MH88625 DID/OPS SLIC Preliminary Information Features • ISSUE 6 Ordering Information Programmable gain, network balance and impedance MH88625 • Transformerless 2-4 wire conversion • Constant current with constant voltage fallback for long loop capability • Pin compatible with MH88632 and MH88628 • Unbalance detection (Tip, Ring ground sensing) • Auto ring trip • On-Hook transmission (ANI) capability • Compatible with requirements of CCITT, DOC/FCC and CSA/UL • Excellent power dissipation (SIL vertical mounting) • 12/16kHz meter pulse injection control • Solid State TIP/RING reversals April 1995 40 Pin SIL Package 0°C to 70°C Description The Mitel MH88625 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 MH88625 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 line card can be implemented with very few external components. Applications • On/Off Premise PBX Line Cards • DID (Direct Inward Dial) Line Cards • Central Office Line Cards VBat RING RF1 RF2 TIP TF1 TF2 UD RNGC RGND VRLY LCA LGND Matched Feed Resistors VDD AGND Switch-hook Threshold Set Loop Current Set Driver Circuitry And Speech Circuit VEE Ring Filter Switch-hook Detect SHK 2-4 Wire Conversion Unbalance Detection Ring Relay Driver Tip/Ring Reversal RRD REVC External Signal Input ESI ESE NS N1 N2 NATT Impedance Network Gain Adjust Z900 Z600 Z1 Z2 GRX1 GRX0 RX GTX1 GTX0 TX FIgure 1 - Functional Block Diagram 2-183 MH88625 Preliminary Information TIP RING TF1 TF2 RF1 RF2 LGND LCA VBat IC RGND VRLY RRD RNGC REVC 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 IC 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 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 IC 11 RGND Relay Driver Ground Connection. 12 VRLY Relay Supply Voltage Connection. 13 RRD Ring Relay Drive (Output). Connects to ring relay coil. 14 RNGC Ring Relay control (Input). A logic low enables the Ring Relay Drive (RRD) output which activates the Ring Relay. The internal auto ring trip circuitry de-activates the relay drive output upon detection of switch-hook. 15 REVC Reversal Control (Input). A logic high reverse the internal Tip and Ring connections. 16 ESI External Signal Input. 12/16kHz meter pulse input. 17 ESE External Signal Enable. 12/16kHz meter pulse enable. 18 AGND 2-184 Description 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. Internal Connection. This pin is internally connected and must be left open. Analog Ground. VDD and VEE return path. MH88625 Preliminary Information Pin Description (Continued) Pin # Name Description 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. 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. Connects to a resistor to AGND for transmit gain adjustment. 29 GRX0 Receive Gain Node 0. Connects to GRX1 for 0dB gain. 30 GRX1 Receive Gain Node 1. Connects to a resistor to AGND to receive gain adjustment. 31 IC 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. Internal Connection. This pin is internally connected and must be left open. 2-185 MH88625 Preliminary Information Absolute Maximum Ratings* Parameter 1 Supply Voltage 2 Storage Temperature Sym Min Max Units Comments VBat VDD -VEE +0.3 -0.3 +0.3 65 6 6 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 20 0 70 °C Comments * Typical figures are at 25° C with nominal + 5V supplies for design aid only. DC Electrical Characteristics‡ 1 6 Min Operating Loop Current ILoop ILoop 16 Var in loop current from nominal ILoop ILoop Operating Currents Typ* Max Units 45 mA mA RLoop=0Ω 2300Ω VBat =-48V RLoop=0Ω, LCA GND IBat 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 PD0 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 ESE NS Low Level Input Voltage High Level Input Voltage VIL VIH 0.8 2.4 V V ESE NS High Level Input Current Low Level Input Current IIH IIL 20 20 µA µA ‡ 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. 2-186 Test Conditions mA mA 3 5 Sym 30 +4 32 2 4 Characteristics VIH=5.0V VIL=0.0V MH88625 Preliminary Information AC Electrical Characteristics‡ Characteristics Sym Min Typ* 1 TX Gain 2 RX Gain 3 Ringing Capability 4 On-Hook Transmission Signal Input Level Gain 6 0 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 Metallic to Longitudinal 11 Longitudinal Current Capability 12 Idle channel Noise Rx to T-R T-R to Tx Transhybrid Loss 14 Unbalanced Detect Threshold 15 Analog Signal Overload Level at Tip and Ring 16 Ringing Signal Voltage 17 Ringing Frequency Test Conditions externally adjustable 0 dB externally adjustable 5 REN 2.0 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 Selectable 20 20 20 dB dB dB 300 to 500Hz 500 to 2500Hz 2500 to 3400Hz 58 53 dB dB 200-1000Hz 3400Hz mA 20mA per lead 40 8 12 NCR NCX THL Units dB 1.75 tR tF 8 13 Max 22 IUB dBrnC dBrnC 40 dB 10 mA 4 90 17 dBm 200-3400Hz T-R=600Ω, VBat=-48V Vrms 33 Hz 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 21 Power supply Rejection Ratio VBat VDD VEE dB 1kHz, 100mVpp PSRR 24 24 24 ‡ AC Electrical Characteristics are over recommended operating conditions unless otherwise stated. * Typical figure are at 25°C with nominal +5V supplies and are for design aid only. 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. 2-187 MH88625 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 MH88625 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 MH88625 is designed to be pin compatible with Mitel’s MH88632 and MH88628. This allows a common PCB design with common gain, input impedance and network balance. The MH88625 SLIC provides a constant current with constant voltage fallback. 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-464A are system level safety standards and performance requirements. As a component of a system, the MH88625 is designed to comply with the applicable requirements of these specifications. 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 MH88625 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. 2-188 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 graph 2 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 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 MH88625’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. MH88625 Preliminary Information 70 60 Constant Voltage Region 50 ILoop (mA) 40 Constant Current Region 30 20 10 0 1kΩ 2kΩ RLoop (Ω) Graph 1 - I Loop/R Loop 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 MH88625’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 MH88625’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 MH88625 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. 2-189 MH88625 Preliminary Information Longitudinal Balance 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. Off-Hook and Dial Pulse Detection 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. Ring Trip Detection 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 approximately 100msecs and the SHK output will go low. The ring relay is automatically disabled by the internal hardware. MH88625 TRANSMIT GAIN: (Tip-Ring to Tx) Z 5kΩ AV = – 20 log 0.5 + ----------- RTX - Z TX 25 5kΩ RTX = -------------------------------- – AV + 10kΩ 10kΩ GTX1 28 GTX0 27 RTX 10 ---------20 – 0.5 Example: RTX = 38kΩ; AV = +4dB Z RECEIVE GAIN: (RX to Tip-Ring) + Z 10kΩ RX GRX1 30 GRX0 10kΩ 5kΩ AV = – 20log 0.5 + ----------- RRX 26 29 RRX 5kΩ RTX = -------------------------------- – AV 10 ---------20 – 0.5 Example: RRX = 4.6kΩ; AV = -4dB Figure 3 - Gain Programming with External Components 2-190 MH88625 Preliminary Information MH88625 MH88625 Z2 Z1 24 Z2 NC 23 Z1 24 NC 23 22 Z900 22 Z900 NC Z600 32 32 NC 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 MH88625 Z2 24 RP 10 x Zin 23 Z2 CP Z1 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 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. Example: 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 2-191 MH88625 Preliminary Information MH88625 N2 N1 MH88625 21 21 N2 20 N1 19 NATT 33 NS 20 19 NATT 33 NS 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 MH88625 N2 21 RP 10 x Zin N2 N1 CP 20 10 x NETBAL 19 N1 RS NATT (RS + 1) NS 33 VDD ZNetbal = 0.1 x 1/RP + S x CP where S = j x w and w = 2 x Π x f Notes: Example: 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 7 - Network Balance Setting with NETBAL not equal to ZNetbal or AT&T 2-192 MH88625 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 Z2 Z1 NA Connect Z1 to Z600 NA Z600 Z900 Resulting input impedance (Zin) NA 600Ω Connect Z1 to Z900 NA Connect Z1 to Z900 900Ω Connect network from Z1 to Z2 NA NA 0.1 x impedance between Z1 & Z2 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 Applications Circuits. Table 4: Network Balance Settings. NS (Input) N2 N1 NATT Low NA NA NA High NA Connect N1 to NATT High Connect network from N1 to AGND equivalent to 10 x NETBAL. Connect network from N1 to N2 equivalent to 10 x Zin. Resulting input impedance (Zin) Equivalent to 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. 2-193 MH88625 Preliminary Information +5V MH88625 MH88625 MH88625 MH88625 R LCA LCA LCA LCA R -5V 8a 8b 8c 8d Figure 8 - Loop Current Setting (See Graph 2) DTMF DTMF tones may be transmitted and received at the 4-wire port. DID Operation For DID operation, the Tip and Ring reversal is controlled by the REVC pin. A logic level one causes Tip and Ring to be reversed. This can be controlled by a Mitel Codec (MT896X) system drive output (refer to Figure 9b). High Voltage capability 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. On-Hook Transmission The MH88625 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 2-194 subscribers set decodes the FSK signal and displays the calling party’s number. Loop Length The MH88625 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. OPS Operation As shown in the application diagram, Figure 9a, the ringing voltage, typically 90Vrms 20Hz biased at V Bat, is applied to the subscriber line through an external relay K1. Enabling of the relay is performed by applying a logic low level to the relay driver control input, RGNDC. Figure 9c, shows how balanced ringing can be accommodated if required. Central Office Operation The MH88625 can be configured for ground start C.O. applications with the addition of Q1, D1 and K2, as shown in Figure 9c. 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 toll call has been dialled. The Tip/Ring reversal can indicate a toll diversion signal. MH88625 Preliminary Information -VBat +5V SYSTEM GROUND LGND VDD RX VR GRX0 VX VBat VEE CODEC GRX1 -5V LCA AGND TX GTXO TF1 MH88625 GTX1 TF2 SHK LINE CONTROLLER LOGIC UD Z1 Z600 TIP RNGC REVC +5V VRLY RING K1 RRD K1 RF1 RF2 ~ 90VRMS 20Hz NS RGND -VBat Figure 9a - 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 2-195 MH88625 Preliminary Information -VBat SYSTEM +5V LGND GROUND VDD VBat VEE RX VR GRX0 VX LOGIC LOGIC LOGIC GRX1 -5V LCA AGND TX GTX0 TF1 MH88625 GTX1 TF2 SHK LINE CONTROLLER LOGIC UD Z1 +5V Z600 TIP RNGC REVC VRLY RING RRD RGND RF1 RF2 NS Figure 9b - DID SLIC Configuration Applications Circuit 2-196 MH88625 Preliminary Information -VBat SYSTEM +5V GROUND VDD LGND VBat VEE MH88625 -5V RX VR GRX0 VX CODEC GRX1 LCA AGND TX GTX0 TF2 GTX1 K1A TF1 SHK LINE CONTROLLER LOGIC UD K2 Z1 +5V Z600 TIP D1 K2 RNGC REVC +5V VRLY Q1 RING K1 RRD RGND K1B RF1 ESE ES1 45VRMS 20Hz ~ ~ 12/16kHz METERING SOURCE RF2 45VRMS 20Hz NS -V Bat Figure 9c - LS/GS C.O. SLIC Applications Circuit - Balanced Ringing 2-197 MH88625 Preliminary Information T T F1 MH88625 R1 PRO1 LINE F2 R R2 R 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 9d - Suggested Protection Circuit 0.080 Max (2.0 Max) Side View 4.20 + 0.020 (50.8 + 0.5) 0.58+0.02 (14.7+0.5) 2 1 40 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 10 - Mechanical Data 2-198 * 0.18 + 0.02 (4.6 + 0.5) 0.100 + 0.10 (2.54 + 0.13)