application note AN578/0393 behaviour of line card protection power crossing a a. bremond figure 1 : test diagram 220v 50hz 1/1 transformer isolation relay 0to4k line a gnd gate lcpxxx power supply 48v +- 1 - introduction the purpose of this document is to explain the behaviour of lcp 150s/1511/1512 devices during the coupling between a telecommunication line and a mains line. 2 - test diagram figure 1 shows the test diagram. the mains 220 v 50 hz is applied to the test assembly through an isolation transformer. a relay driven by a mono-pulse generator allows the conducting time to be adjus ted. the current through the device is adjusted by a series resistor. 0v -48v 0a 02ab0198 figure 2 : voltage and current for a non-firing device 3 - measurements during the tests three kinds of behaviour occur : a) as shown in figure 2 the device acts as a clamping device (non-firing) due to the small value of the current which never exceeds the latching current of the structure. voltage between line a and gnd. current through the line a 1/3
b) in the second operating region the lcpxxx fires and the piece under test is still functional after 15 minutes. - figure 3.1 shows the start of the firing (the peak of the current wave through the device is just over the latching limit). - in figure 3.2 the amplitude of the current wave through the device is greater than in the precedent case, so the device is well fired after a few hundred microseconds. c) in the third operating region the device has been destoyed in a time depending on the current through the lcpxxx. figure 3 : voltages for a firing device 0v -48v 03ab0198 0v -48v 3.1 with i slightly higher than i latch . 3.2 with i considerably higher than i latch . operating region lcp 150 lcp 1512 lcp 1511 a/clamping 0 to 70 ma * o to 70 ma * o to 70 ma * b/non destruc- tive region 0.07 to 2 a * 0.07 to 1.2a* 0.07 to 0.8a * c/destructive region over 2 a * over 1.2 a * over 0.8 a * * rms current 4 - analysis table 1: operating region definition table 1 shows the range of the three operating regions, while figure 4, which illustrates region c, allows us to determine the destruction time limit of each device versus the current through the structure (rms current at 25c). a application note 2/3
figure 4 : characteristics of region c (with vgate = -48 v) lcp150 / 1511 / 1512 0,5 1 2 5 10 20 50 100 0,5 1 2 5 10 20 t(s) i(arms) lcp150 lcp1512 lcp1511 04ab0198 conclusion the devices in the lcpxxx family have common characteristics, divided into three regions : a) clamping mode, still functional after 15 minutes b) crowbar mode (firing) still functional after 15 minutes of test at 25c c) crowbar mode, with a destruction time defined by figure 4. the given curves enable the appropriate series elements to be chosen, for example a ptc device. information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsability 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 mentio ned in this publication are subject to change without not ice. this publication supersedes and replaces all information previously supplied. sgs-thomson microelectronics products are not authorized for use as critical com ponents in life support devices or sys tems without express written approval of sgs-thomson microelectronics. ? 1995 sgs-thomson microelectronics - printed in italy - 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 - thailand - united kingdom - u.s.a. a application note 3/3
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