of the MT8941B is shown in figure 5. the typical peak-to-peak value for this jitter is 0.07ui. the transfer function, which is the ratio of the output jitter to the input jitter (both measured at a particul ar frequency), is shown in figure 6 for dpll #1 and figure 7 for dpll #2. the transfer functi on is measured when the peak-to-peak amplitude of the sinusoidal input jitter conforms to the following: 10 hz - 100 hz : 13.6 s 100 hz - 10 khz : 20 db/decade roll-off > 10 khz : 97.2 ns the ability of a dpll to phase-lock the input signal to the reference signal and to remain locked depends upon its lock-in range. the lock-in range of the dpll is specified in terms of the maximum freq uency variation in the 8 khz reference signal. it is also directly affected by the oscillat or frequency tolerance. table 6 lists different values for the lock-in range and the corresponding oscillator frequency to lerance for dpll #1 and dpll #2. the smaller the tolerance value, the la rger the lock-in range. mode # f0b (khz) c4b (mhz) c8kb (khz) cvb (mhz) 0 i:8 i:4.096 i:x o:1.544 1 i:x o:4.096 i:8 o:1.544 2 o:8 i:4.096 i:x o:1.544 3 o:8 o:4.096 i:8 o:1.544 4 i:8 i:4.096 i:x i:1.544 5 i:x o:4.096 o:8 i:1.544 6 o:8 i:4.096 i:x i:1.544 7 o:8 o:4.096 o:8 i:1.544 8 i:8 i:4.096 i:x o:1.544 9 i:16 o:4.096 i:x o:1.544 10 o:8 i:4.096 i:x o:1.544 11 o:8 o:4.096 i:x o:1.544 12 i:8 i:4.096 i:x i:2.408 13 i:x o:4.096 o:8 i:2.408 14 o:8 i:4.096 i:x i:2.408 15 o:8 o:4.096 o:8 i:2.408 note: i: input o: output x: ?don?t care? input. connect to v dd or v ss.
MT8941B data sheet 10 zarlink semiconductor inc. the t1 and cept standards specify that, for free running e quipment, the output clock tolerance must be less than or equal to 32ppm and 50ppm respectively. this requirement restricts the oscillators of dpll #1 and dpll #2 to have maximum tolerances of 32ppm and 50ppm respectively. table 6 - lock-in range vs. o scillator frequency tolerance figure 5 - the spectrum of the inherent jitter for either pll oscillator clock* tolerance ( ppm) lock-in range ( hz) dpll #1 dpll #2 5 2.55 1.91 10 2.51 1.87 20 2.43 1.79 32 2.33 1.69 50 2.19 1.55 100 1.79 1.15 150 1.39 .75 175 1.19 .55 note: * please refer to the section on ?jitter performance and lock-in range? for recommended oscillato r tolerances for dpll #1 & #2.
MT8941B data sheet 11 zarlink semiconductor inc. figure 6 - the jitter transfer function for pll1 figure 7 - the jitter transfer function for pll2 however, if dpll #1 and dpll #2 are daisy-chained as sh own in figures 9 and 10, the output clock tolerance of dpll #1 will be equal to that of the dpll #2 oscillator when dpll #2 is free-running. in this case, the oscillator tolerance of dpll #1 has no impact on its output clock tolerance. for this reason, it is recommended to use a 32 ppm oscillator for dpll #2 and a 100 ppm oscillator for dpll #1.
MT8941B data sheet 12 zarlink semiconductor inc. differences between MT8941B and mt8940 the MT8941B and mt8940 are pin and mode compatible for mo st applications. however, the user should take note of the following differences between the two parts. figure 8 - application differences between the mt8940 and MT8941B a) distributed timing m u x mt8940 mt8940 8 khz reference signal 8 khz reference signal line card 1 clocks line card n clocks data bus line card 1 line card n MT8941B m u x 8 khz reference signal 8 khz reference signal clocks b) centralized timing data bus
MT8941B data sheet 13 zarlink semiconductor inc. besides the improved jitter performance, the MT8941B differs from the mt8940 in five other areas: 1. input pins on the MT8941B do not incorpor ate internal pull-up or pull-down resi stors. in addition, the output con- figuration of the bidirectional c8kb pin has been converted from an open dr ain output to a totem-pole output. 2. the MT8941B includes a no-correction window to filter out low frequency jitter and wander as illustrated in fig- ure 4. consequently, there is no constant p hase relationship between reference signal f0i of dpll # 1 or c8kb of dpll #2 and the output clocks of dpll #1 or dpll #2. figure 4 shows the new phase relationship between c8kb and the dpll #2 output clocks. figure 8 illustrates an application where the MT8941B cannot replace the mt8940 and suggests an alternative solution. 3. the MT8941B must be reset after power-up in order to guarantee proper operation, which is not the case for the mt8940. 4. for the MT8941B, dpll #2 locks to the falling edge of the c8kb reference signal. dpll#2 of the mt8940 locks on to the rising edge of c8kb. 5. while the mt8940 is available only in a 24 pin plasti c dip, the MT8941B has an additional 28 pin plcc package option. applications the following figures illustrate how the MT8941B can be used in a minimum component count approach in providing the timing and synchronization signals for t he zarlink t1 or cept interfaces, and the st-bus. the hardware selectable modes and the ind ependent control over each p ll adds flexibility to t he interface circuits. it can be easily reconfigured to provide the timing and control signals for both the master and slave ends of the link. synchronization and timing signals for the t1 transmission link figures 9 and 10 show examples of how to generate the ti ming signals for the master and slave ends of a t1 link. at the master end of the link (figure 9), dpll #2 is the sour ce of the st-bus signals derived from the crystal clock. the frame pulse output is looped back to dpll #1 (in norm al mode), which locks to it to generate the t1 line clock. the timing relationship between the 1.544 mhz t1 clock and the 2.048 mhz st-bus clock meets the requirements of the mh89760/760b. the crystal clock at 12.352 mhz is used by dpll #1 to generate the 1.544 mhz clock, while dpll #2 (in free-run mode) uses the 16.384 mhz crystal oscillator to generate the st-bus clocks for system timing. the generated st-bus signals can be used to synchronize the system and the switching equipment at the master end.
MT8941B data sheet 14 zarlink semiconductor inc. figure 9 - synchronization at the mast er end of the t1 transmission link figure 10 - synchronization at the sl ave end of the t1 transmission link crystal clock (16.384 mhz) crystal clock (12.352 mhz) MT8941B ms0 ms1 ms2 ms3 f0i c12i en cv c8kb c16i en c4o en c2o v ss v dd cvb c4b c2o f0b rst mh89760b c1.5i c2i f0i dsti dsto csti csto txt txr rxt rxr mt8980/81 st-bus switch t1 link (1.544 mbps) transmit receive mode of operation for the MT8941B dpll #1 - normal (ms0 = x; ms1 = 0) dpll #2 - free-run (ms0=1; ms2=1; ms3=1) v dd r c crystal clock (16.384 mhz) crystal clock (12.352 mhz) MT8941B ms0 ms1 ms2 ms3 f0i c12i en cv c8kb c16i en c4o en c2o v ss v dd cvb c4b c2o f0b rst mh89760b c1.5i c2i f0i dsti dsto csti csto txt txr rxt rxr mt8980/81 st-bus switch t1 link (1.544 mbps) transmit receive mode of operation for the MT8941B dpll #1 - normal (ms1=0) dpll #2 - normal (ms0=0; ms1=0; ms2=1; ms3=1) v dd r c e8ko
MT8941B data sheet 15 zarlink semiconductor inc. figure 11 - synchronization at the master end of the cept digital transmission link at the slave end of the link (figure 10) both the dplls are in normal mode, with dpll #2 providing the st-bus timing signals locked to the 8 khz frame pulse (e8ko) ex tracted from the received signal on the t1 line. the regenerated frame pulse is looped back to dpll #1 to prov ide the t1 line clock, which is the same as the master end. the 12.352 mhz and 16.384 mhz crystal clock sources are necessary for dpll #1 and #2, respectively. synchronization and timing signals for the cept transmission link the MT8941B can be used to provide the timing and syn chronization signals for th e mh89790/790b, zarlink?s cept (30+2) digital trunk interface hybrid. since the operational frequencies of the st-bus and the cept primary multiplex digital trunk are the same, only dpll #2 is required. crystal clock (16.384 mhz) MT8941B ms0 ms1 ms2 ms3 f0i c12i en cv c8kb c16i en c4o en c2o v ss v dd c4b c2o f0b y o rst transmit receive mt8980/81 st-bus switch mh89790b c2i f0i dsti dsto csti0 csto rxt rxr mode of operation for the MT8941B dpll #1 - not used dpll #2 - free-run (ms 0=1; ms1=0; ms2=1; ms3=1) csti1 outa outb v dd r c cept primary multiplex digital link
MT8941B data sheet 16 zarlink semiconductor inc. figure 12 - synchronization at the slave end of the cept digital transmission link figures 11 and 12 show how the MT8941B can be used to synchronize the st-bus to the cept transmission link at the master and slave ends. generation of st-bus timing signals the MT8941B can source the properly formatted st-bus timing and control signals with no external inputs except the crystal clock. this can be used as the standard timi ng source for st-bus systems or any other system with similar clock requirements. figure 13 shows two such applications using dpll #2. in one case, the MT8941B is in free-run mode with an oscillator input of 16.384 mhz. in the other case, it is in normal mode with the c8kb input tied to v dd . for these applications, dpll #2 does not make any corrections and th erefore, the output signals ar e free from jitter. dpll #1 is completely free. crystal clock (16.384 mhz) MT8941B ms0 ms1 ms2 ms3 f0i c12i en cv c8kb c16i en c4o en c2o v ss v dd c4b c2o f0b y o rst v dd r c mh89790b c2i f0i dsti dsto csti0 csto rxt rxr csti1 outa outb mt8980/81 st-bus switch transmit receive mode of operation for the MT8941B dpll #1 - not used dpll #2 - normal (ms0=0; ms1=0; ms2=1; ms3=1) cept primary multiplex digital link e8ko
MT8941B data sheet 17 zarlink semiconductor inc. figure 13 - generation of the st-bus timing signals * exceeding these values may cause permanent damage. functional operation under these conditions is not implied. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. absolute maximum ratings* - voltages are with respect to ground (v ss ) unless otherwise stated. parameter symbol min. max. units 1 supply voltage v dd -0.3 7.0 v 2 voltage on any pin v i v ss -0.3 v dd +0.3 v 3 input/output diode current i ik/ok 10 ma 4 output source or sink current i o 25 ma 5 dc supply or ground current i dd /i ss 50 ma 6 storage temperature t st -55 125 o c 7 package power dissipation - plastic dip - plcc p d p d 1200 600 mw mw recommended operating conditions - voltages are with respect to ground (v ss ) unless otherwise stated. characteristics sym. min. typ. ? max. units test conditions 1 supply voltage v dd 4.5 5.0 5.5 v 2 input high voltage v ih 2.0 v dd v 3 input low voltage v il v ss 0.8 v 4 operating temperature t a -40 25 85 o c crystal clock (16.384 mhz) MT8941B ms0 ms1 ms2 ms3 f0i c12i en cv c8kb c16i en c4o en c2o ai bi v ss v dd c4b rst c4o c2o c2o f0b st-bus timing signals dpll #1 - not used dpll #2 - normal mode (ms0=0; ms1=0; ms2=1; ms3=1) v dd r c MT8941B ms0 ms1 ms2 ms3 f0i c12i en cv c8kb c16i en c4o en c2o ai bi v ss v dd c4b rst c4o c2o c2o f0b dpll #1 - not used dpll #2 - free-run mode (ms0=1; ms1=0;ms2=1; ms3=1) crystal clock (16.384 mhz) v dd r c st-bus timing signals
MT8941B data sheet 18 zarlink semiconductor inc. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. dc electrical ch aracteristics - voltages are with respect to ground (v ss ) unless otherwise stated. v dd =5.0v 5%; v ss =0v; t a =-40 to 85 c. characteristics sym. min. typ. ? max. units test conditions 1s u p supply current i dd 8 15 ma under clocked condition, with the inputs tied to the same supply rail as the corresponding pull-up /down resistors. 2i n input high voltage (for all the inputs except pin 23) v ih 2.0 v 3 positive-going threshold voltage (for pin 23) v + 3.0 4.0 v 4 input low voltage (for all the inputs except pin 23) v il 0.8 v 5 negative-going threshold voltage (for pin 23) v - 1.0 1.5 v 6o u t output current high i oh -4 ma v oh =2.4 v 7 output current low i ol 4mav ol =0.4 v 8 leakage current on bidirect- ional pins and all inputs except c12i, c16i, rst , ms1, ms0 i il -100 -30 a v in =v ss 9 leakage current on pins ms1, ms0 i il 35 120 av in =v dd 10 leakage current on all three- state outputs and c12i, c16i, rst inputs i il -10 1+10 av i/o =v ss or v dd
MT8941B data sheet 19 zarlink semiconductor inc. ? timing is over recommended temperature & power supply voltages. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. figure 14 - timing information for dpll #1 in normal mode ? timing is over recommended temperature & power supply voltages. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. ac electrical characteristics ? - voltages are with respect to ground (v ss ) unless otherwise stated. (refer to figure 14) characteristics sym. min. typ. ? max. units test conditions 1 d p l l #1 cvb output (1.544 mhz) rise time t r1.5 6 ns 85 pf load 2 cvb output (1.544 mhz) fall time t f1.5 6 ns 85 pf load 3 cvb output (1.544 mhz) clock period t p15 607 648 689 ns 4 cvb output (1.544 mhz) clock width (high) t w15h 318 324 ns 5 cvb output (1.544 mhz) clock width (low) t w15l 277 363 ns 6cv delay (high to low) t 15hl 010ns 7cv delay (low to high) t 15lh -7 3 ns ac electrical characteristics ? - voltages are with respect to ground (v ss ) unless otherwise stated. (refer to figure 15) characteristics sym. min. typ. ? max. units test conditions 1 d p l l #1 c8kb output (8 khz) delay (high to high) t c8hh 0 10 25 ns 85 pf load 2 c8kb output (8 khz) delay (low to low) t c8ll 13 34 ns 85 pf load 3 c8kb output duty cycle 66 50 % % in divide -1 mode in divide - 2 mode 4 inverted clock output delay (high to low) t ichl 01025ns 5 inverted clock output delay (low to high) t iclh 0 7 18 ns
MT8941B data sheet 20 zarlink semiconductor inc. figure 15 - dpll #1 in divide mode figure 16 - timing information on dpll #2 outputs v oh v ol v oh v ol v oh v ol v oh v ol v oh v ol f0b c4b c4o c2o c2o t fpl t fph t fc4 t rc4 t 4olh t 4ohl t 42lh t 42hl t fc2 t rc2 t 2olh t 2ohl t wfp t p2o t w2oh t w2ol t w4oh t w4ol t p4o
MT8941B data sheet 21 zarlink semiconductor inc. ? timing is over recommended temperature & power supply voltages. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. ac electrical characteristics ? -voltages are with respect to ground (v ss ) unless otherwise stated. (refer to figure 16) characteristics sym. min. typ. ? max. units test conditions 1 d p l l #2 c4b output clock period t p4o 213 244 275 ns 85 pf load 2c4b output clock width (high) t w4oh 85 159 ns 3c4b output clock width (low) t w4ol 116 122 ns 4c4b output clock rise time t rc4 6 ns 85 pf load 5c4b clock output fall time t fc4 6 ns 85 pf load 6 frame pulse output delay (high to low) from c4b t fpl 013ns 85 pf load 7 frame pulse output delay (low to high) from c4b t fph 08ns 85 pf load 8 frame pulse (f0b ) width t wfp 225 245 ns 9 c4o delay - low to high t 4olh 015ns 10 c4o delay - high to low t 4ohl 020ns 11 c4b to c2o delay (low to high) t 42lh 03ns 12 c4b to c2o delay (high to low) t 42hl 06ns 13 c2o clock period t p2o 457 488 519 ns 85 pf load 14 c2o clock width (high) t w2oh 207 280 ns 15 c2o clock width (low) t w2ol 238 244 ns 16 c2o clock rise time t rc2 6 ns 85 pf load 17 c2o clock fall time t fc2 6 ns 85 pf load 18 c2o delay - low to high t 2olh -5 2 ns 19 c2o delay - high to low t 2ohl 05 7ns
MT8941B data sheet 22 zarlink semiconductor inc. ? timing is over recommended temperature & power supply voltages. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. * please review the section on "jitter performance and lock-in range". figure 17 - master clock inputs ? timing is over recommended temperature & power supply voltages. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. ac electrical characteristics ? - voltages are with respect to ground (v ss ) unless otherwise stated. (refer to figure 14) characteristics sym. min. typ. ? max. units test conditions 1 c l o c k s master clocks input rise time t r 10 ns 2 master clocks input fall time t f 10 ns 3 master clock period (12.352 mhz)* t p12 80.943 80.958 80.974 ns for dpll #1, while operating to provide the t1 clock signal. 4 master clock period (16.384mhz)* t p16 61.023 61.035 61.046 ns for dpll #2, while operating to provide the cept and st-bus timing signals. 5 duty cycle of master clocks 45 50 55 % 6 lock-in range dpll #1 dpll #2 -2.33 -1.69 +2.33 +1.69 hz with the master frequency tolerance at 32 ppm. ac electrical characteristics ? - voltages are with respect to ground (v ss ) unless otherwise stated. (refer to figure 18) characteristics sym. min. typ. ? max. units test conditions 1f0b input pulse width (low) t wfp 244 ns 2c4b input clock period t p4o 244 ns 3 frame pulse (f0b ) setup time t fs 50 ns 4 frame pulse (f0b ) hold time t fh 25 ns master clock inputs 2.4 v 1.5 v 0.4 v t r t f t p12 or t p16
MT8941B data sheet 23 zarlink semiconductor inc. figure 18 - external inputs on c4b and f0b for the dpll #2 ? timing is over recommended temperature & power supply voltages. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. figure 19 - three state outputs and enable timings ac electrical characteristics ? - voltages are with respect to ground (v ss ) unless otherwise stated. (refer to figure 19) characteristics sym. min. typ. ? max. units test conditions 1 o u t p u t delay from enable to output (high to three state) t phz 16 ns 85 pf load 2 delay from enable to output (low to three state) t plz 12 ns 85 pf load 3 delay from enable to output (three state to high) t pzh 11 ns 85 pf load 4 delay from enable to output (three state to low) t pzl 50 16 ns 85 pf load enable input output low to off output high to off 10% 90% 1.3 v 1.3 v outputs enabled outputs enabled outputs disabled t plz t phz t pzl t pzh t f 6 ns t r 6 ns 3.0 v 2.7 v 1.3 v 0.3 v
MT8941B data sheet 24 zarlink semiconductor inc. ? timing is over recommended temperature & power supply voltages. ? typical figures are at 25 c and are for design aid only: not guaranteed and not subject to production testing. ac electrical characteristics ? - uncommitted nand gate voltages are with respect to ground (v ss ) unless otherwise stated. characteristics sym. min. typ. ? max. units test conditions 1 propagation delay (low to high), input ai or bi to output t plh 11 ns 85 pf load 2 propagation delay (high to low), input ai or bi to output t phl 15 ns 85 pf load

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