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data sheet january 2000 l7556, l7557 low-power slics with battery switch features n auxiliary input for second battery, and internal switch to enable its use to save power n low active power (typical 125 mw during on-hook transmission) n supports meter pulse injection n spare op amp for meter pulse filtering n C16 v to C60 v power supply operation n distortion-free on-hook transmission n convenient operating states: forward powerup disconnect (high impedance) 2-wire wink (zero loop voltage) n adjustable supervision functions: off-hook detector with longitudinal rejection ground key detector ring trip detector n independent, adjustable, dc and ac parameters: dc feed resistance loop current limit termination impedance n thermal protection description these electronic subscriber loop interface circuits (slics) are optimized for low power consumption while providing an extensive set of features. the slics include an auxiliary battery input and a built-in switch. in short-loop applications, they can be used in high battery to present a high on-hook volt- age, and then switched to low battery to reduce off- hook power. the slics also include a summing node for meter pulse injection to 2.2 vrms. a spare, uncommitted op amp is included for meter pulse filtering. the switched battery is applied to the power amplifi- ers of the device. there are two versions. the l7556 has the battery switch completely under processor control. the l7557 can automatically switch to lower battery when appropriate and includes hysteresis to avoid frequent switching. to make the switch silent, an external capacitor can be added to slow the tran- sition. the l7556 is suited for applications serving only short loops, where a high on-hook voltage is required for compatibility with preexisting standards. the l7557 is suited for applications where a full loop range is needed, but low short-loop power is desired. it is a much lower-cost solution than a switching reg- ulator, and also occupies much less pcb area, need- ing only a battery filter capacitor and a diode for implementation. the device is available in a 32-pin plcc package. it is built by using a 90 v complementary bipolar inte- grated circuit (cbic) process.
2 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics table of contents contents page features ..................................................................... 1 description .................................................................. 1 pin information ............................................................ 4 functional description ................................................. 6 absolute maximum ratings ........................................ 6 recommended operating conditions ......................... 7 electrical characteristics ............................................. 7 ring trip requirements ......................................... 11 test configurations .................................................. 12 applications .............................................................. 14 design considerations ........................................... 16 characteristic curves............................................. 17 dc applications ....................................................... 20 battery feed......................................................... 20 switching the battery............................................ 20 overhead voltage ............................................... 21 adjusting overhead voltage ................................ 21 adjusting dc feed resistance.............................. 22 loop range.......................................................... 22 off-hook detection .............................................. 22 ring trip detection.............................................. 23 ring ground detection........................................ 23 ac design ............................................................... 24 first-generation codecs ..................................... 24 second-generation codecs ................................ 24 third-generation codecs .................................... 24 selection criteria ................................................. 24 pcb layout information ............................................ 26 outline diagram......................................................... 27 32-pin plcc ........................................................... 27 ordering information.................................................. 28 tables page table 1. pin descriptions ............................................ 4 table 2. input state coding ........................................ 6 table 3. supervision coding ....................................... 6 table 4. power supply ................................................ 7 table 5. 2-wire port .................................................... 8 table 6. analog pin characteristics ............................ 9 table 7. uncommitted op amp characteristics .......... 9 table 8. ac feed characteristics .............................. 10 table 9. logic inputs and outputs ............................ 11 table 10. parts list for loop start and ground start applications ...................................... 15 table 11. 600 w design parameters ......................... 16 figures page figure 1. functional diagram ..................................... 3 figure 2. pin diagram (plcc chip) ........................... 4 figure 3. ring trip circuits ....................................... 11 figure 4. basic test circuit .......................................12 figure 5. longitudinal balance .................................12 figure 6. longitudinal psrr ....................................13 figure 7. rfi rejection .............................................13 figure 8. longitudinal impedance ............................13 figure 9. metallic psrr ...........................................13 figure 10. ac gains ..................................................13 figure 11. basic loop start application circuit using t7504 type codec ........................14 figure 12. ring ground detection circuit .................14 figure 13. receive gain and hybrid balance vs. frequency ...............................................17 figure 14. transmit gain and return loss vs. frequency ...............................................17 figure 15. typical v cc power supply rejection .......17 figure 16. typical v bat power supply rejection .................................................17 figure 17. loop closure program resistor selection ..................................................18 figure 18. ring ground detection programming .....18 figure 19. loop current vs. loop voltage ................18 figure 20. loop current vs. loop resistance ..........18 figure 21. typical slic power dissipation vs. loop resistance ......................................19 figure 22. power derating ........................................19 figure 23. longitudinal balance resistor mismatch requirements ..........................................19 figure 24. longitudinal balance vs. protection resistor mismatch ...................................19 figure 25. loop current vs. loop voltage ................20 figure 26. slic 2-wire output stage .......................21 figure 27. equivalent circuit for adjusting the over- head voltage ...........................................21 figure 28. equivalent circuit for adjusting the dc feed resistance ......................................22 figure 29. adjusting both overhead voltage and dc feed resistance .....................................22 figure 30. off-hook detection circuit applications .............................................22 figure 31. ring trip equivalent circuit and equivalent application .............................23 figure 32. ac equivalent circuit not including spare op amp ...................................................25 figure 33. ac equivalent circuit including spare op amp ...................................................25
lucent technologies inc. 3 data sheet january 2000 with battery switch l7556, l7557 low-power slics description (continued) 12-2551.a (f) figure 1. functional diagram + C + C C + C + + C a = 4 a = C4 battery agnd v bat2 v cc cf1 pt pr dc resistance adjust dcr icm rtsn rtsp lcth ring ground detector ring trip detector loop closure detector battery feed state control spare op amp dcout vitr b0 rcvp rcvn xmt b1 sn nlc rgdet nrdet cf2 1 v/8 ma switch bgnd i prog bs2 bs1 bs v bat1 l bat v reg power conditioning & reference
4 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics pin information 12-2548.q (f) figure 2. pin diagram (plcc chip) table 1. pin descriptions pin symbol type description 1 v bat2 auxiliary battery supply. negative high-voltage battery, lower in magnitude than v bat1 , used to reduce power dissipation on short loops. 2 i prog i current-limit program input. a resistor to dcout sets the dc current limit of the device. 3 bs i battery switch. see table 2 for description. 4 nc no connection (l7556 only). do not use as a tie point. 4 l bat o lower battery in use (l7557 only). when high, this open-collector output indicates the device has switched to v bat2. to use, connect a 100 k w resistor to v cc . 5 v cc +5 v power supply. 6 rcvp i receive ac signal input (noninverting). this high-impedance input controls the ac differential voltage on tip and ring. 7 rcvn i receive ac signal input (inverting). this high-impedance input controls the ac differ- ential voltage on tip and ring. 8 lcth i loop closure threshold input. connect a resistor to dcout to set off-hook thresh- old. 9 dcout o dc output voltage. this output is a voltage that is directly proportional to the absolute value of the differential tip/ring current. 10 v bat1 battery supply. negative high-voltage power supply, higher in magnitude than v bat2 . b1 xmt nlc nrdet rtsp rtsn pt 5 7 8 9 10 11 12 13 14 15 6 4 3 2 1 32 31 16 18 19 20 17 30 27 26 25 24 23 22 21 28 icm dcr agnd agnd vitr rgdet b0 29 sn bgnd i prog rcvn rcvp v cc lcth v bat1 dcout pr cf2 cf1 nc 32-pin plcc bs2 bs1 v bat2 bs nc l bat
lucent technologies inc. 5 data sheet january 2000 with battery switch l7556, l7557 low-power slics pin information (continued) table 1. pin descriptions (continued) pin symbol type description 11 pr i/o protected ring. the output of the ring driver amplifier and input to loop sensing cir- cuitry. connect to loop through overvoltage protection. 12 cf2 filter capacitor 2. connect a 0.1 f capacitor from this pin to agnd. 13 cf1 filter capacitor 1. connect a 0.47 f capacitor from this pin to pin cf2. 14 vitr o transmit ac output voltage. this output is a voltage that is directly proportional to the differential tip/ring current. 15 icm i common-mode current sense. to program ring ground sense threshold, connect a resistor to v cc and connect a capacitor to agnd to filter 50/60 hz. if unused, the pin can be left unconnected. 16 rgdet o ring ground detect. when high, this open-collector output indicates the presence of a ring ground. to use, connect a 100 k w resistor to v cc . 17 b0 i state control input. b0 and b1 determine the state of the slic. see table 2. 18 agnd analog signal ground. 19 agnd analog signal ground. 20 dcr i dc resistance for low loop currents. leave open for dc feed resistance of 115 w , or short to dcout for 615 w . intermediate values can be set by a simple resistor divider from dcout to ground with the tap at dcr. 21 bgnd battery ground. ground return for the battery supply. 22 pt i/o protected tip . the output of the tip driver amplifier and input to loop sensing circuitry. connect to loop through overvoltage protection. 23 rtsn i ring trip sense negative . connect this pin to the ringing generator signal through a high-value resistor. 24 rtsp i ring trip sense positive . connect this pin to the ring relay and the ringer series resis- tor through a high-value resistor. 25 nrdet o ring trip detector output . when low, this logic output indicates that ringing is tripped. 26 nlc o loop detector output . when low, this logic output indicates an off-hook condition. 27 b1 i/o state control input . b0 and b1 determine the state of the slic. see table 2. pin b1 has a 40 k w pull-up. it goes low in the event of thermal shutdown. 28 xmt o transmit ac output voltage . the output of the uncommitted operational amplifier. 29 sn i summing node . the inverting input of the uncommitted operational amplifier. a resis- tor or network to xmt sets the gain. 30 nc no connection. do not use as a tie point. 31 bs2 battery switch slowdown. a 0.1 f capacitor from bs1 to bs2 will ramp the battery switch transition for applications requiring quiet transition. if not needed, the pin can be left open. 32 bs1 battery switch slowdown. a 0.1 f capacitor from bs1 to bs2 will ramp the battery switch transition for applications requiring quiet transition. if not needed, the pin can be left open.
6 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics functional description table 2. input state coding table 3. supervision coding absolute maximum ratings (t a = 25 c) stresses in excess of the absolute maximum ratings can cause permanent damage to the device. these are absolute stress ratings only. functional operation of the device is not implied at these or any other conditions in excess of those given in the operational sections of the data sheet. exposure to absolute maximum ratings for extended periods can adversely affect device reliability . note: the ic can be damaged unless all ground connections are applied before, and removed after, all other connections. furtherm ore, when powering the device, the user must guarantee that no external potential creates a voltage on any pin of the device that exceeds the device ratings. some of the known examples of conditions that cause such potentials during powerup are the following: 1. an inductor connected to tip and ring can force an overvoltage on v bat through the protection devices if the v bat connections chatter. 2. inductance in the v bat leads could resonate with the v bat filter capacitors to cause a destructive overvoltage. b0 b1 bs state/definition 1 1 1 powerup, forward battery. normal talk and battery feed state. pin pt is positive with respect to pr. on-hook transmission is enabled. v bat1 is applied to entire circuit. 1 1 0 powerup, forward battery. normal talk and battery feed state. pin pt is positive with respect to pr. on-hook transmission is enabled. for the l7556 only, v bat2 is applied to tip/ring drive amplifiers. for the l7557 only, the device compares the magnitude of v bat2 to the voltage necessary to maintain proper loop current. then the device automatically applies v bat2 to tip/ring drive am- plifiers when possible, not affecting the desired dc template. 1 0 1 2-wire wink. pins pt and pr are put at the same potential (near ground). v bat1 is applied to entire circuit. 0 0 1 disconnect. the tip and ring amplifiers are turned off, and the slic goes to a high-impedance state (>100 k w ).v bat1 is applied to entire circuit. pin nlc pin nrdet pin rgdet 0 = off-hook 1 = on-hook 0 = ring trip 1 = no ring trip 1 = ring ground 0 = no ring ground parameter symbol value unit 5 v power supply v cc 7.0 v battery (talking) supply v bat1 C63 v auxiliary battery supply v bat2 C63 v logic input voltage C0.5 to +7.0 v analog input voltage C7.0 to +7.0 v maximum junction temperature t j 165 c storage temperature range t stg C40 to +125 c relative humidity range r h 5 to 95 % ground potential difference (bgnd to agnd) 3 v pt or pr fault voltage (dc) v pt , v pr (v bat1 C 5) to +3 v pt or pr fault voltage (10 x 1000 s) v pt , v pr (v bat1 C 15) to +15 v current into ring trip inputs i rtsp , i rtsn 240 a
lucent technologies inc. 7 data sheet january 2000 with battery switch l7556, l7557 low-power slics recommended operating conditions electrical characteristics minimum and maximum values are testing requirements. typical values are characteristic of the device and are the result of engineering evaluations. typical values are for information purposes only and are not part of the test- ing requirements. minimum and maximum values apply across the entire temperature range (C40 c to +85 c) and the entire battery range unless otherwise specified. typical is defined as 25 c, v cc = 5.0 v, v bat1 = C48 v, v bat2 = C48 v, and i lim = 40 ma. positive currents flow into the device. test circuit is figure 4 unless noted. table 4. power supply 1. this parameter is not tested in production. it is guaranteed by design and device characterization. parameter min typ max unit ambient temperature C40 85 c v cc supply voltage 4.75 5.0 5.25 v v bat1 supply voltage C24 C48 C60 v v bat2 supply voltage C16 C28 v bat1 v loop closure threshold-detection programming range 10 i lim ma dc loop current-limit programming range 5 22 45 ma on- and off-hook 2-wire signal level 1 2.2 vrms ac termination impedance programming range 150 600 1300 w parameter min typ max unit power supplypowerup, no loop current: i cc i bat (v bat = C48 v) power dissipation (v bat = C48 v) 2.8 C2.3 125 155 ma ma mw power supply rejection 500 hz to 3 khz (see figures 5, 6, 15, and 16.) 1 : v cc v bat 35 45 db db thermal protection shutdown (t jc ) 175 c thermal resistance, junction to ambient ( q ja ) 60 c/w
8 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics electrical characteristics (continued) table 5. 2-wire port 1. the longitudinal current is independent of dc loop current. 2. current-limit i lim is programmed by a resistor, r prog , from pin i prog to dcout. i lim is specified at the loop resistance where current limiting begins (see figure 19). select r prog (k w ) =1.67 x i lim (ma). 3. ieee is a registered trademark of the institute of electrical and electronics engineers, inc. 4. longitudinal balance of circuit card will depend on loop series resistance matching (see figure 23 and figure 24). 5. this parameter is not tested in production. it is guaranteed by design and device characterization. parameter min typ max unit tip or ring drive current: = dc + longitudinal + signal currents 65 ma signal current 15 marms longitudinal current capability per wire 1 8.5 15 marms dc loop current limit 2 : r loop = 100 w programmability range accuracy (20 ma < i lim < 40 ma) 5 i lim 45 12 ma ma % powerup open loop voltage levels (includes external diode): differential voltage |v bat + 8.4| |v bat + 7.9| |v bat + 7.4| v disconnect state: pt resistance (v bat < v pt < 0 v) pr resistance (v bat < v pr < 0 v) 100 100 143 133 k w k w ground start state: pt resistance 100 143 k w dc feed resistance (for i loop below regulation level) 95 115 135 w loop resistance range (C3.17 dbm overload into 600 w ; not including protection): i loop = 20 ma at v bat2 = C48 v i loop = 20 ma at v bat2 = C24 v 1885 685 w w longitudinal to metallic balance ieee 3 std. 455 (see figure 6.) 4 : 50 hz to 1 khz 1 khz to 3 khz 64 60 75 70 db db metallic to longitudinal balance: 200 hz to 4 khz 46 db rfi rejection (see figure 7.) 5 : 0.5 vrms, 50 w source, 30% am mod 1 khz 500 khz to 100 mhz C55 C45 dbv
lucent technologies inc. 9 data sheet january 2000 with battery switch l7556, l7557 low-power slics electrical characteristics (continued) table 6. analog pin characteristics 1. loop closure threshold is programmed by resistor rlcth from pin lcth to pin dcout. 2. ring ground threshold is programmed by resistor ricm2 from pin icm to v cc . table 7. uncommitted op amp characteristics parameter min typ max unit differential pt/pr current sense (dcout): gain (pt/pr to dcout) C123 C125 C127 v/a loop closure detector threshold 1 : programming accuracy 20 % ring ground detector threshold 2 : r icm = 154 k w programming accuracy 3 6 10 25 k w % ring trip comparator: input offset voltage 10 mv rcvn, rcvp: input bias current C0.2 C1 a parameter min typ max unit input offset voltage input offset current input bias current differential input resistance 5 10 200 1.5 mv na na m w output voltage swing (r l = 10 k w ) output resistance (a vcl = 1) 3.5 2.0 vpk w small signal gbw 700 khz
10 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics electrical characteristics (continued) table 8. ac feed characteristics 1. set by external components. any complex impedance r1 + r2 || c between 150 w and 1300 w can be synthesized. 2. this parameter is not tested in production. it is guaranteed by design and device characterization. 3. return loss and transhybrid loss are functions of device gain accuracies and the external hybrid circuit. guaranteed performa nce assumes 1% tolerance external components. parameter min typ max unit ac termination impedance 1 : 150 1300 w longitudinal impedance 2 (see figure 8.) 40 46 w total harmonic distortion200 hz to 4 khz 2 : off-hook on-hook 0.3 1.0 % % transmit gain, f = 1 khz (pt/pr to vitr) transmit accuracy in db C122 C0.18 C125 0 C128 0.18 v/a db receive + gain, f = 1 khz (rcvp to pt/pr) receive C gain, f = 1 khz (rcvn to pt/pr) receive accuracy in db 7.84 C7.84 C0.18 8.00 C8.00 0 8.16 C8.16 0.18 db gain vs. frequency (transmit and receive) (600 w termination; reference 1 khz 2 ): 200 hz to 300 hz 300 hz to 3.4 khz 3.4 khz to 16 khz 16 khz to 266 khz C1.00 C0.3 C3.0 0.0 0.0 C0.1 0.05 0.05 0.3 2.0 db db db db gain vs. level (transmit and receive)(reference 0 dbv 2 ): C50 db to +3 db C0.05 0 0.05 db return loss 3 : 200 hz to 500 hz 500 hz to 3400 hz 20 26 24 29 db db 2-wire idle-channel noise (600 w termination): psophometric c-message 3 khz flat C87 2 10 C77 12 20 dbmp dbrnc dbrn transmit idle-channel noise: psophometric c-message 3 khz flat C82 7 15 C77 12 20 dbmp dbrnc dbrn transhybrid loss 3 : 200 hz to 500 hz 500 hz to 3400 hz 21 26 24 29 db db
data sheet january 2000 lucent technologies inc. 11 with battery switch l7556, l7557 low-power slics electrical characteristics (continued) table 9. logic inputs and outputs all outputs except rgdet and l bat are open collectors with internal, 30 k w pull-up resistor. rgdet and l bat are open collectors without internal pull-up. input pin b1 has a 40 k w pull-up; it goes low in the event of thermal shut- down. parameter symbol min typ max unit input voltages: low level (permissible range) high level (permissible range) v il v ih C0.5 2.0 0.4 2.4 0.7 v cc v v input currents: low level (v cc = 5.25 v, v i = 0.4 v) high level (v cc = 5.25 v, v i = 2.4 v) i il i ih C75 C40 C115 C60 C200 C100 a a output voltages (open collector with internal pull-up resistor): low level (v cc = 4.75 v, i ol = 360 a) high level (v cc = 4.75 v, i oh = C20 a) v ol v oh 0 2.4 0.2 0.4 v cc v v ring trip requirements n ringing signal: voltage, minimum 35 vrms , maximum 100 vrms . frequency, 17 hz to 23 hz. crest factor, 1.4 to 2. n ringing trip: 100 ms (typical), 250 ms (v bat = C33 v, loop length = 530 w ). n pretrip: the circuits in figure 3 will not cause ringing trip. 12-2572g (f) figure 3. ring trip circuits ring ring ring 100 w 10 k w 6 m f tip tip tip 2 m f 200 w switch closes <12 ms
12 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics test configurations 12-2564.a (f) figure 4. basic test circuit 12-2584.c (f) figure 5. longitudinal balance v bat1 v cc 0.1 m f 0.1 m f 0.1 m f 95.3 k w 20 k w 0.47 m f 0.1 m f tip xmt 76.8 k w 11 k w rcv 68.1 k w 24.9 k w b1 nlc v bat1 bgnd v cc agnd i prog dcout lcth rtsp rtsn icm vitr sn rcvp b0 cf1 xmt rcvn nrdet rgdet cf2 l7556 slic pt pr bs bs1 bs2 l bat v bat2 0.1 m f v bat2 0.1 m f l7557 100 w 11 k w 100 w ring 100 w r loop 2 m w 2 m w 274 k w 402 w v bat tip ring basic test circuit longitudinal balance = 20 log v s v m 368 w 100 m f 100 m f 368 w v m + C v s
lucent technologies inc. 13 data sheet january 2000 with battery switch l7556, l7557 low-power slics test configurations (continued) 12-2583.b (f) figure 6. longitudinal psrr v s = 0.5 vrms 30% am 1 khz modulation, f = 500 khz 1 mhz device in powerup mode, 600 w termination 5-6756.b (f) * hp is a registered trademark of hewlett-packard company. figure 7. rfi rejection 12-2585.a (f) figure 8. longitudinal impedance 12-2582.b (f) figure 9. metallic psrr 12-2587.e (f) figure 10. ac gains v s 4.7 m f 100 w v bat or v cc disconnect bypass capacitor 56.3 w v bat or v cc tip ring basic test circuit psrr = 20log v s v m 67.5 w 10 m f 10 m f 67.5 w v m + C basic test circuit tip ring v bat 0.01 m f 0.01 m f 600 w 2.15 m f 82.5 w 82.5 w hp * 4935a tims 50 w 1 2 4 6, 7 lb1201 v s tip ring basic test circuit + C + C i long i long v pt v pr z long = or d v pt d i long d v pr d i long v s 4.7 m f 100 w v bat or v cc disconnect v t/r v bat or v cc tip ring basic test circuit + C psrr = 20log v s v t/r 900 w bypass capacitor tip ring basic test circuit 600 w v t/r + C g xmt = v xmt v t/r g rcv = v t/r v rcv xmt rcv v s
14 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics applications 12-2573.y(f) notes: tx = 0 db. rx = 0 db. termination = 600 w. transhybrid = 600 w. figure 11. basic loop start application circuit using t7504 type codec 12-3547(f) figure 12. ring ground detection circuit r prog 66.8 k w r lcth 24.9 k w l7581 relay pt v bat1 c bat1 0.1 m f v bat1 v bat2 c bat2 0.1 m f c cc 0.1 m f v cc v cc rcvn dcout lcth pr rtsp r ts1 402 w c rts2 0.27 m f rtsn r ts2 274 k w r tsn 2.0 m w v ring v bat cf2 cf1 c f1 0.47 m f agnd bgnd i prog vitr rcvp r t1 54.9 k w r t2 18.7 k w r rcv 84.5 k w r hb1 90.9 k w vf x in r x 90.9 k w gsx pwrop dx dr fsx fsep mclk 1/4 t7504 codec control input pcm highway sync and clock C + l7556/l7557 slic b1 control inputs supervision outputs c rts1 0.022 m f r tsp 2.0 m w c f2 0.1 m f agnd bgnd l bat c b1 0.47 m f r gp 57.6 k w c gp 330 pf 10 1 4 5 19 21 14 6 vf x ip asel 7 nlc nrdet 27 17 4 26 25 b0 bs 21 12 13 18 19 agnd 2 v cc 9 8 v cc c cc 0.1 m f 22 11 24 23 5 tip r pt 50 w ring r pr 50 w crowbar protector crowbar protector c b2 0.47 m f d bat v cc 0.47 m f c icm ground start application circuit r gdet icm r gdet r icm2 154 k w 100 k w r gdet
lucent technologies inc. 15 data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) table 10. parts list for loop start and ground start applications * contact your lucent technologies account representative for protector recommendations. choice of this (and all) component(s) s hould be evaluated and confirmed by the customer prior to use in any field or laboratory system. lucent does not recommend use of this p art in the field without performance verification by the customer. this device is suggested by lucent for customer evaluation. the decisio n to use a component should be based solely on customer evaluation. name value function integrated circuits slic l7556/7557 subscriber loop interface circuit (slic). protector crowbar protector* secondary protection. ringing relay l7581 switches ringing signals. codec t7504 first-generation codec. overvoltage protection r pt 50 w , ptc or fusible protection resistor. r pr 50 w , ptc or fusible protection resistor. power supply c bat1 0.1 f, 20%, 100 v v bat1 filter capacitor. c bat2 0.1 f, 20%, 100 v v bat2 filter capacitor. c cc 0.1 f, 20%, 10 v v cc filter. c f1 0.47 f, 20%, 100 v with c f2 , improves idle channel noise. c f2 0.1 f, 20%, 100 v with c f1 , improves idle channel noise. d bat 100 v, 150 ma transient protection diode. dc profile r prog 66.8 k w , 1%, 1/16 w sets dc loop current limit. ac characteristics c b1 0.47 f, 20%, 10 v ac/dc separation capacitor. c b2 0.47 f, 20%, 10 v ac/dc separation capacitor. r t1 54.9 k w , 1%, 1/16 w with r gp and r rcv , sets ac termination impedance. r rcv 84.5 k w , 1%, 1/16 w with r gp and r t1 , sets receive gain. r gp 57.6 k w , 1%, 1/16 w with r t1 and r rcv , sets ac termination impedance and receive gain. c gp 330 pf, 10 v, 20% loop stability. r t2 18.7 k w , 1%, 1/16 w with r x , sets transmit gain in codec. r x 90.9 k w , 1%, 1/16 w with r t2 , sets transmit gain in codec. r hb1 90.9 k w , 1%, 1/16 w sets hybrid balance.
16 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) table 10. parts list for loop start and ground start applications (continued) design considerations table 11 shows the design parameters of the application circuit shown in figure 11. components that are adjusted to program these values are also shown. table 11. 600 w design parameters name value function supervision r lcth 24.9 k w , 1%, 1/16 w sets loop closure (off-hook) threshold. r ts1 402 w , 5%, 2 w ringing source series resistor. r ts2 274 k w , 1%, 1/16 w with c rts2 , forms first pole of a double pole, 2 hz ring trip sense filter. c rts1 0.022 f, 20%, 5 v with r tsn , r tsp , forms second 2 hz filter pole. c rts2 0.27 f, 20%, 100 v with r ts2 , forms first 2 hz filter pole. r tsn 2 m w , 1%, 1/16 w with c rts1 , r tsp , forms second 2 hz filter pole. r tsp 2 m w , 1%, 1/16 w with c rts1 , r tsn , forms second 2 hz filter pole. ground start c icm 0.47 f, 20%, 10 v provides 60 hz filtering for ring ground detection. r gdet 100 k w , 20%, 1/16 w digital output pull-up resistor. r icm2 82.5 k w , 1%, 1/16 w sets ring ground detection threshold. design parameter parameter value components adjusted loop closure threshold 10 ma r lcth dc loop current limit 40 ma r prog dc feed resistance 180 w r pt , r pr 2-wire signal overload level 3.14 dbm ac termination impedance 600 w r t1 , r gp , r rcv hybrid balance line impedance 600 w r hb1 transmit gain 0 db r t2 , r x receive gain 0 db r rcv , r gp , r t1
lucent technologies inc. 17 data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) characteristic curves 12-2828.c (f) figure 13. receive gain and hybrid balance vs. frequency 12-2829.b (f) figure 14. transmit gain and return loss vs. frequency 12-2830.a (f) figure 15. typical v cc power supply rejection 12-2871.a (f) figure 16. typical v bat power supply rejection frequency (hz) 100 C20 C10 0 10 4 C50 C40 C30 1000 hybrid balance (db) receive gain 10 5 100 1000 10 4 C50 C30 C20 C10 0 frequency (hz) C40 transmit gain return loss (db) 10 5 10 100 10 6 C80 C70 C20 C10 0 frequency (hz) 1000 C50 C40 C60 C30 psrr (db) current limit below current limit spec. 10 5 10 4 10 100 10 5 10 6 C80 C70 C20 C10 0 frequency (hz) 1000 10 4 C50 C40 C60 C30 psrr (db) below current limit current limit specification range
18 18 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) characteristic curves (continued) 12-3015 (f) note: v bat = C48 v. figure 17. loop closure program resistor selection 12-3016a (f) notes: tip lead is open. v bat = C48 v. figure 18. ring ground detection programming 12-3050.a(f) notes: v bat1 = C48 v. v bat2 = C28 v. i lim = 22 ma. r dc1 = 115 w . figure 19. loop current vs. loop voltage 12-3051.a(f) notes: v bat1 = C48 v. v bat2 = C28 v. i lim = 22 ma. r dc1 = 115 w . figure 20. loop current vs. loop resistance 0 5 20 25 0 102030 60 loop closure threshold resistor, r lcth (k w ) 50 15 10 40 off-hook threshold loop current (ma) ring ground current detection resistor, r icm (k w ) threshold ring ground current (ma) 35 30 25 20 15 10 5 0 0 50 100 150 200 250 01020 50 0 20 30 40 50 loop voltage (v) 30 40 10 loop current (ma) 1 10 k w i lim C1 rdc 1 l7556 bs = 1, l7557 bs = 0 bs = 0 loop resistance, r loop (w) 0 500 1000 2000 0 20 30 40 50 1500 10 loop current (ma) l7556 bs = 0 bs = 1, l7557 bs = 0
lucent technologies inc. 19 data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) characteristic curves (continued) 12-3052.a (f) notes: v bat1 = C48 v. v bat2 = C28 v. i lim = 22 ma. r dc1 = 115 w . figure 21. typical slic power dissipation vs. loop resistance 12-2825.c (f) figure 22. power derating 12-2559.b (f) figure 23. longitudinal balance resistor mismatch requirements 12-3021 (f) figure 24. longitudinal balance vs. protection resistor mismatch loop resistance, r loop (w) 0 500 1000 2000 0 1000 1500 1500 500 slic power dissipation (mw) bs = 1 l7557 bs = 0 l7556 bs = 0 ambient temperature, t a ( c) 20 40 60 140 180 0 500 1000 1500 2000 80 100 120 160 power (mw) 60 c/w 0 2 3 4 7 8 0204060 protection resistor value ( w ) protection resistor mismatch (%) 100 1 6 5 120 80 49 db, rp matched to 1.5 w 58 db, rp matched to 0.5 w 60 55 50 45 40 0.0 0.5 1.0 1.5 2.0 2.5 protection resistor mismatch ( w ) longitudinal balance (db)
20 20 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) dc applications battery feed the dc feed characteristic can be described by: where: i l = dc loop current. v t/r = dc loop voltage. |v bat | = battery voltage magnitude applied to the power amplifier stage (v bat1 or v bat2 ). v oh = overhead voltage. this is the difference between the battery voltage and the open loop tip/ring voltage. r l = loop resistance, not including protection resistors. r p = protection resistor value. r dc = slic internal dc feed resistance. the design begins by drawing the desired dc template. an example is shown in figure 25. 12-3050.f (f) notes: v bat1 = C48 v. v bat2 = C28 v. i lim = 22 ma. r dc1 = 115 w . figure 25. loop current vs. loop voltage starting from the on-hook condition and going through to a short circuit, the curve passes through two regions: region 1; on-hook and low loop currents. the slope corresponds to the dc resistance of the slic, r dc1 (default is 115 w typical). the open circuit voltage is the battery voltage less the overhead voltage of the device, v oh (default is 7.9 v typical). these values are suitable for most applications, but can be adjusted if needed. for more information, see the sections entitled adjust- ing dc feed resistance or adjusting overhead volt- age. region 2; current limit. the dc current is limited to a value determined by external resistor r prog . this region of the dc template has a high resistance (10 k w ). calculate the external resistor as follows: r prog (k w ) = 1.67 i lim (ma) switching the battery the l7556 and l7557 slics provide an input for an auxiliary battery. called v bat2 , this power supply should be lower in magnitude than the primary battery, v bat1 . under an acceptable loop condition, v bat2 can be switched to provide the loop power through the out- put amplifiers of the slic. the dc template, described in the last section, is determined by the battery that is activatedeither v bat1 or v bat2 . which device will be best for you? that mainly depends on your loop range requirements. if you have only short loops and no on-hook voltage requirements, you don't need a battery switch at all. use the l7551 instead. if you have only to guarantee a short loop range, e.g., 22 ma into 530 w , consider the l7556. the minimum v bat2 can be determined by the standard dc equations. in these applications, the off-hook detector can be used to indicate when to switch the battery. just make sure the off-hook detector will also function as required with v bat2 as well as v bat1 . consider an off-hook threshold of 10 ma. this could represent a 1000 w loop with a 48 v v bat1 active or a 2000 w loop with a 28 v v bat2 active. in this case, if the loop is below 1000 w or above 2000 w , off-hook detection will be accurate. between 1000 w and 2000 w , the detector is battery-dependent. this condi- tion must be avoided. in our example, since the maxi- mum loop is 530 w , the 10 ma detector is perfectly acceptable. if the ptt would like a short loop system that can also serve long loops, the off-hook detector is not the best indicator, and better loop intelligence is needed. in this case, the l7557 can be used. it has an internal com- parator that senses when there is enough potential at v bat2 to switch without affecting the loop current. in this case, the loop range is determined by v bat1 , and v bat2 is only switched in when the loop is short enough to use it. this switching is automatic and includes hys- teresis to avoid oscillation when the loop length is close to the v bat2 switch threshold. i l v bat v oh C r l 2r p r dc ++ --------------------------------- - = v tr v bat v oh C () r l r l 2r p r dc ++ -------------------------------------------- = 01020 50 0 20 30 40 50 loop voltage (v) 30 40 10 loop current (ma) 1 10 k w i lim C1 rdc 1
lucent technologies inc. 21 data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) dc applications (continued) overhead voltage in order to drive an on-hook ac signal, the slic must set up the tip and ring voltage to a value less than the battery voltage. the amount that the open loop voltage is decreased relative to the battery is referred to as the overhead voltage. expressed as an equation: v oh = | v bat | C (v pt C v pr ) without this buffer voltage, amplifier saturation will occur and the signal will be clipped. the device is auto- matically set at the factory to allow undistorted on-hook transmission of a 3.17 dbm signal into a 900 w loop impedance. for applications where higher signal levels are needed, e.g., periodic pulse metering, the 2-wire port of the slic can be programmed with pin dcr. the drive amplifiers are capable of 4 vrms minimum (vamp). referring to figure 26, the internal resistance has a worst-case value of 46 w . so, the maximum sig- nal the device can guarantee is: thus, r p 35 w allows 2.2 vrms metering signals. the next step is to determine the amount of overhead volt- age needed. the peak voltage at output of tip and ring amplifiers is related to the peak signal voltage by: 12-2560.e (f) figure 26 . slic 2-wire output stage in addition to the required peak signal level, the slic needs about 2 v from each power supply to bias the amplifier circuitry. it can be thought of as an internal saturation voltage. combining the saturation voltage and the peak signal level, the required overhead can be expressed as: where v sat is the combined internal saturation voltage between the tip/ring amplifiers and v bat (5.4 v typ.). r p ( w ) is the protection resistor value, and 40 w is the output series resistance of each internal amplifier. z t/r ( w ) is the ac loop impedance. example 1, on-hook transmission of a meter pulse: signal level: 2.2 vrms into 200 w 35 w protection resistors i loop = 0 (on-hook transmission of the metering signal) v oh = 5.4 + (2.2) = 10.8 v accounting for v sat tolerance of 0.5 v, a nominal overhead of 11.3 v would ensure transmission of an undistorted 2.2 v metering signal. adjusting overhead voltage to adjust the open loop 2-wire voltage, pin dcr is programmed at the midpoint of a resistive divider from ground to either C5 v or v bat . in the case of C5 v, the overhead voltage will be independent of the battery voltage. figure 27 shows the equivalent input circuit to adjust the overhead voltage. 12-2562 (f) figure 27. equivalent circuit for adjusting the overhead voltage the overhead voltage is programmed by using the fol- lowing equation: v oh = 7.9 C 4 v dcr v tr 4 v z t/r z t/r 2r p 46 + () + ----------------------------------------- ? ?? = vamp = v t/r 1 2r p 40 w + () z tr ------------------------------ + ? ?? l l r p r p 40 w 40 w v amp + C [z t/r ] + C v t/r v oh v sat 1 2r p 40 w + () z tr ------------------------------ + ? ?? v tr + = l 1 235 40 + () 200 ----------------------------- - + ? ?? 2 dcr 25 k w 30% r1 r2 C5 v 7.9 4 5 r 1 25 k w || r 2 r 1 25 k w || + ------------------------------------- - ? ?? C ? ?? C = 7.9 20 r 1 25 k w || r 2 r 1 25 k w || + ------------------------------------- - ? ?? + =
22 22 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) dc applications (continued) adjusting dc feed resistance the dc feed resistance may be adjusted with the help of figure 28. 12-2560 (f) figure 28. equivalent circuit for adjusting the dc feed resistance the above paragraphs describe the independent set- ting of the overhead voltage and the dc feed resis- tance. if both need to be set to customized values, combine the two circuits as shown in figure 29. 12-2561 (c) figure 29. adjusting both overhead voltage and dc feed resistance this is an equivalent circuit for adjusting both the dc feed resistance and overhead voltage together. the adjustments can be made by a simple superposi- tion of the overhead and dc feed equations: when selecting external components, select r1 on the order of 5 k w to minimize the programming inaccuracy caused by the internal 25 k w resistor. lower values can be used; the only disadvantage is the power consump- tion of the external resistors. loop range the equation below can be rearranged to provide the loop range for a required loop current: off-hook detection the loop closure comparator has built-in longitudinal rejection, eliminating the need for an external 60 hz filter. the loop closure detection threshold is set by resistor r lcth . referring to figure 30, nlc is high in an on-hook condition (i tr = 0, v dcout = 0) and v lcth = 0.05 ma x r lcth . the off-hook comparator goes low when v lcth crosses zero and then goes neg- ative: 12-2553g(f) figure 30. off-hook detection circuit applications dcr r1 r3 dcout 25 k w 30% r dc 115 w 500 w d v dcr d v dcout -------------------- + = 115 w 500 w r 1 25 k w || r 3 r 1 25 k w || + --------------------------------- - ? ?? + = dcr 25 k w 30% r1 r3 dcout r2 C5 v v lcth = 0.05 ma x r lcth + v dcout = 0.05 ma x r lcth C 0.125 v/ma x i tr r ltch (k w ) = 2.5 x i tr (ma) v oh 7.9 20 r 1 25 k w r 3 || || r 2 r 1 25 k w r 3 || || + ---------------------------------------------- ? ?? + = r dc 115 w 500 w r 1 25 k w || r 2 r 1 25 k w || + ------------------------------------- - ? ?? + = r l v bat v oh C i l ---------------------------- 2r p C r dc C = r l itr r p r p ring C + dcout r lcth lcth nlc tip 0.125 v/ma 0.05 ma C +
lucent technologies inc. 23 data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) dc applications (continued) ring trip detection the ring trip circuit is a comparator that has a special input section optimized for this application. the equiva- lent circuit is shown in figure 31, along with its use in an application using unbalanced, battery-backed ring- ing. 12-3014.f (f) figure 31. ring trip equivalent circuit and equivalent application the comparator input voltage compliance is v cc to v bat , and the maximum current is 240 a in either direction. its application is straightforward. a resistance (r tsn + r ts2 ) in series with the r tsn input establishes a current which is repeated in the r tsp input. a slightly lower resistance (r tsp ) is placed in series with the r tsp input. when ringing is being injected, no dc current flows through r ts1 , and so the r tsp input is at a lower potential than r tsn . when enough dc loop current flows, the r tsp input voltage increases to trip the com- parator. in figure 31, a low-pass filter with a double pole at 2 hz was implemented to prevent false ring trip. the following example illustrates how the detection cir- cuit of figure 31 will trip at 12.5 ma dc loop current using a C48 v battery. i n = = 17.9 a the current i n is repeated as i p in the positive compar- ator input. the voltage at comparator input r tsp is: using this equation and the values in the example, the voltage at input r tsp is C12 v during ringing injection (i loop(dc) = 0). input r tsp is therefore at a level of 5 v below r tsn . when enough dc loop current flows through r ts1 to raise its dc drop to 5 v, the comparator will trip. in this example, i loop(dc) = = 12.5 ma ring ground detection pin icm sinks a current proportional to the longitudinal loop current. it is also connected to an internal compar- ator whose output is pin rgdet. in a ground start application where tip is open, the ring ground current is half differential and half common mode. in this case, to set the ring ground current threshold, connect a resis- tor r icm from pin icm to v cc . select the resistor according to the following relation: the above equation is shown graphically in figure 18. it applies for the case of tip open. the more general equation can be used in ground key application to detect a common-mode current i cm : + C r loop 15 k w 7 v i p = i n rtsn rts2 2 m w 2 m w c rts1 c rts2 274 k w phone hook switch rc phone v ring v bat nrdet r ts1 r tsp i n rtsn C + 0.022 m f 0.27 m f 402 w r tsp 7 C 48 C () C 2.289 k w ----------------------------- v rtsp v bat i loop dc () + r ts1 i p r tsp + = 5 v 402 w ------------------ r icm k w () v cc 228 i rg ma () ---------------------- = r icm k w () v cc 114 i cm ma () ---------------------- =
24 24 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) ac design there are four key ac design parameters. termination impedance is the impedance looking into the 2-wire port of the line card. it is set to match the impedance of the telephone loop in order to minimize echo return to the telephone set. transmit gain is measured from the 2-wire port to the pcm highway, while receive gain is done from the pcm highway to the transmit port. finally, the hybrid balance network cancels the unwanted amount of the receive signal that appears at the transmit port. at this point in the design, the codec needs to be selected. the discrete network between the slic and the codec can then be designed. here is a brief codec feature and selection summary. first-generation codecs these perform the basic filtering, a/d (transmit), d/a (receive), and -law/a-law companding. they all have an op amp in front of the a/d converter for transmit gain setting and hybrid balance (cancellation at the summing node). depending on the type, some have differential analog input stages, differential analog output stages, and -law/a-law selectability. this generation of codecs has the lowest cost. they are most suitable for applica- tions with fixed gains, termination impedance, and hy- brid balance. second-generation codecs this class of devices includes a microprocessor inter- face for software control of the gains and hybrid bal- ance. the hybrid balance is included in the device. ac programmability adds application flexibility and saves several passive components and also adds several i/o latches that are needed in the application. however, it does not have the transmit op amp, since the transmit gain and hybrid balance are set internally. third-generation codecs this class of devices includes the gains, termination impedance, and hybrid balanceall under micropro- cessor control. depending on the device, it may or may not include latches. selection criteria in the following examples, use of a first-generation codec is shown. the equations for second- and third- generation codecs are simply subsets of these. there are two examples. the first shows the simplest circuit, which uses a minimum number of discrete components to synthesize a real termination impedance. the sec- ond example shows the use of the uncommitted op amp to synthesize a complex termination. the design has been automated in a dos based program, avail- able on request. in the codec selection, increasing software control and flexibility are traded for device cost. to help decide, it may be useful to consider the following. will the appli- cation require only one value for each gain and imped- ance? will the board be used in different countries with different requirements? will several versions of the board be built? if so, will one version of the board be most of the production volume? does the application need only real termination impedance? does the hybrid balance need to be adjusted in the field?
lucent technologies inc. 25 data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) ac design (continued) selection criteria (continued) ac equivalent circuits using a t7513 codec are shown in figures 32 and 33. 12-2554j (f) figure 32. ac equivalent circuit not including spare op amp 12-3013b (f) figure 33. ac equivalent circuit including spare op amp r p pr 40 w z t r p pt 40 w v t/r i t/r a v = C1 a v = 1 C0.125 v/ma r t1 r rcv r hb1 r t2 vitr rcvn rcvp r x vgsx vf x in vf x ip vfr (pwrop) t7513 codec v s z t/r a v = 4 r g C + C + C + + C slic r p pr 40 w z t r p pt 40 w v t/r i t/r a v = C1 a v = 1 C0.125 v/ma r t3 r rcv r hb1 r t6 vitr rcvn rcvp r x vgsx vf x in vf x ip vfr (pwrop) t7513 codec v s z t/r a v = 4 r gn C + C + C + + C C + xmt agnd r t4 z t5 sn slic
26 26 lucent technologies inc. data sheet january 2000 with battery switch l7556, l7557 low-power slics applications (continued) ac design (continued) selection criteria (continued) example 1, real termination: the following design equations refer to the circuit in figure 32. use these to synthesize real termination impedance. termination impedance: z t = receive gain: g rcv = g rcv = transmit gain: g tx = g tx = x hybrid balance: h bal = 20log to optimize the hybrid balance, the sum of the currents at the vfx input of the codec op amp should be set to 0. the following expressions assume the test network is the same as the termination impedance. h bal = 20log r hb = example 2, complex termination: for complex termination, the spare op amp is used (see figure 33). the hybrid balance equation is the same as in exam- ple 1. pcb layout information make the leads to bgnd and v bat as wide as possible for thermal and electrical reasons. also, maximize the amount of pcb copper in the area ofand specifically onthe leads connected to this device for the lowest operating temperature. when powering the device, ensure that no external potential creates a voltage on any pin of the device that exceeds the device ratings. in this application, some of the conditions that cause such potentials during pow- erup are the following: 1) an inductor connected to pt and pr (this can force an overvoltage on v bat through the protection devices if the v bat connection chatters), and 2) inductance in the v bat lead (this could resonate with the v bat filter capacitor to cause a destructive overvoltage). this device is normally used on a circuit card that is subjected to hot plug-in, meaning the card is plugged into a biased backplane connector. in order to prevent damage to the ic, all ground connections must be applied before, and removed after, all other connec- tions. v tr i tr C -------------- z t r p 80 w 1000 1 r t1 r gp -------- - r t1 r rcv ----------- - ++ ----------------------------------- ++ = v tr v fr ------------- - 8 1 r rcv r t1 --------------- r rcv r gp --------------- ++ ? ?? 1 z t z t/r ------------ - + ? ?? ------------------------------------------------------------------------------------- v gsx v tr -------------- - r x C r t2 ----------- 125 z tr ------------- v gsx v fr -------------- - r x r hb ----------- - g tx C g rcv ? ?? r x g tx g rcv ------------------------ - z t 2r p 80 w 1000 1 r t3 r gn --------- r t3 r rcv ----------- - ++ ----------------------------------- z t5 r t4 --------- () ++ = 2r p 80 w kz t5 () ++ = g rcv 8 1 r rcv r t3 ------------- - r rcv r gn ------------- - ++ ? ?? 1 z t z t/r ---------- + ? ?? ----------------------------------------------------------------------------- = g tx r x C r t6 ---------- - 125 z t/r ---------- z t5 r t4 --------- =
lucent technologies inc. 27 data sheet january 2000 with battery switch l7556, l7557 low-power slics outline diagram 32-pin plcc dimensions are in millimeters. note: the dimensions in this outline diagram are intended for informational purposes only. for detailed schemat- ics to assist your design efforts, please contact your lucent technologies sales representative. 5-3813f 0.10 seating plane 0.38 min typ 1.27 typ 0.330/0.533 1 430 5 13 21 29 14 20 12.446 0.127 11.430 0.076 pin #1 identifier zone 14.986 0.127 13.970 0.076 3.175/3.556
l u cent t e chnolo g ies inc . res e rves t h e ri g ht t o mak e chan g es t o the p rod u ct(s ) o r i n for m atio n con t aine d he r ein with o ut n o tice. n o li a bil i t y is assu m ed a s a r esult o f thei r us e or a pplicatio n . no r igh t s und e r a n y p aten t accom p a ny th e sale of a ny suc h pro d uct(s ) or in f or m ation. co p yrigh t ? 200 0 luce n t t echn o logies i n c. all righ t s rese r ved january 2000 ds00 - 060alc (replaces d s 97-172 a lc) f o r a d d i ti o n a l i n fo r m a t i o n , c o n ta c t y o u r m i c r o e l e c t r o n i c s g r o u p a cc o u n t m a n a ge r o r t h e f o l l o wi n g: i n terne t : http://ww w .lucent.com/micro e-m a il: do c m a ste r @mi c ro . luc e nt.com n . a m e r ic a : m i c r o e l e c t r o n i cs g r o u p, l u c e nt t e c hn o l o g i e s i n c ., 5 5 5 u n i o n b o u l e v a r d , r o o m 3 0 l - 1 5 p - b a , a l l e nt o wn , p a 1 8 1 0 3 1 - 80 0 - 37 2 - 2 4 4 7 , f a x 6 1 0 - 7 1 2 - 4 10 6 ( i n c a n a d a : 1 - 8 0 0 - 5 5 3 - 2 44 8 , f a x 6 1 0 -7 1 2 - 4 1 0 6 ) a s i a p a cif i c : m i c r o e l e c t r o n i cs g r o u p, l u c e nt t e c hn o l o g i e s s i ng a p o r e p t e . l t d ., 7 7 s c i en c e p a r k d r i v e, # 0 3 - 1 8 c i nt e c h ii i , s i n g a po r e 1 1 8 256 t el . ( 6 5 ) 77 8 8 83 3 , f a x ( 6 5 ) 7 7 7 74 9 5 c h i n a: m i c r o e l e c t r o n i cs g r o u p, l u c e n t t e c h n o l og i e s ( c h i n a ) c o ., l t d., a- f2 , 2 3 / f , z ao f o n g u n i v e rs e b u i l d i n g , 1 8 0 0 zh o n g s h a n x i ro a d, s h an g h a i 2 00 2 3 3 p . r. ch i na t e l . ( 8 6 ) 2 1 6 4 4 0 0 4 6 8 , e x t . 3 1 6 , f a x ( 86 ) 21 64 4 0 06 5 2 j a p a n : m i cr o e l e c t r o n i cs g r o u p, l u c e nt t e c hn o l o g i e s j a p a n l t d ., 7 - 18 , h i g a s h i - g o t a n d a 2 - c h o m e , s h i n a g a wa - k u , t o k y o 1 4 1 , j a p a n t e l . ( 8 1) 3 5 4 21 1 60 0 , f a x ( 8 1 ) 3 5 4 2 1 17 0 0 e u r op e : d a t a r e qu e s t s : m ic r oe l e c tro n ic s g r ou p d a t a li n e : t e l. ( 4 4 ) 7 0 0 0 5 8 2 36 8 , f a x (4 4 ) 1 1 89 3 2 8 1 48 t e c h n i c a l in q u i r i e s : g e r ma n y : ( 4 9 ) 89 9 5 0 8 6 0 (munich ) , united kingdom: ( 4 4 ) 1 3 4 4 8 6 5 9 0 0 ( a scot) , f r a n ce: ( 3 3 ) 1 4 0 8 3 6 8 0 0 (p a r i s), s we d e n : ( 4 6) 8 5 9 4 6 07 00 ( s tockholm), f i nland: ( 3 58 ) 9 4 35 4 2 80 0 ( h e l si n k i ), i t a l y : ( 3 9 ) 0 2 6 6 0 8 13 1 (m i l a n ) , s p a i n : ( 3 4 ) 1 8 0 7 1 4 4 1 (madrid) d a t a s h e et january 2000 with battery switch l7556, l7557 low-power slics ordering information device part no. d escription package comcode a tt l 75 5 6aau low-pow e r slic wi t h battery switch 3 2 -pin p l cc 1 0 73 8 56 6 8 a tt l 75 5 6aau-tr low-pow e r slic wi t h battery switch 3 2 -pin plcc ( t ape and re e l) 1 0 77 4 95 0 9 a tt l 75 5 7aau low-pow e r slic wi t h battery switch 3 2 -pin p l cc 1 0 73 8 58 4 1 a tt l 75 5 7aau-tr low-pow e r slic wi t h battery switch 3 2 -pin plcc ( t ape and re e l) 1 0 77 4 95 1 7

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