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| (R) MH88634K Central Office Interface Circuit Preliminary Information Features * * * Loop Start Trunk Interface 600 Ohm input impedance Line state detection outputs: - forward loop - reverse loop - ringing voltage - service out Transformerless 2W to 4W conversion One loop start relay driver +/- 5V operation MH88634K ISSUE 3 April 1995 Ordering Information 21 Pin SIL Package 0C to 70C * * * Description The Mitel MH88634K Central Office Trunk Interface circuit provides a complete audio and signalling link between audio switching equipment and a central office. The functions provided by the MH88634K include 2-4 Wire conversion, 600 Ohm input impedance and network balance. The device is fabricated as a thick film hybrid incorporating various technologies for optimum circuit design and very high reliability. Applications Interface to Central Office for: * * * * * * * PABX Key Telephone Systems Channel Bank Voice Mail Terminal Equipment Digital Loop Carrier Optical Multiplexer RING TIP VDD VEE AGND RV FL RL SO Dummy Ringer Status Detection XLA XLB XLC XLD LRC LRD Loop Termination Receive Gain Rx 2 - 4 Wire Hybrid Loop Relay Driver Impedance Matching Network Balance Transmit Gain Tx VRLY RGND Figure 1 - Functional Block Diagram 2-261 MH88634K Preliminary Information TIP RING XLA XLD XLB XLC IC IC IC SO Rx VEE Tx RV FL RL VDD AGND LRC VRLY LRD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Figure 2 - Pin Connections Pin Description Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Name TIP RING XLA XLD XLB XLC IC IC IC SO Rx VEE Tx RV Description Tip Lead. Connects to the "Tip" lead of the central office Ring Lead: Connects to the "Ring" lead of the central office Loop Relay Contact A:. Connects to XLB through the Loop relay (K1) contacts when the relay is activated. This operates the internal active termination circuitry. Loop Relay Contact D: See XLC for description Loop Relay Contact B: See XLA for description Loop Relay Contact C: Connects to XLD through the loop relay (K1) contacts when the relay is activated. This operates the internal active termination circuitry. Internal Connection: This pin is internally connected and must be left open. Internal Connection.: This pin is internally connected and must be left open. Internal Connection: This pin is internally connected and must be left open. Service Out Detect (Output). A logic low indicates that the central office "Tip" and "Ring" are out of service. Receive (Input): 4-Wire ground (AGND) referenced audio input. Negative Supply Voltage. -5V Transmit (Output). 4-Wire ground (AGND) referenced audio output. Ring Voltage Detect (Output). A logic low indicates that ringing voltage is across the Tip and Ring leads. Note that this output toggles at the ringing cadence and not at the ringing frequency. Forward Loop Detect (Output). In the on-hook state, a logic low output indicates that forward loop battery is present. In the off-hook state, a logic low indicates that forward loop current is present Reverse Loop Detect (Output): In the on-hook state, a logic low output indicates that reverse loop battery is present. In the off-hook state, a logic low output indicates that reverse loop current is present. Reverse loop refers to the Tip lead negative respect to the Ring lead. 15 FL 16 RL 2-262 Preliminary Information Pin Description (Continued) Pin # 17 18 19 Name VDD AGND LRC Positive Supply Voltage:. +5V Analog Ground: 4-wire ground. Connected to system ground. Description MH88634K Loop Relay Control (Input): A logic high activates the Loop Relay Driver output (LRD). The Loop Relay activates internal circuitry which provides a DC termination across Tip and Ring. Used for line seizure and dial pulsing. Relay Positive Supply Voltage: Typically +5V. Connects to the relay coil and the relay supply voltage Loop Relay Drive (Output): Connects to the Loop Relay Coil. A logic low activates the relay. An internal clamp diode from VRLY to LRD is provided. 20 21 VRLY LRD Functional Description The MH88634K is a COIC (Central Office Interface Circuit) used to interface the Central Office 2-Wire Analog Trunks. The COIC provides a Loop Start interface function. Incoming analog (voiceband) signals from the 2-Wire circuit are applied differentially across Tip and Ring, the output of which is applied to the 2 to 4 wire converter with a fixed gain to the Tx output. The outgoing analog signals are applied to Rx. The audio signals undergo 4 to 2 wire conversion with a fixed gain, and are differentially applied to Tip and Ring. Forward loop and reverse loop detect - the FL output provides a logic low when either forward loop battery or forward loop current is detected (ring lead voltage negative with respect to tip lead). The RL output provides a logic low when either reverse loop battery or reverse loop current is detected (tip lead voltage negative with respect to ring lead). Service Out detect - the SO output will detect the loop current between 5mA to 10.13 mA as "out of service" during the DC termination. The Central Office applies -48V battery to the line but limits the loop current to this range to indicate the line is out of service. FL and RV outputs will not go low is the loop current is less than 12.5mA. DC Loop Termination The line is provided with an active DC load termination when a logic high is applied to the LRC (Loop Start Relay) input. The termination is similar to a DC resistance of less than 275 ohms. An external relay is used to activate internal circuitry which switches the termination in and out of the loop. This is used for both seizing the line as well as generating dial pulses. Line Impedance The input impedance of the MH88634K is 600 ohms. The network balance is also set at 600 ohm to maximize the Transhybrid Balance. Transmit and Receive Gain Transmit Gain (Tip-Ring) is set at 0dB and Receive Gain (Rx to Tip-Ring) is set at -2dB. Supervision Features The supervision circuitry provides the signalling status outputs. The ringing voltage, forward current, reverse current and Service Out. Ringing Voltage detect - the RV output provides a logic low when ringing voltage is detected. This sector includes a ringing filter which ensures that the output toggles at the ringing cadence and not at the ringing frequency. Typically, this output goes low 50ms after the ringing voltage is applied and remains low for 50ms after ringing voltage is removed. 2-263 MH88634K DC Electrical Characteristics Characteristics 1 2 3 FL RL SO RV LRD LRC Supply Current Power Consumption Low Level Output Voltage High Level Output Voltage Sink Current, Relay to VDD Clamp Diode Current Low Level Input Voltage High Level Input Voltage High Level Input Current Low Level Input Current Sym IDD IEE PC VOL VOH IOL ICD VIL VIH IIH IIL 3.7 100 150 0.8 2.0 40 40 Min 0.5 0.5 Typ* Max 13 13 137 0.5 Preliminary Information Units mA mA mW V V mA mA V V A A Test Conditions VBAT not connected IOL = 4mA IOH = 100A VOL = 0.35V not continuous 4 5 6 VIH = 5.0V * Typical figures are at 25C with nominally +5V supplies and are for design use only. DC Electrical Characteristics are over recommended operating conditions unless otherwise stated. Absolute Maximum Ratings* Voltages are with respect to AGND Parameters 1 DC Supply Voltages Sym VBAT VDD VEE VVRLY TS Min 0 -0.3 0.3 -0.3 -55 Max -60 7 -7 7 +125 Units V V V V C 2 3 DC Ring Relay Voltage Storage Temperature * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Recommended Operating Conditions Parameters 1 2 3 DC Supply Voltages DC Ring Relay Voltage Operating Temperature Symbol VDD VEE VVRLY TOP 0 Min 4.75 -4.75 Typ* 5.0 -5.0 5.0 Max 5.25 -5.25 15 70 Units V V V C Comments * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. 2-264 Preliminary Information Loop Electrical Characteristics* Characteristics 1 2 3 Ringing Voltage Ringing Frequency Ringer Equivalence number REN Symbol VR Min 40 16 0.5 Typ 90 20 1 Max 130 33 2 Units Vrms Hz MH88634K Test Conditions Dummy Ringer is 17K in series with 330nF. Type A ringing mA mA @ 20mA, -42.5V @ 20mA @ 1000Vac 50 or 60 Hz LRC = 0v LRC = 5V LRC = 0v LRC = 5V VBAT = -48V 4 5 6 7 8 Operating Loop Current Operating Loop Resistance Off-Hook DC Resistance Leakage Current (Tip-Ring to AGND) FL Threshold Tip-Ring (On-hook) Tip-ring Current (Off-Hook) RL Threshold Tip-Ring (On-Hook) Tip-Ring current (Off-Hook) SO Detect 15 0 250 70 1800 275 10 +30 12.5 -30 -12.5 -10.13 +40 15 -40 -15 -12.4 Vdc mA Vdc mA mA 9 10 * Loop Electrical Characteristics are over recommended operating conditions unless otherwise stated. Typical figures are at 25C and are for design aid only. AC Electrical Characteristics * Characteristics 1 2 3 2-wire Input Impedance Return Loss at 2-wire (Zin = Ref = 600) Longitudinal to Metallic Balance Transhybrid Loss Gain (voltage) 2 wire to Tx Gain (Voltage) Rx to 2 wire Input impedance at Rx Output impedance at Tx Signal Overload Level at 2-wire output at Tx THD 1.0 1.0 NC 13 13 PSRR 30 30 dB dB dBrnc dBrnc Ripple 0.1V, 1kHz % % Input 0.5V, 1kHz @ Rx Input 0.5V, 1kHz @ Tip-Ring 4.0 0.95 THL Sym Zin RL 20 58 58 53 20 -0.25 -2.25 10 5 0 -2 0.25 -1.75 Min Typ 600 Max Units dB dB 200-3400 Hz 200Hz 1000Hz 3.4kHz 200-3400Hz 1024Hz Spec Freq Test Conditions 4 5 6 7 8 9 dB d dB k dBm Vrms % THD < 5% Ref 600 @ 20mA 10 Total Harmonic Distortion at 2-wire at Tx 11 Idle Channel Noise at 2-Wire at Tx 12 Power Supply Rejection Ratio at 2-wire and Tx VDD VEE * AC Electrical Characteristics are over recommended operating conditions unless otherwise stated. Typical figures are at 25C and are for design aid only. 2-265 MH88634K Side View 0.080 Max (2.0 Max) Preliminary Information 2.10 + 0.040 (53.3 + 1.0) 0.56 Max (14.2 Max) 0.010 + 0.002 (0.25 + 0.05) 0.27 Max (6.9 Max) Notes: 1) Not to scale 2) Dimensions in inches). 3) (Dimensions in millimetres). *Dimensions to centre of pin & tolerance non accumulative. * 0.05 + 0.01 (1.3 + 0.5) * 0.05 + 0.02 (1.225 + 0.05) 0.020 + 0.005 (0.51 + 0.13) * * 0.18 + 0.02 (4.6 + 0.5) 0.100 + 0.010 (2.54 + 0.26) Figure 3 - Mechanical Data MH88634K Tip Ring Protection Circuit TIP TX RING Audio Out RX K1 LRD Audio In VRLY LRC Loop Relay Control XLA K1 XLB RL SO Reverse Loop Service Loop RV FL Ring Detect Forward Loop NOTES: 1) See Figure 5 for Protection Circuit. 2) K1 Electro Mechanical 2 form A. XLC K1 XLD VDD AGND VEE +5V -5V Figure 4 - Typical LS-GS Application Circuit 2-266 Preliminary Information MH88634K MH88634K TIP Protection Circuit TIP F1 RV1 R1 RV3 RING RING F2 R2 RV2 AGND NOTES 1) F1, F2 are 1 AMP 250 VAC Slow-blow fuse e.g. Littlefuse 230 2AG 2) R1, 2 2.4 Ohm, 5% 1/2W, 100V Flame Rated resistor e.g., Allen Bradley EB24G5-L05 3) RV1, 2, 3 250 VAC 351 Metal Oxide Varistor e.g. OHIZUMI, 025ONC 12D Figure 5 - External Application Circuit 2-267 MH88634K Notes: Preliminary Information 2-268 |
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