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| MH88500 (R) Hybrid Subscriber Line Interface Circuit (SLIC) Preliminary Information Features * * * * * * * * * * Differential to single ended conversion No transformers required Minimum installation space Off-Hook detection and LED indicator drive Relay drive output Battery and ringing feed to line Logic interface: MUTE, OFHK, RC Mute of incoming audio Dial pulse detection Voltage surge protection MH88500 ISSUE 5 April 1995 Ordering Information 20 Pin SIL Package 0C to 70C Description The Mitel MH88500 Subscriber Line Interface Circuit provides a complete interface between the telephone line and a speech switch requiring only single bidirectional switch per crosspoint. The functions provided by the MH88500 include bidirectional differential to single ended conversion in the speech path, line battery feed, ringing feed and loop and dial pulse detection. The device is fabricated as a thick film hybrid in a 20-pin `single-in-line' package allowing optimum circuit board packing density. Applications Line Interface for: * PABX * * Intercoms Key Systems VA1 VA2 VB VC1 GND TIP RING RING FEED Loop Feed/ Ring Feed Speech Circuit JUNCTOR VA2 CD VB MUTE OFHK RD RC RGND Loop Detection Relay Drive Circuit LED THRESH ADJ VC2 Figure 1 - Functional Block Diagram 2-33 MH88500 TIP VA1 RING RING FEED IC VC1 GND VB LED OFHK THRESH ADJ VA2 GND VC2 MUTE JUNCTOR RD RGND RC CD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Preliminary Information Figure 2 - Pin Connections Pin Description Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Name TIP VA1 RING RING FEED IC VC1 GND VB LED OFHK THRESH ADJ VA2 GND VC2 MUTE JUNCTOR RD RGND RC CD Description Tip Lead. Connects to the "Tip" lead (A-wire) of the telephone line. Positive Line Feed Supply Voltage. Normally connected to VA2. Ring Lead. Connects to the "Ring" lead (B-wire) of the telephone line. Negative Line Feed Voltage and Ringing Input. Normally connected to Ring Relay. Internal Connection. Leave open circuit. Use for testing only. Sense Input. Normally connected to negative line feed voltage supply. Analog ground (0V). Internally connected to pin 13. Negative Analog Supply Voltage. LED Drive Output. Drives an LED directly. Off-Hook condition, logic low. Logic Low Output. Indicates closed loop condition (Off-Hook and dial pulsing). Allows adjustment of OFHK detection threshold. Positive Power Supply Voltage. Normally connected to VA1. Analog Ground (0V). Internally connected to pin 7. Loop Detector Voltage Supply.Connected to negative line feed voltages supply. Input mutes the incoming audio. Active low. Receive/transmit audio speech path. (referenced to 0V GND) Relay Drive Output. Open collector sinks current when RC high. Diode clamp protected. Ground for Relay Drive Circuit. Ring Control Input. Active high. Clamping Diode. Normally connected to relay positive voltage. 2-34 Preliminary Information Functional Description Speech Circuit The speech circuit converts the bidirectional TIP and RING line pair to a bidirectional single ended junctor line. Figure 3 illustrates a typical connection between two SLIC's through two crosspoint switches. This configuration gives optimum transhybrid loss as seen from Figure 4 given that the output impedance of the Junctor line is 604. The MUTE input mutes signals coming from TIP and RING to the junctor line while allowing the signal from the junctor to the tip-ring pair to be transmitted. MH88500 Line Feed/Ring Feed Circuit The line feed circuit provides loop current and the ability to apply ringing onto TIP and RING. The impedance from Ring Feed to GND is 600 which gives the loop current as: IL = Voltage at RING FEED pin Telephone Impedance + 600 Amps The positive supply for the line feed circuit is VA1 through the loop current is determined from RING FEED and GND. Relay Drive Circuit The relay drive circuit switches ringing onto RING FEED (Fig.7). The diode is present to suppress voltage transients during relay switches caused by the inductive coils of the relay. Ringing voltage includes AC ringing (90V typically) an dDC line feed voltage (-24V typically). Loop Detection The loop detection circuit determines whether a low enough impedances is across TIP and RING to be recognized as an off-hook condition. (Threshold impedance = 5.4k with no adjustment) This threshold level can be adjusted by the use of external resistors as shown in Figure 6. OFHK has low output drive capability so it may drive CMOS operating with different power supplies. MH88500 1 TIP TIP JUNC RING 3 RING CROSSPOINT SWITCH 16 75 MH88500 1 TIP TIP JUNC RING 3 RING CROSSPOINT SWITCH 16 75 Figure 3 - SLIC Crosspoint Switch Connection 2-35 MH88500 Absolute Maximum Ratings Parameter 1 Voltage Supplies - VRef to GND Symbol VA1, VA2 VB VC1, VC2 2 3 4 5 Clamp Diode Breakdown Voltage-VRef to RGND Operating Temperature Storage Temperature Power Dissipation VCD TAMB TSTG PD Preliminary Information Min Max Units V -18 -35 +18 V V +15 0 -40 +70 +100 1.2 V C C Watt Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. AC Electrical Characteristics Voltages are with respect to ground (VSS), TA = 25C, unless otherwise stated. Test conditions unless noted, VA1=VA2=+7V, VB=8V, VC2=-24V(+5%). Characteristics 1 Junctor to differential output (tipring) gain. Differential Input (tip-ring) to junctor gain On/Off Hook Detection Threshold Loop Resist Loop Current 4 5 6 7 8 Trans Hybrid Loss Passband Linearity Power Supply Rejection Ratio (VC to Junctor) Common Mode Rejection Ratio (Tip and Ring to Junctor) Low Frequency Cutoff (3dB) Junctor to Line Line to Junctor High Frequency Cutoff (3dB) Line to Junctor Junctor to Line Longitudinal Balance Tip (or Ring) to ground AC input impedance Junctor output impedance Sym AJL Min 2.18 Typ 2.25 7 0.321 Max 2.32 Units V/V dB V/V dB Test Conditions 1kHz, 400mVRMS source on pin 16. Note 2 1kHz, 1VRMS Source on pins 1&3. Note 1,2 2 ALJ 0.303 0.321 3 RThresh IThresh 4.0 3.6 5.4 4.0 55 +1 6.0 5.3 k mA dB Note 1. Note 1 Notes 1,2. See Figure 2 dB dB dB Notes 1,2 Notes 1,2 Notes 1,2 PSRR CMRR 40 40 FLLJ FLJL FHLJ FHJL 53 20 800 500 65 Hz Hz kHz kHz dB Notes 1,2 Notes 1,2 Notes 1,2 Notes 1,2 Note 1 9 10 11 12 ZI ZOJ 300 604 Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Typical figures are at 25C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing. Note 1: 754 connected between JUNCTOR (pin 16) and OV. Note 2: 604 connected between TIP (pin 1) and RING (pin 3). 2-36 Preliminary Information DC Electrical Characteristics Characteristics 1 S U P P L Y MH88500 . Sym VA1,VA2 VB VC1,VA2 IA1 Min -13 -30 Typ -24 Max +13 Units V V V mA mA mA mA mA V V Test Conditions Operating Supply Voltages -20 Operating Supply Currents IA2 IB IC1 IC2 High Level Input Voltage MUTE RC VIH 2 7 8 6 .2 .1 4.2 3 .8 1 3 VIH VIL 4 5 I N P U T S Low Level Input Voltage MUTE RC High Level Input Current MUTE RC Low Level input Current MUTE RC Sink Current LED RD V VIL IIH IIH IIL IIL ILED IRD IRLY VOH VOL IOH IOL -28 700 100 1 2 65 65 6 -6.5 10 10 6 100 100 A A A A mA mA mA V V A VOFHK, -6V CD=RC=5V,RGD=0V VRRD<1.5V RC=RGND=0V, CD=5V VRRD <1.5V LED Unconnected LED Unconnected 6 7 8 9 10 11 12 O U T P U T S Diode Clamp Current High Level Output Voltage Low Level Output Voltage OFHK High Level Output Current Low Level Output Current Typical figures are at 25C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing. TRANSHYBRID LOSS (dB) 10 20 30 40 50 60 550 600 650 700 750 800 850 900 950 LOAD IMPEDANCE ON JUNCTOR () Figure 4 - Return Loss VS Junctor Load Impedance 2-37 MH88500 VO Preliminary Information 5 16 1 VTR VTR 604 MH88500 754 604 10F 200 VS 5 1 16 MH88500 10H 3 54 3 VX CAN BE MEASURED THAT VTP=2VX=2VTR (a) TRANSHYBRID LOSS = - 20LOG (VO) (b) 2VS Figure 5 - Transhybrid Loss Test Circuit R and RTHRESH (k) (a) GND R and RTHRESH (k) (a) VC2 R R MH88500 11 THRESH ADJ MH88500 11 THRESH ADJ R= R (k) (48 x RTHRESH) -28.8 5.4 - RTHRESH R (k) 2000 R= (912 x RTHRESH) +604 RTHRESH - 5.4 120 100 80 60 40 20 1000 1 2 3 4 5 6 10 20 30 40 RTHRESH (k) (a) RTHRESH (k) (b) Figure 6 - Off-Hook Threshold Adjust 2-38 Preliminary Information MH88500 VA1 TIP LINE FEED/ RING FEED RING -24VDC -24VDC +90VAC RING FEED +V CLAMP DIODE CD RELAY COIL MH88500 RD RELAY DRIVE CIRCUIT RC RGND Figure 7 - Relay Drive Circuit 2-39 MH88500 Preliminary Information +7v +5V +5V -24VDC 90VAC -24VDC CONTROL LOGIC A0 A1 A2 00 01 02 03 04 05 06 07 2 15 19 10 16 12 9 20 17 4 TIP 1 3 MH88500 RING 8 -8V 6 14 7 MD74SC137 1 OF 8 DECODER ADDRESS OUT A0 A1 A2 00 01 02 03 04 05 06 07 MD74SC137 1 OF 8 DECODER 5 MORE SLICS -24V 0V +5V +7V +5V -24VDC 90VAC -24VDC 2 15 19 10 16 -8V +7V 5 MORE SLICS +5V 12 9 20 17 4 TIP 1 3 RING 7 MH88500 8 6 -24V +5V 14 0V A0-A2/D0-D3 J0 2 15 19 10 16 12 9 20 17 4 TIP 1 3 -24VDC 90VAC -24VDC MT8812 J1 Crosspoint J 2 Switch L0 J3 -L7 MH88500 RING 8 6 14 7 A0 A1 A2 CMOS 4512 8-INPUT MUX SELECT OUTPUT D0 D1 D2 | | D7 -8V -24V 0V Figure 8 - PABX Typical Application 2-40 Preliminary Information MH88500 Side View 0.080 Max (2.0 Max) 2.00 + 0.020 (50.8 + 0.5) 0.52+0.02 (13.2+0.5) 1234 19 20 0.010 + 0.002 (0.25 + 0.05) 0.12 Max (3.1 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 (1.3 + 0.05) 0.020 + 0.05 (0.51 + 0.13) * * 0.100 + 0.10 (2.54 + 0.13) 0.18 + 0.02 (4.6 + 0.5) Figure 9 -Mechanical Data 2-41 MH88500 Notes: Preliminary Information 2-42 |
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