# US 2019/0173381 A1 · Current sensing with rdson correction > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0173381 A1 - Document ID: US20190173381A1 - Status: Published application - Kind: A1 - Application number: 16/270,499 - Filed: 2019-02-07 - Published: 2019-06-06 - Earliest claimed: 2014-08-27 - Applicants: Renesas Electronics America Inc. - Inventors: Robert H. ISHAM; Thomas HAYES; Andrew L. Webb; Julio REYES - Web page: https://patentgrep.com/patent/US20190173381A1 ## CPC - H02M 3/158: including plural semiconductor devices as final control devices for a single load - G01K 13/00: Thermometers specially adapted for specific purposes - G01R 19/0092: {Measuring current only} - H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators - G01R 35/005: {Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence)} - H02M 1/0009: {Devices or circuits for detecting current in a converter} - H02M 1/32: Means for protecting converters other than automatic disconnection - H02M 3/157: with digital control - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract Current sensing with RDSON correction is disclosed. In an embodiment, a method comprises: measuring an approximate temperature of a MOS transistor switch by a temperature sensor to yield a measured temperature; calculating a corrected temperature from the measured temperature using a stored temperature sensor gain and offset correction function; measuring a gate drive voltage for the MOS transistor; calculating a voltage correction factor using a stored voltage correction function, wherein the stored voltage correction function is a function of the corrected temperature and the gate drive voltage; measuring a RDSON voltage drop across the MOS transistor switch to yield a measured RDSON voltage drop; and calculating the current using the measured RDSON drop and the voltage correction factor. ## Claims ### Claim 1 A method for operating a MOS transistor switch comprising: calculating a voltage correction factor as a function of a gate drive voltage of the MOS transistor switch; measuring a RDSON voltage drop across the MOS transistor switch to yield a measured RDSON voltage drop; and calculating a current of the MOS transistor switch using the measured RDSON voltage drop and the voltage correction factor. ### Claim 2 (depends on 1) The method of claim 1, further comprising: measuring an approximate temperature of a MOS transistor switch by a temperature sensor to yield a measured temperature; calculating a corrected temperature from the measured temperature using a stored temperature sensor gain and offset correction function; and measuring the gate drive voltage for the MOS transistor, wherein the stored voltage correction function is a further function of the corrected temperature. ### Claim 3 (depends on 2) The method of claim 2, wherein the stored temperature sensor gain and offset correction function are determined using a regression fit function during a calibration process. ### Claim 4 (depends on 3) The method of claim 3, wherein the regression fit function is a linear regression fit function. ### Claim 5 (depends on 1) The method of claim 1, wherein calculating the current comprises multiplying the measured RDSON voltage drop by the voltage correction factor to yield a corrected RDSON voltage drop and calculating the current from the corrected RDSON voltage drop using Ohm's Law. ### Claim 6 (depends on 1) The method of claim 1, wherein the stored voltage correction function is determined using a regression fit function during a calibration process. ### Claim 7 (depends on 6) The method of claim 6, wherein the regression fit function is a linear regression fit function. ### Claim 8 A current sensor comprising: a processing device; an on-chip temperature sensor, coupled to provide a measured temperature signal of a MOS transistor switch to the processing device; a memory device coupled to the processing device and configured to store a temperature sensor gain and offset correction function and a voltage correction function; and wherein the processing device is configured to: receive a gate drive voltage for the MOS transistor switch; receive the measured temperature signal and calculate a corrected temperature from the measured temperature signal using the stored temperature sensor gain and offset correction function; instruct at least one circuit element to multiply a measured RDSON voltage drop by a voltage correction factor to yield a corrected RDSON voltage drop, wherein the voltage correction factor is determined using the stored voltage correction function; and calculate a current of the MOS transistor switch from the corrected RDSON voltage drop for use by a voltage regulator to regulate a voltage signal. ### Claim 9 (depends on 8) The current sensor of claim 8, wherein the at least one circuit element is configured to measure the RDSON voltage drop across the MOS transistor switch to yield the measured RDSON voltage drop. ### Claim 10 (depends on 8) The current sensor of claim 8, wherein the processing device is configured to calculate the corrected temperature from the measured temperature signal by multiplying the measured temperature signal by a temperature gain factor to yield a product and adding a temperature offset factor to the product to yield the corrected temperature, wherein the temperature gain factor is determined using the stored temperature sensor gain and offset correction function and the measured temperature. ### Claim 11 (depends on 8) The current sensor of claim 8, wherein the processing device is configured to calculate the corrected temperature from the measured temperature signal by adding a temperature offset factor to the measured temperature to yield a sum and multiplying the sum by a temperature gain factor to yield the corrected temperature, wherein the temperature gain factor and the temperature offset factor are determined using the stored temperature sensor gain and offset correction function and the measured temperature. ### Claim 12 (depends on 8) The current sensor of claim 8, wherein the at least one circuit element comprises single variable gain amplifier. ### Claim 13 (depends on 8) The current sensor of claim 8, wherein the at least one circuit element comprises: a gain amplifier coupled to the MOS transistor switch and configured to measure the RDSON voltage drop across the MOS transistor switch; and an attenuating digital-to-analog converter coupled to the gain amplifier and the processing device, wherein the attenuating digital-to analog converter is configured to attenuate the output of the gain amplifier to yield the corrected RDSON voltage drop, as instructed by the processing device. ### Claim 14 (depends on 13) The current sensor of claim 13, further comprising a buffer, coupled to the attenuating digital-to-analog converter, and configured to buffer the corrected RDSON voltage drop. ### Claim 15 (depends on 8) The current sensor of claim 8, wherein the current sensor is included in the voltage regulator. ### Claim 16 A system comprising: a power source configured to provide a voltage signal; a voltage regulator configured to regulate the voltage signal from the power source and produce an output voltage signal, wherein the voltage regulator includes a MOS transistor switch used in producing the output voltage signal, and wherein the voltage regulator includes a calibrated current sensor used to sense current though the MOS transistor switch, wherein the calibrated current sensor comprises: a processing device; an on-chip temperature sensor, coupled to provide a measured temperature signal of a MOS transistor switch to the processing device; a memory device coupled to the processing device and configured to store a temperature sensor gain and offset correction function and a voltage correction function; and wherein the processing device is configured to: receive a gate drive voltage for the MOS transistor switch; receive the measured temperature signal and calculate a corrected temperature from the measured temperature signal using the stored temperature sensor gain and offset correction function; instruct at least one circuit element to multiply a measured RDSON voltage drop by a voltage correction factor to yield a corrected RDSON voltage drop, wherein the voltage correction factor is determined using the stored voltage correction function; and calculate a current of the MOS transistor switch from the corrected RDSON voltage drop for use by a voltage regulator to regulate a voltage signal.