MH88520-1 German Subscriber Line Interface Circuit (SLIC) Preliminary Information Features April 1995 ISSUE 4 • Differential to single ended conversion • Transformerless 2-2 wire conversion • Minimum installation space • Off-Hook detection and LED indicator drive • Relay drive output • Battery and ringing feed to line • Logic interface: MUTE, SHK, RRC • Mute of incoming audio • Dial pulse detection • Voltage surge protection • German complex input impedance Ordering Information MH88520-1 0°C to 70°C Description The Mitel MH88520-1 German 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 MH88520-1 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’ (SIL) package allowing optimum circuit board packing density and very high reliability. Applications Line Interface for: • Intercoms • Key Systems • PABX 20 Pin SIL Package TIP (A) RING (B) RING FEED 1 RING FEED 2 JUNC Loop Feed/ Ring Feed Speech Circuit MUTE VRLY SHK RRD RRC RGND Loop Detection Relay Drive Circuit VBAT AGND VDD LED THRESH ADJ VEE Figure 1 - Functional Block Diagram 2-63 MH88520-1 Preliminary Information TIP IC RING RF1 IC RF2 IC VEE LED SHK THRESH ADJ VDD AGND VBAT MUTE JUNC RRD RGND RRC VRLY 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Figure 2 - Pin Connections Pin Description Pin # Name 1 TIP Tip Lead. Connects to the “Tip” lead (A-wire) of the telephone line. 2 IC Internal Connection. Leave open circuit. 3 RING Ring Lead. Connects to the “Ring” lead (B-wire) of the telephone line. 4 RF1 Ring Feed 1. Connect to the Ring Relay contact. See Figure 5. 5 IC 6 RF2 7 IC 8 VEE Negative Power Supply Voltage. Normally -5V. 9 LED LED Drive (Output). Drives an LED directly. A logic low indicates an off-hook condition. 10 SHK Switch Hook Detect (Output). A logic low indicates an off-hook and dial pulsing condition. Open collector output with 10kΩ internal pull up to VDD. 11 THRESH ADJ 12 VDD 13 AGND 14 VBAT 15 MUTE MUTE (Input). A logic low will mute signals coming from Tip-Ring to the JUNC pin. 16 JUNC JUNCTOR. Ground (AGND) referenced transmit and receive speech path. 17 RRD Ring Relay Drive (Output). Connects to the ring relay coil. A logic low activates the relay. 18 RGND Relay Ground. Return path for relay supply voltage. Normally connected to AGND. 19 RRC Ring Relay Control (Input). A logic high activates the Ring Relay Drive (RRD) outputs. 20 VRLY Relay Positive Supply voltage. Normally +5V. Connects to the relay coil and the relay supply voltage. An internal clamp diode from VRLY to GRND is provided. 2-64 Description Internal Connection. Leave open circuit. Ring Feed 2. Connect to normally closed contact of Ring Relay. See Figure 5. Internal Connection. Leave open circuit. Allows adjustment of SHK detection threshold as shown in Figure 6. Positive Power Supply Voltage. Normally +5V. This provides current for both internal circuitry as well as the loop. Analog Ground. Supply and Battery Ground. Battery Supply Voltage. Normally -24V. This provides current to the loop. MH88520-1 Preliminary Information Functional Description the SLIC, and converts the ground referenced input signal at JUNC of the SLIC into the non-balanced output signal at Tip-Ring of the telephone line. The BORSH Functions Mute The MH88520-1 performs all of the Borsh functions of Battery Feed Overvoltage Protection, Ringing, Supervision and Hybrid (2-2 Wire). A logic low at the MUTE input results in muted signals coming from Tip and Ring to the JUNC terminal while allowing signals from the JUNC terminal to Tip and Ring to be transmitted. Return Loss at Tip-Ring Overvoltage Protection To maximise return loss, the impedance at Tip-Ring should match the SLIC’s impedance (220R + 820R // 115nF). However, the SLIC’s input impedance is dependent on the JUNCTOR termination resistance. Therefore the JUNCTOR must be terminated with 754Ω. The MH88520-1 is protected from short term (1ms) (+250V) between Tip and Ring, Tip and Ground, and Ring and Ground. However, additional protection circuitry may be needed depending upon the requirements which must be met for the final equipment. Figure 3 illustrates a typical connection between two SLICs through two crosspoint switches. Optimum return loss occurs when the JUNCTOR is terminated with 754Ω. Since the JUNCTOR input/output impedances is 604Ω and the crosspoint switch resistances are 75Ω + 75Ω, this configuration gives optimum return loss as shown in Figure 4. Loop Detection The loop detection circuit determines whether a low enough path is across Tip and Ring to be recognised as an off-hook condition. (Threshold impedance = 5.4kΩ with no adjustment). This threshold level can be adjusted by the use of external resistors as shown in Figure 6. When an off-hook condition occurs the SHK and LED outputs toggle to a logic low level. These outputs also toggle during incoming dial pulses. Hybrid The 2-2 wire hybrid circuit converts the incoming balanced signal at Tip and Ring of the telephone line into a ground referenced output signal at JUNC of 75Ω MH88520-1 1 TIP 16 TIP JUNC RING 3 CROSSPOINT SWITCH RING SLIC 1 MH88520-1 1 TIP TIP 75Ω 16 JUNC RING 8 RING SLIC 2 CROSSPOINT SWITCH Figure 3 - SLIC Crosspoint Switch Connection 2-65 MH88520-1 Preliminary Information Ringing Line Impedance The relay drive circuit switches ringing onto Ring Feed (Fig. 7). The diode is present to suppress voltage transients during relay switching caused by the inductive coils of the relay. Ringing voltage included ac ringing (90VRMS typically) and DC line feed voltage (-24V typically). The MH88520-1’s Tip-Ring (Zin) impedance is fixed at the German complex impedance. For correct SLIC impedance, JUNC must be appropriately terminated. See AC Electrical Characteristics. 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 600Ω dc (although for ac it is optimised for a German complex impedance) which gives the loop current as: Voltage at Ring Feed pin Telephone Impedance + 600 Amps The positive supply for the line feed circuit is VDD though the loop current is determined from Ring Feed and GND. TYPICAL RETURN LOSS (dB) Transmit and Receive Gain Transmit Gain (JUNC to Tip-Ring) and Receive Gain (Tip-Ring to JUNC) are fixed (See AC Electrical Characteristics). For correct gain, the SLIC input impedance must match theline impedance and JUNC must be appropriately terminated. Digital Applications The 2-wire junctor output can be converted to a 4-wire circuit using the MH88524 (2-4 wire converter). This 4 wire circuit can be interfaced to a filter/codec to use in digital voice switched systems. Alternatively the MH88600/MH88612, digital ONS SLIC can be used. 10 20 30 40 50 60 550 600 650 700 750 800 850 900 LOAD IMPEDANCE ON JUNCTOR (Ω) Figure 4 - Return Loss VS Junctor Load Impedance 2-66 950 MH88520-1 Preliminary Information Absolute Maximum Ratings† Parameter 1 Voltage Supplies Referenced to GND Symbol Min Max Units VDD -0.3 +15 V VEE -15 0.3 V VBat -35 0.3 V +32 V 2 Clamp Diode Breakdown Voltage-VRef to RGND VRLY 3 Operating Temperature TAMB 0 +70 °C 4 Storage Temperature TS -55 +125 °C 5 Power Dissipation PD 4 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 = 25°C, unless otherwise stated. Test conditions unless noted, VDD=5V, VEE=-5V, VBat=-24V). Characteristics Typ‡ Max Units Test Conditions 0 dB 1kHz, 0.5V source on pin 16. Note 2 dB 1kHz, 0.5V Source Applied on pins 1&3 Note 1, 2 mA Note 1 30 dB Notes 1,2 ±1.0 dB Notes 1,2 200Hz - 3400Hz PSRR PSRR PSRR 30 40 40 dB dB dB Notes 1,2. Ripple 0.1V 1kHz CMRR 40 dB Notes 1,2 1kHz, 0.5V 50 dB Notes 1 604 Ω 30 dB 1kHz Notes 1,2 3 dB Notes 1,2 105 V RMS 25 60 Ηz -80 -80 -70 -75 dBmp dBmp Notes 1,2 dB Notes 1,2 Sym Min 1 Junctor to Differential Output (tip-ring) Gain -7.0 2 Differential; Input (tip-ring) to Junctor Gain 0.0 3 On/Off Hook Detection Threshold Loop Current 4 Transhybrid Loss 5 Passband Frequency Response 6 Power Supply Rejection Ratio (@ Junctor) 7 Common Mode Rejection Ratio (Tip and Ring to Junctor) 8 Longitudinal Balance 9 Junctor Output Impedance 10 Return Loss at Tip, Ring 11 Max. Signal Level 12 Max. Ringing Voltage 13 Max. Ringing Frequency 14 Idle Channel Noise VBAT VDD VEE Mute Attenuation 8.0 46 ZOJ 18 at T-R at Junctor 15 IThresh NTR NJ 10 30 12 † Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. ‡ Typical figures are at 25°C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing. Note 1: 754Ω connected between JUNCTOR (pin 16) and 0V. Note 2: German Impedance connected between TIP (A) (pin 1) and RING (B) (pin 3). 2-67 MH88520-1 Preliminary Information . DC Electrical Characteristics Sym Min Typ‡ Max Units Operating Supply Voltages VDD VEE VBat 4.5 -5.5 -30 5 -5 -24 5.5 -4.5 -20 V V V Operating Supply Currents IDD Characteristics 1 2 S U P P L Y 3 4 5 I N P U T S 6 8 6 1 IEE IBat mA mA mA Test Conditions On Hook High Level Input Voltage MUTE RRC VIH Low Level Input Voltage MUTE RRC VIL 0.8 0.5 V V High Level Input Current MUTE RRC IIH IIH -28 700 µA µA Low Level Input Current MUTE RRC IIL IIL 100 10 µA µA 200 mA mA VRLY = RRC= 5V RGND = 0V VRRD < 1.5V mA RRC=RGND=0V VRLY = 5V VRRD > 4.5V VIH 2.0 4.5 V V VIL Sink Current 7 ILED IRRD 65 1.5 100 IRLY 65 100 High Level Output Voltage SHK VOH 4.5 5 5.5 V LED Unconnected Low Level Output Voltage SHK VOL 0 .01 0.7 V LED Unconnected 11 Low Level Output Current IOL 12 Power Consumption PC 13 Max. Operating loop RL RL LED RRD 8 9 10 O U T P U T S Relay to VDD Diode Clamp Current 4 µA mW 600 900 Ω Ω 400Ω Loop at 18mA, 24V at 18mA, 30V ‡ Typical figures are at 25°C with nominal+ 5V supplies and are for design aid only: not guaranteed and not subject to production testing. MH88520 Input Impedance 2-68 Variant Country Impedance 01 GERMANY 220Ω + 820Ω // 115nF MH88520-1 Preliminary Information MH88520-1 1 TIP Optional Protection Circuit RING TIP 16 3 AUDIO INPUT/OUTPUT JUNC RING 15 MUTE CONTROL INPUT MUTE Earth Ground 10 4 K1 LED R1 6 ∼ RINGING GENERATOR 90VRMS SWITCH HOOK OUTPUT SHK RF1 RF2 RRC 9 19 OFF-HOOK LED DS1 RING CONTROL INPUT 17 RRD 14 VBAT K1 VRLY 20 VEE AGND VDD RGND -24V 13 8 12 18 Notes: R1= 200Ω, 1/4W, 5% K1= Relay E/M 5V, 1Form C C1, C2 = 0.1uF, 50V, Ceramic +5V -5V C1 C2 Figure 5 - Typical Application Circuit GND R and RTHRESH (kΩ) VBAT R and RTHRESH (kΩ) RG RV 11 SLIC SLIC 11 THRESH ADJ THRESH ADJ RV= (100 x VDD) - (6000 x I) (501 x I) - VDD RG = 6000 x I VDD - (501 x I) R (kΩ) R (kΩ) RG(kΩ) (a) I = Threshold current 60 50 40 30 20 10 RV(kΩ) (b) 400 in Amps VDD = +5V 2 3 4 5 200 6 7 8 10 15 20 25 Figure 6 - Off-Hook Threshold Adjust 2-69 MH88520-1 Preliminary Information VDD TIP(a) LINE FEED/ RING FEED RING -24VDC +90VAC RING FEED 1 RING FEED 2 HYBRID CLAMP DIODE +5V VRLY RELAY COIL RRD RELAY DRIVE CIRCUIT RRC RGND Figure 7 - Relay Drive Circuit 2-70 MH88520-1 Preliminary Information +7v +5V CONTROL -24VDC 90VAC -24VDC 00 01 02 03 04 05 06 07 A0 A1 A2 LOGIC 2 12 1 TIP MH88520-1 19 3 RING 16 ADDRESS OUT 9 20 17 4 15 10 MD74SC137 1 OF 8 DECODER +5V 8 6 14 7 -8V -24V 0V +5V +7V +5V 5 MORE SLICS -24VDC 90VAC 00 01 A0 A1 A2 -24VDC 02 12 9 20 17 4 TIP 2 03 04 05 06 07 15 MH88520-1 19 10 8 16 -8V MD74SC137 1 OF 8 DECODER 6 +7V +5V 3 RING 14 -24V 1 7 0V +5V -24VDC 90VAC 5 MORE SLICS A0-A2/D0-D3 J0 MT8812 J1 Crosspoint J 2 Switch J3 -L7 L0 A0 A1 A2 CMOS 4512 8-INPUT MUX SELECT OUTPUT D0 D1 D2 | | D7 -24VDC 2 15 12 9 20 17 4 19 MH88520-1 10 1 TIP RING 16 8 -8V 6 14 -24V 3 7 0V Figure 8 - PABX Typical Application 2-71 MH88520-1 Preliminary Information 0.080 Max (2.0 Max) Side View 2.00+ 0.020 (50.8 + 0.5) 0.58+0.02 (14.7+0.5) 1 2 3 4 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) Figure 9 - Mechanical Data 2-72 * 0.8 + 0.02 (4.6 + 0.5) 0.100 + 0.10 (2.54 + 0.13)