MH88628 Central Office SLIC Preliminary Information Features • ISSUE 5 April 1995 Ordering Information Programmable gain, network balance and impedance MH88628 40 Pin SIL Package • Transformerless 2-4 wire conversion • Constant current with constant voltage fallback for long loop capability • Pin compatible with MH88632, MH88620 and MH88628 Applications • Unbalanced detection (Tip, Ring ground sensing) • On/Off Premise PBX Line Cards • DID (Direct Inward Dial) Line Cards • Auto ring trip with zero crossing • Central Office Line Cards • On-Hook transmission (ANI) capability • Compatible with requirements of CCITT, DOC/FCC and CSA/UL Description • Excellent power dissipation (SIL vertical mounting) • 12/16kHz meter pulse injection control • Solid State TIP/RING reversals • Ringing amplifier The Mitel MH88628 SLIC provides all of the functions required to interface 2-wire off premise subscriber loops to a serial TDM, PCM, switching network of a modern PBX. The MH88628 is manufactured using thick-film hybrid technology which offers high voltage capability, reliability and high density resulting in significant printed circuit board area savings. A complete C.O. line card can be implemented with very few external components. VBat RING RF1 RF2 TIP TF1 TF2 0°C to 70°C LCA LGND Matched Driver Feed Circuitry and Resistors VDD Loop Current Set VEE AGND Switch-hook Threshold Set Ring Filter Switch-hook Detect Speech Circuit SHK NS UD VRLY RNGD RD 2-4 Wire Conversion Unbalanced Detection External Signal Input Decoder Circuit Ringing Amplifier SEL1 SEL2 ACRI DCRI ESI ESE N1 N2 NATT Impedance Network Gain Adjust Z900 Z600 Z1 Z2 GRX1 GRX0 RX GTX1 GTX0 TX Figure 1 - Functional Block Diagram 2-199 MH88628 Preliminary Information TIP RING TF1 TF2 RF1 RF2 LGND LCA VBat DCRI RGND VRLY RD SEL1 SEL2 ESI ESE AGND NATT N1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 N2 Z900 Z1 Z2 TX RX GTX0 GTX1 GRX0 GRX1 ACRI Z600 NS SHK UD IC IC IC VEE VDD 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Figure 2 - Pin Connections Pin Description Description Pin # Name 1 TIP 2 RING 3 TF1 Tip Feed 1. Access point for balanced ringing. Normally connects to TF2. 4 TF2 Tip Feed 2. Access point for balanced ringing. Normally connects to TF1. 5 RF1 Ring Feed 1. Access point for balanced ringing. Normally connects to RF2. 6 RF2 Ring Feed 2. Access point for balanced ringing. Normally connects to RF1. 7 LGND 8 LCA Current Limit Set (Input). The current limit is set by connecting an external resistor to ground. For 30mA default current, this pin is tied to GND. 9 VBat Battery Voltage. Typically -48Vdc is applied to this pin. 10 DCRI DC Ringing Voltage Input. A continuous 120Vdc is applied to this input. 11 RGND Relay Driver Ground Connection. 12 VRLY Relay Supply Voltage Connection. 13 RD 14 SEL1 Select 1 (Input). Refer to Table 5 15 SEL2 Select 2 (Input). Refer to Table 5. 16 ESI External Signal Input. 12/16kHz meter pulse input. 17 ESE External Signal Enable. Applies the external signal to the line. 18 AGND Analog Ground. VDD and VEE return path. 19 NATT Network Balance AT+T Node. Connects to N1 for a network balance impedance of AT&T compromise (350Ω + 1kΩ // 210nF); the device’s input impedance must be set to 600Ω. This node is active only when NS is at logic high. This node should be left open circuit when not used. 2-200 Tip Lead. Connects to the “Tip” lead of subscriber line. Ring Lead. Connects to the “Ring” lead of the subscriber line. Battery Ground. VBat return path. Connected to system’s energy dumping ground. Ring Drive (Output). Connects to ring relay coil. MH88628 Preliminary Information Pin Description (Continued) Pin # Name Description 20 N1 Network Balance Node 1(Input). 0.1 times the impedance between pins N1 and N2 must match the device’s input impedance, while 0.1 times the impedance between pins N1 and AGND is the device’s network balance impedance. This node is active only when NS is at logic high. This node may be terminated when not used (i.e., NS at logic low). 21 N2 Network Balance Node 2 (Output). See N1 for description. 22 Z900 23 Z1 Line Impedance Node 1 (Input). 0.1 times the times the impedance between pins Z1 and Z2 is the device’s line impedance. This node must always be connected. 24 Z2 Line Impedance Node 2 (Output). 0.1 times the times the impedance between pins Z1 and Z2 is the device’s line impedance. This node should be left open circuit when not used. 25 TX Transmit (Output). 4-Wire (AGND) referenced audio output. 26 RX Receive (Input). 4-Wire (AGND) referenced audio input. 27 GTX0 Transmit Gain Node 0. Connects to GTX1 for 0dB transmit gain. 28 GTX1 Transmit Gain Node 1. A resistor to AGND provides transmit gain adjustment. 29 GRX0 Receive Gain Node 0. Connects to GRX1 for 0dB gain. 30 GRX1 Receive Gain Node 1. A resistor to AGND provides receive gain adjustment. 31 ACRI AC Ringing Voltage Input. A 1.5Vrms 20Hz signal is applied to this input. 32 Z600 Line Impedance 600Ω Node (Output). Connects to Z1 for a line impedance of 600Ω. This pin should be left open circuit when not used. 33 NS Network Balance Setting (Input). The logic level at NS selects the network balance impedance. A logic 0 enables an internal balance equivalent to the input impedance (Zin). While a logic 1 enables an external balance 0.1 times the impedance between pins N1 and AGND balanced to 0.1 times the impedance between pins N1 and N2. The impedance between N1 and N2 must be equivalent to 10 times the input impedance (Zin). 34 SHK Off-Hook Indication (Output). A logic low output indicates when the subscriber equipment has gone Off-Hook. 35 UD Unbalance Detect (Output). A log IC low output indicates when the DC current flow in the Tip and Ring leads is unbalanced, indicating that the subscriber equipment has grounded the Ring lead. 36,37,38 IC Internal Connection. These pins are internally connected and must be left open 39 VEE Negative Supply Voltage. -5V dc. 40 VDD Positive Supply Voltage. +5V dc. Line Impedance 900Ω Node. Connects to Z1 for a line impedance of 900Ω. This node should be left open circuit when not used. 2-201 MH88628 Preliminary Information Absolute Maximum Ratings* Parameter 1 Supply Voltage 2 Storage Temperature Sym Min Max Units Comments VBat VDD VEE VDCRI +0.3 -0.3 +0.3 -0.3 65 6 -6 140 V V V V With respect LGND TS -40 +125 °C * Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied. Recommended Operating Conditions Parameter Sym Min Typ* Max Units 1 Supply Voltage VBat VDD VEE -44 4.75 -4.75 -48 +5.0 -5.0 -60 5.25 -5.25 V V V 2 Operating Temperature TOP 0 20 70 °C 3 AC Ring Generator 33 Vrms Hz 130 Vdc Typ* Max Voltage Frequency 4 90 17 Comments DCRI Input DC Voltage VDCRI 110 120 * Typical figures are at 25° C with nominal + 5V supplies for design aid only. DC Electrical Characteristics‡ Characteristics Sym Operating Loop Current Var in loop current from nominal ILoop ILoop ILoop ILoop Operating Currents Min Test Conditions 30 ±2 mA mA mA mA RLoop=0Ω 2300Ω VBat =-48V RLoop=0Ω, LCA GND IBat 32 mA IBat 2 mA IDD IEE 25 25 mA mA RLoop =0 (off Hook), LCA=GND RLoop = open (OnHook) On-hook or Off-Hook On-Hook or Off-Hook Power Dissipation PDO PD1 2 300 W mW Active Standby/Idle SHK UD Low level Output Voltage High Level Output Voltage VOL VOH 0.5 3.7 V V IOL = 400µA IOH= 40µA SEL1 SEL2 ESE NS Low Level Input Voltage High Level Input Voltage VIL VIH 0.8 2.4 V V High Level Input Current Low Level Input Current IIH IIL 20 20 µA µA 1 2 3 45 Units 16 4 5 6 ‡ 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. 2-202 VIH=5.0V VIL=0.0V MH88628 Preliminary Information AC Electrical Characteristics‡ Characteristics Sym Min Typ* Max Units Test Conditions 1 TX Gain 0 dB externally adjustable 2 RX Gain 0 dB externally adjustable 3 Ringing Capability 5 REN 4 On-Hook Transmission Signal Input Level Gain 6 5 External Signal Output Level 6 SHK Rise Time Fall time 7 2-Wire Termination Impedance Off-Hook Detect Threshold 9 2-Wire Return Loss 10 Longitudinal Balance Longitundinal to Metallic 11 Longitudinal Current Capability 12 Idle channel Noise Rx to T-R T-R to Tx 13 Transhybrid Loss 14 Unbalanced Detect Threshold 15 Analog Signal Overload Level At Tip and Ring Vrms dB VBat=-48V T-R load = 10kΩ min. 2.25 Vrms VBat= -48V, T-R load= 200Ω LCA=0V, Zo-600Ω, Gain=0dB 1 1 ms ms Dial Pulse Detection 600/ 900 Ω 10 mA 1.75 tR tF 8 2.0 Selectable 20 20 20 dB dB dB 300 to 500Hz 500 to 2500Hz 2500 to 3400Hz 58 53 dB dB 200-1000Hz 1kHz - 3k4Hz mA 20mA per lead 40 NCR NCX THL 22 IUB 8 12 dBrnC dBrnC 40 dB 10 mA 4 T-R=600Ω, VBat=-48V 16 Ringing Signal Voltage 17 Ringing Frequency 18 Ring Trip Delay 100 ms 19 Absolute Gain, Variation +0.1 dB 0dB at T-R, 1kHz 20 Relative Gain, reference to 1kHz +0.05 dB 300-3400Hz dB 1kHz, 100mVpp 21 90 dBm 200-3400Hz 17 Vrms 33 Power Supply Rejection Ratio PSRR VBat 24 VDD 24 VEE 24 * Typical figure are at 25°C with nominal +5V supplies and are for design aid only. Hz ‡ AC Electrical Characteristics are over recommended operating conditions unless otherwise stated. Notes: Impedance set by external network of 600Ω or 900Ω default. External network for test purposes consists of 2200Ω + 8200Ω // 11.5nF between pins Z1 and Z2, the equivalent Zin has 1/10th the impedance and is equivalent o 220Ω+820Ω // 115nF. Test condition uses a Zin value of 600Ω, 900Ω and the above external network. Test conditions use a transmit and receive gain set to 0dB default and a Zin value of 600Ω unless otherwise stated. “Ref” indicates reference impedance which is equivalent to the termination impedance. “Net” indicates network balance impedance. Refer to Table 1, 2 for TX, RX gain adjustment. 2-203 MH88628 Preliminary Information Functional Description Loop Current Setting The SLIC uses a transformerless electronic 2-wire to 4-wire conversion which can be connected to a Codec to interface the 2 wire subscriber loops to a time division multiplexed (TDM) pulse code modulated (PCM) digital switching network. For analog applications, the Tx and Rx of the 2-4 wire converter can be connected directly to an analog crosspoint switch such as the MT8816. Powering of the line is provided through precision battery feed resistors. The MH88628 also contains control, signalling and status circuitry which combines to provide a complete functional solution which simplifies the manufacture of line cards. This circuitry is illustrated in the functional block diagram in Fig. 1. The MH88628 is designed to be pin compatible with Mitel’s MH88632 and MH88625. This allows a common PCB design with common gain, input impedance and network balance. The MH88628 SLIC is a constant current with constant voltage fallback design. This design feature provides for long loop capability regardless of the constant current setting. Refer to Graph 1. Approvals FCC part 68, CCITT, DOC CS-03, UL 1459, CAN/ CSA 22.2 No.225-M90 and ANSI/EIA/TIA-464-A are system level safety standards and performance requirements. As a component of a system, the MH88628 is designed to comply with the applicable requirements of these specifications. The LCA (Loop Current Adjust) pin is an input to an internal resistor divider network which generates a bias voltage. The loop current is proportional to this voltage. The loop current can be set between 20 and 45mA by various connections to the LCA pin as illustrated in Table 5 and Figure 8. The loop current during a fault condition will be limited to a safe level. Primary over-current protection is inherent in the current limiting feature of the 200Ω battery feed resistors. Refer to Graph 1. Receive and Transmit Audio Path The audio signal of the 2-wire side is sensed differentially across the external 200Ω feed resistors and is passed on to a second differential amplifier stage in the 2W/4W conversion block. This block sets the transmit gain on the 4-wire side and cancels signals originating from the receive input before outputting the signal. Programmable Transmit and Receive Gain Battery Feed The loop current for the subscriber equipment is sourced through a pair of matched 200Ω resistors connected to the Tip and Ring. The two wire loop is biased such that the Ring lead is 2V above VBat (typically -46V) and the Tip lead is 2V below LPGD (typically -2V) during constant voltage, constant current mode. The SLIC is designed for a nominal battery voltage of -48Vdc and can provide the maximum loop current of 45mA under the condition. The MH88628 is designed to operate down to a minimum of 16mA dc, with a battery voltage of -44V. The Tip and Ring output drivers can operate within 2V of VBat and LGND rails. This permits a maximum loop range of 2300Ω. 2-204 Transmit Gain (Tip-Ring to Tx) and Receive Gain (Rx to Tip-Ring) are programmed by connecting external resistors (RRX and RRT) from GRXI to AGND and from GTX1 to AGND as indicated in Figure 3 and Tables 1 and 2. The programmable gain range is from -12dB to +6dB; this wide range will accommodate any loss plan. Alternatively, the default Receive Gain of 0dB and Transmit Gain of 0dB can be obtained by connecting GRX0 to GRX1 and GTX0 to GTX1. In addition, a Receive gain of +6dB and Transmit Gain of +6dB can be obtained by not connecting resistors RRX and RTX. For correct gain programming, the MH88628’s Tip-Ring impedance (Zin) must match the line termination impedance. For optimum performance, resistor RRX should be physically located as close as possible to the GRX1 input pin, and resistor RTX should be physically located as close as possible to the GTX1 input pin. MH88628 Preliminary Information 70 60 Constant Voltage Region 50 40 ILoop (mA) Constant Current Region 30 20 10 0 1kΩ 2kΩ RLoop (Ω) Graph 1 - ILoop/RLoop Characteristics Two wire Port Termination Impedance The AC termination impedance of 600 or 900Ω, of the 2W port, is set using active feedback paths to give the desired relationship between the line voltage and the line current. The loop current is sensed differentially across the two feed resistors and converted to a single ended signal. This signal is fed back to the Tip/Ring driver circuitry such that impedance in the feedback path gets reflected to the two wire port. The MH88628’s Tip-Ring impedance (Zin) can be set to 600Ω, 900Ω or to a user selectable value. Thus, Zin can be set to any international requirement. The connection to Z1 determines the input impedance. With Z1 connected to Z600, the line impedance is set to 600Ω. With Z1 connected to Z900, the line impedance is set to 900Ω. A user defined impedance can be selected which is 0.1 times the impedance between Z1 and Z2. For example, with 2200Ω in series with 11.5nF in parallel with 8200Ω, all between Z1 and Z2, the devices line impedance will be 220Ω in series with 115nF in parallel with 820Ω. See Table 3 and Figures 4 & 5. Network Balance Transhybrid loss is maximized when the line termination impedance and SLIC network balance are matched. The MH88628’s network balance impedance set can be set to Zin, AT&T (350Ω + 1kΩ //210nF) or to a user selectable value. Thus, the network balance impedance can be set to any international requirement, A logic level control input NS selects the balance mode. With NS at logic low, an internal network balance impedance is matched to the line impedance (Zin). With NS at logic high, a user defined network balance impedance is selected which is 0.1 times the impedance between N1 and AGND. For example, with 2200Ω in series with 11.5nF in parallel with 8200Ω, all between N1 and AGND, and NS at logic high, the devices network balance impedance is 220Ω in series with 115nF in parallel with 820Ω; the impedance between N1 and N2 must be equivalent to 10 times the input impedance (Zin). In addition, with NS at logic high, an AT&T network balance impedance can be selected by connecting NATT to N1; in this case, no additional network is required between N1 and N2. See Table 4 and Figure 6. 12/16kHz Meter Pulse The MH88628 provides control of an external signal path to the driver. A 12/16kHz continuous signal can be applied to the ESI pin. Control of the ESE input allows the metering signal to be transmitted to the line. Unbalanced Detection The Unbalanced Detect (UD) pin goes low when the DC current through the two battery feed resistors is unbalanced i.e., when the average DC current into the Ring lead exceeds the current flow out of the Tip lead (indicating that the Ring lead has been grounded). When the SLIC is interfaced to ground start subscriber equipment during the idle state, the UD output is monitored for indication of the subscribers Ring Ground signal. The maximum loop current supplied by the feed circuitry under this condition is limited. 2-205 MH88628 Preliminary Information Longitudinal Balance Ring Trip Detection The longitudinal balance specifies the degree of common mode rejection in the 2 to 4 wire direction. Precision laser trimming of internal resistors in the hybrid ensures good overall longitudinal balance. The interface circuitry can operate in the presence of induced longitudinal currents of up to 40mA at 60Hz. The interface permits detection of an Off-Hook condition during the ringing. If the subscriber set goes Off-Hook when the ringing signal has been applied, the DC loop current flow will be detected within approx. 100msecs and the SHK output will go low. The ring relay is automatically disabled by the internal hardware. Off-Hook and Dial Pulse Detection Control Decode The SHK pin goes low when the DC-loop current exceeds a specified level. The threshold level is internally set by the bias voltage of the switch-hook detect circuitry. Dial pulse can be detected by monitoring the interruption rate at the SHK pin. These dial pulses would be debounced by the system’s software. The different modes of operation are selected by decoding the SEL1 and SEL2 inputs (see Table 5). DTMF The DTMF tones are transmitted and received at the 4-wire port. MH88628 Z Transmit Gain: - Z (Tip-Ring to Tx) TX 25 + 10kΩ AV= -20log 10kΩ GTX1 28 GTX0 27 RTX RTX = 5kΩ ] [ 0.5 + RTX 5kΩ 10(-AV/20)-0.5 Example RTX=38kΩ; AV= +4dBV Z + RX 10kΩ 10kΩ 26 GRX1 30 GRX0 29 RRX Receive Gain: (RX to Tip-Ring) AV= -20log RRX = 5kΩ ] [ 0.5 + RRX 5kΩ 10 (-AV/20) -0.5 Example: RRX=4.6kΩ; AV= -4dBV Figure 3 - Gain Programming with External Components 2-206 MH88628 Preliminary Information 24 Z2 MH88628 Z2 NC MH88628 23 Z1 Z1 24 NC 23 22 22 Z900 Z900 NC 32 NC Z600 32 Z600 Input impedance (Zin) set to 600Ω Input Impedance (Zin) set to 900Ω Note: Make connection between Z1 and other points as short as possible Figure 4 - Input Impedance (Zin) Settings with Zin equal to 600 or 900Ω Z2 10 x Z in 24 RP 10 x Zin MH88628 Z1 Z2 CP 23 22 Z1 RS Z900 Z600 32 Zin = 0.1 x [ RS + 1 1/RP + (S x CP) ] where S = j x w and w = 2 x Π x f Example: Notes: 1) The 10xZin network must be set to 10 x the desired input impedance (Zin). 2) The network balance must be set to the desired network balance. See section on network balance. 3) Make connection between Z1 and component as short as possible. If RS = 2200Ω, RP = 8200Ω, CP= 11.5nf Then the input impedance (Zin) is 220Ω in series with 820Ω in parallel with 115nF. Figure 5 - Input Impedance (Zin) Settings with Zin not equal to 600 to 900Ω 2-207 MH88628 Preliminary Information N2 MH88628 N1 NATT NS 21 21 N2 MH88628 20 20 N1 19 NATT 33 NS 19 33 VDD Network balance is set to the input Impedance (Zin) Network balance is set to the AT&T compromise network (350Ω + 1000Ω // 210nF) impedance. The input impedance must be set to 600W. Note: Make connection between Z1 and other points as short as possible Figure 6 - Network Balance Setting with NETBAL equal to Z in or AT&T 10 x Zin N2 MH88628 N1 21 RP 10 x Zin N2 10 x NETBAL N1 20 19 CP RS NATT 1 ZNETBAL = 0.1 x 33 NS [ RS + 1/RP + (S x CP) ] VDD where S = j x w and w = 2 x Π x f Example: Notes: 1) The 10xZin network must be set to 10 x the desired input impedance (Zin). 2) The network balance must be set to the desired network balance. See section on network balance. 3) Make connection between Z1 and component as short as possible. If RS = 2200Ω, RP = 8200Ω, CP= 11.5nf Then the network balance impedance (ZNETBAL) is 220Ω in series with 820Ω in parallel with 115nF. Figure 7 - Network Balance Setting with NETBAL not equal to Zin or AT&T 2-208 MH88628 Preliminary Information Tables 1 & 2: Transmit and Receive Gain Programming Transmit Gain (dB) RTX Resistor Value (Ω) +6.0 No Resistor +4.0 38.3k Results in 0dB overall gain when used with Mitel A-law codec (i.e. MT8965) +3.7 32.4k Results in 0dB overall gain when used with Mitel µ-law codec (i.e. MT8964) 0.0 GTX0 to GTX1 -3.0 5.49k Notes -6.0 3.32k -12.0 1.43k Receive Gain (dB) RRX Resistor Value (Ω) +6.0 No Resistor 0.0 GRX0 to GRX1 -3.0 5.49k -3.7 4.87k Results in 0dB overall gain when used with Mitel A-law codec (i.e. MT8965) -4.0 4.64k Results in 0dB overall gain when used with Mitel µ-law codec (i.e. MT8964) -6.0 3.32k -12.0 1.43k Notes Note 1: See Figures 3 and 4 for additional details. Note 2: Overall gain refers to the receive path of PCM to 2-wire, and transmit path of 2-wire to PCM. Table 3: Input Impedance Settings Z900 Resulting input impedance (Zin) NA 600Ω NA Connect Z1 to Z900‘ 900Ω NA NA 0.1 x impedance between Z1 & Z2 Z2 Z1 NA Connect Z1 to Z600 NA Connect Z1 to Z9000 Connect network from Z1 to Z2 Z600 Note 1: NA indicates high impedance (10kΩ) connection to this pin does not effect the resulting network balance. Note 2: See Figure 4 & 5 for Application Circuits. Table 4: Network Balance Settings NS (Input) N2 N1 NATT Resulting input impedance (Zin) Low NA NA NA Equivalent to Zin High NA High Connect N1 to NATT Connect network from N1 to AGND equivalent to 10 x NETBAL. Connect network from N1 to N2 equivalent to 10 x Zin. AT&T compromise (350Ω + 1kΩ // 210nF) Zin must be 600Ω NA 0.1 x impedance between N1 & N2 Note 1: NA indicates high impedance (10kΩ) connection to this pin does not effect the resulting network balance. Note 2: Low indicates Logic Low. Note 3: See Figures 6 and 7 for Application Circuit. 2-209 MH88628 Preliminary Information +5V R LCA LCA LCA R -5V 8a 8c 8b Loop Current Setting Figure 8 - Loop Current Setting High Voltage capability Loop Length Inherent in the thick-film process is the ability of the substrate to handle high voltage. The standard Mitel thick-film process provides dielectric strengths of greater than 1000VAC or 1500VDC. The thick-film process allows easy integration of surface mount components such as the high voltage bi-polar power transistor line drivers. This allows for simplier, less elaborate and less expensive protection circuitry required to handle high voltage transients and fault conditions caused by lightning, induced voltages and power line crossings. The MH88628 can accommodate loop length of up to 2300Ω minimum (including the subscriber equipment). This corresponds to approximately 8km using 26AWG twisted pair or 15km using 24AWG twisted pair. On-hook Transmission The MH88628 provides for on-hook transmission which supports features such as Automatic Numbers Identification (ANI). The (ANI) information is a FSK signal originating from and sent by the C.O. during the off period of the ringing voltage being sent to the subscribers set. The signal is present during the off period between the first and second ring. The subscribers set decodes the FSK signal and displays the calling party’s number. TIP Disable A relay driver, controlled by SEL1 and SEL2, is provided to drive a relay which can be used to disable the TIP line when the MH88628 is used for a ground start central office interface. 2-210 Central Office Operation The MH88628 can be configured for ground start C.O. applications with the addition of Q1, D1 and K2, as shown in Figure 9. Ground start requires control of the Tip lead to remove battery ground from subscriber loop. For loop start applications, control of the Tip lead is not required. C.O’s perform Tip/Ring reversals to indicate that a tool call has been dialled. The Tip/ring reversal can indicate a toll diversion signal. Internal Ringing Amplifier Operation The MH88628 offers an on-board ringing amplifier. A 1.5 VRMS, 20Hz signal is amplified internally and applied to TIP and RING leads in a balanced configuration. A +120Vdc supply are applied continuously to the MH88628. The decode signals on SEL1 and SEL2 enable the ringing signal to the TIP and RING when required. MH88628 Preliminary Information -VBat SYSTEM +5V GROUND VBat VDD VEE MH88628 -5V RX VR GRX0 VX CODEC GRX1 LCA AGND TX GTX0 TF1 GTX1 TF2 SHK P R O T E C T I LINE CONTROLLER TIP UD LOGIC Z1 Z600 SEL1 SEL2 RING O N ESE 12/16kHz RF1 ESI Metering Source K1B ACRI +5V K1 RF2 1.5VRMS 20Hz Source DCRI VRLY + RD 120VDC Supply RGND NS Figure 9 - OPS SLIC Configuration Applications Circuit - Normal Ringing Graph 2 - Loop Current Setting 65mA (Ω/10) ILoop/mA 50 To -5V O/C LCA 40 35.3mA 30 LCA = 0V 28.48m 20 To +5V 10K 100K (Ω/10 + 10mA) 1M R(LCA) Ω 2-211 MH88628 Preliminary Information Table 5: Control Decode Table Mode Condition SEL1 SEL:2 1 Normal Operation 0 0 2 Apply internal balanced ringing 1 0 3 Reverse TIP and RING 0 1 4 Enable Relay Driver 1 1 Table 6: Loop Current Setting Loop Current Ref. Fig # 20 8a Connect 10kΩ from LCA to +5V 25 8a Connect 22kΩ from LCA to +5V 30 8a Connect 36kΩ from LCA to +5V 35 8c LCA open circuit 40 8b Connect 24kΩ to -5V 45 8b Connect 10kΩ from LCA to -5V LCA Pin Connection PRIMARY MDF PROTECTION T SECONDARY PROTECTION HEAT COIL T F1 R1 MH88628 PRO1 GAS TUBE F2 R2 R R HEAT COIL SUGGESTED COMPONENTS: F1, F2 1A, 250VAC, SLO-BLOW LITTLEFUSE 230 2AG R1, R2, 10Ω, 1000V, 1/2W RESISTOR (FLAME RATED) PRO1 SOLID STATE TRANSIENT SUPPRESSOR, EG TISP2300L, P2703AB F1, R1 AND F2, R2 MAY BE FUSIBLE RESISTORS OR PTCs Figure 10 - Typical Protection Circuit 2-212 MH88628 Preliminary Information 0.080 Max (2.0 Max) Side View 4.20 + 0.020 (50.8 + 0.5) 0.80+0.03 (20.3+0.76) 1 2 3 4 39 40 0.010 + 0.002 (0.25 + 0.05) 0.12 Max (3.1 Max) 1 2 3 0.05 + 0.01 (1.3 + 0.5) Notes: 1) Not to scale 2) Dimensions in inches). 3) (Dimensions in millimetres). *Dimensions to centre of pin & tolerance non accumulative. * 0.25 + 0.02 (6.35 + 0.05) * 0.020 + 0.05 (0.51 + 0.13) * 0.175 + 0.02 (4.445 + 0.5) 0.100 + 0.10 (2.54 + 0.13) Figure 11 - Mechanical Data 2-213 MH88628 Notes: 2-214 Preliminary Information