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| L3845 TRUNK INTERFACE ON CHIP POLARITY GUARD MEETS DC LINE CHARACTERISTICS OF EITHER CCITT AND EIA RS 464 SPECS PULSE FUNCTION HIGH AC IMPEDANCE OFF HOOK-STATUS DETECTION OUTPUT LOW EXTERNAL COMPONENT COUNT Minidip SO8 DESCRIPTION The circuit provides DC loop termination for analog trunk lines. The V-I characteristics is equivalent to a fixed voltage drop (zener like characteristic) in series with an external resistance that determines the slope of the DC characteristic. An external low voltage electrolytic capacitor causes the circuit to exhibit a very high impedance to all AC signal above a minimum frequency that is determined by the capacitor itself and by a 20 K nominal resistor integrated on the chip. The Off-Hook status is detected all the time a typic of 8 mA is flowing into the circuit. In this condition a constant current generator is activated to BLOCK DIAGRAM ORDERING NUMBERS: L3845B L3845D supply an external device (typically an optocoupler) without affecting the AC characteristic of the circuit. When Pulse Dialing is required the PULSE input (pin 3) connected to V- causes the device to reduce the fixed DC voltage drop and to exhibit a pure resistive impedance equal to the external resistor. IN1 1 8 3 POLARITY GUARD DC LINE TERMINATION OF HOOK DETECTION CIRCUIT V+ PULSE 4 HD0 IN2 7 5 ACT R2 R3 C1 S1 S2 6 DCT 2 V- R1 D96TL263 June 1996 1/7 This is advanced information on a new product now in development or undergoing evaluation. Details are subject to change without notice. L3845 ABSOLUTE MAXIMUM RATINGS Symbol VL IL Ptot Top Tsrg, Tj Max Line Current Total Power Dissipation at Tamb = 70 C Operating Temperature Storage and Junction Temperature Parameter Max Line Voltage (pulse duration 10 ms max) Value 20 150 800 - 40 to + 70 - 55 to + 150 Unit V mA mW C C PIN CONNECTION (Top view) THERMAL DATA Symbol Rth j-amb Parameter Thermal Resistance Junction-ambient (*) Max. Minidip 80 SO8 140 to 180 Unit C/W (*) Mounted on FR4 Boards 2/7 L3845 DC ELECTRICAL CHARACTERISTICS (IL = 10 mA to 100 mA, R1 = 56 , S1 = Open, Tamb = + 25 C, unless otherwise specified) Symbol VL Parameter Line Voltage (normal mode) Test Condition PULSE = Open IL = 10 mA IL = 20 mA IL = 100 mA PULSE = V- IL = 20 mA IL = 35 mA IL = 80 mA 6.5 Min. Typ. Max. 5 6 12 4 5.5 9.5 9.5 Unit V V V V V V mA VLP Line Voltage (pulse mode) Ihn ON/OFF-Hook Line Current Detection Threshold OFF/ON-Hook Line Current Detection Threshold OFF-Hook Output Drive Current at Pin HDO Pulse Input Low Voltage Pull-up Input Current at Pin PULSE (pulse mode) Imput Current at Pin Pulse (normal mode) IL = 100 mA Pulse = V- IL = 10 mA IL 20 mA Ihf 5 9.2 mA IOUT 1.5 2 0.8 20 3 mA mA V A A VPM IPM INM AC ELECTRICAL CHARACTERISTICS (I L = 10mA to 100mA, R1 = 56, R2 = 470K, R3 = 130 K, Tamb = + 25 C, unless otherwise specified) Symbol ZL Parameter AC Line Impedance Test Condition S1 = Open, S2 = Open C 1 = 2.2mF f = 1KHz S1 = Open, S2 = Open f = 1KHz VAC-L = 775mVrms IL = 15 to 100mA S1 = Closed; S2 = Open VAC-L = 1.3Vrms S1 = Open; S2 = Closed VAC-L = 1.9Vrms 2 2(*) Min. Typ. 20 Max. Unit K Sending/Receiving Distortion 2 % Sending/Receiving Distortion Sending/Receiving Distortion (*) Not tested, guaranteed only by design. % % APPLICATION INFORMATION With the use of this circuit it is possible to terminate an analog trunk so that all the DC current component is flowing in the TRUNK TERMINATION CIRCUIT while the AC component is decoupled with a low voltage capacitor and can be used with a small and low cost audio coupler transformer to provide the AC balancing termination and two to four wire conversion. Therefore it is usefull both for MODEM and PABX systems. Figure 1 gives the typical application circuit ; it is worth to note that the TRUNK TERMINATION CIRCUIT, together with the LS5018 transient suppressor provides a compact and low cost module fully protected against lightning or overvoltages frequently present on telephone lines. The PULSE input when connected to V- allows the device to reduce the Line Voltage and to show a resistive impedance equal to R1 to the line. When PULSE input is left open, this function is disable. 3/7 L3845 Figure 1: Typical Application. 4/7 L3845 MINIDIP PACKAGE MECHANICAL DATA DIM Min. A a1 B b b1 D E e e3 e4 F i L Z 3.18 7.95 2.54 7.62 7.62 6.6 5.08 3.81 1.52 0.125 0.51 1.15 0.356 0.204 1.65 0.55 0.304 10.92 9.75 0.313 0.100 0.300 0.300 0260 0.200 0.150 0.060 mm Typ. 3.32 0.020 0.045 0.014 0.008 0.065 0.022 0.012 0.430 0.384 Max. Min. inch Typ. 0.131 Max. 5/7 L3845 SO8 PACKAGE MECHANICAL DATA DIM Min. A a1 a2 a3 b b1 C c1 D E e e3 F L M S 3.8 0.4 4.8 5.8 1.27 3.81 4.0 1.27 0.6 8 (max.) o mm Typ. Max. 1.75 0.1 0.25 1.65 0.65 0.35 0.19 0.25 0.85 0.48 0.25 0.5 45 (typ.) 5.0 6.2 0.189 0.228 o inch Min. Typ. Max. 0.069 0.004 0.010 0.065 0.026 0.014 0.007 0.010 0.033 0.019 0.010 0.020 0.197 0.244 0.050 0.150 0.150 0.016 0.157 0.050 0.024 6/7 L3845 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 mentioned 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 express written approval of SGS-THOMSON Microelectronics. (c) 1994 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. 7/7 |
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