CLP200M-TR

® CLP200M OVERVOLTAGE AND OVERCURRENT PROTECTION FOR TELECOM LINE Application Specific Discretes A.S.D. MAIN APPLICATIONS Any telecom equipment submitted to transient overvoltages and lightning strikes such as : Analog and ISDN line cards PABX Main Distribution Frames Primary protection modules s s s s DESCRIPTION The CLP200M is designed to protect telecommunication equipment. It provides both a transient overvoltage protection and an overcurrent protection. It is housed in a PowerSO-10TM package. FEATURES Dual bidirectional protection device. High peak pulse current : ipp = 100a (10/1000 µs surge) Max. voltage at switching-on : 290v Min. current at switching-off : 150ma Failure status output pin s s s s s PowerSO-10TM SCHEMATIC DIAGRAM FS TIP S 1 BENEFITS Both primary and secondary protection levels in one device. Voltage and current controlled suppression. Surface Mounting with PowerSO-10TM package. Line card cost reduction thanks to the very low power rating of external components required : balanced resistors, ring relay, low voltage SLIC protection s s s s bs O let o od Pr e ct u (s) Ob - so TIP L TIP L TIP L te le ro P uc d s) t( NC RING S RING L RING L RING L TAB is connected to GND July 2003- Ed : 4B 1/21 CLP200M COMPLIES WITH THE FOLLOWING STANDARDS: CCITT K20 VDE0433 VDE0878 IEC61000-4-5 FCC Part 68 BELLCORE TR-NWT-001089 Peak Surge Voltage (V) 6000 6000 4000 6000 4000 1500 800 2500 1000 Voltage Waveform (µs) 10/700 10/700 1.2/50 10/700 1.2/50 10/160 10/560 2/10 10/1000 Current Waveform (µs) 5/310 5/310 1/20 5/310 8/20 10/160 10/560 2/10 10/1000 Admissible Ipp (A) 150 150 100 150 100 200 100 500 100 Necessary Resistor (Ω) - BLOCK DIAGRAM TIPL TIPS Overcurrent detector OR SW3 FS SW4 SW2 OR SW1 Overvoltage detector bs O let o Pr e Pin 1 2 du o RINGL (s) ct Ob - so te le Overvoltage reference (+/- 215 V) ro P uc d GND s) t( Overvoltage detector Overvoltage reference (+/- 215 V) Overcurrent detector RINGS Symbol FS TIPS TIPL RINGL RINGS NC GND Description Failure Status TIP (SLIC side) TIP (Line side) RING (Line side) RING (SLIC side) Not connected Ground 3/4/5 6/7/8 9 10 TAB 2/21 CLP200M APPLICATION NOTE 1. INTRODUCTION The aim of this section is to show the behavior of our new telecom line protection device. This device includes a primary protection level and is suitable for main distribution frames and line cardsThis protection concept is explained and, in addition, the CLP200M performances are analysed when facing different surges as described in the CCITT recommendations. Fig. 1 : Subscriber line protection topology 2. STMicroelectronics CLP200M CONCEPT 2.1 Evolution of the SLIC protection Over the years, the silicon protection performances have considerably changed. The first generation of products like SMTHBTxx and SMTHDTxx offered fixed overvoltage protection against surges on either TIP or RING line in four packages. The following generation like THBTxx and THDTxx still offered fixed overvoltage protection against surges on both TIP and RING lines in two packages. The next step was the introduction of the LCP1511D which brought the advantage of full programmable voltage. Today, the CLP200M combines the features of all the previous generations. In addition to that, it offers an overcurrent detection when operating in speech mode and also a Failure Status output signal. "PRIMARY PROTECTION" "SECONDARY PROTECTION" telecommunication CLP200M SLIC line MDF EXCHANGE LINE CARD "SECONDARY PROTECTION" telecommunication CLP200M line THDTxx or LPC1511D or LB200B SLIC Fig. 2 : Line card protection MDF EXCHANGE LINE CARD bs O Figure 1 is a simplified block diagram of a subscriber line protection that is mainly used so far. This shows two different things : A “primary protection” located on the Main Distribution Frame (MDF) eliminates coarsely the high energy environmental disturbances (lightning transients and AC power mains disturbances) A “secondary protection” located on the line card includes a primary protection level (first stage) and a residual protection (second stage) which eliminates finely the remaining transients that have not been totally suppressed by the first stage. The CLP200M can be used both in MDFs and in line cards. In that case, any line card may be swapped from one MDF to another one without reducing the efficiency of the whole system protection. The CCITT requirements are different for these two protection locations (MDFs and line cards). Concerning the “primary protection”, the CCITT requires a 4kV, 10/700µs surge test whereas the “secondary protection” has to withstand a 1kV, 10/700µs surge test. The explanations which follow are basically covering the line card application. s s let o Pr e du o ct (s) Ob - Programmable thanks to any external voltage reference so te le ro P I uc d s) t( Programmable thanks to an external resistor + I SWON V - I SWON Line card operating conditions The figure 2 summarizes the performance of the CLP200M which basically holds the SLIC inside its correct voltage and current values. 3/21 CLP200M APPLICATION CIRCUIT : CLP200M in line card Fig. 3 : CLP200M in line card I Fuse TIP R sense TIPL TIPS 1 -Vbat Rp Overcurrent detector 2 Overvoltage detector Overvoltage reference (+/- 215 V) External voltage reference TIP -Vbat OR SW3 SW1 (*) SLIC FS SW4 SW2 OR Overvoltage detector Overvoltage reference (+/- 215 V) GND Rp 1 RING 2 Overcurrent detector Ring Generator RINGL RINGS RING Fuse R sense (*) LCP1511D or THDT series s bs O Figure 3 above shows the topology of a protected analog subscriber line at the exchange side. The CLP200M is connected to the ring relay via two balanced Rp resistors, and to the Subscriber Line Interface Circuit. A second device is located near the SLIC : it can be either a LCP1511D or a THDT series. These two devices are complementary and their functions are explained below : The first stage based on CLP200M manages the high power issued from the external surges. When used in ringing mode, the CLP200M operates in voltage mode and provides a symmetrical and bidirectional overvoltage protection at +/-215 V on both TIP and RING lines. When used in speech mode, the CLP200M operates in current mode and the activation current of the CLP200M is adjusted by RSENSE. let o Pr e du o (s) ct so Ob - The second stage is the external voltage reference device which defines the firing threshold voltage during the speech mode and also assumes a residual power overvoltage suppression. This protection stage can be either a fixed or programmable breakover device. The THDTxx family acts as a fixed breakover device while the LCP1511D operates as a programmable protection. Thanks to this topology, the surge current in the line is reduced after the CLP200M. Because the remaining surge energy is low, the power ratings of Rp, the ring relay contacts and the external voltage reference circuit may be downsized. This results in a significant cost reduction. s te le ro P uc d s) t( 4/21 CLP200M 2.3 Ringing mode Fig. 4 : Switching by voltage during ringing mode. Fuse TIP ILG R sense ILG A1 TIPL TIPS 1/2 CLP200M Rp Overcurrent detector 2 Overvoltage detector 1 2 1 -215 +215 VLG Overvoltage reference (+/- 215 V) VLG OR SW3 SW1 FS 3 GND In ringing mode (Ring relay in position 2), the only protection device involved is the CLP200M. In normal conditions, the CLP200M operates in region 1 of A1 curve, and is idle. If an overvoltage occuring between TIP (or RING) and GND reaches the internal overvoltage refe-rence (+/- 215V), the CLP200M acts and the line is short-circuited to GND. At this time the operating point moves to region 2 for positive surges (region 3 for negative surges). Once the surge current disappears, the device returns to its initial state (region 1). Fig. 5a : Method to adjust the reference voltage. Fuse TIP For surges occuring between TIP and RING, the CLP200M acts in the same way. This means that the CLP200M ensures a tripolar protection. When used alone, the CLP200M acts at the internal overvoltage reference level (+/- 215V). Furthermore, it is possible to adjust this threshold level to a lower voltage by using : up to 4 fixed external voltage reference (VZ1 to VZ4) (see fig.5a). . R sense TIPL O bs let o ro P e FS du OR (s) ct so Ob - te le ro P uc d s) t( 1 Rp TIPS VZ1 2 Overcurrent detector Overvoltage detector SW3 SW1 Overvoltage reference (+/- 215 V) VZ2 GND SW4 SW2 OR Overvoltage detector Overvoltage reference (+/- 215 V) VZ3 Overcurrent detector VZ4 RINGL RINGS 1 RING Fuse R sense Rp 2 5/21 CLP200M external reference supplies, Vb1 and Vb2 (see fig.5b).. Fig. 5b : Method to adjust the reference voltage. s 1 Fuse TIP R sense Rp TIPL TIPS 2 Overcurrent detector VB1 Overvoltage reference (+/- 215 V) OR SW3 SW1 Overvoltage detector FS SW4 SW2 OR Overvoltage detector Overvoltage reference (+/- 215 V) GND VB2 Overcurrent detector RINGL RINGS RING Fuse R sense 2.4 Speech mode Fig. 6 : Switching by current during speech mode. Fuse TIP ILG R sense TIPL TIPS Overcurrent detector SW3 SW1 FS bs O In speech mode (Ring relay in position 1), the protection is provided by the combination of both CLP200M and the external voltage reference device. In normal conditions, the working point of this circuit is located in region 4 of A2 curve : the CLP200M is idle. When a surge occurs on the line, the external voltage reference device clamps at GND or -Vbat respectively for positive and negative surges. This generates a current which is detected by RSENSE and causes the protection to act : the line is short-circuited to GND. let o Pr e OR od Overvoltage detector uc (s) t VLG GND so Ob 1 2 External voltage reference eP let ro uc d 1 Rp 2 s) t( ILG A2 5 4 Rp -Vbat -VREF2 Overvoltage reference (+/- 215 V) VREF1 6 VLG The operating point moves to region 5 for positive surges or region 6 for negative surges. Once the surge current falls below the switching-off current ISWOFF, the CLP200M returns to its initial state (region 4). Furthermore, the CLP200M switches when an overvoltage, either positive or negative, occurs either : simultaneously on both TIP and RING lines versus GND. between TIP and RING. on TIP (or RING) versus GND. s s s 6/21 CLP200M Fig. 7a and 7b RSENSE. ISWON (mA) 500 -20°C 25°C 75°C : Switching-on current versus 2.5 . Failure Status The CLP200M has an internal feature that allows the user to get a Failure Status (FS) indication. When the CLP200M is short-circuiting the line to GND, a signal can be managed through pin 1. This signal can be used to turn a LED on in order to provide a surge indication. It may also be used with a logic circuitry to count the number of disturbances appearing on the lines. Fig. 8 : Failure Status circuit and diagnostic. 300 200 100 Rsense 3 5 7 Rsense (Ω) 9 11 13 1 FAILURE CLP200M 1k Iswon @ 25°C (mA) 500 Iswon min negative Iswon max negative Iswon min positive Iswon min positive STATUS 300 Rsense +12V 200 100 3 5 7 Rsense (Ω) 9 11 If a surge exceeding the maximum ratings of the CLP200M occurs on the line, the device will fail in a short-circuit state. The choice of the switching-on current is function of the RSENSE resistors. In normal operating condition, only the negative current of the signal is of interest. This current (typically below -150 mA) should not activate the protection device CLP200M. Therefore the level of activation is to be chosen just above this limit (typically -200 mA). This level is adjusted through RSENSE. Figures 7a and 7b enable the designers to choose the right RSENSE value. bs O let o Pr e du o (s) ct so Ob Ipp (A) 1000 100 Fig. 9 : Operation limits and destruction zone of the CLP200M. te le ro P uc d s) t( 10 0.01 0.1 t (ms) 1 10 EXAMPLE : The choice of RSENSE = 4 Ω ensures a negative triggering of -220 mA min and -320 mA max. In this case, the positive triggering will be 180mA min and 280 mA max. s s The figure 9 shows two different curves : The lower one indicates the maximum guaranted working limits of the CLP200M. The upper curve shows the limit above which the CLP200M is completely destructed . In this case, the Fail Diagnostic pin is on. 7/21 CLP200M 3. CLP200M TESTS RESULTS ACCORDING TO CCITT K20 RECOMMENDATIONS 3.1 CCITT K20 Recommendations In respect with the CCITT recommendations, the CLP200M has to withstand three kinds of disturbances. 3.1.1. Lightning simulation (Test 2, table 2/K20) This test shall be done in transversal and longitudinal modes as shown in figure 10. Fig. 10 : Transversal and longitudinal test topologies. 3.1.3. Power contact (Test 3, table 1/K20) This test shall be done with the test circuit of figure 12. Vac(max) = 220VRMS , with switch S in each position and duration 15 min. Fig. 12 : Power contact test circuit. Fig. 11 : Power induction test circuit. 1µF R1 A 100 S2 S1 R2 ITEM UNDER TEST BE 1µF 15 25 A or B ITEM UNDER B or A 4kv 20µF 50 0.2µF TEST E TRANSVERSAL TEST 25 15