# US 10,481,624 B2 · Bandgap reference circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,481,624 B2 - Document ID: US10481624B2 - Status: Granted - Kind: B2 - Application number: 16/377,297 - Filed: 2019-04-08 - Published: 2019-08-01 - Granted: 2019-11-19 - Earliest claimed: 2017-04-27 - Assignees: Pixart Imaging Inc. - Applicants: PixArt Imaging Inc. - Inventors: Kok-Siang Tan - Web page: https://patentgrep.com/patent/US10481624B2 ## CPC - G05F 1/468: {characterised by reference voltage circuitry, e.g. soft start, remote shutdown} - G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES ## Abstract A bandgap reference circuit including a clamp circuit is provided. The bandgap reference circuit performs the calibration only for one time in a normal mode to store a control code of a reference generator of the clamp circuit. In a suspend mode, the control code is used for controlling the reference generator to cause the clamp circuit to provide a desired source voltage, and a bandgap reference voltage source is shut down to reduce the power consumption. ## Claims ### Claim 1 A bandgap reference circuit, comprising: a bandgap reference voltage source configured to provide a bandgap voltage; a clamp circuit, comprising: a reference generator configured to output a first reference voltage; and a plurality of clamp switches configured to determine the first reference voltage outputted by the reference generator; and a calibration engine, coupled to the bandgap reference voltage source and a clamp voltage, and configured to control a combination of the plurality of clamp switches according to a voltage difference between the clamp voltage and the bandgap voltage. ### Claim 2 (depends on 1) The bandgap reference circuit as claimed in claim 1, wherein the reference generator comprises a reference current source and a diode bank, and the calibration engine is configured to control a conducting state of the plurality of clamp switches to change a connection of the diode bank. ### Claim 3 (depends on 1) The bandgap reference circuit as claimed in claim 1, wherein the reference generator comprises a reference current source and a transistor bank, and the calibration engine is configured to control a conducting state of the plurality of clamp switches to change a connection of the transistor bank. ### Claim 4 (depends on 1) The bandgap reference circuit as claimed in claim 1, wherein the reference generator comprises multiple reference current sources and one diode, and the calibration engine is configured to control a conducting state of the plurality of clamp switches to change a connection between the multiple reference current sources and the one diode. ### Claim 5 (depends on 1) The bandgap reference circuit as claimed in claim 1, wherein the clamp circuit further comprises an operational amplifier having a positive input terminal, a negative input terminal and an output terminal, the positive input terminal is configured to receive the first reference voltage, and the output terminal is feedback to the negative input terminal via a feedback resistor. ### Claim 6 (depends on 1) The bandgap reference circuit as claimed in claim 1, wherein the clamp circuit further comprises a comparator, which is coupled to the clamp voltage via one input thereof and coupled to the calibration engine via an output thereof. ### Claim 7 (depends on 6) The bandgap reference circuit as claimed in claim 6, further comprising an analog buffer coupled between the bandgap reference voltage source and another input of the comparator. ### Claim 8 (depends on 1) The bandgap reference circuit as claimed in claim 1, wherein the clamp circuit further comprises an output switch coupled in front of a downstream circuit. ### Claim 9 (depends on 8) The bandgap reference circuit as claimed in claim 8, further comprising a regulator coupled between the output switch and the downstream circuit. ### Claim 10 (depends on 9) The bandgap reference circuit as claimed in claim 9, wherein when the output switch is not conducted, the bandgap reference voltage source and the regulator are activated, and the clamp circuit is shut down in a normal mode but activated in a calibration mode. ### Claim 11 A bandgap reference circuit, comprising: a bandgap reference voltage source configured to provide a bandgap voltage; a clamp circuit, comprising: a reference generator configured to output a first reference voltage; and a plurality of clamp switches configured to determine the first reference voltage outputted by the reference generator; and a calibration engine, coupled to the bandgap reference voltage source and the reference generator, and configured to control a combination of the plurality of clamp switches according to a voltage difference between the first reference voltage and the bandgap voltage. ### Claim 12 (depends on 11) The bandgap reference circuit as claimed in claim 11, wherein the reference generator comprises a reference current source and a diode bank, and the calibration engine is configured to control a conducting state of the plurality of clamp switches to change a connection of the diode bank. ### Claim 13 (depends on 11) The bandgap reference circuit as claimed in claim 11, wherein the reference generator comprises a reference current source and a transistor bank, and the calibration engine is configured to control a conducting state of the plurality of clamp switches to change a connection of the transistor bank. ### Claim 14 (depends on 11) The bandgap reference circuit as claimed in claim 11, wherein the reference generator comprises multiple reference current sources and one diode, and the calibration engine is configured to control a conducting state of the plurality of clamp switches to change a connection between the multiple reference current sources and the one diode. ### Claim 15 (depends on 11) The bandgap reference circuit as claimed in claim 11, wherein the clamp circuit further comprises an operational amplifier having a positive input terminal, a negative input terminal and an output terminal, the positive input terminal is configured to receive the first reference voltage, and the output terminal is feedback to the negative input terminal via a feedback resistor. ### Claim 16 (depends on 11) The bandgap reference circuit as claimed in claim 11, wherein the clamp circuit further comprises a comparator, which is coupled to the reference generator via one input thereof and coupled to the calibration engine via an output thereof. ### Claim 17 (depends on 16) The bandgap reference circuit as claimed in claim 16, further comprising an analog buffer coupled between the bandgap reference voltage source and another input of the comparator. ### Claim 18 (depends on 11) The bandgap reference circuit as claimed in claim 11, wherein the clamp circuit further comprises an output switch coupled in front of a downstream circuit. ### Claim 19 (depends on 18) The bandgap reference circuit as claimed in claim 18, further comprising a regulator coupled between the output switch and the downstream circuit. ### Claim 20 (depends on 19) The bandgap reference circuit as claimed in claim 19, wherein when the output switch is not conducted, the bandgap reference voltage source and the regulator are activated, and the clamp circuit is shut down in a normal mode but activated in a calibration mode.