Application Note December 2001 AN9947.1 Author: LaFontaine R
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HC55185 IDT821068 Programmable Octal CODEC
Application Note December 2001 AN9947.1
Author: LaFontaine
Reference Design using HC55185 IDT821068 Programmable Octal CODEC
purpose this application note provide reference design HC55185 IDT821068 Programmable Octal CODEC. network requirements many countries require analog subscriber line circuit (SLIC) terminate subscriber line with impedance voiceband frequencies which complex, rather than resistive (e.g. 600). HC55185 accomplishes this impedance matching with single network connected between pin. IDT821068 Octal CODEC uses integrated programmable realize Impedance Matching, Transhybrid Balance, Frequency Response Correction Gain Setting functions. Discussed this application note following: 2-wire impedance matching Receive gain (4-wire 2-wire) transmit gain (2-wire 4-wire) calculations Reference design both +680||0.1µF (China Complex Impedance)
impedance. formula program HC55185 match 2-wire impedance shown Equation
133.3 133.3 (EQ.
value with protection resistors 66.9k. closest standard value 66.5k.
SLIC Active Mode
Figure shows simplified transmission model HC55185 connection IDT821068 SLIC. Circuit analysis HC55185 yields following design equations: Sense Amplifier configured input differential amplifier with gain 3/4. voltage output sense amplifier (VSA) calculated using superposition. VSA1 voltage resulting from VSA2 voltage resulting from (reference Figure
(EQ. (EQ. (EQ. (EQ. (EQ.
Impedance Matching
Impedance matching HC55185 subscriber load important optimization 2-wire return loss, which turn cuts down echoes voice communication path. Impedance matching HC55185 accomplished making SLIC's impedance (ZO, Figure equal desired terminating impedance minus value protection resistors (RP). With HC55185 programmed match 600, IDT821068 uses integrated programmable realize
RING INTERSIL HC55185
Where equal IMRSENSE (RSENSE
(EQ.
voltage equal
(EQ.
defined Figure note polarity assigned VTR:
0.47µF
(EQ.
0.47µF RESISTIVE 66.5k 133.3(600 2*49) 66.9k VALUE 66.5k
4.7µF
FIGURE IMPEDANCE MATCHING
1-888-INTERSIL 321-724-7143
Intersil (and design) trademark Intersil Americas Inc. Copyright Intersil Americas Inc. 2001. Rights Reserved
Application Note 9947
Setting equal zero, substituting Equation into Equation defining -VTR/IM will enable user determine require feedback match line impedance V2W.
133.33 (EQ.
(EQ.
Loop Equation Tip/Ring interface
(EQ.
Substitute Equation into Equation combine terms source impedance device defined 2Rp. line impedance. defined
133.33 Node Equation HC55185 input (EQ. (EQ. (EQ.
where: input voltage pin. internal node voltage that function loop current output Sense Amplifier. Internal current SLIC that difference between input receive current feedback current. metallic current. protection resistor (typical 49.9). external resistor/network matching line impedance. ring voltage output pins SLIC.
(EQ.
Substitute Equation into Equation
Loop Equation HC55185 feed amplifiers load (EQ. (EQ.
Substitute Equation into Equation
ring voltage including voltage across protection resistors. line impedance. source impedance device.
Substitute Equation -V2w/ZL into Equation
RSENSE
INTERSIL HC55185 RECEIVE BLOCK VOUT1 VIN1
IDT821068 CHANNEL FILTER FILTER CHANNEL CHANNEL
RING
FEED AMPLIFIER
DR1/DD FEED AMPLIFIER FEEDBACK AMPLIFIER IM30 SENSE AMPLIFIER CHANNEL CHANNEL CHANNEL CHANNEL CHANNEL CORE PCM/GCI INTERFACE DX1/DU
RSENSE
FIGURE HC55185 SIMPLIFIED TRANSMISSION CIRCUIT IDT821068
Application Note 9947 HC55185 Receive Gain (VRX V2W)
4-wire 2-wire gain across HC55185 equal divided input voltage VRX, reference Figure receive gain calculated using Equation Equation expresses receive gain (VRX V2W) terms network impedances. From Equation value match line impedance (ZL) HC55185 plus protection resistors RP). This results 4-wire 2-wire gain shown Equation
(EQ.
Substituting Equation into Equation defining -V2W/ZL results Equation VTX.
(EQ.
Combining Equations results Equation
(EQ.
more useful form equation rewritten terms /V2W. voltage divider equation written convert from shown Equation
(EQ.
Receive Gain Across System
receive gain across system defined gain from highway phone (V2W). With receive gain through HC55185 receive gain across system entirely controlled programming IDT821068. IDT821068 program receive gain across system ways (reference Figure first programming signal gain analog form. analog receive gain, also known Digital Analog (D/A) gain, programmed IDT821068 either -6dB. second programming signal gain (via. coefficients) when digital form. digital form receive path programmed from -12dB with minimum 0.1dB steps. This results possible receive gain (D/A) programming range from +6dB -18dB. Note: Analog gain brings less noise than digital gain. When allocating CODEC gain, majority required gain should preformed analog stage. Reference section titled "Information Required Calculate IDT821068 CODEC Coefficients" information obtaining coefficients your design.
Substituting rearranging Equation terms results Equation
2V2W (EQ.
Substituting Equation into Equation results equation 2-wire 4-wire gain that's function synthesized input impedance SLIC protection resistors.
0.416 (EQ.
600, programmed with 498.76 (66.5k/133.33), equal 49.9. This results 2-wire 4-wire gain 0.416 -7.6dB.
Transmit Gain Across System
transmit gain across system defined gain from phone 2-wire side (V2W) highway. Setting gain IDT821068 will have account attenuated signal through HC55185. system gain entirely controlled programming IDT821068. IDT821068 program transmit gain across system ways (reference Figure first programming signal gain analog form. analog transmit gain, also known Analog Digital (A/D) gain, programmed IDT821068 either +6dB. second programming signal gain (via. coefficients) when digital form. digital form transmit path programmed from -6dB +12dB with minimum 0.1dB steps. This results possible transmit gain (A/D) programming range from -6dB +18dB. Note: Analog gain brings less noise than digital gain. When allocating CODEC gain, majority required gain should preformed analog stage. Reference section titled "Information Required Calculate IDT821068 CODEC Coefficients" information obtaining coefficients your design.
Transmit Gain Across HC55185 VTX)
2-wire 4-wire gain equal VTX/EG with reference Figure
Loop Equation (EQ.
From Equation with
(EQ.
Substituting Equation into Equation simplifying.
(EQ.
Application Note 9947
INTERSIL HC55185 4.7µF RING 0.47µF 0.47µF VIN1 ANALOG GAIN +6dB CHANNEL DIGITAL GAIN -6dB +12dB FILTER TRANSMIT PATH DR1/DD CORE PCM/GCI INTERFACE DX1/DU IDT821068 DIGITAL GAIN +6dB -12dB FILTER
CHANNEL VOUT1 ANALOG GAIN -6dB
RECEIVE PATH
CHANNEL
FIGURE RECEIVE GAIN G(4-2), TRANSMIT GAIN (2-4)
Transhybrid Balance G(4-4)
Transhybrid balance measure well input signal canceled (that being received SLIC) from transmit signal (that being transmitted from SLIC CODEC). Without this function, voice communication would difficult because echo. Transhybrid balancing filter inside IDT821068 used adjust transhybrid balance ensure echo cancellation meets ITU-T specifications. coefficient Echo Cancellation ECF.
Frequency Response Correction
filter receive path filter transmit path programmed correct frequency distortion caused impedance matching filters. coefficients Frequency Response Correction receive path transmit path.
FIGURE COEFFICIENT OPERATION SCREEN
Reference Design HC55185 IDT821068 With Load
design criteria follows: 4-wire 2-wire gain (DR1/DD V2W) equal 2-wire 4-wire gain (V2W DX1/DU) equal 49.9 Figure gives reference design using Intersil HC55185 IDT821068 Programmable Octal CODEC. Also shown Figure voltage levels specific points circuit.
Information Required Calculate IDT821068 CODEC Coefficients
calculate IDT821068 coefficient, customers should provide following information about their subscriber line card: Accurate SLIC PSPICE model. provided .lib file PSPICE schematic file. System Impedance Gain (Transmit path Receive path) Using coefficients provided IDT, overall performance system will pass ITU-T requirements. When button selected from Operation General Interface screen, Operation screen will appear (Figure From this screen, user configure coefficients current channel.
Impedance Matching
2-wire impedance matched line impedance using Equation repeated here Equation
133.3 (EQ.
line impedance 600, equals:
133.3 66.9k (EQ.
closest standard value would 66.5k.
Application Note 9947
G4-2
0dBm0(600) 0.7745VRMS 0dBm0(600) 0.7745VRMS 0dBm0(600) 0.7745VRMS 4.7µF -7.5769dBm0(600) 0.3239VRMS
G2-4
SYSTEM REQUIREMENTS: IMPEDANCE: TRANSMIT GAIN (A/D): RECEIVE GAIN (D/A):
0dBm0(600) 0.7745VRMS
INTERSIL HC55185 RING 0.47µF VIN1 VOUT1
CHANNEL ANALOG GAIN ANALOG GAIN CHANNEL
IDT821068 DIGITAL GAIN DIGITAL GAIN +1.6dB
RECEIVE PATH DR1/DD CORE PCM/GCI INTERFACE DX1/DU
TRANSMIT PATH
0.47µF 90.9k
CHANNEL
0dBm0(600) 0.7745VRMS
NOTE: Reference Table coefficients. FIGURE REFERENCE DESIGN HC55185 IDT821068 WITH LOAD IMPEDANCE
However, would very convenient cost effective system manufacturers only type line card meet different impedance requirements different gain requirements. programmability IDT821068 help system manufactures reach this goal. using different coefficients tweaking value this reference design meet both 680||0.1µF impedance requirements. obtain best results, should optimized value. experimental experience, recommended 90.9k With optimized value selected 90.9k coefficients different Transmit Gains (A/D) Receive Gains (with line impedance 600) given Tables Although impedance matching resistor (RS) HC55185 been changed, contribution from IDT821068 allows system still match load. With load matched, 2-wire 4-wire gain (Equation still equal -7.6dB.
Figure gives reference design using Intersil HC55185 IDT821068 Programmable Octal CODEC. Also shown Figure voltage levels specific points circuit. Note: transmit gain system (-2.19dB(811) -3.5dB(600)) explained following section.
Adjustment -3.5dBm0 Load Referenced
voltage equivalent 0dBm0 into (0dBm0(811)) calculated using Equation (811 impedance complex China load 1020Hz).
0dBm 0.90055V 0.001
(EQ.
gain referenced back 0dBm0(600) equal
0.90055V GAIN 1.309dB 0.7745V (EQ.
Specific Implementation China
design criteria China specific solution follows: Desired line circuit impedance 680//0.1µF Receive gain (V2W/(DR1/DD)) -3.5dB Transmit gain ((DX1/DU)/V2W) 0dBm0 defined into complex impedance 1020Hz 49.9
adjustment -3.5dBm0 load referenced
Adjustment 3.5dBm0 1.309dBm0 2.19 (EQ.
voltage load (referenced 600) given Equation
2.19 0.60196V (EQ. 0.001
Application Note 9947
G4-2
-2.19dBm0(600) 0.60196VRMS RING INTERSIL HC55185 0.47µF 90.9k -2.19dBm0(600) 0.60196VRMS 4.7µF
-2.19dBm0(600) 0.60196VRMS 0.47µF VIN1 VPWRO+ VOUT1
SYSTEM REQUIREMENTS: IMPEDANCE: 200+600||0.1µF TRANSMIT GAIN (A/D): RECEIVE GAIN (D/A): -3.5dB IDT821068 DIGITAL GAIN -2.19dB DIGITAL GAIN +1.6dB
0dBm0(600) 0.7745VRMS
CHANNEL ANALOG GAIN ANALOG GAIN +6dB CHANNEL
RECEIVE PATH
TRANSMIT PATH DR1/DD CORE PCM/GCI INTERFACE DX1/DU
CHANNEL
-9.3294dBm0(600) 0.26461RMS
G2-4
VPCMOUT -3.5dBm0(600) 0.51769VRMS
NOTE: Reference Table coefficients. FIGURE REFERENCE DESIGN HC55185 IDT821068 WITH CHINA COMPLEX LOAD IMPEDANCE
Impedance Matching
With optimized value selected 90.9k coefficients different Transmit Gains (A/D) Receive Gains (with line impedance 680||0.1µF) given Tables
TABLE COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (0dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
Application Note 9947
TABLE COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (0dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB) (Continued) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
TABLE COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (-3.5dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
Application Note 9947
TABLE COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (-3.5dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB) (Continued) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
Application Note 9947
TABLE COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (-7.0dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
Application Note 9947
TABLE COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (-7.0dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB) (Continued) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
TABLE 0.1µF COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (0dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB)) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
Application Note 9947
TABLE 0.1µF COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (0dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB)) (Continued) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
TABLE 0.1µF COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (-3.5dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB)) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
Application Note 9947
TABLE 0.1µF COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (-3.5dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB)) (Continued) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
Application Note 9947
TABLE 0.1µF COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (-7.0dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
Application Note 9947
TABLE 0.1µF COEFFICIENTS, SYSTEM GAINS: (TRANSMIT GAIN (0dB), RECEIVE GAIN (-7.0dB)), CODEC ANALOG GAINS: (TRANSMIT PATH +6dB, RECEIVE PATH 0dB) (Continued) COEFFICIENT IMF: ECF: ACT: ACR: CHANNEL
COEFFICIENT IMF: ECF: ACT: ACR:
CHANNEL
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