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| (R) MH88400 Line Interface Circuit Preliminary Information Features * * * * * * * * * * FAX and Modem interface Suitable for V.29 FAX & V.22 bis Data Allows caller identification Variants match German, UK, 600 & 900 network impedances Isolation circuitry conforms to international PTT requirements Transformerless 2-4 Wire conversion Loop start operation Pulse and DTMF operation Accommodates external monitor phone Line state detection outputs: -loop current/ringing outputs -monitor phone switch hook Single +5V operation ISSUE 1 April 1995 Ordering Information MH88400-1 14 Pin DIL Package MH88400-2 14 Pin DIL Package MH88400-3 14 Pin DIL Package 0C to 70C Description The Mitel MH88400 Line Interface Circuit provides a complete audio and signalling link between audio equipment and central office. The functions provided by the MH88400 include 2-4 Wire conversion, loop seizure, external monitor phone switch hook status and ringing voltage and loop current detection. The device is fabricated as a thick film hybrid which incorporates various technologies for optimum circuit design, high voltage isolation and very high reliability. Variants are provided to meet German (-1) and UK (-3) and general 600 (-2) line impedance (see section on Line Impedances). Isolation Barrier Power Supply * Applications Interface to Central Office for: * DAA * Modem * FAX * Answering Machine * Terminal Equipment Transformer Isolation VDD AGND TIP RING Active Termination OptoIsolation OptoIsolation Audio Buffer Logic Input Buffer VR LC TXIN TF RLS Audio Input Buffer Input Buffer OptoIsolation OptoIsolation Audio Buffer Ring & Loop Buffer Switch Hook Buffer VX RVLC PHS OptoIsolation SHK NETWORK CONNECTIONS USER CONNECTIONS Figure 1 - Functional Block Diagram 2-11 MH88400 Preliminary Information VDD AGND LC RVLC SHK VX VR 1 2 3 4 5 6 7 14 13 12 11 10 9 8 TIP RLS PHS TF TXIN RING NC Figure 2 - Pin Connections Pin Description Pin # 1 2 3 4 Name VDD AGND LC RVLC Description Positive Power Supply Voltage. +5V. Analog Ground. 4-Wire Ground. Normally connected to System Ground, Loop Control (Input). A logic low activates internal circuitry which provides a dc termination across Tip and Ring. Used for seizing the line and dial pulsing Ring Voltage and Current Detect (Output). A logic low indicates that loop current is detected. The loop current can be due to the external monitor phone or the MH88400 in the off- hook mode. The RVLC outputs pulses when the external monitor phone is dial pulsing or when the MH88400 is dial pulses via the LC input. In addition, when the MH88400 is in the on-hook mode, a pulsing output indicates that ringing voltage is across the Tip and Ring leads; the pulsing outputs frequency is twice the ringing frequency. Switch Hook Detect (Output). This is an optional output which can be used with the PHS input and an external phone. When loop current flows from PHS to TIP, SHK goes to logic low. Transmit (Output). 4-Wire ground(AGND) referenced audio output, biased at 2.5V. Outputs for both off-hook and on-hook. Receive (Input). 4-Wire ground (AGND) referenced audio input, biased at 2.5V. LC must be activated low and loop current must be flowing. No Connection. This pin is not connected internally Ring Lead. Connects to the "Ring" lead of the central office through a relay contact. The central office "Tip" and "Ring" leads may be interchanged Transmit (Input). Connects to the "Ring" lead of the central office through a coupling capacitor. Tip Feed. Connects to the "Tip" lead of the central office through an internal resistor and an optional external resistor. Monitor Phone Sense (Input). This is an optional input which can be used with the SHK output and an external phone. When loop current flows from PHS to TIP, SHK goes to logic low. Ring Loop Sense (Input). Sense node for ringing voltage detector and the loop current detector. Tip Lead. Connects to the "Tip" lead of the central office through an optional relay contact. The central office "Tip" and "Ring" leads may be interchanged. 5 SHK 6 7 8 9 10 11 12 VX VR NC RING TXIN TF PHS 13 14 RLS TIP 2-12 Preliminary Information Functional Description The MH88400 Line Interface Circuit is a COIC (Central Office Interface Circuit) used to interface FAX's Modems or user defined equipment to Central Office 2-Wire Analog Trunks. MH88400 In addition, when the MH88400 is in the on-hook mode, a pulsing output indicates that ringing voltage is across the tip and ring leads; the pulsing output frequency is twice the ringing frequency. See Figure 3. Ringing frequency may require external validation. An RC monostable is usually satisfactory for this purpose or this may also be achieved using software applications. Opto-Isolation The isolation barrier is designed to meet regulatory requirements for a reinforced barrier of 3kVac. It provides full isolation of mains voltages up to 250V RMS and all telecom voltages. In order that this barrier is not bypassed a creepage/clearance distance of 6.4mm minimum must be maintained between wiring, pcb tracking, etc., connected to external circuitry on either side of the barrier. To make this requirement simpler, pins on the MH88400 connected to opposite sides of the barrier are on opposite sides of the package. 2-4 Wire Conversion The 2-4 Wire conversion circuit converts the balanced full duplex signal at Tip and Ring of the central office line into a transmit ground referenced signal at VX (Transmit) of the MH88400. It also converts the receive ground referenced signal at VR (Receive) of the MH88400 into a balanced transmit signal at Tip and Ring of the central office line. In full duplex transmission, the Tip-Ring signal consists of an audio signal from the central office as well as an audio signal due to the VR input. Consequently, both of these signals will appear at the VX output. The degree to which the 2-4 wire conversion circuit minimizes the contribution of the VR signal at the VX output is specified as transhybrid loss (THL). A simple THL cancellation circuit as shown in figure 7 can be used for certain applications to give the required VX/VR signal separation. The MH88400 is then suitable to drive a COMBO 2 CODEC or a VLSI MODEM device. External Protection Circuit To meet regulatory high voltage requirement, an external protection circuit is required. The protection circuit shown in Figure 3 (Clamp Diode D1) is recommended. DC Loop Termination The DC loop termination circuitry provides the loop with an active DC load termination when a logic low is applied to the LC (Loop Control) input. The termination is simpler to a resistance of approximately 300 (loop current dependant). Internal optically isolated circuitry is used to switch the termination in and out the loop. This is used for both seizing the line as well as generating dial pulses. Line Impedance The MH88400 is suitable to drive a COMBO 2 CODEC or a VLSI modem device. The MH88400 provides a fixed Tip-Ring impedance which conforms to the following PTT requirements. MH88400-1 Zin = 200 + 820 // 115nF Germany FTZ MH88400-2 600 MH88400-3 Zin = 370 + 620 // 310nF UK BSI Supervision Features The supervision circuitry is capable of detecting ringing voltage and loop current as well as the status of an optional external monitor phone. The RVLC (Ring Voltage Loop Current Detect) output provides a logic low when loop current due to the external monitor phone or due to the MH88400 being in the off-hook mode is detected. The RVLC outputs pulses when the external monitor phone is dial pulsing or when the MH88400 is dial pulsing via the LC mode. 2-13 MH88400 Parameter 1 2 3 4 5 DC Supply Voltage Storage Temperature DC Loop Voltage Ringing Voltage Loop Current Symbol VDD TS VBAT VR ILoop Preliminary Information . Absolute Maximum Ratings* - All voltages are with respect to AGND unless otherwise specified. Min -0.3 -55 -100 Max 6 +80 +100 120 90 Units V C V VRMS mA * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Recommended Operating Conditions Parameters 1 2 3 DC Supply Voltages Operating Temperature Ringing Voltage Sym VDD TOP VR Min 4.5 0 75 Typ 5.0 Max 5.5 70 Units V C VRMS VBAT=-48V Test Conditions Typical figures are at 25C with nominal +5V supplies and are for design aid only. Loop Electrical Characteristics* Characteristics 1 2 3 4 5 6 Ringing Voltage Ringing Frequency On-Hook 2-wire Impedance Operating Loop Current Operating Loop Resistance Off-Hook DC Resistance -1 & -2 Variants -3 Variant 7 8 9 10 Leakage Current (2-Wire to AGND) Leakage Current on Hook (Tip to Ring) DC Resistance during dialling -1 variant Dial Pulse Distortion ON Off 0 9 200 220 +4 0 +8 +2 ms ms 310 160 350 300 250 400 10 No Detect Detect Sym VR 27 15 40k 80 4000 480 480 300 450 10 10 68 Min Typ Max 20 Units VRMS VRMS Hz mA A A VBAT=-48V, ILoop=10mA ILoop=20mA ILoop=40mA ILoop=40mA ILoop=20mA 100VDC VBAT=50V ILoop=20-40mA 1kHz Test Conditions * Loop Electrical Characteristics are over recommended operating conditions unless otherwise stated. Typical figures are at 25C and are for design aid only. Note: All of the above characteristics use a test circuit as per Figure 3. 2-14 Preliminary Information DC Electrical Characteristics Characteristics 1 2 3 4 5 RVLC SHK MH88400 Sym IDD PC VOL VOH VIL VIH IIH IIL 3.8 0.9 3.5 0.6 1 Min Typ 15 75 0.4 Max Units mA mW V V V V m A Test Conditions VDD = 5.0V, ILoop=40mA VDD = -5.0V,ILoop=40mA IOL = 1.0mA IOH = 1.0mA Supply Current Power Consumption Low Level Output Voltage High level Output Voltage Low Level Input Voltage High level Input Voltage High Level Input Current Low Level Input Current VIH = 5.0V VIL = 0.0V DC Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. Typical figures are at 25C with nominal+ 5V supplies and are for design aid only. Note: See figure 3a and 3b. AC Electrical Characteristics - MH88400 All Variants Characteristics 1 2 3 4 5 6 7 Input Impedance VR Output Impedance at VX Transmit Gain (2-Wire to VX) -0.4 Frequency Response Gain (relative to Gain @ 1kHz) Receive Gain (VR to 2-wire) 3.5 Frequency Response Gain (relative to Gain @ 1kHz) Signal Output Overload Level -3.0 0.0 +2.0 -3.0 0.0 +2.0 THD at 2-wire at VX 9 Power Supply Reject Ratio at 2-wire at VX PSRR 35 10 dB dB 0.9 1.2 % % dBm dBm dBm dBm dBm dBm 0 0 dB dB -2.4 -3.0 dB dB Sym Min Typ 47 5 Max Units k dB Input 0.5V at 1kHz offhook 300 Hz 3400 Hz Test Conditions dB Input 0.5V at 1kHz 300 Hz 3400 Hz THD <5% @ 1kHz ILoop =10-40mA VDD=4.5V VDD=5.0V VDD=5.5V VDD=4.5V VDD=5.0V VDD=5.5V Input 0.5V at 1kHz DC loop = 1000 VDD=5.0V Ripple 0.1V,1kHz on VDD at 2-Wire at Vx 8 Total Harmonic Distortion AC Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. Typical figures are at 25C and are for design aid only. Note 1: All of the above characteristics use a test circuit as per Figure 3. Note 2: All of the above test conditions use a test source impedance which matches the device's impedance. Note 3: dBm is referenced to 600 unless otherwise stated. Note 4: THD is measured with a "Weight" filter. 2-15 MH88400 AC Electrical Characteristics - MH88400-1 Characteristics 1 2 2-Wire input Impedance (200 + 820 //115nF) Return Loss at 2-Wire (200 + 820 //115nF) Longitudinal to Metallic Balance Sym Zin RL 20 20 20 40 55 53 Nc at 2-Wire At VX -84 -81 -78 Min Typ 900 22 24 26 65 60 60 Max Preliminary Information Units dB dB dB dB dB dB dBmp dBmp Test Conditions @ 1kHz 300-500Hz 500-2500Hz 2500-3400Hz 50-300Hz 300-1000Hz 1000-4000Hz 3 4 Idle Channel Noise AC Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. Typical figures are at 25C and are for design aid only. Note 1: All of the above characteristics use a test circuit as per Figure 3. Note 2: All of the above test conditions use a test source impedance which matches the device's impedance. Note 3: dBm is referenced to 600 unless otherwise stated. Note 4: THD is measured with "Weight" filter. AC Electrical Characteristics - MH88400-2 Characteristics 1 2 3 4 2-Wire Input Impedance -2 (600) Return Loss at 2-Wire (Reference -2 =600) Longitudinal to Metallic Balance Idle Channel Noise at 2-Wire at VX Nc -84 -81 -78 dBrnp dBrnp Sym ZIn RL 20 50 Min Typ 600 24 60 Max Units dB dB Test Conditions @ 1kHz 300-3400Hz 300-3400Hz AC Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. Typical figures are at 25C and are for design aid only. AC Electrical Characteristics - MH88400-3 Characteristics 1 2 3 4 2-Wire Input Impedance (370 + 620 // 310nF) Return Loss at 2-Wire (370 + 620 // 310nF) Longitudinal to Metallic Balance Idle Channel Noise at 2-Wire at VX Nc -80 -80 -70 -70 dBmp dBmp Sym Zin RL 18 50 Min Typ 700 20 60 Max Units dB dB Test Conditions @ 1kHz 200-2400Hz 300-3400Hz AC Electrical Characteristics are over Recommended Operating Conditions unless otherwise stated. Typical figures are at 25C and are for design aid only. Note 1: All of the above characteristics use a test circuit as per Figure 3. Note 2: All of the above test conditions use a test source impedance which matches the device's impedance. Note 3: dBm is referenced to 600 unless otherwise stated. Note 4: THD is measured with "weight" filter. 2-16 Preliminary Information However, by adding external resistors to the VX output, the Transmit Gain can be reduced as shown in Figure 5. To limit the output current drawn, the minimum recommended resistance to ground is 2k. MH88400 Overall Transmit Gain = -0.4 dB + 20log (R4 / (R4 + R3)) The output impedance of the VX output is about 5, therefore, with two external 1k resistors configured as per Figure 5, this will result in 6dB of attenuation for a total gain of -6.4dB. For correct gain, the MH88400 input impedance must match the line impedance. TIP-RING Drive Circuit The audio input ground (AGND) referenced signal at VR, biased at 2.5V, is converted to a balanced output signal at Tip-Ring. 2-4 wire isolation is achieved through optical isolation. The LC input is activated, low, and loop current must be flowing. Receive Gain Receive Gain (VR to Tip-Ring) is fixed as indicated in "AC Electrical Characteristics". However, by adding a single external resistor in series with the VR input, the Receive Gain can be reduced. Overall Receive Gain = 3.5dB + 20log (47k /(47k + Rext), The input impedance of the VR input is 47k, therefore, an external 100k resistor in series with this input will result in 9.9dB of attenuation for a total gain of -6.4dB. For correct gain, the MH88400 input impedance must match the line impedance. TIP-RING Receive Circuit The differential audio signal at Tip-Ring is converted to a ground (AGND) referenced signal, biased at 2.5V, at the VX output. 2-4 Wire isolation is achieved through a combination of optical isolation and transformerler isolation. The receive circuit operated with or without loop current and LC can be either high or low. Signal reception with no loop current can be used for on-hook reception of, for example, caller identification signals. Transmit Gain Transmit Gain (Tip-Ring to VX) is fixed as indicated in "AC Electrical Characteristics". 14 13 R1 TIP 11 C2 D1 TIP RLS MH88400 VX 6 Audio Output 7 VR Audio Input TF TXIN 10 RVLC 4 Ring Voltage & Loop Current Detect Output 3 RING 9 RING VDD AGND LC Loop Control Input 1 + C1 2 +5V NOTES: Calls are set up and cleared in this mode by the external controller. It turns on the loop via Loop Control, dialling by pulsing loop control (or via DTMF tones) and clearing down by turning Loop Control off. 1) C1: 10F, 6V Tantalum 2) C2: 0.1F, 250V (Typical Value) 3) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180 4) VX and VR are biased at 2.5V, therefore, coupling capacitors may be required depending on application. 5) VX and VR are biased at 2.5V, therefore, coupling capacitors may be required depending on application. Figure 3 - Typical Application Circuit 2-17 MH88400 Preliminary Information 14 13 TIP R1 11 MH88400 TIP RLS 6 VX 7 Audio Output VR TF Audio Input D1 R2 C2 10 TXIN RVLC 4 Ring Voltage & Loop Current Detect Output RING Line Relay Input 9 3 RING VDD 1 AGND 2 + C1 +5V 1) R1: 39,1/2W,5%,current limiting resistor for use in Germany. 2) R2: 18k 3) C1: 10F, 6V Tantalum 4) C2: 0.47F, 100V LC Loop Control Input K1 5) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180 6) VX and VR are biased at 2.5V, therefore, coupling capacitors may be required depending on application. NOTES: C2 must be 0.1F for correct operation. R2 & C2 form a dummy ringer, where R2 is on the hybrid and C2 must be fitted by the customer. To initate a manual call, lift the handset. The RVLC pin will indicate that the line as been seized by the monitor phone. The required number is then dialled and the connections established. During this phase the Loop Control input should be turned ON to ensure that when the relay K1 is operated and the monitor phone removed from the line loop current is still maintained. On receipt of the correct progress tones the external controller should control the data transmission and clear down the call when it is completed by turning the Loop Control OFF. For applications in some countries such as Germany the MH88422 can not be used with an optional telephone but may still be used in a combined telephone/fax machine. Figure 4 - Typical Application Circuit with Dummy Ringer and Monitor Phone R4 1K Audio Output 14 13 TIP R1 11 C2 D1 10 9 TIP RLS MH88400 6 VX R3 1K 7 VR R2 100K 4 RVLC Ring Voltage & Loop Current Detect Output 3 Audio Input TF TXIN RING RECEIVE GAIN: Audio input to Tip-Ring =20log(R2/(R2+47K))+3.5dB =6.5dB TRANSMIT GAIN: Tip-Ring to Audio Output =20log(R4(R3+R4))-0.4dB =-6.4dB Note: The VX output gain has been reduced by 6dB (to -6.4dB) and the VR input gain has been reduced by 10dB (to -6.5dB) in this example. RING VDD AGND 2 + C1 +5V LC Loop Control Input 1 1) R1: 39,1/2W,5%,current limiting resistor for use in Germany 2) C1: 10F, 6V Tantalum 3) C2: 0.1F, 250V (Typical Value) 4) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180 5) VX and VR are biased at 2.5V, therefore, coupling capacitors may be required depending on application. 6) (R3+R4) should be > 2k to prevent overload. Figure 5 - Typical Application Circuit for Gain Adjustment 2-18 Preliminary Information MH88400 R3 1K C5 22nF VR 7 C3 Audio Input 0.1F RVLC 4 Ring Voltage & Loop Current Detect Output RING VDD 1 + C1 +5V AGND LC R4 Audio Output L1 4.7mH 14 13 TIP R1 1K C2 D1 10 9 11 TIP RLS MH88400 6 VX TF TXIN RING 3 Loop Control Input 2 Meter Pulse Detector Note: Meter pulses at high frequency (16kHz or 12kHz) and high level (10V RMS) are used in some countries. The VX amplifier has a low pass filter which attenuates by typically 15dB at 16kHz. If this proves insufficient for specific applications, an LC notch is recommended. This should provide a further 20dB of rejection at 16 of 12kHz with only 0.5dB of loss at 3.4kHz (after allowing for the overall 6dB loss caused by R3, R4). 1) R1: 39,1/2W,5%, current limiting resistor for use in Germany. 2) C1: 10F, 6V Tantalum 3) C2: 0.1F, 250V 4) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180. 5) L1: 4.7mH 5%, eg, Siemens B78108-S 6) C5: 22nF 5% for 16kHz 39nF for 12kHz Figure 6 - Typical Application Circuit with Meter Pulse Filter and Coupling Capacitors 560pF 5% 100k 1% 68k From VR 10nF 68k 1% 1% 62k 1% A1 VX Out 5% - A1 + + 100k 100nF 10pF 100k 1% 100k From VX Note: Amplifier A1 provides a frequency equivalent to the VX path in the MH88400. This provides the correct phase/amplitude response to enable cancellation to take place in amplifier A2. Typical THL figures of 15-20dB can be achieved with the values and tolerances shown. The VR input should be driven from a low impedance < 600R. This circuit will function correctly for all variants provided the termination impedance of the external line at the 2W connection is equal to the characteristics impedance of the MH88400. If it is desired to operate with impedances different from the MH88400 impedances, the frequency compensation networks around A1 must be filtered. Because of the wide variety of impedances which are in typical use it is not possible to specify the required values. 0V Figure 7 -Transhybrid Loss (THL) Cancellation Circuit 2-19 MH88400 Preliminary Information L1 14 13 TIP RLS MH88400 6 VX 7 Audio Output VR 11 TIP C3 D1 10 9 L2 C4 C2 TXIN TF RVLC Audio Input 4 Ring Voltage & Loop Current Detect Output RING RING VDD 1 + C1 +5V AGND 2 LC 3 Loop Control Input Notes: 1) C1: 10F, 6V Tantalum 2) C2: 0.1F, 250V 3) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180 4) C3: 4.7nF; C4: 1.0nF Ceramic 10% 5) L1, L2: 1mH 5%, eg, Siemens B78108-S1105-J Figure 8 - Typical Application Circuit showing Noise Filter Network for Outband noise reduction 1.50 Max (38.0 Max) 0.90 Typ (22.9 Typ) 1.05 Max (26.7 Max) (1.3 Typ) *0.05 Typ 0.35 Max (8.9 Max) 0.12 Min 0.20 Max (3.0 Min 5.1 Max) Notes: 1) Not to scale 2) Dimensions in inches). 3) (Dimensions in millimetres). *Dimensions to centre of pin. *0.11 Typ (2.9 Typ) 0.20 0.005 (0.5 0.12) *0.200 0.005 (5.08 0.12) Figure 9 - Mechanical Data for 14 Pin DIL Hybrid 2-20 |
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