 |
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
| Datasheet File OCR Text: |
| Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Features s Description These electronic subscriber loop interface circuits (SLICs) are optimized for low power consumption while providing an extensive set of features. The SLICs include an auxiliary battery input and a built-in switch. In short-loop applications, they can be used in high battery to present a high on-hook voltage, and then switched to low battery to reduce offhook power. The SLICs also include a summing node for meter pulse injection to 2.2 Vrms. A spare, uncommitted op amp is included for meter pulse filtering. The switched battery is applied to the power amplifiers of the device. There are two versions. The L7556 has the battery switch completely under processor control. The L7557 can automatically switch to lower battery when appropriate and includes hysteresis to avoid frequent switching. To make the switch silent, an external capacitor can be added to slow the transition. The L7556 is suited for applications serving only short loops, where a high on-hook voltage is required for compatibility with preexisting standards. The L7557 is suited for applications where a full loop range is needed, but low short-loop power is desired. It is a much lower-cost solution than a switching regulator, and also occupies much less PCB area, needing only a battery filter capacitor and a diode for implementation. The device is available in a 32-pin PLCC package. It is built by using a 90 V complementary bipolar integrated circuit (CBIC) process. Auxiliary input for second battery, and internal switch to enable its use to save power Low active power (typical 125 mW during on-hook transmission) Supports meter pulse injection Spare op amp for meter pulse filtering -16 V to -60 V power supply operation Distortion-free on-hook transmission Convenient operating states: -- Forward powerup -- Disconnect (high impedance) -- 2-wire wink (zero loop voltage) Adjustable supervision functions: -- Off-hook detector with longitudinal rejection -- Ground key detector -- Ring trip detector Independent, adjustable, dc and ac parameters: -- dc feed resistance -- Loop current limit -- Termination impedance Thermal protection s s s s s s s s s L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Table of Contents Contents Page Figures Page Features ..................................................................... 1 Description .................................................................. 1 Pin Information ............................................................ 4 Functional Description ................................................. 6 Absolute Maximum Ratings ........................................ 6 Recommended Operating Conditions ......................... 7 Electrical Characteristics ............................................. 7 Ring Trip Requirements ......................................... 11 Test Configurations .................................................. 12 Applications .............................................................. 14 Design Considerations ........................................... 16 Characteristic Curves............................................. 17 dc Applications ....................................................... 20 Battery Feed......................................................... 20 Switching the Battery............................................ 20 Overhead Voltage ............................................... 21 Adjusting Overhead Voltage ................................ 21 Adjusting dc Feed Resistance.............................. 22 Loop Range.......................................................... 22 Off-Hook Detection .............................................. 22 Ring Trip Detection.............................................. 23 Ring Ground Detection........................................ 23 ac Design ............................................................... 24 First-Generation Codecs ..................................... 24 Second-Generation Codecs ................................ 24 Third-Generation Codecs .................................... 24 Selection Criteria ................................................. 24 PCB Layout Information ............................................ 26 Outline Diagram......................................................... 27 32-Pin PLCC ........................................................... 27 Ordering Information.................................................. 28 Tables Page Table 1. Pin Descriptions ............................................ 4 Table 2. Input State Coding ........................................ 6 Table 3. Supervision Coding ....................................... 6 Table 4. Power Supply ................................................ 7 Table 5. 2-Wire Port .................................................... 8 Table 6. Analog Pin Characteristics ............................ 9 Table 7. Uncommitted Op Amp Characteristics .......... 9 Table 8. ac Feed Characteristics .............................. 10 Table 9. Logic Inputs and Outputs ............................ 11 Table 10. Parts List for Loop Start and Ground Start Applications ...................................... 15 Table 11. 600 Design Parameters ......................... 16 Figure 1. Functional Diagram ..................................... 3 Figure 2. Pin Diagram (PLCC Chip) ........................... 4 Figure 3. Ring Trip Circuits ....................................... 11 Figure 4. Basic Test Circuit .......................................12 Figure 5. Longitudinal Balance .................................12 Figure 6. Longitudinal PSRR ....................................13 Figure 7. RFI Rejection .............................................13 Figure 8. Longitudinal Impedance ............................13 Figure 9. Metallic PSRR ...........................................13 Figure 10. ac Gains ..................................................13 Figure 11. Basic Loop Start Application Circuit Using T7504 Type Codec ........................14 Figure 12. Ring Ground Detection Circuit .................14 Figure 13. Receive Gain and Hybrid Balance vs. Frequency ...............................................17 Figure 14. Transmit Gain and Return Loss vs. Frequency ...............................................17 Figure 15. Typical VCC Power Supply Rejection .......17 Figure 16. Typical VBAT Power Supply Rejection .................................................17 Figure 17. Loop Closure Program Resistor Selection ..................................................18 Figure 18. Ring Ground Detection Programming .....18 Figure 19. Loop Current vs. Loop Voltage ................18 Figure 20. Loop Current vs. Loop Resistance ..........18 Figure 21. Typical SLIC Power Dissipation vs. Loop Resistance ......................................19 Figure 22. Power Derating ........................................19 Figure 23. Longitudinal Balance Resistor Mismatch Requirements ..........................................19 Figure 24. Longitudinal Balance vs. Protection Resistor Mismatch ...................................19 Figure 25. Loop Current vs. Loop Voltage ................20 Figure 26. SLIC 2-Wire Output Stage .......................21 Figure 27. Equivalent Circuit for Adjusting the Overhead Voltage ...........................................21 Figure 28. Equivalent Circuit for Adjusting the dc Feed Resistance ......................................22 Figure 29. Adjusting Both Overhead Voltage and dc Feed Resistance .....................................22 Figure 30. Off-Hook Detection Circuit Applications .............................................22 Figure 31. Ring Trip Equivalent Circuit and Equivalent Application .............................23 Figure 32. ac Equivalent Circuit Not Including Spare Op Amp ...................................................25 Figure 33. ac Equivalent Circuit Including Spare Op Amp ...................................................25 2 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Description (continued) BGND AGND VBAT2 VBAT1 IPROG LBAT BS1 BS2 VCC BS BATTERY SWITCH POWER CONDITIONING & REFERENCE VREG CF1 CF2 DCOUT + 1 V/8 mA VITR - SN PT A=4 SPARE OP AMP - XMT + - PR A = -4 RCVN RCVP + B0 DCR dc RESISTANCE ADJUST BATTERY FEED STATE CONTROL B1 LCTH LOOP CLOSURE DETECTOR + NLC - RTSP RTSN RING TRIP DETECTOR + NRDET - RGDET ICM RING GROUND DETECTOR 12-2551.a (F) Figure 1. Functional Diagram Lucent Technologies Inc. 3 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Pin Information VBAT2 IPROG NC LBAT BS1 BS2 31 4 VCC RCVP RCVN LCTH DCOUT VBAT1 PR CF2 CF1 5 6 7 8 9 10 11 12 13 14 VITR 3 2 1 32 30 29 28 27 26 SN XMT B1 NLC NRDET RTSP RTSN PT BGND 32-PIN PLCC NC 25 24 23 22 20 DCR 21 15 ICM BS 16 RGDET 17 B0 18 AGND 19 AGND 12-2548.q (F) Figure 2. Pin Diagram (PLCC Chip) Table 1. Pin Descriptions Pin 1 2 3 4 4 5 6 7 8 9 10 Symbol Type Description VBAT2 -- Auxiliary Battery Supply. Negative high-voltage battery, lower in magnitude than VBAT1, used to reduce power dissipation on short loops. IPROG I Current-Limit Program Input. A resistor to DCOUT sets the dc current limit of the device. BS I Battery Switch. See Table 2 for description. NC -- No Connection (L7556 Only). Do not use as a tie point. LBAT O Lower Battery in Use (L7557 Only). When high, this open-collector output indicates the device has switched to VBAT2. To use, connect a 100 k resistor to VCC. VCC -- +5 V Power Supply. RCVP I Receive ac Signal Input (Noninverting). This high-impedance input controls the ac differential voltage on tip and ring. RCVN I Receive ac Signal Input (Inverting). This high-impedance input controls the ac differential voltage on tip and ring. LCTH I Loop Closure Threshold Input. Connect a resistor to DCOUT to set off-hook threshold. DCOUT O dc Output Voltage. This output is a voltage that is directly proportional to the absolute value of the differential tip/ring current. VBAT1 -- Battery Supply. Negative high-voltage power supply, higher in magnitude than VBAT2. 4 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Pin Information (continued) Table 1. Pin Descriptions (continued) Pin 11 12 13 14 15 Symbol Type Description PR I/O Protected Ring. The output of the ring driver amplifier and input to loop sensing circuitry. Connect to loop through overvoltage protection. CF2 -- Filter Capacitor 2. Connect a 0.1 F capacitor from this pin to AGND. CF1 -- Filter Capacitor 1. Connect a 0.47 F capacitor from this pin to pin CF2. VITR O Transmit ac Output Voltage. This output is a voltage that is directly proportional to the differential tip/ring current. ICM I Common-Mode Current Sense. To program ring ground sense threshold, connect a resistor to VCC and connect a capacitor to AGND to filter 50/60 Hz. If unused, the pin can be left unconnected. RGDET O Ring Ground Detect. When high, this open-collector output indicates the presence of a ring ground. To use, connect a 100 k resistor to VCC. B0 I State Control Input. B0 and B1 determine the state of the SLIC. See Table 2. AGND -- Analog Signal Ground. AGND -- Analog Signal Ground. DCR I dc Resistance for Low Loop Currents. Leave open for dc feed resistance of 115 , or short to DCOUT for 615 . Intermediate values can be set by a simple resistor divider from DCOUT to ground with the tap at DCR. BGND -- Battery Ground. Ground return for the battery supply. PT I/O Protected Tip. The output of the tip driver amplifier and input to loop sensing circuitry. Connect to loop through overvoltage protection. RTSN I Ring Trip Sense Negative. Connect this pin to the ringing generator signal through a high-value resistor. RTSP I Ring Trip Sense Positive. Connect this pin to the ring relay and the ringer series resistor through a high-value resistor. NRDET O Ring Trip Detector Output. When low, this logic output indicates that ringing is tripped. NLC O Loop Detector Output. When low, this logic output indicates an off-hook condition. B1 I/O State Control Input. B0 and B1 determine the state of the SLIC. See Table 2. Pin B1 has a 40 k pull-up. It goes low in the event of thermal shutdown. XMT O Transmit ac Output Voltage. The output of the uncommitted operational amplifier. SN I Summing Node. The inverting input of the uncommitted operational amplifier. A resistor or network to XMT sets the gain. NC -- No Connection. Do not use as a tie point. BS2 -- Battery Switch Slowdown. A 0.1 F capacitor from BS1 to BS2 will ramp the battery switch transition for applications requiring quiet transition. If not needed, the pin can be left open. BS1 -- Battery Switch Slowdown. A 0.1 F capacitor from BS1 to BS2 will ramp the battery switch transition for applications requiring quiet transition. If not needed, the pin can be left open. 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Lucent Technologies Inc. 5 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Functional Description Table 2. Input State Coding B0 B1 1 1 1 1 BS 1 0 State/Definition Powerup, Forward Battery. Normal talk and battery feed state. Pin PT is positive with respect to PR. On-hook transmission is enabled. VBAT1 is applied to entire circuit. Powerup, Forward Battery. Normal talk and battery feed state. Pin PT is positive with respect to PR. On-hook transmission is enabled. For the L7556 only, VBAT2 is applied to tip/ring drive amplifiers. For the L7557 only, the device compares the magnitude of VBAT2 to the voltage necessary to maintain proper loop current. Then the device automatically applies VBAT2 to tip/ring drive amplifiers when possible, not affecting the desired dc template. 2-Wire Wink. Pins PT and PR are put at the same potential (near ground). VBAT1 is applied to entire circuit. Disconnect. The tip and ring amplifiers are turned off, and the SLIC goes to a high-impedance state (>100 k).VBAT1 is applied to entire circuit. 1 0 0 0 1 1 Table 3. Supervision Coding Pin NLC 0 = off-hook 1 = on-hook Pin NRDET 0 = ring trip 1 = no ring trip Pin RGDET 1 = ring ground 0 = no ring ground Absolute Maximum Ratings (TA = 25 C) Stresses in excess of the Absolute Maximum Ratings can cause permanent damage to the device. These are absolute stress ratings only. Functional operation of the device is not implied at these or any other conditions in excess of those given in the operational sections of the data sheet. Exposure to Absolute Maximum Ratings for extended periods can adversely affect device reliability. Parameter 5 V Power Supply Battery (Talking) Supply Auxiliary Battery Supply Logic Input Voltage Analog Input Voltage Maximum Junction Temperature Storage Temperature Range Relative Humidity Range Ground Potential Difference (BGND to AGND) PT or PR Fault Voltage (dc) PT or PR Fault Voltage (10 x 1000 s) Current into Ring Trip Inputs Note: Symbol VCC VBAT1 VBAT2 -- -- TJ Tstg RH -- VPT, VPR VPT, VPR IRTSP, IRTSN Value 7.0 -63 -63 -0.5 to +7.0 -7.0 to +7.0 165 -40 to +125 5 to 95 3 (VBAT1 - 5) to +3 (VBAT1 - 15) to +15 240 Unit V V V V V C C % V V V A The IC can be damaged unless all ground connections are applied before, and removed after, all other connections. Furthermore, when powering the device, the user must guarantee that no external potential creates a voltage on any pin of the device that exceeds the device ratings. Some of the known examples of conditions that cause such potentials during powerup are the following: 1. An inductor connected to tip and ring can force an overvoltage on VBAT through the protection devices if the VBAT connections chatter. 2. Inductance in the VBAT leads could resonate with the VBAT filter capacitors to cause a destructive overvoltage. 6 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Recommended Operating Conditions Parameter Ambient Temperature VCC Supply Voltage VBAT1 Supply Voltage VBAT2 Supply Voltage Loop Closure Threshold-detection Programming Range dc Loop Current-limit Programming Range On- and Off-hook 2-wire Signal Level ac Termination Impedance Programming Range Min -40 4.75 -24 -16 -- 5 -- 150 Typ -- 5.0 -48 -28 10 22 1 600 Max 85 5.25 -60 VBAT1 ILIM 45 2.2 1300 Unit C V V V mA mA Vrms Electrical Characteristics Minimum and maximum values are testing requirements. Typical values are characteristic of the device and are the result of engineering evaluations. Typical values are for information purposes only and are not part of the testing requirements. Minimum and maximum values apply across the entire temperature range (-40 C to +85 C) and the entire battery range unless otherwise specified. Typical is defined as 25 C, VCC = 5.0 V, VBAT1 = -48 V, VBAT2 = -48 V, and ILIM= 40 mA. Positive currents flow into the device. Test circuit is Figure 4 unless noted. Table 4. Power Supply Parameter Power Supply--Powerup, No Loop Current: ICC IBAT (VBAT = -48 V) Power Dissipation (VBAT = -48 V) Power Supply Rejection 500 Hz to 3 kHz (See Figures 5, 6, 15, and 16.)1: VCC VBAT Thermal Protection Shutdown (Tjc) Thermal Resistance, Junction to Ambient (JA) Min -- -- -- 35 45 -- -- Typ 2.8 -2.3 125 -- -- 175 60 Max -- -- 155 -- -- -- -- Unit mA mA mW dB dB C C/W 1. This parameter is not tested in production. It is guaranteed by design and device characterization. Lucent Technologies Inc. 7 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Electrical Characteristics (continued) Table 5. 2-Wire Port Parameter Tip or Ring Drive Current: = dc + Longitudinal + Signal Currents Signal Current Longitudinal Current Capability per 2 Min 65 15 8.5 -- 5 -- Typ -- -- 15 ILIM -- -- Max -- -- -- -- 45 12 Unit mA mArms mArms mA mA % V k k k Wire1 dc Loop Current Limit : RLOOP = 100 Programmability Range Accuracy (20 mA < ILIM < 40 mA) Powerup Open Loop Voltage Levels (includes external diode): |VBAT + 8.4| |VBAT + 7.9| |VBAT + 7.4| Differential Voltage Disconnect State: PT Resistance (VBAT < VPT < 0 V) PR Resistance (VBAT < VPR < 0 V) Ground Start State: PT Resistance dc Feed Resistance (for ILOOP below regulation level) Loop Resistance Range (-3.17 dBm overload into 600 ; not including protection): ILOOP = 20 mA at VBAT2 = -48 V ILOOP = 20 mA at VBAT2 = -24 V Longitudinal to Metallic Balance--IEEE 3 Std. 455 (See Figure 6.)4: 50 Hz to 1 kHz 1 kHz to 3 kHz Metallic to Longitudinal Balance: 200 Hz to 4 kHz RFI Rejection (See Figure 0.5 Vrms, 50 Source, 30% AM Mod 1 kHz 500 kHz to 100 MHz 7.)5: 100 100 100 95 143 133 143 115 -- -- -- 135 1885 685 -- -- -- -- 64 60 46 75 70 -- -- -- -- dB dB dB -- -55 -45 dBV 1. The longitudinal current is independent of dc loop current. 2. Current-limit ILIM is programmed by a resistor, RPROG, from pin IPROG to DCOUT. ILIM is specified at the loop resistance where current limiting begins (see Figure 19). Select RPROG (k) =1.67 x ILIM (mA). 3. IEEE is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc. 4. Longitudinal balance of circuit card will depend on loop series resistance matching (see Figure 23 and Figure 24). 5. This parameter is not tested in production. It is guaranteed by design and device characterization. 8 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Electrical Characteristics (continued) Table 6. Analog Pin Characteristics Parameter Differential PT/PR Current Sense (DCOUT): Gain (PT/PR to DCOUT) Loop Closure Detector Threshold1: Programming Accuracy Ring Ground Detector Threshold2: RICM = 154 k Programming Accuracy Ring Trip Comparator: Input Offset Voltage RCVN, RCVP: Input Bias Current Min -123 -- 3 -- -- -- Typ -125 -- 6 -- -- -0.2 Max -127 20 10 25 10 -1 Unit V/A % k % mV A 1. Loop closure threshold is programmed by resistor RLCTH from pin LCTH to pin DCOUT. 2. Ring ground threshold is programmed by resistor RICM2 from pin ICM to VCC. Table 7. Uncommitted Op Amp Characteristics Parameter Input Offset Voltage Input Offset Current Input Bias Current Differential Input Resistance Output Voltage Swing (RL = 10 k) Output Resistance (AVCL = 1) Small Signal GBW Min -- -- -- -- -- -- -- Typ 5 10 200 1.5 3.5 2.0 700 Max -- -- -- -- -- -- -- Unit mV nA nA M Vpk kHz Lucent Technologies Inc. 9 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Electrical Characteristics (continued) Table 8. ac Feed Characteristics Parameter ac Termination Impedance1: 2 2 Min 150 -- -- -- -122 -0.18 7.84 -7.84 -0.18 Typ -- 40 -- -- -125 0 8.00 -8.00 0 0.0 0.0 -0.1 -- 0 24 29 -87 2 10 -82 7 15 24 29 Max 1300 46 0.3 1.0 -128 0.18 8.16 -8.16 0.18 0.05 0.05 0.3 2.0 0.05 -- -- -77 12 20 -77 12 20 -- -- Unit % % V/A dB -- -- dB dB dB dB dB dB dB dB dBmp dBrnC dBrn dBmp dBrnC dBrn dB dB Longitudinal Impedance (See Figure 8.) Total Harmonic Distortion--200 Hz to 4 kHz : Off-hook On-hook Transmit Gain, f = 1 kHz (PT/PR to VITR) Transmit Accuracy in dB Receive + Gain, f = 1 kHz (RCVP to PT/PR) Receive - Gain, f = 1 kHz (RCVN to PT/PR) Receive Accuracy in dB Gain vs. Frequency (transmit and receive) (600 termination; reference 1 kHz2): -1.00 200 Hz to 300 Hz -0.3 300 Hz to 3.4 kHz -3.0 3.4 kHz to 16 kHz -- 16 kHz to 266 kHz Gain vs. Level (transmit and receive)(reference 0 dBV2): -50 dB to +3 dB Return 200 Hz to 500 Hz 500 Hz to 3400 Hz 2-wire Idle-channel Noise (600 termination): Psophometric C-message 3 kHz Flat Transmit Idle-channel Noise: Psophometric C-message 3 kHz flat Transhybrid Loss3: 200 Hz to 500 Hz 500 Hz to 3400 Hz Loss3: -0.05 20 26 -- -- -- -- -- -- 21 26 1. Set by external components. Any complex impedance R1 + R2 || C between 150 and 1300 can be synthesized. 2. This parameter is not tested in production. It is guaranteed by design and device characterization. 3. Return loss and transhybrid loss are functions of device gain accuracies and the external hybrid circuit. Guaranteed performance assumes 1% tolerance external components. 10 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Electrical Characteristics (continued) Table 9. Logic Inputs and Outputs All outputs except RGDET and LBAT are open collectors with internal, 30 k pull-up resistor. RGDET and LBAT are open collectors without internal pull-up. Input pin B1 has a 40 k pull-up; it goes low in the event of thermal shutdown. Parameter Input Voltages: Low Level (permissible range) High Level (permissible range) Input Currents: Low Level (VCC = 5.25 V, VI = 0.4 V) High Level (VCC = 5.25 V, VI = 2.4 V) Output Voltages (open collector with internal pull-up resistor): Low Level (VCC = 4.75 V, IOL = 360 A) High Level (VCC = 4.75 V, IOH = -20 A) Symbol VIL VIH IIL IIH VOL VOH Min -0.5 2.0 -75 -40 0 2.4 Typ 0.4 2.4 -115 -60 0.2 -- Max 0.7 VCC -200 -100 0.4 VCC Unit V V A A V V Ring Trip Requirements s Ringing signal: -- Voltage, minimum 35 Vrms, maximum 100 Vrms. -- Frequency, 17 Hz to 23 Hz. -- Crest factor, 1.4 to 2. Ringing trip: -- 100 ms (typical), 250 ms (VBAT = -33 V, loop length = 530 ). Pretrip: -- The circuits in Figure 3 will not cause ringing trip. 200 TIP SWITCH CLOSES <12 ms 6 F TIP 10 k RING RING s s 2 F TIP 100 RING 12-2572g (F) Figure 3. Ring Trip Circuits Lucent Technologies Inc. 11 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Test Configurations VBAT1 0.1 F VBAT2 0.1 F VCC 0.1 F VBAT1 VBAT2 BGND VCC AGND BS1 LBAT TIP 100 BS2 PT VITR RLOOP 100 L7556 L7557 SLIC 100 PR DCOUT 68.1 k 0.1 F 24.9 k LCTH RCVN IPROG RCVP B0 B1 BS NLC NRDET RGDET CF1 CF2 11 k 20 k SN 95.3 k XMT XMT 76.8 k 11 k RCV 0.47 F RING 2 M RTSP 402 RTSN 274 k 2 M ICM VBAT 0.1 F 0.1 F 12-2564.a (F) Figure 4. Basic Test Circuit 100 F TIP VS 368 368 + VM BASIC TEST CIRCUIT RING - 100 F LONGITUDINAL BALANCE = 20 log VS VM 12-2584.c (F) Figure 5. Longitudinal Balance 12 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Test Configurations (continued) ILONG TIP VBAT OR VCC 100 4.7 F VS VBAT OR VCC 67.5 TIP 10 F + VM - 67.5 56.3 RING 10 F PSRR = 20log VS VM 12-2583.b (F) DISCONNECT BYPASS CAPACITOR ILONG + VPT - - VPR + BASIC TEST CIRCUIT RING BASIC TEST CIRCUIT ZLONG = VPR VPT OR ILONG ILONG 12-2585.a (F) Figure 8. Longitudinal Impedance VBAT OR VCC 100 4.7 F VS VBAT OR VCC TIP DISCONNECT BYPASS CAPACITOR Figure 6. Longitudinal PSRR 0.01 F 600 50 VS 0.01 F 82.5 TIP 1 6, 7 LB1201 4 2 V BAT BASIC TEST CIRCUIT RING 82.5 + 900 VT/R BASIC TEST CIRCUIT - RING 2.15 F PSRR = 20log VS VT/R 12-2582.b (F) HP * 4935A TIMS Figure 9. Metallic PSRR VS = 0.5 Vrms 30% AM 1 kHz MODULATION, f = 500 kHz--1 MHz DEVICE IN POWERUP MODE, 600 TERMINATION 5-6756.b (F) * HP is a registered trademark of Hewlett-Packard Company. TIP XMT BASIC TEST CIRCUIT RING RCV VS Figure 7. RFI Rejection 600 + VT/R - VXMT GXMT = VT/R GRCV = VT/R VRCV 12-2587.e (F) Figure 10. ac Gains Lucent Technologies Inc. 13 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Applications VBAT1 CBAT1 0.1 F CBAT2 0.1 F 1 21 4 5 CCC 0.1 F 19 AGND CB1 0.47 F 14 RT2 18.7 k RT1 54.9 k CB2 0.47 F RCVP 22 L7581 RELAY 11 PT L7556/L7557 SLIC RGP 57.6 k CGP 330 pF 6 RRCV 84.5 k VFXIN RHB1 90.9 k - + DX PCM HIGHWAY DR FSX FSEP MCLK SYNC AND CLOCK CONTROL INPUT RX 90.9 k GSX VCC RPROG 66.8 k 9 RLCTH VCC 24.9 k CCC 0.1 F 8 5 2 DBAT 10 DCOUT LCTH VCC IPROG VBAT1 VBAT2 BGND LBAT VCC VITR CROWBAR PROTECTOR TIP RPT 50 RPR 50 RING CROWBAR PROTECTOR VFXIP PWROP ASEL PR RCVN B1 B0 BS RTSP NLC NRDET CF1 13 AGND AGND 18 19 BGND 21 7 27 CONTROL 17 INPUTS 4 26 SUPERVISION 25 OUTPUTS 1/4 T7504 CODEC RTSP 2.0 M RTS1 402 CRTS2 0.27 F RTS2 274 k VRING CRTS1 0.022 F 24 23 RTSN 2.0 M RTSN CF2 12 CF1 0.47 F CF2 0.1 F 12-2573.Y(F) VBAT Notes: Tx = 0 dB. Rx = 0 dB. Termination = 600 . Transhybrid = 600 . Figure 11. Basic Loop Start Application Circuit Using T7504 Type Codec VCC RGDET 100 k RGDET ICM CICM 0.47 F RICM2 154 k RGDET GROUND START APPLICATION CIRCUIT 12-3547(F) Figure 12. Ring Ground Detection Circuit 14 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Applications (continued) Table 10. Parts List for Loop Start and Ground Start Applications Name Integrated Circuits SLIC Protector Ringing Relay Codec Overvoltage Protection RPT RPR Power Supply CBAT1 CBAT2 CCC CF1 CF2 DBAT dc Profile RPROG ac Characteristics CB1 CB2 RT1 RRCV RGP CGP RT2 RX RHB1 Value L7556/7557 Crowbar protector* L7581 T7504 50 , PTC or Fusible 50 , PTC or Fusible 0.1 F, 20%, 100 V 0.1 F, 20%, 100 V 0.1 F, 20%, 10 V 0.47 F, 20%, 100 V 0.1 F, 20%, 100 V 100 V, 150 mA 66.8 k, 1%, 1/16 W 0.47 F, 20%, 10 V 0.47 F, 20%, 10 V 54.9 k, 1%, 1/16 W 84.5 k, 1%, 1/16 W 57.6 k, 1%, 1/16 W 330 pF, 10 V, 20% 18.7 k, 1%, 1/16 W 90.9 k, 1%, 1/16 W 90.9 k, 1%, 1/16 W Function Subscriber loop interface circuit (SLIC). Secondary protection. Switches ringing signals. First-generation codec. Protection resistor. Protection resistor. VBAT1 filter capacitor. VBAT2 filter capacitor. VCC filter. With CF2, improves idle channel noise. With CF1, improves idle channel noise. Transient protection diode. Sets dc loop current limit. ac/dc separation capacitor. ac/dc separation capacitor. With RGP and RRCV, sets ac termination impedance. With RGP and RT1, sets receive gain. With RT1 and RRCV, sets ac termination impedance and receive gain. Loop stability. With RX, sets transmit gain in codec. With RT2, sets transmit gain in codec. Sets hybrid balance. * Contact your Lucent Technologies account representative for protector recommendations. Choice of this (and all) component(s) should be evaluated and confirmed by the customer prior to use in any field or laboratory system. Lucent does not recommend use of this part in the field without performance verification by the customer. This device is suggested by Lucent for customer evaluation. The decision to use a component should be based solely on customer evaluation. Lucent Technologies Inc. 15 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Applications (continued) Table 10. Parts List for Loop Start and Ground Start Applications (continued) Name Supervision RLCTH RTS1 RTS2 CRTS1 CRTS2 RTSN RTSP Ground Start CICM RGDET RICM2 Value 24.9 k, 1%, 1/16 W 402 , 5%, 2 W 274 k, 1%, 1/16 W 0.022 F, 20%, 5 V 0.27 F, 20%, 100 V 2 M, 1%, 1/16 W 2 M, 1%, 1/16 W 0.47 F, 20%, 10 V 100 k, 20%, 1/16 W 82.5 k, 1%, 1/16 W Function Sets loop closure (off-hook) threshold. Ringing source series resistor. With CRTS2, forms first pole of a double pole, 2 Hz ring trip sense filter. With RTSN, RTSP, forms second 2 Hz filter pole. With RTS2, forms first 2 Hz filter pole. With CRTS1, RTSP, forms second 2 Hz filter pole. With CRTS1, RTSN, forms second 2 Hz filter pole. Provides 60 Hz filtering for ring ground detection. Digital output pull-up resistor. Sets ring ground detection threshold. Design Considerations Table 11 shows the design parameters of the application circuit shown in Figure 11. Components that are adjusted to program these values are also shown. Table 11. 600 Design Parameters Design Parameter Loop Closure Threshold dc Loop Current Limit dc Feed Resistance 2-wire Signal Overload Level ac Termination Impedance Hybrid Balance Line Impedance Transmit Gain Receive Gain Parameter Value 10 mA 40 mA 180 3.14 dBm 600 600 0 dB 0 dB Components Adjusted RLCTH RPROG RPT, RPR -- RT1, RGP, RRCV RHB1 RT2, RX RRCV, RGP, RT1 16 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Applications (continued) 0 Characteristic Curves -10 -20 PSRR (dB) -30 -40 -50 CURRENT LIMIT BELOW CURRENT LIMIT SPEC. 0 RECEIVE GAIN -10 -60 -20 (dB) -70 -80 10 HYBRID BALANCE 100 1000 104 105 106 -30 FREQUENCY (Hz) 12-2830.a (F) -40 -50 100 1000 104 105 Figure 15. Typical VCC Power Supply Rejection FREQUENCY (Hz) 12-2828.c (F) Figure 13. Receive Gain and Hybrid Balance vs. Frequency 0 -10 -20 PSRR (dB) -30 -40 SPECIFICATION RANGE CURRENT LIMIT 0 TRANSMIT GAIN -10 -50 -60 -70 BELOW CURRENT LIMIT -20 (dB) -30 RETURN LOSS -40 -50 100 -80 10 100 1000 104 105 106 FREQUENCY (Hz) 12-2871.a (F) Figure 16. Typical VBAT Power Supply Rejection 1000 10 4 10 5 FREQUENCY (Hz) 12-2829.b (F) Figure 14. Transmit Gain and Return Loss vs. Frequency Lucent Technologies Inc. 17 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Applications (continued) 50 Characteristic Curves (continued) 40 OFF-HOOK THRESHOLD LOOP CURRENT (mA) 25 LOOP CURRENT (mA) 30 1 10 k L7556 BS = 0 20 BS = 1, L7557 BS = 0 ILIM 20 15 -1 Rdc1 10 10 0 0 5 Notes: VBAT1 = -48 V. VBAT2 = -28 V. LOOP CLOSURE THRESHOLD RESISTOR, RLCTH (k) 12-3015 (F) 10 20 30 40 50 LOOP VOLTAGE (V) 12-3050.a(F) 0 0 10 20 30 40 50 60 ILIM = 22 mA. Rdc1 = 115 . Note: VBAT = -48 V. Figure 19. Loop Current vs. Loop Voltage Figure 17. Loop Closure Program Resistor Selection 50 THRESHOLD RING GROUND CURRENT (mA) 35 30 25 20 15 10 5 0 0 50 100 150 200 250 Notes: VBAT1 = -48 V. 12-3016a (F) LOOP CURRENT (mA) 40 30 BS = 1, L7557 BS = 0 L7556 BS = 0 20 10 0 0 500 1000 1500 2000 LOOP RESISTANCE, RLOOP (W) 12-3051.a(F) RING GROUND CURRENT DETECTION RESISTOR, RICM (k) Notes: Tip lead is open. VBAT = -48 V. VBAT2 = -28 V. ILIM = 22 mA. Rdc1 = 115 . Figure 18. Ring Ground Detection Programming Figure 20. Loop Current vs. Loop Resistance 18 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Applications (continued) Characteristic Curves (continued) PROTECTION RESISTOR MISMATCH (%) 8 7 6 5 4 3 2 1 0 0 L7556 BS = 0 20 40 60 80 100 120 PROTECTION RESISTOR VALUE () 12-2559.b (F) 49 dB, RP MATCHED TO 1.5 1500 SLIC POWER DISSIPATION (mW) BS = 1 1000 58 dB, RP MATCHED TO 0.5 L7557 BS = 0 500 0 0 500 1000 1500 2000 LOOP RESISTANCE, RLOOP (W) 12-3052.a (F) Figure 23. Longitudinal Balance Resistor Mismatch Requirements Notes: VBAT1 = -48 V. VBAT2 = -28 V. ILIM = 22 mA. Rdc1 = 115 . LONGITUDINAL BALANCE (dB) 60 55 Figure 21. Typical SLIC Power Dissipation vs. Loop Resistance 50 45 2000 40 0.0 1500 POWER (mW) 0.5 1.0 1.5 2.0 2.5 PROTECTION RESISTOR MISMATCH () 12-3021 (F) 1000 60 C/W Figure 24. Longitudinal Balance vs. Protection Resistor Mismatch 500 0 20 40 60 80 100 120 140 160 180 AMBIENT TEMPERATURE, TA (C) 12-2825.c (F) Figure 22. Power Derating Lucent Technologies Inc. 19 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Region 1; On-hook and low loop currents. The slope corresponds to the dc resistance of the SLIC, RDC1 (default is 115 typical). The open circuit voltage is the battery voltage less the overhead voltage of the device, VOH (default is 7.9 V typical). These values are suitable for most applications, but can be adjusted if needed. For more information, see the sections entitled Adjusting dc Feed Resistance or Adjusting Overhead Voltage. Region 2; Current limit. The dc current is limited to a value determined by external resistor RPROG. This region of the dc template has a high resistance (10 k). Calculate the external resistor as follows: RPROG (k) = 1.67 ILIM (mA) Switching the Battery The L7556 and L7557 SLICs provide an input for an auxiliary battery. Called VBAT2, this power supply should be lower in magnitude than the primary battery, VBAT1. Under an acceptable loop condition, VBAT2 can be switched to provide the loop power through the output amplifiers of the SLIC. The dc template, described in the last section, is determined by the battery that is activated--either VBAT1 or VBAT2. Which device will be best for you? That mainly depends on your loop range requirements. If you have only short loops and no on-hook voltage requirements, you don't need a battery switch at all. Use the L7551 instead. If you have only to guarantee a short loop range, e.g., 22 mA into 530 , consider the L7556. The minimum VBAT2 can be determined by the standard dc equations. In these applications, the off-hook detector can be used to indicate when to switch the battery. Just make sure the off-hook detector will also function as required with VBAT2 as well as VBAT1. Consider an off-hook threshold of 10 mA. This could represent a 1000 loop with a 48 V VBAT1 active or a 2000 loop with a 28 V VBAT2 active. In this case, if the loop is below 1000 or above 2000 , off-hook detection will be accurate. Between 1000 and 2000 , the detector is battery-dependent. This condition must be avoided. In our example, since the maximum loop is 530 , the 10 mA detector is perfectly acceptable. If the PTT would like a short loop system that can also serve long loops, the off-hook detector is not the best indicator, and better loop intelligence is needed. In this case, the L7557 can be used. It has an internal comparator that senses when there is enough potential at VBAT2 to switch without affecting the loop current. In this case, the loop range is determined by VBAT1, and VBAT2 is only switched in when the loop is short enough to use it. This switching is automatic and includes hysteresis to avoid oscillation when the loop length is close to the VBAT2 switch threshold. Lucent Technologies Inc. Applications (continued) dc Applications Battery Feed The dc feed characteristic can be described by: VBAT - VOH IL = --------------------------------RL + 2RP + Rdc VT R = ( VBAT - VOH ) x RL ------------------------------------------RL + 2RP + Rdc where: IL = dc loop current. VT/R = dc loop voltage. |VBAT| = battery voltage magnitude applied to the power amplifier stage (VBAT1 or VBAT2). VOH = overhead voltage. This is the difference between the battery voltage and the open loop tip/ring voltage. RL = loop resistance, not including protection resistors. RP = protection resistor value. Rdc = SLIC internal dc feed resistance. The design begins by drawing the desired dc template. An example is shown in Figure 25. 50 40 LOOP CURRENT (mA) 30 1 10 k ILIM 20 -1 Rdc1 10 0 0 10 20 30 40 50 LOOP VOLTAGE (V) 12-3050.f (F) Notes: VBAT1 = -48 V. VBAT2 = -28 V. ILIM = 22 mA. Rdc1 = 115 . Figure 25. Loop Current vs. Loop Voltage Starting from the on-hook condition and going through to a short circuit, the curve passes through two regions: 20 Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch 2 ( RP + 40 ) = VSAT + 1 + ----------------------------- VT R - ZT R Applications (continued) dc Applications (continued) Overhead Voltage In order to drive an on-hook ac signal, the SLIC must set up the tip and ring voltage to a value less than the battery voltage. The amount that the open loop voltage is decreased relative to the battery is referred to as the overhead voltage. Expressed as an equation: VOH = VOH where VSAT is the combined internal saturation voltage between the tip/ring amplifiers and VBAT (5.4 V typ.). RP () is the protection resistor value, and 40 is the output series resistance of each internal amplifier. ZT/R () is the ac loop impedance. Example 1, on-hook transmission of a meter pulse: Signal level: 2.2 Vrms into 200 35 protection resistors ILOOP = 0 (on-hook transmission of the metering signal) 2 ( 35 + 40 ) VOH = 5.4 + 1 + ----------------------------- 2 (2.2) = 10.8 V 200 Accounting for VSAT tolerance of 0.5 V, a nominal overhead of 11.3 V would ensure transmission of an undistorted 2.2 V metering signal. Adjusting Overhead Voltage To adjust the open loop 2-wire voltage, pin DCR is programmed at the midpoint of a resistive divider from ground to either -5 V or VBAT. In the case of -5 V, the overhead voltage will be independent of the battery voltage. Figure 27 shows the equivalent input circuit to adjust the overhead voltage. |VBAT| - (VPT - VPR) Without this buffer voltage, amplifier saturation will occur and the signal will be clipped. The device is automatically set at the factory to allow undistorted on-hook transmission of a 3.17 dBm signal into a 900 loop impedance. For applications where higher signal levels are needed, e.g., periodic pulse metering, the 2-wire port of the SLIC can be programmed with pin DCR. The drive amplifiers are capable of 4 Vrms minimum (VAMP). Referring to Figure 26, the internal resistance has a worst-case value of 46 . So, the maximum signal the device can guarantee is: ZT/R VT R = 4 V ---------------------------------------- ZT/R + 2 ( RP + 46- ) Thus, RP 35 allows 2.2 Vrms metering signals. The next step is to determine the amount of overhead voltage needed. The peak voltage at output of tip and ring amplifiers is related to the peak signal voltage by: 2 ( RP + 40 ) Vamp = VT/R 1 + ----------------------------- ZT R R1 25 k 30% DCR R2 -5 V RP VT/R + [ZT/R] - RP 40 + VAMP 40 - 12-2562 (F) Figure 27. Equivalent Circuit for Adjusting the Overhead Voltage The overhead voltage is programmed by using the following equation: VOH = 7.9 - 4 VDCR R1 || 25 k = 7.9 - 4 - 5 x ------------------------------------- R2 + R1 || 25 k- 12-2560.e (F) Figure 26. SLIC 2-Wire Output Stage In addition to the required peak signal level, the SLIC needs about 2 V from each power supply to bias the amplifier circuitry. It can be thought of as an internal saturation voltage. Combining the saturation voltage and the peak signal level, the required overhead can be expressed as: R1 || 25 k = 7.9 + 20 ------------------------------------- R2 + R1 || 25 k- Lucent Technologies Inc. 21 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 This is an equivalent circuit for adjusting both the dc feed resistance and overhead voltage together. The adjustments can be made by a simple superposition of the overhead and dc feed equations: R1 || 25 k || R3 VOH = 7.9 + 20 --------------------------------------------- R2 + R1 || 25 k || R3 R1 || 25 k = 115 + 500 ------------------------------------- R2 + R1 || 25 k- Applications (continued) dc Applications (continued) Adjusting dc Feed Resistance The dc feed resistance may be adjusted with the help of Figure 28. R1 DCR R3 25 k 30% RDC DCOUT 12-2560 (F) Figure 28. Equivalent Circuit for Adjusting the dc Feed Resistance When selecting external components, select R1 on the order of 5 k to minimize the programming inaccuracy caused by the internal 25 k resistor. Lower values can be used; the only disadvantage is the power consumption of the external resistors. Loop Range The equation below can be rearranged to provide the loop range for a required loop current: VDCR Rdc = 115 + 500 -------------------VDCOUT R1 || 25 k = 115 + 500 --------------------------------- R3 + R1 || 25 k The above paragraphs describe the independent setting of the overhead voltage and the dc feed resistance. If both need to be set to customized values, combine the two circuits as shown in Figure 29. RL = --------------------------- - 2RP - Rdc - VBAT - VOH IL Off-Hook Detection The loop closure comparator has built-in longitudinal rejection, eliminating the need for an external 60 Hz filter. The loop closure detection threshold is set by resistor RLCTH. Referring to Figure 30, NLC is high in an on-hook condition (ITR = 0, VDCOUT = 0) and VLCTH = 0.05 mA x RLCTH. The off-hook comparator goes low when VLCTH crosses zero and then goes negative: VLCTH = 0.05 mA x RLCTH + VDCOUT = 0.05 mA x RLCTH - 0.125 V/mA x ITR RLTCH (k) = 2.5 x ITR (mA) R1 25 k 30% DCR R2 -5 V R3 DCOUT 12-2561 (C) Figure 29. Adjusting Both Overhead Voltage and dc Feed Resistance RP RL ITR TIP + - RING 0.125 V/mA DCOUT RLCTH 0.05 mA + - LCTH NLC 12-2553g(F) RP Figure 30. Off-Hook Detection Circuit Applications 22 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch The following example illustrates how the detection circuit of Figure 31 will trip at 12.5 mA dc loop current using a -48 V battery. - 7 - ( - 48 ) IN = ----------------------------2.289 k = 17.9 A Applications (continued) dc Applications (continued) Ring Trip Detection The ring trip circuit is a comparator that has a special input section optimized for this application. The equivalent circuit is shown in Figure 31, along with its use in an application using unbalanced, battery-backed ringing. PHONE HOOK SWITCH RLOOP RC PHONE The current IN is repeated as IP in the positive comparator input. The voltage at comparator input RTSP is: VRTSP = VBAT + ILOOP ( dc ) x RTS1 + IP x RTSP Using this equation and the values in the example, the voltage at input RTSP is -12 V during ringing injection (ILOOP(dc) = 0). Input RTSP is therefore at a level of 5 V below RTSN. When enough dc loop current flows through RTS1 to raise its dc drop to 5 V, the comparator will trip. In this example, RTSP + IP = IN IN - RTSN 15 k + - NRDET RTSP 2 M RTS1 402 CRTS2 0.27 F RTS2 RTSN 274 k 2 M VRING VBAT CRTS1 0.022 F 7V 5V ILOOP(dc) = ----------------402 = 12.5 mA Ring Ground Detection Pin ICM sinks a current proportional to the longitudinal loop current. It is also connected to an internal comparator whose output is pin RGDET. In a ground start application where tip is open, the ring ground current is half differential and half common mode. In this case, to set the ring ground current threshold, connect a resistor RICM from pin ICM to VCC. Select the resistor according to the following relation: RICM ( k ) = VCC x 228 --------------------IRG ( mA ) 12-3014.f (F) Figure 31. Ring Trip Equivalent Circuit and Equivalent Application The comparator input voltage compliance is VCC to VBAT, and the maximum current is 240 A in either direction. Its application is straightforward. A resistance (RTSN + RTS2) in series with the RTSN input establishes a current which is repeated in the RTSP input. A slightly lower resistance (RTSP) is placed in series with the RTSP input. When ringing is being injected, no dc current flows through RTS1, and so the RTSP input is at a lower potential than RTSN. When enough dc loop current flows, the RTSP input voltage increases to trip the comparator. In Figure 31, a low-pass filter with a double pole at 2 Hz was implemented to prevent false ring trip. The above equation is shown graphically in Figure 18. It applies for the case of tip open. The more general equation can be used in ground key application to detect a common-mode current ICM: RICM ( k ) = VCC x 114 --------------------ICM ( mA ) Lucent Technologies Inc. 23 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Third-Generation Codecs This class of devices includes the gains, termination impedance, and hybrid balance--all under microprocessor control. Depending on the device, it may or may not include latches. Selection Criteria In the following examples, use of a first-generation codec is shown. The equations for second- and thirdgeneration codecs are simply subsets of these. There are two examples. The first shows the simplest circuit, which uses a minimum number of discrete components to synthesize a real termination impedance. The second example shows the use of the uncommitted op amp to synthesize a complex termination. The design has been automated in a DOS based program, available on request. In the codec selection, increasing software control and flexibility are traded for device cost. To help decide, it may be useful to consider the following. Will the application require only one value for each gain and impedance? Will the board be used in different countries with different requirements? Will several versions of the board be built? If so, will one version of the board be most of the production volume? Does the application need only real termination impedance? Does the hybrid balance need to be adjusted in the field? Applications (continued) ac Design There are four key ac design parameters. Termination impedance is the impedance looking into the 2-wire port of the line card. It is set to match the impedance of the telephone loop in order to minimize echo return to the telephone set. Transmit gain is measured from the 2-wire port to the PCM highway, while receive gain is done from the PCM highway to the transmit port. Finally, the hybrid balance network cancels the unwanted amount of the receive signal that appears at the transmit port. At this point in the design, the codec needs to be selected. The discrete network between the SLIC and the codec can then be designed. Here is a brief codec feature and selection summary. First-Generation Codecs These perform the basic filtering, A/D (transmit), D/A (receive), and -law/A-law companding. They all have an op amp in front of the A/D converter for transmit gain setting and hybrid balance (cancellation at the summing node). Depending on the type, some have differential analog input stages, differential analog output stages, and -law/A-law selectability. This generation of codecs has the lowest cost. They are most suitable for applications with fixed gains, termination impedance, and hybrid balance. Second-Generation Codecs This class of devices includes a microprocessor interface for software control of the gains and hybrid balance. The hybrid balance is included in the device. ac programmability adds application flexibility and saves several passive components and also adds several I/O latches that are needed in the application. However, it does not have the transmit op amp, since the transmit gain and hybrid balance are set internally. 24 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Applications (continued) ac Design (continued) Selection Criteria (continued) ac equivalent circuits using a T7513 Codec are shown in Figures 32 and 33. RX VGSX - + RP PT 40 AV = 1 VS + IT/R ZT VT/R - RP PR 40 AV = -1 SLIC T7513 CODEC 12-2554j (F) -0.125 V/mA VITR RT2 VFXIN VFXIP - + ZT/R - AV = 4 + RCVN RCVP RT1 RHB1 RRCV VFR (PWROP) RG Figure 32. ac Equivalent Circuit Not Including Spare Op Amp ZT5 RX VGSX - + RP PT 40 AV = 1 VS + IT/R ZT VT/R - RP PR 40 AV = -1 -0.125 V/mA VITR RT4 SN AGND RCVN RCVP - + XMT RT6 VFXIN VFXIP RT3 RHB1 RRCV RGN VFR (PWROP) - + ZT/R - AV = 4 + SLIC T7513 CODEC 12-3013b (F) Figure 33. ac Equivalent Circuit Including Spare Op Amp Lucent Technologies Inc. 25 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Example 2, Complex Termination: For complex termination, the spare op amp is used (see Figure 33). ZT5 1000 ZT = 2RP + 80 + ---------------------------------- ( --------- ) RT3 RT4 RT3 1 + -------- + ----------RGN RRCV = 2RP + 80 + k ( ZT5 ) 8 grcv = ---------------------------------------------------------------------------RRCV ZT 1 + RRCV + ------------- 1 + --------- ------------ RT3 RGN ZT/R Applications (continued) ac Design (continued) Selection Criteria (continued) Example 1, Real Termination: The following design equations refer to the circuit in Figure 32. Use these to synthesize real termination impedance. Termination Impedance: VT R ZT = -------------- IT R 1000 ZT = RP + 80 + ---------------------------------RT1 RT1 1 + -------- + ----------RGP RRCV Receive Gain: VT R grcv = ------------VFR 8 grcv = -----------------------------------------------------------------------------------ZT RRCV RRCV 1 + -------------- + -------------- 1 + ------------ RT1 RGP ZT/R Transmit Gain: VGSX gtx = -------------VT R - RX 125 gtx = ---------- x ------------RT2 ZT R -RX 125 ZT5 gtx = ---------- x --------- x --------RT6 ZT/R RT4 The hybrid balance equation is the same as in Example 1. PCB Layout Information Make the leads to BGND and VBAT as wide as possible for thermal and electrical reasons. Also, maximize the amount of PCB copper in the area of--and specifically on--the leads connected to this device for the lowest operating temperature. When powering the device, ensure that no external potential creates a voltage on any pin of the device that exceeds the device ratings. In this application, some of the conditions that cause such potentials during powerup are the following: 1) an inductor connected to PT and PR (this can force an overvoltage on VBAT through the protection devices if the VBAT connection chatters), and 2) inductance in the VBAT lead (this could resonate with the VBAT filter capacitor to cause a destructive overvoltage). This device is normally used on a circuit card that is subjected to hot plug-in, meaning the card is plugged into a biased backplane connector. In order to prevent damage to the IC, all ground connections must be applied before, and removed after, all other connections. Hybrid Balance: VGSX hbal = 20log -------------VFR To optimize the hybrid balance, the sum of the currents at the VFX input of the codec op amp should be set to 0. The following expressions assume the test network is the same as the termination impedance. RX hbal = 20log ----------- - gtx x grcv RHB RX RHB = -----------------------gtx x grcv 26 Lucent Technologies Inc. Data Sheet January 2000 L7556, L7557 Low-Power SLICs with Battery Switch Outline Diagram 32-Pin PLCC Dimensions are in millimeters. Note: The dimensions in this outline diagram are intended for informational purposes only. For detailed schematics to assist your design efforts, please contact your Lucent Technologies Sales Representative. 12.446 0.127 11.430 0.076 PIN #1 IDENTIFIER ZONE 1 30 4 5 29 13.970 0.076 14.986 0.127 13 21 14 20 3.175/3.556 SEATING PLANE 0.10 1.27 TYP 0.38 MIN TYP 0.330/0.533 5-3813F Lucent Technologies Inc. 27 L7556, L7557 Low-Power SLICs with Battery Switch Data Sheet January 2000 Ordering Information Device Part No. ATTL7556AAU ATTL7556AAU-TR ATTL7557AAU ATTL7557AAU-TR Description Low-Power SLIC with Battery Switch Low-Power SLIC with Battery Switch Low-Power SLIC with Battery Switch Low-Power SLIC with Battery Switch Package 32-Pin PLCC 32-Pin PLCC (Tape and Reel) 32-Pin PLCC 32-Pin PLCC (Tape and Reel) Comcode 107385668 107749509 107385841 107749517 For additional information, contact your Microelectronics Group Account Manager or the following: INTERNET: http://www.lucent.com/micro E-MAIL: docmaster@micro.lucent.com N. AMERICA: Microelectronics Group, Lucent Technologies Inc., 555 Union Boulevard, Room 30L-15P-BA, Allentown, PA 18103 1-800-372-2447, FAX 610-712-4106 (In CANADA: 1-800-553-2448, FAX 610-712-4106) ASIA PACIFIC: Microelectronics Group, Lucent Technologies Singapore Pte. Ltd., 77 Science Park Drive, #03-18 Cintech III, Singapore 118256 Tel. (65) 778 8833, FAX (65) 777 7495 CHINA: Microelectronics Group, Lucent Technologies (China) Co., Ltd., A-F2, 23/F, Zao Fong Universe Building, 1800 Zhong Shan Xi Road, Shanghai 200233 P. R. China Tel. (86) 21 6440 0468, ext. 316, FAX (86) 21 6440 0652 JAPAN: Microelectronics Group, Lucent Technologies Japan Ltd., 7-18, Higashi-Gotanda 2-chome, Shinagawa-ku, Tokyo 141, Japan Tel. (81) 3 5421 1600, FAX (81) 3 5421 1700 EUROPE: Data Requests: MICROELECTRONICS GROUP DATALINE: Tel. (44) 7000 582 368, FAX (44) 1189 328 148 Technical Inquiries: GERMANY: (49) 89 95086 0 (Munich), UNITED KINGDOM: (44) 1344 865 900 (Ascot), FRANCE: (33) 1 40 83 68 00 (Paris), SWEDEN: (46) 8 594 607 00 (Stockholm), FINLAND: (358) 9 4354 2800 (Helsinki), ITALY: (39) 02 6608131 (Milan), SPAIN: (34) 1 807 1441 (Madrid) Lucent Technologies Inc. reserves the right to make changes to the product(s) or information contained herein without notice. No liability is assumed as a result of their use or application. No rights under any patent accompany the sale of any such product(s) or information. Copyright (c) 2000 Lucent Technologies Inc. All Rights Reserved January 2000 DS00-060ALC (Replaces DS97-172ALC) |
Price & Availability of ATTL7556AAU
 |
|
|
|
|
All Rights Reserved © IC-ON-LINE 2003 - 2022 |
| [Add Bookmark] [Contact Us] [Link exchange] [Privacy policy] |
|
Mirror Sites : [www.datasheet.hk]
[www.maxim4u.com] [www.ic-on-line.cn]
[www.ic-on-line.com] [www.ic-on-line.net]
[www.alldatasheet.com.cn]
[www.gdcy.com]
[www.gdcy.net] |