application note slic l3000n/l3092 performance analysis with -24v battery by w.rossi introduction this technical note describes the l3000n/l3092 slic performances when used with a battery volt- age of 24v. all the main characteristics are ana- lyzed and compared with the results obtained with a standard battery voltage of 48v. the following data were obtained from a typical device in order to have an idea on how dc char- acteristic, power consumption, ringing voltage and ac performances are influenced by a re- duced battery voltage. power consumption table 1 shows the l3000n-l3092 current con- sumption with two batteries combination v b- =- 48v; v b+ = 72v and v b- = -24v; v b+ = +50v. the measurements are made in the different operat- ing modes (power down; stand-by; conversion with i l =0;i l = 40ma and ringing without ac line load (ringing equivalent number ren = 0). table 1: slic typical current consumption with different battery voltages. current consumption (ma) 48v +72v 24v +60v pw - down 0000 sby (i l = 0) 1.93 0 1.9 0 cvs (i l = 0) 4.91 4.4 0 cvs (i l = 40ma) 52.2 50 0 ring (0 ren) 13.4 10.8 10.0 7.9 dc characteristics in fig 1 you can see the typical dc characteristics for the two battery voltages: feeding resistance was set to 2 x 200 w (rfs = 200 w ). the typical current value versus loop resistance is given by: i l = ilim for r l < |v b - | - 5v ilim - 2rfs i l = |v b - | - 5v r l + 2rfs for r l > |v b - | - 5v ilim - 2rfs where rfs represents the resistance of each side of the traditional feeding system (most com- mon values for rfs are 200, 400 and 500 w ). maximum loop lenght two are the parameters influenced by line lenght increment: the first is the dc line current and the second is the maximum ac signal that can be sent without distortion (thd = 1%). here below are shown the typical maximum loop resistance values and the relative line current in corrispon- dance of which distortion is still less than 1% for +4dbm (1.23 vrms) ac signals. the slic feed- ing resistance is set 2 x 200 w . v b- = -48v v b- = -24v rmax. = 2200 w rmax. = 940 w i l = 16.61ma i l = 14.47ma on/off hook current thresholds here below are reported the typical values of the dc current thresholds used by the slic to detect the on hook and off hook line conditions. AN498/0994 figure 1: l3000n/l3092dc characteristic with a2x200 w feeding resistance. 1/3
v b = 48v --------------- on/off hook commutation il = 8.10ma vl = 40.58v rl = 5k w off/on hook commutation. il = 5.91ma vl = 41.30v rl = 7k w v b = 24v --------------- on/off hook commutation il = 8.10ma vl = 16.52v rl = 2k w off/on hook commutation. il = 5.82ma vl = 17.44v rl = 3k w v b = 24v ac performances all the ac performances: txgain, rx gain, re- turn loss, transhybrid loss and longitudinalbal- ance were measured and no significative vari- ations were found changing from 48v to 24v of battery voltage. grx, gtx and thl variation were inside 0.03db; rl inside .07db and longitudinal balance inside .9db. ringing performances l3000n/l3092 slic injects directly the ringing signal into the line. the ringing signal has a dc component superimposed with the ac one. the maximum ringing amplitude that can be ob- tained by l3000n without distortion depends on the total battery voltage available: let: vbt = |vb+| + |vb-| vring = 0.58vbt - 8.6 (vrms) (1) vdcring = 0.1736vbt + 0.75 (v) ex: vb+ = 72v; vb- = -48v vring = 0.58 x 120 - 8.6 = 61vrms vdcring = 21.6v vb+ = 50v; vb- = -24v vring = 0.58 x 74 - 8.6 = 34.3vrms vdcring = 13.6v from eq. (1): vbt = (vring + 8.6)/0.58 conclusions the measurements carried on show that it is pos- sible to make the slic working also with reduced battery voltage (down to 24v) without any degra- dation in terms of ac performances. it should be noted that with 24 battery voltage you can get good performances up to 950 w of loop lenght. in case you need higher line currents you can increase the battery voltage of the amount you need, optimizing in this way power dissipation. application note 2/3
information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of sgs-thomson microelectronics. specifications men- tioned in this publication are subject to change without notice. this publication supersedes and replaces all information previously supplied. sgs-thomson microelectronics products are not authorized for use as critical components in life support devices or systems without ex- press written approval of sgs-thomson microelectronics. ? 1995 sgs-thomson microelectronics - all rights reserved sgs-thomson microelectronics group of companies australia - brazil - france - germany - hong kong - italy - japan - korea - malaysia - malta - morocco - the netherlands - singapore - spain - sweden - switzerland - taiwan - thaliand - united kingdom - u.s.a. application note 3/3
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