# US 8,787,559 B2 · Codec circuit for POTS system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,559 B2 - Document ID: US8787559B2 - Status: Granted - Kind: B2 - Application number: 13/406,567 - Filed: 2012-02-28 - Published: 2012-06-21 - Granted: 2014-07-22 - Earliest claimed: 2007-01-15 - Assignees: Lantiq Deutschland GmbH - Applicants: Christian Jenkner; Gerhard Noessing; Richard Gaggl; Joachim Pichler - Inventors: Christian Jenkner; Gerhard Noessing; Richard Gaggl; Joachim Pichler - Web page: https://patentgrep.com/patent/US8787559B2 ## CPC - H04M 9/00: Arrangements for interconnection not involving centralised switching - A61F 7/12: Devices for heating or cooling internal body cavities - A61F 2007/126: {for invasive application, e.g. for introducing into blood vessels} - H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08) - A61F: FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS (dental prosthetics A61C) ## Abstract A CODEC circuit for POTS system comprises a digital circuit for outputting a digital control signal having a first bit width, the digital control signal being indicative of a voltage to be applied to a POTS subscriber line pair. Further, the CODEC comprises a noise shaper coupled to an output of the digital circuit for generating a noise-shaped control signal and a digital-to-analog converter coupled to an output of the noise shaper, the input of the digital-to-analog converter having a second bit width being larger than 1 and smaller than the first bit width. ## Claims ### Claim 1 An apparatus that drives a subscriber line pair to a target DC line current, the apparatus comprising: a current detector that senses an actual DC line current on the subscriber line pair; a feedback loop that feeds back a control variable of the current based on the sensed actual DC line current; a noise shaper that shapes a control signal based on the control variable such that a quantizer error of the control signal is minimized; a generator that generates a DC line current to drive the subscriber line pair; and a controller that adjusts the control variable such that the actual DC line current is adjusted to be equal to the target DC line current. ### Claim 2 (depends on 1) The apparatus according to claim 1, wherein the noise shaper is configured to reduce the bit width of the sensed actual DC line current. ### Claim 3 (depends on 1) The apparatus according to claim 1, wherein the noise shaper is configured to be switched off during operation of the apparatus. ### Claim 4 (depends on 1) The apparatus according to claim 1, further comprising an oversampling circuit coupled to the output of the current detector. ### Claim 5 (depends on 4) The apparatus according to claim 4, wherein the oversampling circuit comprises: a first interpolation circuit configured to enhance a first sampling rate at an input of the oversampling circuit to an intermediate sampling rate. ### Claim 6 (depends on 5) The apparatus according to claim 5, wherein the oversampling circuit comprises: a second interpolation circuit configured to enhance the intermediate sampling rate to a second sampling rate at an output of the oversampling circuit. ### Claim 7 (depends on 6) The apparatus according to claim 6, wherein the second sampling rate is of the order of 1 MHz. ### Claim 8 (depends on 5) The apparatus according to claim 5, wherein the first sampling rate is of the order of 1 to 10 kHz. ### Claim 9 (depends on 5) The apparatus according to claim 5, wherein the intermediate sampling rate is of the order of 500 kHz. ### Claim 10 (depends on 4) The apparatus according to claim 4, wherein the oversampling circuit comprises a low pass filter for suppressing mirror frequencies. ### Claim 11 (depends on 1) The apparatus according to claim 1, further comprising a circuit that monitors a quantity indicative of a transient response of the digital control signal. ### Claim 12 (depends on 1) The apparatus according to claim 1, further comprising a disable circuit that disables the noise shaper if the quantity indicative of a transient response of the digital control signal is smaller than a threshold. ### Claim 13 (depends on 1) The apparatus according to claim 1, further comprising: a digital-to-analog converter; and a low pass filter that filters a signal converted by the digital-to-analog converter. ### Claim 14 (depends on 13) The apparatus according to claim 13, wherein a cut-off frequency of the low pass filter is higher than 100 Hz. ### Claim 15 (depends on 13) The apparatus according to claim 13, wherein a cut-off frequency of the low pass filter is higher than 500 Hz. ### Claim 16 (depends on 13) The apparatus according to claim 13, wherein a cut-off frequency of the low pass filter is about or higher than 1000 Hz. ### Claim 17 (depends on 13) The apparatus according to claim 13, wherein an output is electrically connected to a node located between the output of the digital-to-analog converter and the input of the low pass filter. ### Claim 18 (depends on 1) The apparatus according to claim 1, wherein the control signal is configured to drive an external power supply of a Subscriber Line Interface Circuit (SLIC). ### Claim 19 (depends on 1) The apparatus according to claim 1, wherein the actual DC line current represents voice data. ### Claim 20 (depends on 1) The apparatus according to claim 1, wherein the noise shaper is incorporated into a CODEC that receives voice data. ### Claim 21 A method for driving a subscriber line pair to a target DC line current, the method comprising the steps of: sensing an actual DC line current on the subscriber line pair; feeding back a control variable of the current based on the sensed actual DC line current; noise shaping a control signal based on the control variable such that a quantizer error of the control signal is minimized; generating a DC line current to drive the subscriber line pair; and controlling the control variable such that the actual DC line current is adjusted to be equal to the target DC line current. ### Claim 22 (depends on 21) The method according to claim 21 wherein the noise shaping step reduces the bit width of the sensed actual DC line current. ### Claim 23 (depends on 21) The method according to claim 21, wherein the noise shaping is switched off during normal operation. ### Claim 24 (depends on 21) The method according to claim 21, further comprising the step of oversampling the output of the current detector. ### Claim 25 (depends on 24) The method according to claim 24, wherein the oversampling comprises: a first interpolation configured to enhance a first sampling rate at an input of the oversampling circuit to an intermediate sampling rate. ### Claim 26 (depends on 25) The method according to claim 25, wherein the oversampling circuit comprises: a second interpolation circuit configured to enhance the intermediate sampling rate to a second sampling rate at an output of the oversampling circuit. ### Claim 27 (depends on 26) The method according to claim 26, wherein the oversampling circuit comprises a low pass filter for suppressing mirror frequencies. ### Claim 28 (depends on 26) The method according to claim 26, wherein the second sampling rate is of the order of 1 MHz. ### Claim 29 (depends on 25) The method according to claim 25, wherein the first sampling rate is of the order of 1 to 10 kHz. ### Claim 30 (depends on 25) The method according to claim 25, wherein the intermediate sampling rate is of the order of 500 kHz. ### Claim 31 (depends on 21) The method according to claim 21, further comprising the step of monitoring a quantity indicative of a transient response of the digital control signal. ### Claim 32 (depends on 21) The method according to claim 21, further comprising the step of disabling noise shaping if the quantity indicative of a transient response of the digital control signal is smaller than a threshold. ### Claim 33 (depends on 21) The method according to claim 21, further comprising the steps of: digital-to-analog converting the control variable; and low pass filtering a signal converted by the digital-to-analog converter. ### Claim 34 (depends on 33) The method according to claim 33, wherein a cut-off frequency of the low pass filtering is higher than 100 Hz. ### Claim 35 (depends on 33) The method according to claim 33, wherein a cut-off frequency of the low pass filtering is higher than 500 Hz. ### Claim 36 (depends on 33) The method according to claim 33, wherein a cut-off frequency of the low pass filtering is about or higher than 1000 Hz. ### Claim 37 (depends on 21) The method according to claim 21, wherein the control signal is configured to drive an external power supply of a Subscriber Line Interface Circuit (SLIC). ### Claim 38 (depends on 21) The method according to claim 21, wherein the actual DC line current represents voice data. ### Claim 39 (depends on 21) The method according to claim 21, wherein the noise shaping reduces the bit width of the sensed actual DC line current.