HC-5504B Data Sheet July 1998 File Number EIA/ITU PABX SLIC with 40mA Loop Feed Features The Intersil SLIC incorporates many of the BORSHT functions on a single IC chip. This includes DC battery feed, a ring relay driver, supervisory and hybrid functions. This device is designed to maintain transmission performance in the presence of externally induced longitudinal currents. Using the unique Intersil dielectric isolation process, the SLIC can operate directly with a wide range of station battery voltages. • Pin for Pin Replacement for the HC-5504 The SLIC also provides selective denial of power. If the PBX system becomes overloaded during an emergency, the SLIC will provide system protection by denying power to selected subscriber loops. The Intersil SLIC is ideally suited for the design of new digital PBX systems by eliminating bulky hybrid transformers. Ordering Information PART NUMBER TEMP. RANGE (oC) 2886.5 • Capable of 5V or 12V (VB+) Operation • Monolithic Integrated Device • DI High Voltage Process • Compatible With Worldwide PBX Performance Requirements • Controlled Supply of Battery Feed Current for Short Loops (41mA) • Internal Ring Relay Driver • Allows Interfacing With Negative Superimposed Ringing Systems • Low Power Consumption During Standby • Switch Hook Ground Key and Ring Trip Detection Functions • Selective Denial of Power to Subscriber Loops PACKAGE PKG. NO. HC1-5504B-5 0 to 75 24 Ld CERDIP F24.6 HC1-5504B-9 -40 to 85 24 Ld CERDIP F24.6 HC3-5504B-5 0 to 75 24 Ld PDIP E24.6 HC3-5504B-9 -40 to 85 24 Ld PDIP E24.6 HC4P5504B-5 0 to 75 28 Ld PLCC N28.45 HC4P5504B-9 -40 to 85 28 Ld PLCC N28.45 HC9P5504B-5 0 to 75 24 Ld SOIC M24.3 HC9P5504B-9 -40 to 85 24 Ld SOIC M24.3 Applications • Solid State Line Interface Circuit for Analog and Digital PBX Systems • Direct Inward Dial (DID) Trunks • Voice Messaging PBXs • Related Literature - AN549, The HC-5502S/4X Telephone Subscriber Line Interface Circuits (SLIC) - AN571, Using Ring Sync with HC-5502A and HC-5504 SLICs Pinouts RFS 3 22 C4 VB+ 4 21 RX C3 5 DG C4 23 AG AG 2 TX RING N/C 24 TX TIP 1 RING TIP HC-5504B (PLCC) TOP VIEW RFS HC-5504B (PDIP, CERDIP, SOIC) TOP VIEW 4 3 2 1 28 27 26 VB + 5 25 RX 20 +IN C3 6 24 +IN 6 19 -IN DG 7 23 -IN RS 7 18 OUT N/C 8 22 N/C RD 8 17 C2 RS 9 21 OUT TF 9 16 RC RD 10 20 C2 RF 10 15 PD TF 19 RC 51 12 13 14 15 16 17 18 N/C SHD GKD PD 13 SHD BG BG 12 11 VB- 14 GKD RF 11 VB - CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. http://www.intersil.com or 407-727-9207 | Copyright © Intersil Corporation 1999 HC-5504B Absolute Maximum Ratings (Note 1) Thermal Information Maximum Continuous Supply Voltages (VB-) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -60V to 0.5V (VB+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5V to 15V (VB+ - VB-) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75V Relay Drive Voltage (VRD) . . . . . . . . . . . . . . . . . . . . . . . -0.5V to 15V Thermal Resistance (Typical, Note 2) θJA (oC/W) CERDIP Package. . . . . . . . . . . . . . . . . . . . . . . . . . . 52 PDIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 PLCC Package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Maximum Junction Temperature (Hermetic Packages) . . . . . .175oC Maximum Junction Temperature (Plastic Packages) . . . . . . . .150oC Maximum Storage Temperature Range . . . . . . . . . . -65oC to 150oC Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . .300oC (PLCC and SOIC - Lead Tips Only) Operating Conditions Operating Temperature Range HC-5504B-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0oC to 75oC HC-5504B-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40oC to 85oC Relay Driver Voltage (VRD) . . . . . . . . . . . . . . . . . . . . . . . . . 5 to 12V Positive Supply Voltage (VB+) . . . . . . . 4.75 to 5.25 or 10.8 to 13.2V Negative Supply Voltage (VB-). . . . . . . . . . . . . . . . . . . . . -42 to -58V High Level Logic Input Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . 2.4V Low Level Logic Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 0.6V Loop Resistance (RL) . . . . . . . . . . . . . . . . . . . . . . . . . 200 to 1200Ω Die Characteristics Transistor Count. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Diode Count. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Die Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 x 102 Substrate Potential. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Connected Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bipolar-DI CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. NOTES: 1. Absolute maximum ratings are limiting values, applied individually, beyond which the serviceability of the circuit may be impaired. Functional operability under any of these conditions is not necessarily implied. 2. θJA is measured with the component mounted on an evaluation PC board in free air. Electrical Specifications Unless Otherwise Specified, VB- = -48V, VB+ = 12V and 5V, AG = BG = DG = 0V, Typical Parameters TA = 25oC. Min-Max Parameters are Over Operating Temperature Range PARAMETER CONDITIONS MIN TYP MAX UNITS On Hook Power Dissipation ILONG = 0 (Note 3), VB+ = 12V - 170 235 mW Off Hook Power Dissipation RL = 600Ω, ILONG = 0 (Note 3), VB+ = 12V - 425 550 mW Off Hook IB+ RL = 600Ω, ILONG = 0 (Note 3), TA = -40oC - - 6.0 mA Off Hook IB+ RL = 600Ω, ILONG = 0 (Note 3), TA = 25oC - - 5.3 mA Off Hook IB- RL = 600Ω, ILONG = 0 (Note 3) - 35 41 mA Off Hook Loop Current RL = 1200Ω, ILONG = 0 (Note 3) - 21 - mA Off Hook Loop Current RL = 1200Ω, VB- = -42V, ILONG = 0 (Note 3) TA = 25oC 17.5 - - mA Off Hook Loop Current RL = 200Ω, ILONG = 0 (Note 3) 36 41 48 mA - 14 - mA RING to Ground - 55 - mA TIP to RING - 41 - mA TIP and RING to Ground - 55 - mA Fault Currents TIP to Ground Ring Relay Drive VOL IOL = 62mA - 0.2 0.5 V Ring Relay Driver Off Leakage VRD = 12V, RC = 1 = HIGH, TA = 25oC - - 100 µA Ring Trip Detection Period RL = 600Ω - 2 3 Ring Cycles Switch Hook Detection Threshold SHD = VOL 10 - - mA SHD = VOH - - 5 mA 52 HC-5504B Electrical Specifications Unless Otherwise Specified, VB- = -48V, VB+ = 12V and 5V, AG = BG = DG = 0V, Typical Parameters TA = 25oC. Min-Max Parameters are Over Operating Temperature Range (Continued) PARAMETER CONDITIONS Ground Key Detection Threshold Loop Current During Power Denial MIN TYP MAX UNITS GKD = VOL 20 - - mA GKD = VOH - - 10 mA RL = 200Ω - ±2 - mA 0 - 5 ms Dial Pulse Distortion Receive Input Impedance (Note 3) - 110 - kΩ Transmit Output Impedance (Note 3) - 10 20 Ω 2-Wire Return Loss SRL LO Referenced to 600Ω + 2.16µF (Note 3) - 15.5 - dB ERL - 24 - dB SRL HI - 31 - dB 58 65 - dB 2-Wire On Hook 60 63 - dB 4-Wire Off Hook 50 58 - dB - - 23 dBrnC - - -67 dBm0p - ±0.05 ±0.2 dB - ±0.02 ±0.05 dB - 1 5 dBrnC - -89 -85 dBm0p - - 2 ms Longitudinal Balance 1VRMS 200Hz - 3400Hz (Note 3) IEEE Method 0oC ≤ TA ≤ 75oC 2-Wire Off Hook Low Frequency Longitudinal Balance Insertion Loss R.E.A. Method (Note 3), RL = 600Ω 0oC ≤ TA ≤ 75oC at 1kHz, 0dBm Input Level, Referenced 600Ω 2-Wire to 4-Wire, 4 Wire to 2-Wire Frequency Response 200Hz - 3400Hz Referenced to Absolute Loss at 1kHz and 0dBm Signal Level (Note 3) Idle Channel Noise (Note 3) 2-Wire to 4-Wire, 4 Wire to 2-Wire Absolute Delay (Note 3) 2-Wire to 4-Wire, 4 Wire to 2-Wire Trans Hybrid Loss Balance Network Set Up for 600Ω Termination at 1kHz 36 40 - dB Overload Level VB+ = +5V 1.5 - - VPEAK 2-Wire to 4-Wire, 4 Wire to 2-Wire VB+ = 12V 1.75 - - VPEAK Level Linearity At 1kHz Referenced to 0dBm Level (Note 3) +3 to -40dBm - - ±0.05 dB -40 to -50dBm - - ±0.1 dB -50 to -55dBm - - ±0.3 dB 15 - - dB VB+ to Transmit 15 - - dB VB- to 2-Wire 15 - - dB VB- to Transmit 15 - - dB 2-Wire to 4-Wire, 4 Wire to 2-Wire Power Supply Rejection Ratio VB+ to 2-Wire (Note 3) 30 - 60Hz, RL = 600Ω 53 HC-5504B Electrical Specifications Unless Otherwise Specified, VB- = -48V, VB+ = 12V and 5V, AG = BG = DG = 0V, Typical Parameters TA = 25oC. Min-Max Parameters are Over Operating Temperature Range (Continued) PARAMETER CONDITIONS MIN TYP MAX UNITS 30 - - dB VB+ to Transmit 30 - - dB VB- to 2-Wire 30 - - dB VB- to Transmit 30 - - dB - - ±100 µA - - 0.8 V 2.0 - 5.5 V - 0.1 0.5 V ILOAD 80µA, VB+ = 12V 2.7 5.0 5.5 V ILOAD 40µA, VB+ = 5V 2.7 - 5.0 V VB+ to 2-Wire 200 - 16kHz, RL = 600Ω 0V ≤ VIN ≤ 5V Logic Input Current (RS, RC, PD) Logic Inputs Logic ‘0’ VIL Logic ‘1’ VIH Logic Outputs Logic ‘0’ VOL ILOAD 800µA, VB+ = 12V, 5V Logic ‘1’ VOH Uncommitted Op Amp Specifications PARAMETER CONDITIONS MIN TYP MAX UNITS Input Offset Voltage - ±5 - mV Input Offset Current - ±10 - nA Input Bias Current - 20 - nA Differential Input Resistance (Note 3) - 1 - MΩ Output Voltage Swing RL = 10K, VB+ = 12V - ±6.2 ±6.6 VPEAK RL = 10K, VB+ = 5V - ±3 - VPEAK Output Resistance AVCL = 1 (Note 3) - 10 - Ω Small Signal GBW (Note 3) - 1 - MHz NOTES: 3. These parameters are controlled by design or process parameters and are not directly tested. These parameters are characterized upon initial design release, upon design changes which would affect these characteristics, and at intervals to assure product quality and specification compliance. 4. ILONG = Longitudinal Current 54 HC-5504B Pin Descriptions 28 PIN PLCC 24 PIN DIP/SOIC SYMBOL DESCRIPTION 2 1 TIP An analog input connected to the TIP (more positive) side of the subscriber loop through a 150Ω feed resistor and a ring relay contact. Functions with the Ring terminal to receive voice signals from the telephone and for loop monitoring purposes. 3 2 RING An analog input connected to the RING (more negative) side of the subscriber loop through a 150Ω feed resistor and a ring relay contact. Functions with the Tip terminal to receive voice signals from the telephone and for loop monitoring purposes. 4 3 RFS Senses ring side of loop for ground key and ring trip detection. During ringing, the ring signal is inserted into the line at this node and RF is isolated from RFS via a relay. 5 4 VB+ Positive Voltage Source - Most positive supply. VB+ is typically 12V or 5V. 6 5 C3 Capacitor #3 - An external capacitor to be connected between this terminal and analog ground. Required for proper operation of the loop current limiting function, and for filtering VB-. Typical value is 0.3µF, 30V. 7 6 DG (Note 5) Digital Ground - To be connected to zero potential and serves as a reference for all digital inputs and outputs on the SLIC microcircuit. 9 7 RS Ring Synchronization Input - A TTL-compatible clock input. The clock should be arranged such that a positive pulse transition occurs on the zero crossing of the ring voltage source, as it appears at the RFS terminal. For Tip side injected systems, the RS pulse should occur on the negative going zero crossing and for Ring injected systems, on the positive going zero crossing. This ensures that the ring relay activates and deactivates when the instantaneous ring voltage is near zero. If synchronization is not required, the pin should be tied to 5V. 10 8 RD Relay Driver - A low active open collector logic output. When enabled, the external ring relay is energized. 11 9 TF Tip Feed - A low impedance analog output connected to the TIP terminal through a 150Ω feed resistor. Functions with the RF terminal to provide loop current, feed voice signals to the telephone set, and sink longitudinal current. 12 10 RF Ring Feed - A low impedance analog output connected to the RING terminal through a 150Ω feed resistor. Functions with the TF terminal to provide loop current, feed voice signals to the telephone set, and sink longitudinal current. 13 11 VB- Negative Voltage Source - Most negative supply. VB- is typically -48V with an operational range of -42V to -58V. Frequently referred to as “battery”. 14 12 BG (Note 5) Battery Ground - To be connected to zero potential. All loop current and some quiescent current flows into this ground terminal. 16 13 SHD Switch Hook Detection - A low active LS TTL - compatible logic output. This output is enabled for loop currents exceeding 10mA and disabled for loop currents less than 5mA. 17 14 GKD Ground Key Detection - A low active LS TTL - compatible logic output. This output is enabled if the DC current into the ring lead exceeds the DC current out of the tip lead by more than 20mA, and disabled if this current difference is less than 10mA. 18 15 PD Power Denial - A low active TTL - Compatible logic input. When enabled, the switch hook detect (SHD) and ground key detect (GKD) are not necessarily valid, and the relay driver (RD) output is disabled. 19 16 RC Ring Command - A low active TTL - Compatible logic input. When enabled, the relay driver (RD) output goes low on the next high level of the ring sync (RS) input, as long as the SLIC is not in the power denial state (PD = 0) or the subscriber is not already off- hook (SHD = 0). 20 17 C2 Capacitor #2 - An external capacitor to be connected between this terminal and digital ground. Prevents false ground key indications from occurring during ring trip detection. Typical value is 0.15µF, 10V. This capacitor is not used if ground key function is not required and (Pin 17) may be left open or connected to digital ground. 21 18 OUT 23 19 -IN 55 The analog output of the spare operational amplifier. The output voltage swing is typically ±5V. The inverting analog input of the spare operational amplifier. HC-5504B Pin Descriptions (Continued) 28 PIN PLCC 24 PIN DIP/SOIC SYMBOL 24 20 +IN The non-inverting analog input of the spare operational amplifier. 25 21 RX Receive Input, 4-Wire Side - A high impedance analog input which is internally biased. Capacitive coupling to this input is required. AC signals appearing at this input differentially drive the Tip feed and Ring feed terminals, which in turn drive tip and ring through 300Ω of feed resistance on each side of the line. 26 22 C4 Capacitor #4 - An external capacitor to be connected between this terminal and analog ground. This capacitor prevents false ground key indication and false ring trip detection from occurring when longitudinal currents are induced onto the subscriber loop from near by power lines and other noise sources. This capacitor is also required for the proper operation of ring trip detection. Typical value is 0.5µF, to 1.0µF, 20V. This capacitor should be nonpolarized. 27 23 AG (Note 5) Analog Ground - To be connected to zero potential and serves as a reference for the transmit output (TX) and receive input (RX) terminals. 28 24 TX Transmit Output, 4-Wire Side - A low impedance analog output which represents the differential voltage across Tip and Ring. Transhybrid balancing must be performed (using the SLIC microcircuit’s spare op amp) beyond this output to completely implement two to four wire conversion. This output is unbalanced and referenced to analog ground. Since the DC level of this output varies with loop current, capacitive coupling to the next stage is essential. NC No internal connection. 1, 8, 15, 22 DESCRIPTION NOTE: 5. All grounds (AG, BG, and DG) must be applied before VB+ or VB-. Failure to do so may result in premature failure of the part. If a user wishes to run separate grounds off a line card, the AG must be applied first. Functional Diagram RING SYNC RING COMMAND RING TRIP RS RC RD RING CONTROL SHD SWITCH HOOK DETECTION GKD GROUND KEY LOOP MONITORING DETECTION 1/2 RING RELAY TIP TIP 150Ω - DIFF AMP TX + 150Ω TRANSMIT OUTPUT TF 2 WIRE LOOP VB SECONDARY PROTECTION BATTERY FEED OUT +1 BG VB- RF LOOP CURRENT LIMITER RFS 1/2 RING RELAY LINE DRIVERS 150Ω -1 RING 150Ω RING VOLTAGE RING POWER DENIAL VB - 56 PD SLIC MICROCIRCUIT +IN + OP AMP - -IN RX RECEIVE INPUT HC-5504B Schematic Diagram SLIC FUNCTIONAL SCHEMATIC Pin Numbers for DIP/SOIC Package 21 22 11 12 23 6 4 20 19 18 RX C4 VBAT BAT GND ANA GND DIG GND VB+ + - OUT V B+ VB+ VB1 VB2 VB3 VB4 VB5 +5V VOLTAGE AND CURRENT BIAS NETWORK A-400 TIP FEED AMP TF 9 R17 + VB+ VBAT VB2 RING TRIP DETECTOR R12 R7 QD3 QD36 VB+ R8 R10 RING FEED SENSE R9 R22 3 V B+ R11 VBAT V + VBAT R23 B IB7 2 R1 - - 13 VB1 IB6 QD27 R14 R18 R21 SHD SH - + QD28 RC THERMAL LIMITING LOAD CURRENT LIMITING I B2 16 RFC VB5 A-300 RING FEED AMP 10 - PD VB5 + 15 + VBAT R19 IB5 R13 VBAT VBAT VBAT C3 TX RS RD 5 24 7 8 57 17 V B+ VBAT/2 REFERENCE VB2 C2 STTL AND LOGIC INTERFACE VBAT VBAT R6 R15 RF SWITCH HOOK DETECTOR IB6 R16 14 + VB3 V B+ - GKD GND SHORTS CURRENT LIMITING IB1 R5 A-100 TRANSV’L I/V AMP R2 VB4 IB8 + R4 VBAT + VBAT + R3 RING GK R20 A-200 LONG’L I / V AMP 1 5V IB10 VB+ 5V - TIP VBAT IB3 IB1 IB2 IB3 IB4 IB5 IB6 IB7 IB8 VBAT IB9 IB10 IB11 - IB4 A-500 OP AMP HC-5504B Schematic Diagram (Continued) LOGIC GATE SCHEMATIC C2 GK 1 LOGIC BIAS 2 DELAY 4 SH 6 8 7 9 3 5 12 16 10 13 11 RELAY DRIVER 14 15 TTL TO STTL TTL TO STTL TTL TO STTL TO R21 STTL TO TTL C B A A STTL TO TTL B RS RC PD C RD SHD GKD SCHOTTKY LOGIC Overvoltage Protection and Longitudinal Current Protection TABLE 1. PARAMETER TEST CONDITION PERFORMANCE (MAX) UNITS The SLIC device, in conjunction with an external protection bridge, will withstand high voltage lightning surges and power line crosses. Longitudinal Surge 10µs Rise/ ±1000 (Plastic) VPEAK 1000µs Fall ±500 (Ceramic) VPEAK High voltage surge conditions are as specified in Table 1. Metallic Surge 10µs Rise/ ±1000 (Plastic) VPEAK 1000µs Fall ±500 (Ceramic) VPEAK T/GND 10µs Rise/ ±1000 (Plastic) VPEAK R/GND 1000µs Fall ±500 (Ceramic) VPEAK T/GND 11 Cycles 700 (Plastic) VRMS R/GND Limited to 10ARMS 350 (Ceramic) VRMS The SLIC will withstand longitudinal currents up to a maximum or 30mARMS , 15mARMS per leg, without any performance degradation. 50/60Hz Current All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certification. Intersil semiconductor products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see web site http://www.intersil.com 58 HC-5504B Applications Diagram 5V TO 12V SYSTEM CONTROLLER 15 RS1 CS1 RB1 SUBSCRIBER LOOP 14 7 16 POWER SWITCH GROUND RING RING SYNC CMD DENIAL HOOK KEY 8 DETECT DETECT RD RX 1 TIP TX RB2 9 SLIC +IN TIP FEED HC-5504B -IN OP AMP VB K1 K1A TIP 13 1 PRIMARY PROTECTION OUT BALANCE NETWORK C5 21 C6 24 20 C7 PCM SWITCHING FILTER/ NETWORK CODEC ZB R1 19 R3 R2 18 K1B 10 RS2 CS2 RING RB3 3 RING FEED C2 RING FEED SENSE RB4 2 RING C3 C4 NEG. BATT. BATT. GND. DIG. GND. ANA. GND. VB+ 11 12 6 23 4 PTC -48V C8 C9 17 5 22 C4 + C3 + C2 VB + 150VPEAK (MAX) RING GENERATOR Z1 -48V FIGURE 1. TYPICAL LINE CIRCUIT APPLICATION WITH THE MONOLITHIC SLIC Typical Component Values C2 = 0.15µF, 10V R1 = R2 = R3 = 100kΩ (0.1% Match Required, 1% absolute value) ZB = 0 for 600Ω Terminations (Note 7). C3 = 0.3µF, 30V C4 = 0.5µF to 1.0µF, 10%, 20V (Should be nonpolarized) C5 = 0.5µF, 20V C6 = C7 = 0.5µF (10% Match Required) (Note 7) C8 = 0.01µF, 100V C9 = 0.01µF, 20V, ±20% RB1 = RB2 = RB3 = RB4 = 150Ω (0.1% Match Required, 1% absolute value). RS1 = RS2 =1kΩ, typically. CS1 = CS2 = 0.1µF, 200V typically, depending on VRING and line length. Z1 = 150V to 200V transient protection. PTC used as ring generator ballast. NOTES: 6. Secondary protection diode bridge recommended is a 2A, 200V type. 7. To obtain the specified transhybrid loss it is necessary for the three legs of the balance network, C6-R1 and R2 and C7-ZB-R3 , to match in impedance to within 0.3%. Thus, if C6 and C7 are 1µF each, a 20% match is adequate. It should be noted that the transmit output to C6 sees a 22V step when the loop is closed. Too large a value for C6 may produce an excessively long transient at the op amp output to the PCM Filter/CODEC. A 0.5µF and 100kΩ gives a time constant of 50ms. The uncommitted op amp output is internally clamped to stay within ±5.5V and also has current limiting protection. 8. All grounds (AG, BG, and DG) must be applied before VB+ or VB-. Failure to do so may result in premature failure of the part. If a user wishes to run separate grounds off a line card, the AG must be applied first. 9. Application shows Ring Injected Ringing, Balanced or Tip injected configuration may be used. 10. Pin numbers given for DIP/SOIC package. 59