Search

US-12620829-B2 - Circuit device and real-time clock device

US12620829B2US 12620829 B2US12620829 B2US 12620829B2US-12620829-B2

Abstract

A circuit device includes a main power supply terminal, a backup power supply terminal, a voltage detection circuit, a register section, a processing circuit, and a power supply control circuit. A main power supply voltage is supplied through the main power supply terminal. A backup power supply voltage from a backup element is supplied through the backup power supply terminal. The voltage detection circuit detects the backup power supply voltage and outputs backup voltage data corresponding to the backup power supply voltage. Threshold voltage data is stored in the register section. The processing circuit compares the backup voltage data with the threshold voltage data. The power supply control circuit performs charging control on the backup element for charging with the main power supply voltage on the basis of the result of a comparison made by the processing circuit.

Inventors

  • Yasuhiro Sudo

Assignees

  • SEIKO EPSON CORPORATION

Dates

Publication Date
20260505
Application Date
20240926
Priority Date
20230927

Claims (12)

  1. 1 . A circuit device comprising: a main power supply terminal for receiving a main power supply voltage; a backup power supply terminal for receiving a backup power supply voltage from a backup element; a voltage detection circuit that detects the backup power supply voltage and outputs backup voltage data corresponding to the backup power supply voltage; a register section storing threshold voltage data for comparison with the backup voltage data; a processing circuit that compares the backup voltage data with the threshold voltage data; and a power supply control circuit that performs charging control on the backup element for charging with the main power supply voltage based on a result of a comparison made by the processing circuit, wherein the voltage detection circuit includes a voltage sensor to which the backup power supply voltage is input as detection target voltage and from which the backup voltage data is output as voltage data, and the voltage sensor includes: an oscillation circuit for voltage detection, an oscillation frequency of the oscillation circuit varying with a supply current; a current supply circuit that supplies the oscillation circuit for voltage detection with the supply current, an amperage of the supply current varying with the detection target voltage; a counter circuit that performs, in a given period, count processing on an output clock signal from the oscillation circuit for voltage detection; and an arithmetic circuit that performs arithmetic computations to obtain the voltage data corresponding to the detection target voltage on the basis of a count value obtained in the count processing performed in a state in which the oscillation circuit for voltage detection is supplied with the supply current.
  2. 2 . The circuit device according to claim 1 , wherein threshold voltage data for full charge detection is stored in the register section as the threshold voltage data, and when the backup voltage data exceeds the threshold voltage data for full charge detection, the power supply control circuit performs control to stop charging the backup element with the main power supply voltage.
  3. 3 . The circuit device according to claim 1 , wherein threshold voltage data for recharge detection is stored in the register section as the threshold voltage data, and when the backup voltage data falls below the threshold voltage data for recharge detection, the power supply control circuit performs control to start charging the backup element with the main power supply voltage.
  4. 4 . The circuit device according to claim 1 , wherein threshold voltage data for detection of a drop in the backup power supply voltage is stored in the register section as the threshold voltage data.
  5. 5 . The circuit device according to claim 1 , wherein the threshold voltage data is multi-bit data.
  6. 6 . The circuit device according to claim 1 , wherein the voltage detection circuit includes a comparator circuit that compares the main power supply voltage with a threshold voltage for detection of a drop in the main power supply voltage, and when the main power supply voltage falls below the threshold voltage for voltage drop detection, a power supply voltage that is to be supplied to internal circuitry of the circuit device is switched from the main power supply voltage to the backup power supply voltage by the power supply control circuit.
  7. 7 . The circuit device according to claim 1 , further comprising an interface circuit for access to the register section.
  8. 8 . The circuit device according to claim 7 , wherein the threshold voltage data is provided to the register section through the interface circuit.
  9. 9 . The circuit device according to claim 7 , wherein the backup voltage data detected by the voltage detection circuit is stored in the register section, and the interface circuit outputs the backup voltage data stored in the register section.
  10. 10 . The circuit device according to claim 9 , wherein the backup voltage data at a time specified through the interface circuit is stored in the register section.
  11. 11 . The circuit device according to claim 1 , further comprising an interrupt generation circuit that generates an interrupt signal based on the result of the comparison of the backup voltage data and the threshold voltage data.
  12. 12 . A real-time clock device comprising: the circuit device according to claim 1 ; and a resonator, wherein the circuit device includes the oscillation circuit that generates a clock signal by causing the resonator to oscillate, and a time measurement circuit that performs time measurement processing based on the clock signal.

Description

The present application is based on, and claims priority from JP Application Serial Number 2023-164648, filed Sep. 27, 2023, the disclosure of which is hereby incorporated by reference herein in its entirety. BACKGROUND 1. Technical Field The present disclosure relates to circuit devices, real-time clock devices, and the like. 2. Related Art A real-time clock device disclosed in JP-A-2014-017965, which is an example of the related art, detects voltage by intermittently turning on a switch disposed between a main power supply terminal and a backup power supply terminal. Accordingly, the real-time clock device enables switching between a main power supply and a backup power supply. Backup elements supplied with backup power supply voltage are charged with the main power supply in accordance with the results of voltage detection. The technique disclosed in JP-A-2014-017965 involves the use of comparator circuits that compare the backup power supply voltage with a fixed value of reference voltage to detect voltage. In such a case, it is difficult to perform flexible charging control on various backup elements. SUMMARY An aspect of the present disclosure relates to a circuit device that includes a main power supply terminal, a backup power supply terminal, a voltage detection circuit, a register section, a processing circuit, and a power supply control circuit. A main power supply voltage is supplied through the main power supply terminal. A backup power supply voltage from a backup element is supplied through the backup power supply terminal. The voltage detection circuit detects the backup power supply voltage and outputs backup voltage data corresponding to the backup power supply voltage. Threshold voltage data for comparison with the backup voltage data is stored in the register section. The processing circuit compares the backup voltage data with the threshold voltage data. The power supply control circuit performs charging control on the backup element for charging with the main power supply voltage on the basis of the result of a comparison made by the processing circuit. Another aspect of the present disclosure relates to a real-time clock device that includes the circuit device described above and a resonator. The circuit device includes an oscillation circuit and a time measurement circuit. The oscillation circuit generates a clock signal by causing the resonator to oscillate. The time measurement circuit performs time measurement processing based on the clock signal. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an example configuration of a circuit device according to an embodiment. FIG. 2 illustrates the example configuration of the circuit device according to the embodiment in greater detail. FIG. 3 illustrates examples of registers included in a register section. FIG. 4 illustrates an example configuration of a voltage detection circuit. FIG. 5 illustrates an example configuration of a real-time clock device including the circuit device. FIG. 6 illustrates the operation of a power supply control circuit on a power-up. FIG. 7 illustrates an example of switching control performed by the power supply control circuit. FIG. 8 illustrates another example of the switching control performed by the power supply control circuit. FIG. 9 illustrates latch control performed on backup voltage data. FIG. 10 illustrates the latch control performed on the backup voltage data. FIG. 11 illustrates examples of registers included in an interrupt generation circuit. FIG. 12 illustrates a configuration example of a voltage sensor. FIG. 13 is a signal waveform diagram illustrating the operation of the voltage sensor. DESCRIPTION OF EMBODIMENTS The following describes an embodiment of the present disclosure. It should be noted that the embodiment described below does not unduly limit the scope of what is hereinafter claimed. Furthermore, not all of the features described in the following embodiment are essential features of the present disclosure. 1. Circuit Device and Real-Time Clock Device FIG. 1 illustrates an example configuration of a circuit device 20 according to an embodiment. The circuit device 20 includes a voltage detection circuit 30, a register section 40, a processing circuit 50, a power supply control circuit 60, a main power supply terminal TVDD, and a backup power supply terminal TVBAT. The circuit device 20 may include a ground terminal TGND. For example, the circuit device 20 is an integrated circuit (IC) formed in a semiconductor process. Specifically, the circuit device 20 is a semiconductor chip including a semiconductor substrate and circuit elements formed on the semiconductor substrate. The circuit device 20 may be regarded as a semiconductor device including a semiconductor chip mounted in a package. The configuration of the circuit device 20 according to the present embodiment is not limited to the one illustrated in FIG. 1. A wide range of variations can be devised by omitting some of t