MH89726/728 MT8972 Loop Extender Circuits Advance Information Features ISSUE 2 November 1990 Ordering Information • • • • • • Operates from single or dual power supply MH89726 extends transmission performance for the MT8972 (DNIC) at 160kbit/s line rate MH89728 extends transmission performance for the MT8972 (DNIC) at 80kbit/s line rate MH89726 and MH89728 are pin for pin compatible with each other Compact SIL package Over 6km loop range on 24 AWG MH89726/728 10 Pin SIL Package 0°C to 70°C Description The MH89728 and MH89726 are thick film hybrid devices which may be used to extend the operating range of the MT8972 (DNIC). The hybrids combine signal equalization and amplification for the receive and transmit paths on each device. Applications • • • • Digital subscriber lines Digital PABX line cards and telephone sets High speed, limited distance modem ISDN U - Interface The small size of these hybrids makes them suitable for line card or terminal use with the MT8972. The gain of the transmit signal may be adjusted through the use of an external resistor. TXGAIN Pre- TXIN TX Equalizer Amplifier TXOUT Phase Compensator RXOUT RXIN - Pre- RX Canceller Amplifier RXIN + VBias TEST V+ V- Figure 1 - Functional Block Diagram 9-127 MH89726/728 Advance Information TXGAIN TXOUT RXIN + RXIN VVBias V+ TEST RXOUT TXIN 1 2 3 4 5 6 7 8 9 10 Figure 2 - Pin Connections Pin Description Pin # Pin Name 1 TXGAIN Transmit Gain. To be connected to Pin 2. An increase in gain can be achieved by connecting an external resistor REXT between Pin 1 and Pin 2. The resultant gain is calculated using; A= (R/24) + 2.8, where A=Gain and R= REXT (kΩ). 2 TXOUT Transmit Output. Connect to the termination network. 3 RXIN- Negative Receive Signal. Connect to TXOUT, Pin 2. 4 RXIN+ Positive Receive Signal. Connected to line transformer. 5 V- 6 VBias 7 V+ 8 TEST Test. Used for production testing. Leave unconnected. 9 RXOUT Receive Output. Connect to LIN (Pin 21) of MT8972. 10 TXIN Transmit Input. Connect to LOUT (Pin 1) of MT8972. 9-128 Description Negative power supply. Internal Bias Voltage. Connect to GND through 0.33 µF for single power supplies. Connect to GND directly for split power supplies. Positive power supply. MH89726/728 Advance Information Functional Description The LEC is powered typically from ±15 Volts if dual power supplies are available. Alternately 0 to +30 Volts, or -30 to 0 Volts can be used if only a single power supply is available. The MH89726/728 are 10 pin SIL thick film hybrid circuits that may be used to extend the loop range capability of the MT8972 (DNIC). For a detailed description of the DNIC, refer to the MT8972 data sheet. Applications Figure 3 shows a typical connection diagram of the MT8972 and MH89726/728. RXOUT and TXIN of the LEC are connected to LOUT and LIN of the DNIC respectively. Pins 5, 6 and 7 are the power supply pins, with the voltages being supplied as indicated in the table . An external resistor, REXT, may be used to increase the gain of the transmitter. Without REXT, TXGAIN and TXOUT are shorted together resulting in a transmit power level of +10 dBm. Figure 1 shows a block diagram of the Loop Extender Circuit (LEC). The LEC takes the line signal which is transmitted by the DNIC on LOUT, preequalizes, and amplifies it before sending it to the termination network. The gain of the TX amplifier is adjustable by using an external resistor between pins 1 and 2. If no external resistor is added, TXGAIN and TXOUT must be shorted together, and the default gain condition exists. This gain results in a transmit signal power level of +10 dBm. RLL, RL, and CL comprise the termination network and are used to match the characteristic impedance of the transmission line. This provides the 4 wire to 2 wire hybrid conversion necessary for twisted pair transmission. On the receive side, the LEC receives the differential line signal from the transformer, and performs firstorder pre-cancellation as well as gain and phase adjustment of the receive signal. The signal is then output on RXOUT which is connected to LIN of the MT8972. Figure 4 shows a typical application of the LEC. On short loops, jumpers (or switches) could be used to remove the LEC from the circuit. For longer loops, the jumpers could be changed to include the LEC in the signal path. Tables 1 and 2 show typical results obtained by using the LEC with the MT8972. Actual distance achieved may vary depending on the characteristics of the transmission cable being used. Most important factors include cable attenuation (dB/km), bridged taps, and crosstalk interference. D1, D2 IN5817 Rext Set for different gain requirements MH89726 or MH89728 RLL RL CL + 5V 10 9 8 7 6 5 4 3 2 22 1 Rext 1 MH89726 160 kbit/s MH89728 80 kbit/s 3.9kΩ, 5% 430Ω, 2% 15nF, 5% 3kΩ, 5% 430Ω, 2% 12nF, 5% RLL To Power Supplies MT8972 (DNIC) RL D1 21 11 D2 Pin 6 (VBias) Pin 5 (V-) + 15V DUAL GND GND SINGLE GND* + 30V SINGLE GND* *Use 0.33µF capacitor to GND - 15V - 30V GND Power Supply Pin 7 (V +) CL AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA AA 1.0µF 100kΩ 0.33µF Figure 3 - Typical Connection Diagram for MT8972 and MH89726/728 9-129 MH89726/728 Advance Information MH89726 (160 kbit/s) CONFIGURATION CABLE 24 AWG (8.0 dB/km at 120 kHz) 26 AWG (11.5 dB/km at 120 kHz) DNIC to DNIC 0.0 to 4.1 km 0.0 to 3.0 km DNIC with LEC to DNIC with LEC 0.65 to 5.1 km 0.5 to 3.6 km Table 1 - Typical Transmission Performance at 160 kbit/s MH89728 (80 kbit/s) CONFIGURATION CABLE 24 AWG (6.9 dB/km at 60 kHz (Note 1) 26 AWG (10.0 dB/km at 60 kHz) DNIC to DNIC 0.0 to 5.2 km 0.0 to 3.4 km DNIC with LEC to DNIC and LEC 0.9 to 6.5 km 0.65 to 4.1 km Table 2 - Typical Transmission Performance at 80 kbit/s Note 1: The attenuation of the cable as specified by Bell System Technical Reference PUB 62411. CB 80 kbit/s RA = 390Ω CA = 22nF CB = 3.3nF 160 kbit/s RA = 390Ω CA = 22nF CB = 1.5nF MT8972 1 LOUT RA CA +5V 2:1 D1 LIN 21 LEIN LOOP EXTENDER and Network Termination D2 1.0µF LEOUT1 Twisted Pair Copper 24-26 Gauge LEOUT2 0.33µF NOTES: -D1, D2 IN5817 (Schottky) -Solid jumpers used to connect the loop extender -Dotted jumpers connect MT8972 without loop extender Figure 4 - Typical Application of the Loop Extender 9-130 MH89726/728 Advance Information Recommended Operating Conditions Characteristics Sym Min Typ Max Units Test Conditions 1 + 15 V Supply VDD 13.5 15.0 16.5 V Note 1 2 - 15 V Supply VSS -16.5 -15.0 -13.5 V Note 2 3 Standby Current IS 3.0 mA Note 1: A single voltage supply of +30V±10% can be used on VDD with VBias grounded through a 0.33 µF capacitor and V SS grounded. Note 2: A single voltage supply of -30V±10% can be used on VSS with VBias grounded through a 0.33 µF capacitor and V DD grounded. A.C. Electrical Characteristics Characteristics Sym Min Typ Max Units Test Conditions 1 Active Current IA 7.0 mA @ 60 kHz for 80 kbit/s @120 kHz for 160 kbit/s 2 TX Gain ATX 9.0 dB @ 60 kHz for 80 kbit/s @120 kHz for160 kbit/s 3 TX Phase Angle ΦTX -170.0 ° @ 60 kHz for 80 kbit/s @120 kHz for 160 kbit/s 4 RX Gain ARX 0.0 dB @ 60 kHz for 80 kbit/s @120 kHz for160 kbit/s 5 RX Phase Angle ΦRX 12.0 ° @ 60 kHz for 80 kbit/s @120 kHz for160 kbit/s 6 Line Power 10.0 dBm With 2:1 transformer 9-131 MH89726/728 Advance Information 0.140 (0.356) 1.020 - 0.980 (2.590 - 2.490) 0.405 - 0.345 (1.029 -0.876) 0.190 - 0.180 (0.483 - 0.457) 0.01 (0.025) 0.105 - 0.095 (0.241 - 0.267) 0.025 - 0.015 (0.064 - 0.038) All dimensions are in inches (centimeters). Figure 4 - Mechanical Data 9-132