MH88524 Dual 2-4 Wire Circuit Preliminary Information Features ISSUE 4 Ordering Information • Full duplex operation • Two complete circuits per package • Transformerless 2-4 Wire (4-2 Wire) conversion • + 5V operation • Wide bandwidth (50kHz) • Small Package Size 4-2 Wire and 2-4 Wire conversion for: • MH88630/631, MH88632, MH88500 & MT8840 • PBX • Key Telephone System • Channel bank • Voice Mail • Terminal Equipment • Digital Loop Carrier • Modem • Intercom Receive Gain Circuit1 TX1 Transmit Gain Circuit 1 RX2 TX2 Receive Gain Circuit 2 MH88524 10 Pin SIL Package 0°C to 70°C Description Applications RX1 April 1995 The Mitel MH88524 (Dual 2-4 wire Circuit) provides two independent interfaces between4-Wire devices such as the MH88631 COIC (Central Office Interface CIrcuit) and a speech switch such as the MT8814 (Analog Switch Array), requiring only a single bidirectional switch per crosspoint. The MH88524 can accommodate two full duplex audio links. The device is fabricated as a thick film hybrid which incorporates various technologies for optimum circuit design and very high reliability. JUN1 2-4 Wire Circuit 1 2-4 Wire Circuit 2 JUN2 Transmit Gain Circuit 2 VDD VEE AGND Figure 1 - Functional Block Diagram 2-73 MH88524 Preliminary Information RX1 JUN1 TX1 VDD AGND VEE IC TX2 JUN2 RX2 1 2 3 4 5 6 7 8 9 10 Figure 2 - Pin Connections Pin Description Pin # Name Description 1 RX1 Receive 1 (Input). 4-Wire ground (AGND) referenced audio output. 2 JUN1 Junctor 1 (Transmit and Receive). Ground referenced transmit and receive speech path. 3 TX1 Transmit 1. 4-Wire ground (AGND) referenced audio output. 4 VDD Positive Supply Voltage. Typically +5V. 5 AGND 6 VEE 7 IC 8 TX2 9 JUN2 Junctor 2 (Transmit and Receive). Ground referenced transmit and receive speech path. 10 RX2 Receive 2 (Input). 4-Wire ground (AGND) referenced audio output. Analog Ground. 2-Wire and 4-Wire ground. Normally connected to System Ground. Negative Supply Voltage. Typically -5V. Internal Connection. This pin is internally connected. Transmit 2 (Output). 4-Wire ground AGND) referenced audio output. Absolute Maximum Ratings* Parameter 1 DC Supply Voltage 2 Storage Temperature Sym Min Max Units Comments VDD VEE -0.3 +0.3 15 -15 V V With respect LGND TS -55 125 °C * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Recommended Operating Conditions Parameter Sym Typ* Min Max Units 1 DC Supply Voltage VDD VEE 5.0 -5.0 4.75 -4.75 10 -10 V V 2 Operating Temperature TOP 0 70 °C * Typical figures are at 25°C with nominal +5V supplies and are for design aid only. 2-74 Comments MH88524 Preliminary Information DC Electrical Characteristics ‡ Characteristics Sym Min Typ* Max Units Test Conditions 1 Supply Current IDD PEE 4 4 mA VDD = +5.0 VEE = 5.0 2 Power Dissipation PC 40 mW VDD = +5.0 VEE = 5.0 ‡ DC Electrical Characteristics are over recommended operating conditions unless otherwise stated. * Typical figures are at 25°C with nominal +5V supplies and are for design aid only. AC Electrical Interdependence Characteristics‡ Characteristics 1 2 Sym Min Typ* Max Units Cross, Circuit 1 or 2 Test Conditions Input 1.0V JUN1 to JUN2 JUN1 to TX2 RX1 to JUN2 RX1 to TX2 80 80 80 80 JUN1 to JUN2 JUN1 to TX2 RX1 to JUN2 RX1 to TX2 60 60 60 60 dB dB dB dB 200Hz-3400Hz 200Hz-50kHz dB dB dB dB Crosstalk, Circuit 1 or 2 Input 1.0V JUN1 to JUN2 JUN1 to TX2 RX1 to JUN2 RX1 to TX2 80 80 80 80 dB dB dB dB 200Hz-3400Hz JUN1 to JUN2 JUN1 to TX2 RX1 to JUN2 RX1 to TX2 60 60 60 60 dB dB dB dB 200Hz-50kHz ‡ AC Electrical Characteristics are over recommended operating conditions unless otherwise stated. * Typical figures are at 25°C with nominal +5V supplies and are for design aid only. 2-75 MH88524 Preliminary Information AC Electrical Characteristics ‡ Characteristics Sym Min Typ* Max 46 40 Units 1 Return Loss at junctor① (Ref. = 604Ω) 2 Impedance at Junctor 3 Transhybrid Loss② (Junctor - 754Ω) 42 36 dB dB 200-3400Hz 200-50kHz 4 Transhybrid Loss ③ (Frequency = 1kHz) 18 21 dB dB Junctor = 600Ω Junctor = 900Ω 5 Transhybrid Loss (Frequency = 50kHz) 15 18 dB dB Junctor = 600Ω Junctor = 900Ω 6 Input Impedance at RX 10k Ω 7 Output Impedance at TX ARJ Gain RX to Junctor 9 Frequency Response Gain (relative to gain at 1kHz) 10 Gain junctor to TX 11 Frequency Response Gain relative to gain at 1kHz -0.1 -0.1 12 Signal Output Overload Level at TX at Junctor 6.0 6.0 14 Idle Channel Noise 1.00 0.0 -0.1 -0.1 AJT Total Harmonic Distortion RX to Junctor Junctor to TX RX to Junctor Junctor to TX 0.99 -0.1 0.99 -0.1 1.00 0 200-3400Hz 200-50kHz Ω 604 8 13 dB dB Test Conditions 5 Ω 1.01 0.1 V/V dBV Input 0.5V 1kHz 0.1 1.0 dB dB 200-3400Hz 200-50kHz 1.01 0.1 V/V dBV Input 0.5V 1kHz 0.1 0.1 dB dB 200-3400Hz 200Hz-50kHz dBm dBm THD %THD<5% Reference: 600Ω Reference: 754Ω 0.4 0.4 1.0 1.0 % % % % Input 0.5V 1kHz 200-3400Hz 200-3400Hz 200-50kHz 200-50kHz 2 2 dBrnC dBrnC Reference: 600Ω Reference 754Ω Nc at TX at Junctor Power Supply Rejection Ratio PSRR at TX and Junctor 40 VDD VEE 40 * Typical figure are at 25°C with nominal +5V supplies and are for design aid only. Ripple 0.1V 1kHz 15 dB dB ‡ AC Electrical Characteristics are over recommended operating conditions unless otherwise stated. Both of the 2-4 Wire circuits are tested. TX, RX and Junctor actually refer to TX1, RX1 and JUN1; and TX2, RX2 and JUN2. All of the above test conditions use 754Ω connected between Junctor and AGND, unless otherwise stated. All the above test conditions use 200Hz to 3400Hz unless otherwise stated. Notes: ① RX is connected to AGND, see Figure 3. ② See Figure 5. ③ See Figure 4. 2-76 MH88524 Preliminary Information Functional Description The MH88524 is a Dual 2-4 Wire Circuit used to interface between ground reference 2-Wire circuitry and ground referenced 4-Wire circuitry. The device can accommodate two full duplex audio links. Hybrid The 2-4 Wire hybrid circuit separates the ground reference full duplex signal at JUNi (where i=1 or 2) of the switched line into receive and transmit ground referenced signals the RXi (Receive) and TXi (Transmit). The hybrid also prevents the input signal at RXi from appearing at TXi. The degree to which the hybrid minimises the contribution to the RXi signal at the TXi output is specified as transhybrid loss. For maximising transhybrid loss, see the Transhybrid Loss section. The 4-Wire side can be interfaces to a COIC such as the MH88631 for use in analog voice switched systems; or a filter/codec, such as the Mitel MT896X, for use in digital voice switched systems. The 2-wire side can be interfaces to a crosspoint switch such as the MT8816 or a junctor SLIC such as the MH88510 for use in analog voice switched systems. Return Loss at Junctor The MH88524’s Junctor impedance (Zin) is fixed at 604Ω nominal when RXi and TXi in a feedback loop as shown in Figure 6, the JUNi impedance will change, see Return Loss with Interface Circuit. Return Loss with Interface Circuit To maximise return loss at Tip-Ring of the Interface Circuit, the termination impedance at Tip-Ring of the Interface Circuit (COIC or SLIC) should match the Interface Circuit’s input impedance (600Ω, 900Ω or complex). However, with the inclusion of the MH88524, the interface circuit’s input impedance is dependent on the JUNi termination resistance. For optimum return loss the JUNi should be terminated with 754Ω. Figure 6, shows, illustrates a typical connection between an Interface Circuit (MH88631) and the MH88524. Note how the return loss occurs when JUNi is terminated with 754Ω. Figure 8 illustrates a typical connection between two interface circuits (MH88631), through an MH88524 and two crosspoint switches. Optimum return loss occurs when JUNi is terminated with 754Ω. Since the JUNi input/output impedance is 604Ω, the MH88510 JUNC input/output impedance is 604Ω, and the crosspoint switches resistance are 75W + 75Ω, this configuration gives optimum return loss. Transhybrid Loss THL = log (VRX/VTX) Transhybrid loss is maximised when the JUNi termination impedance is 754W. In addition, good transhybrid loss is indicated in Figure 4 and AC Electrical Characteristics. Fixed Transmit and Receive Gain Transmit Gain (JUNi to TXi, TXi/JUNi) and receive Gain (RXi to JUNi, JUNi/RXi) are both fixed at 0dBV providing the MH88524 JUNi impedance is 754Ω. Application with MT8840, MH88500 and MH88524 Figure 11 illustrates an application for the MH88524’s wide bandwidth. The MT8840 requires a 2-4 Wire converter which has good transhybrid loss at 32kHz. Since the MH88524 operates to 50kHz, it is ideal for this application. In addition, if a SLIC (Subscriber Line Interface Circuit) is required, the MH88500 can also be used since it also has a 604Ω Junctor and a wide bandwidth. Mechanical Data See Figure 12. 2-77 MH88524 RETURN LOSS Preliminary Information TX1 TYPICAL RETURN (dB) 0 LOSS Ref: 604Ω 10 TX1 20 MH88524 JUN1 AGND 30 40 50 100,000 10,000 1000 100 Frequency (Hz) Figure 3 - Return Loss at Junctor vs Frequency with MH88524 TRANSHYBRID LOSS MH88524 JUN1 TX1 JUNCTOR RESISTANCE 10 20 TX1 30 AGND 40 TYPICAL 50 TRANSHYBRID LOSS (dB) 60 550 600 650 700 750 800 850 900 950 Frequency (Hz) Figure 4 - Transhybrid Loss vs Junctor Resistance with MH88524 0 MH88524 754Ω JUN1 10 TX1 JUNCTOR RESISTANCE 20 TX1 30 AGND TYPICAL TRANSHYBRID LOSS (dB) 40 50 100 10,000 1000 Frequency (Hz) Figure 5 - Transhybrid Loss vs Frequency with MH88524 2-78 100,000 MH88524 Preliminary Information JUNCTOR RESISTANCE MH88631 MH88524 JUN1 TX1 RX1 TIP TX1 TX1 RING RETURN LOSS AGND FREQ = 1000Hz 10 20 30 40 TYPICAL RETURN 50 LOSS (dB) 60 JUNCTOR RESISTANCE (Ω) 550 650 600 800 750 700 850 900 950 Figure 6 - Return Loss vs Junctor Resistance with MH88631 and MH88524 1 RECEIVE 1 INPUT 3 TRANSMIT 1 OUTPUT 10 RECEIVE 1 INPUT TRANSMIT 2 OUTPUT RX1 JUN1 2 JUNCTOR1 INPUT/OUPUT 9 JUNCTOR 2 INPUT/OUTPUT TX1 JUN2 RX2 8 TX2 VDD 4 +5V AGND 5 VEE 6 -5V Figure 7 - MH88524 Application Circuit 2-79 MH88524 Preliminary Information TO CO LINE MH88524 (1/2) MH88631 TIP 1 T RING 1 R VX RX1 VR TX1 JUN1 AGND RX1 RECEIVE 1 INPUT TIP 2 MH88524 (1/2) MH88631 TO CO LINE VX T e.g. MT8804 MT8816 etc. RX2 JUN2 Notes: See MH88631, MT8804 and MT8816 data sheets for device details. VR RING 2 TX2 R Figure 8 - Application Circuit with MH88631, Crosspoint Switch and MH88524 MH88524 MH88631 TO CO LINE TIP 1 T RING 1 R VX RX1 VR TX1 RECEIVE 1 INPUT JUN1 AGND RX1 e.g MT8804 MT8816 etc. MH88510 TO CO LINE TIP 2 (1/2) T JUNC Notes: See MH88631, MT8804 and MT8816 data sheets for device details. RING 2 R AGND Figure 9 - Application Circuit with MH88631, MH88510, Crosspoint Switch and MH88524 2-80 MH88524 Preliminary Information MH88524 VIN RX1 RX1 754Ω JUN1 TX1 RX2 JUN2 754Ω VOUT JUN2 TX2 VOUT TX2 VDD AGND Notes 1) In addition to the above test circuit: Apply VIN JUN1 and measure VOUT TX2 and VOUT JUN1. Apply VIN JUN2 and measure VOUT TX1 and VOUT JUN1 Apply VIN RX2 and measure VOUT TX1 and VOUT JUN1. 2) All ground connections are star configured (i.e., single point ground). +5V V EE -5V CT (Crosstalk) calculation Examples: CT = 20xlog (VIN RX1/VOUT JUN2) CT = 20xlog (VIN RX1/VOUT TX2) Figure 10 - Application Circuit for Crosstalk Test Analog Signal Input MH88524 Digital Data Input (2kHz max) MT8840 TX0 TXD1 Digital Data Output RXD0 VSS RX1 32kHz ASK plus Analog Input/Output JUN1 TX1 AGND RX1 High Pass Filter Analog Signal Output Low Pass Filter MH88500 TIP JUNCTOR GND To Telephone Station Set Input/Output RING Notes: 1) See MT8840 data sheet for device details. 2) See MH88500 data sheet for device details. Note that this device is optional in this applications circuit. 3) High Pass Filter is typically 2nd order 15kHz 4) Low Pass Filter is typically 2nd order 4kHz Figure 11 - Application Circuit with MT8840, MH88500 and MH88524 2-81 MH88524 Preliminary Information Side View 0.080 Max (2.0 Max) 1.00 + 0.03 (25.4 + 0.0.08) 0.56+0.02 (14.2+0.5) 1 2 3 4 9 10 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 12 - Mechanical Data 2-82 * 0.18+ 0.02 (4.6 + 0.5) 0.100 + 0.10 (2.54 + 0.13)