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| (R) MH88612C Subscriber Line Interface Circuit Preliminary Information Features * * * * * * * * * * Input impedance 200 + 560 // 0.1F Transformerless 2-wire to 4-wire conversion Battery and ringing feed to line Off-hook and dial pulse detection Ring ground over-current protection Adjustable constant current feed Relay drive output Power VBat Denial Wide Operating Range Programmable Receive Gain MH88612C ISSUE 4 April 1995 Ordering Information 20 Pin SIL Package 0C to 70C Description The SLIC provides a complete interface between a switching system and subscriber loop. Functions provided include battery feed and ringing feed to the subscriber line, 2-Wire to 4-Wire hybrid interfacing, constant current feed and dial pulse detection. The device is fabricated using thick film hybrid technology in a 20-pin single in-line package. Applications Line interface for: * * * * PABX Intercoms Key Telephone Systems Control Systems VBat VDD VEE GNDA GS TF TIP RING RF RV VRLY RC RD Current & Voltage Sensing 2-Wire to 4-Wire Conversion VR VX Over Current Protection Relay Drive Circuit Loop Supervision VRef CAP Constant Current Feed SHK FIgure 1 - Functional Block Diagram 2-113 MH88612C IC TF IC VR VRef VEE GNDA GS VX TIP RING RF VDD RC RD RV VRLY IC VBat CAP SH K 0 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 # 0 1 2 3 4 Name IC TF IC VR VRef Description Internal Connection. No pin fitted in this position. Tip Feed. Connects to external diode to LPGND for protection. Internal Connection. No pin fitted in this position. Voice Receive (input) is the 4 wire analog signal to the SLIC. Voltage Reference to set the constant current feed to the subscriber line. Constant current feed can be adjusted by the input voltage on the VRef. This pin can also be grounded for normal 21mA loop current. Negative Power Supply voltage. (-5V). Analog Ground. (0V) Gain setting (Input). A logic low at this input adds an additional -0.5dB gain in the receive direction. This gain is in addition to the gain set by the Codec. A high adds 0dB gain. Voice Transmit (Output) is the 4-wire analog signal from the SLIC. Connects to the "Tip" lead of the telephone line. Connects to the "Ring" lead of the telephone line. Ring Feed (Input). is connected via the ring relay to either negative battery feed voltage, (RV), or ringing voltage input. Positive Power Supply Voltage. (+5V) Relay Control (Input). Active high will apply ringing to the line. Output Drive Sources current when RC is at a logic high. Ring Feed Voltage connects to pin 11 (RF) through a normally closed relay contact. Relay voltage Supply. (+5V) Internal Connection. No pin fitted in this position. Negative Battery Feed Supply Voltage. (-48V) Connects external capacitor to ground for ring trip. Switch Hook Detect (Output). Active high. 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 VEE GNDA GS VX TIP RING RF VDD RC RD RV VRLY IC VBat CAP SHK 2-114 Preliminary Information Functional Description The SLIC performs a transformerless 2-wire to 4-wire conversion of the analog signal. The 2-wire circuit is the balanced line going to the subscriber loop, while the 4-wire circuit is the audio signal going to and from devices such as the voice codec or switching circuit. The SLIC also provides a switch hook (SHK) status output which goes high when the telephone is set off-hook. MH88612C For applications requiring dial pulse detection the capacitor connection to ground should be controlled so that the capacitor is only connected during ringing. During off-hook conditions (closed loop), the capacitor should be switched out. This can be performed using a transistor, relay to system drive output of a codec. Applying GNDA to Ring Trip Filter Control pin will switch in the filter, whilst removing GNDA, (with the switch in a tristate condition), will switch out the filter. For applications using DTMF signalling, the capacitor can be permanently connected to ground. Once an off-hook condition has been detected a logic low on the Relay Control (RC) input deactivates the relay (K1) to disconnect the ringing voltage from pin 11 (RF)and reconnect to pin 15 (RV). At that time the SLIC will revert to constant current feed operation. Constant Current Feed The SLIC employs a complex feedback circuit to supply a constant feed current to the line. This is done by sensing the sum of the voltages across the internal feed resistors and comparing it to an input reference voltage (VRef) that determines the constant feed current. If VRef (pin 4) is externally grounded, the constant current is set at 21mA. For a constant current setting between 18mA and 30mA, VRef can be set between -8.75 Vdc and -6.35 Vdc. The relationship is detailed in the formula below: ILoop = [-2.6(VRef) + 21.5] mA +2mA Current Limit The Tip or Ring may accidentally short to ground. In such a case, current will only flow through the feed resistor. This high current will be sensed and reduced by the current limit circuit to a lower value to protect the internal circuitry. Switch Hook Detection When the DC current exceeds an internal threshold level, the switch hook (SHK) will go high. If the loop resistance is so high that V Bat can no longer supply the required amount of loop current as determined by constant current supply circuit, the output of the switch hook (SHK) will go low to indicate that the loop resistance is too high and the line is on hook. Receive Gain The MH88612C Receive Gain (VR to 2-wire) can be adjustable by -0.5dB if GS is taken logic low or by 0dB if GS is taken logic high. When the MH88612C issued with an off hybrid MT896x codec the Receive Gain can be set to either -3.5dB or -7dB by writing to control Register A of Codec and programming GS appropriately. Ringing And Ring Trip Detection In Figure 3 a ringing signal (e.g. 90 Vrms superimposed on -48 VDC) is applied to the line by disconnecting pin 15 (RV) from pin 11 (FR), and connecting the ringing voltage at pin 11 (RF) by use of the relay K1. The SLIC can detect an off-hook condition during ringing but there is a large AC component which must be filtered out to give a true off-hook condition at SHK. A 1F capacitor connected from pin 19 (CAP) to ground will provide adequate attenuation when ringing is applied. 2-115 MH88612C Applications Component List Preliminary Information = 1/4 W, + 10% 200 = 1/4W, 5%, 470K = Cap. Elec., 1.0F, + 10%, 25V = Diode Rect., 200V, 1A, IN4003 = Relay E/M, 5 or 6V, 1 form C Decoupling capacitors (Cap. Cer 0.1F, 50% + 20%) should be added to VDD, V EE, VBat, VRef and V RLY. Options RV1, RV2= 160 Vrms, 250V 10J R1 R2, C1 D1,D2 K1 90 VRMS SUPERIMPOSED ON -48VDC VBat R1 K1 11 D4 D1 D2 MH88612C RF 15 RV 3 VR 1 D3 TF VX 8 VBat TIP 9 RV1 4 VRef 20 RV2 SHK RING RC 13 +5V 16 K1 10 7 GS VRLY RD VBat VDD 18 12 VEE 5 CAP GNDA 6 19 C1 Ring Trip Filter Control 14 + R2 -48V +5V -5V Figure 3 - Application Circuit 2-116 Preliminary Information Absolute Maximum Ratings* Parameter 1 DC Supply Voltage Symbol VDD VEE VBat TSTG PD Min -0.3 +0.3 0.3 -40 Max +15 -15 -60 100 MH88612C Units V V V C 2 3 Storage Temperature Package Power Dissipation 2 w * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Recommended Operating Conditions Parameter 1 Operating Supply Voltage Sym VDD VEE VRef VBat VRLY 2 Operating Temperature TO 0 * Typical figures are at 25C and are for design aid only. Min 4.75 -4.75 -27 Typ* 5.0 -5.0 0 -48 5 Max 5.25 -5.25 -60 70 Units V V V V V C Comments Adjustable DC Electrical Characteristics Characteristics 1 Supply Current - Voltages are with respect to GNDA unless otherwise stated. Sym VDD VEE VBat IDD IEE IBAT PC ILoop ILoop RLoop Min 0.8 0.5 0.0 Typ* 5 3 2 210 1410 Max 12 10 2.5 Units mA mA mA mW mW Test Conditions Idle State Standby Active VRef = GNDA, V Bat = -48V Adjustable with Ext. VRef input, VBat = -48V VBat = -48V @ I Loop = 18mA, RLoop includes telephone set 2 3 4 5 Power Consumption Constant Current Line Feed Adjustable Loop Current Range Operating Loop Resistance 18 18 21 24 30 1850 mA mA 6 7 Ring Ground Over-Current protection Off-Hook Detect Output Low Current (On-hook) Output High Current (Off-hook) Off- Hook Detect Output Low Current (on-hook) Input High Current. (activation) RC Control Input Input Low Volt. (no activation) Input High Volt. (activation) RC control Input Input Low Current (no activation) Input high current (activation) VOL VOH IOL IOH VIL VIH IIL IIH 0.0 2.7 40 mA Active high logic 0.4 5.25 8 -400 0.7 V V mA A Active high logic V V A A 8 9 2.0 -50 50 10 DC Electrical Characteristics are over recommended operating supply voltages. * Typical figures are at 25C with nominal +/-5V supplies and are for design aid only. 2-117 MH88612C AC Electrical Characteristics Characteristics 1 2 3 4 5 6 7 Ringing Voltage Ringer Equivalence Number Ring Trip Detect time Input AC Impedance 2-wire (1) Input Impedance at VR Output Impedance at VX Gain 2-wire to VX Gain relative to Gain @ 1kHz -0.5 -0.22 Zin Preliminary Information Sym VRING REN Min 40 Typ* Max 90 25 3 Units Vrms Hz ms k dB Test Conditions Superimposed on VBat =-48V 100 719 100 10 0 0.1 0.1 @1020Hz dB dB Input 3 dBm, 1kHz across Tip and Ring, 300Hz & 3k4Hz 600Hz & 2k4Hz ZLoad See Note (1). Input 1.0Vrms, 1kHz @ VR 8 Gain VR to 2-wire 0 -0.6 Gain relative to Gain @ 1kHz with GS @ logic high -0.5 0.22 20 30 -0.4 0.1 0.1 dB dB dB dB dB with GS @ at logic high with GS @ at logic low 300Hz & 3k4Hz 600Hz & 2k4Hz ZLoad, See Note (1). Input 0.5 Vrms , across Tip and Ring, ZLoad = complex network. See Note (1). Input 0.5V Vrms, ZLoad= complex network. See Note (1). Input 1 Vrms Input 3dBm, 1 kHz across Tip and Ring, Input 1.0 Vrms 1kHz at VR Input 1 Vrms, 1KHz 9 2-wire Return Loss over 300-3400Hz Transhybrid Loss over 300-3400 Hz Longitudinal to Metallic Balance over 300-3400 Hz Total Harmonic Distortion at VX at Tip and Ring THD THL 10 20 35 dB 11 12 46 55 dB 0.1 0.1 CMRR 40 50 1.0 1.0 % % dB 13 Common Mode Rejection Ratio 2-wire to VX Idle channel Noise (at VX) (at T & R) 14 Nc 14 -76 12 -78 20 20 20 30 30 30 dBrnC dBrnp dBrnC dBrnp dB dB dB C- Message psophemetric C- Message psophometric 1 VPP ripple, 1kHz on VDD/VEE//VBat,measure at Vx and across Tip and Ring 15 Power supply rejection ratio VDD VEE VBat PSRR * Typical figure are at 25C and are for design aid only: not guaranteed and not subject to production testing. Note (1): Zin = 200 + 560 //0.1F 2-118 Preliminary Information MH88612C Side View 0.080 Max (2.0 Max) 2.13 Max (54.34 Max) 0.6 Max (15.3 Max) 1 20 0.010 + 0.002 (0.25 + 0.05) 0.27 Max (6.9 Max) * 0.025 Max Notes: 1) Not to scale 2) Dimensions in inches). 3) (Dimensions in millimetres). *Dimensions to centre of pin & tolerance non accumulative. * 0.100 + 0.010 (2.54 + 0.26) 0.180 + 0.02 (4.6 + 0.5) 0.05 + 0.02 (1.3 + 0.5) * 0.15 + 0.02 (3.81 + 0.5) 0.020 typ Figure 4 - Mechanical Data 2-119 MH88612C Notes: Preliminary Information 2-120 |
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