MH88634 Central Office Interface Circuit Preliminary Information Features ISSUE 2 Ordering Information • Loop Start Trunk Interface • 600 ohm input impedance, -2 variant • Line state detection outputs: forward loop, reverse loop, ringing voltage, switch hook On-hook reception • Transformerless 2W to 4W conversion • One loop start relay driver • +/- 5V operation • Small footprint area (<4.75cm 2) MH88634-2 Description The Mitel MH88634 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 MH88634 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. 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 Dummy Ringer XLA XLB XLC XLD LRC LRD 21 Pin SIL Package 0°C to 70°C Applications • April 1995 FL RL SHK Status Detection Receive Gain Loop Termination Rx 2-4 Wire Hybrid Loop Relay Driver Transmit Gain Impedance Matching VRLY Tx Network Balance RGND Figure 1 - Functional Block Diagram 2-253 MH88634 Preliminary Information TIP RING XLA XLD XLB XLC IC IC IC SHK 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 # Name 1 TIP 2 RING 3 XLA 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. 4 XLD Loop Relay Contact D: See XLC for description 5 XLB Loop Relay Contact B: See XLA for description 6 XLC 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. 7 IC Internal Connection: This pin is internally connected and must be left open. 8 IC Internal Connection.: This pin is internally connected and must be left open. 9 IC Internal Connection: This pin is internally connected and must be left open. 10 SHK 11 Rx 12 VEE 13 Tx Transmit (Output). 4-Wire ground (AGND) referenced audio output. 14 RV 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. 15 FL 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. 16 RL 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. 17 VDD 2-254 Description Tip Lead: Connects to the “Tip” lead of the central office Ring Lead: Connects to the “Ring” lead of the central office Switch Hook (Output). A logic low indicates either forward or reverse loop current. Receive (Input): 4-Wire ground (AGND) referenced audio input. Negative Supply Voltage. -5V Positive Supply Voltage: +5V MH88634 Preliminary Information Pin Description (Continued) Pin # Name 18 AGND 19 LRC 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. 20 VRLY Relay Positive Supply Voltage. Typically +5V. Connects to the relay coil and the relay supply voltage 21 LRD 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. Description Analog Ground. 4-wire ground. Connected to system ground Functional Description The MH88634 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. 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. voltage is applied and remains low for 50ms after ringing voltage is removed. 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) SHK output is active if either forward loop or reverse loop current is detected. Line Impedance The input impedance of the MH88634-2 is 600 ohms. The network balance is also set at 600 ohms 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 signally status outputs. The ringing voltage, forward current, reverse current and switch hook. 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 2-255 MH88634 Preliminary Information Absolute Maximum Ratings* Voltages are with respect to AGND Parameters Sym Min Max Units 1 DC Supply Voltages VBAT VDD VEE 0 -0.3 0.3 -60 7 -7 V V V 2 DC Ring Relay Voltage VRLY -0.3 7 V 3 Storage Temperature TS -55 +125 °C * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Recommended Operating Conditions Parameters Symbol Min Typ* Max Units 4.75 -4.75 5.0 -5.0 5.25 -5.25 V V 5.0 15 V 70 °C 1 DC Supply Voltages VDD VEE 2 DC Ring Relay Voltage VRLY 3 Operating Temperature TOP 0 Comments * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. DC Electrical Characteristics† Characteristics Sym Min Typ* Max Units Test Conditions 1 Supply Current IDD IEE 13 13 mA mA 2 Power Consumption PC 137 mW FL RL SHK RV Low Level Output Voltage VOL -.3 0.5 V IOL = 4mA High Level Output Voltage VOH 3.7 5.25 V IOH = 100µA 4 LRD Sink Current, Relay to VDD Clamp Diode Current IOL ICD 100 150 5 LRC Low Level Input Voltage High Level Input Voltage VIL VIH 2.0 High Level Input Current Low Level Input Current IIH VIH 3 6 mA mA 0.8 V V 40 40 µA µA † DC Electrical Characteristics are over recommended operating conditions unless otherwise stated. * Typical figures are at 25°C with nominally +5V supplies and are for design use only. 2-256 VBAT not connected VOL = 0.35V not continuous VIH = 5.0V MH88634 Preliminary Information Loop Electrical Characteristics* Characteristics 1 Ringing Voltage 2 Ringing Frequency 3 Ringer Equivalence Number 4 Operating Loop Current 5 Off-Hook DC Resistance 6 Leakage Current (Tip-Ring to AGND) 7 FL Threshold Tip-Ring (On-hook) Tip-ring Current (Off-Hook) 8 Symbol VR REN Min Typ† Max Units 40 90 110 Vrms 16 20 33 Hz 0.5 1 2 16 Dummy ringer is 17K in series with 330nF. Type A ringing 70 mA 280 Ω 10 mA @ 1000Vac +30 +10 † +40 15 Vdc mA LRC = 0v LRC = 5V -30 -8 † -40 -15 Vdc mA LRC = 0v LRC = 5V 270 RL Threshold Tip-Ring (On-Hook) Tip-Ring (Off-Hook) Test Conditions @ 20mA * DC Electrical Characteristics are over recommended operating conditions unless otherwise stated. † Typical figures are at 25°C and are for design aid only. AC Electrical Characteristics * Characteristics Symbol 1 2-wire Input Impedance (-2 variant) Zin 2 Return Loss at 2-wire (Zin = Ref = 600) RL 3 Longitudinal to Metallic Balance 4 Transhybrid Loss 5 Gain (voltage) 2 wire to Tx 6 Gain (Voltage) Rx to 2 wire 7 Input impedance at Rx 8 Output impedance at Rx 9 Signal Overload Level at 2-wire output at Tx 10 11 12 Total Harmonic Distortion at 2-wire output at Tx Idle Channel Noise at 2-Wire at Tx Power Supply Rejection Ratio at 2-wire and Tx VDD VEE THL Min Typ† Max Units Test Conditions Ω 600 20 dB 200-3400 Hz 58 58 53 dB 200Hz 1000Hz 3.4kHz 20 dB 200-3400Hz 0 dΒ 1024Hz -2 dB Spec Freq 10 kΩ Ω 5 4.0 0.95 dBm Vrms % THD < 5% Ref 600Ω @ 20mA THD 1.0 1.0 NC % % Input 0.5V, 1kHz @ Rx Input 0.5V, 1kHz @ Tip-Ring dBrnC 15 15 PSRR Ripple 0.1V, 1kHz 25 dB 25 dB dB dB * AC Electrical Characteristics are over recommended operating conditions unless otherwise stated. † Typical figures are at 25°C and are for design aid only. 2-257 MH88634 Preliminary Information Side View 0.080 Max (2.0 Max) 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) 0.18 + 0.02 (4.6 + 0.5) * * 0.05 + 0.02 (1.225 + 0.05) 0.020 + 0.005 (0.51 + 0.13) * 0.100 + 0.010 (2.54 + 0.26) Figure 3 - Mechanical Data MH88634 Tip Tip Protection Circuit Ring +5V TX Audio Out RX Audio In RV Ring Detect FL Forward Loop RL Reverse Loop Ring K1 LRD VRLY LRC Loop Relay Control XLA K1 SHK XLB NOTES: 1) See Figure 5 for Protection Circuit. 2) K1 Electro Mechanical 2 form A. XLC K1 XLD VDD +5V AGND VEE -5V Figure 4 - Typical LS-GS Application Circuit 2-258 Switch Hook MH88634 Preliminary Information Protection Circuit RV1 TIP F1 MH88634 TIP 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, 22.4W, 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 2-259 MH88634 Notes: 2-260 Preliminary Information