Semiconductor integrated circuit, a contactless information medium having the semiconductor integrated circuit, and a method of driving the semiconductor integrated circuit

• US 6,659,352 B1
• Filed: 05/31/2000
• Issued: 12/09/2003
• Est. Priority Date: 06/02/1999
• Status: Expired due to Term

• Current Assignee: Panasonic Semiconductor Solutions Co., Ltd. (Winbond Electronics Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Inoue, Atsuo, Matsuura, Taketoshi, Sumi, Tatsumi, Asada, Hiroaki, Nakane, Joji
• Primary Examiner(s): KIM, AHSHIK
• Application Number:
  US09/584,542
• Time in Patent Office: 1,287 Days
• Field of Search: 235/492, 235/487
• US Class Current: 235/492
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter

Abstract

A semiconductor integrated circuit which obtains a driving power from a carrier onto which data has been piggybacked, the semiconductor integrated circuit being characterized by demodulating data by correctly discriminating it even when the obtained power supply voltage has become overvoltage, and characterized by effectively using the power supplied by the carrier. The semiconductor integrated circuit includes: a two-voltage rectifier circuit as a power source circuit 111; a voltage regulator circuit 112 which exercises a control so that a power with a higher voltage (VDDH) used for demodulating data does not exceed a certain voltage value; a resistor 141; and a capacitor 142. With this construction, the voltage input to a regulator circuit 1121 as the reference voltage changes in correspondence to the change in voltage VDDH which is caused by the change in amplitude.

Claims

1. A semiconductor integrated circuit comprising:

a rectifier circuit which rectifies AC power to DC power;

a regulator circuit which includes an input terminal for receiving the DC power, an output terminal, and a control terminal for receiving a reference voltage, and exercises control so that a voltage output from the output terminal does not exceed a voltage value determined from the reference voltage received by the control terminal; and

a reference voltage changing circuit which changes the reference voltage received by the control terminal in correspondence to voltage change of the DC power.

2. The semiconductor integrated circuit of claim 1, wherein the reference voltage changing circuit includes:

a reference voltage generation circuit which includes a reference voltage output terminal for outputting the reference voltage; and

a CR time-constant circuit which includes a capacitor and a resistor connected in series, one end of the capacitor being connected to the input terminal and one end of the resistor being connected to the reference voltage output terminal, wherein

the control terminal is connected to a node disposed between the capacitor and the resistor.

3. The semiconductor integrated circuit of claim 2, wherein

the capacitor is a MOS transistor, wherein

a source, a drain, and a substrate of the MOS transistor are connected to the input terminal, and a gate of the MOS transistor is connected to a node disposed between the resistor and the control terminal.

4. The semiconductor integrated circuit of claim 2, wherein the reference voltage changing circuit further includes:

a second capacitor connected at one end to the control terminal and at another end to a ground line.

5. The semiconductor integrated circuit of claim 1, wherein the reference changing circuit includes:

a reference voltage generation circuit which includes a reference voltage output terminal for outputting the reference voltage;

a first capacitor connected at one end to the input terminal; and

a second capacitor connected at one end to the reference voltage output terminal and connected at another end to another end of the first capacitor, wherein

the control terminal is connected to a node disposed between the first capacitor and the second capacitor.

6. The semiconductor integrated circuit of claim 2 further comprising:

a power-on reset circuit whose output changes from a first output level to a second output level a predetermined time after the rectifier circuit starts outputting the DC power; and

a switching device which has at least a first terminal, a second terminal, and a third terminal, the first terminal being connected to an output terminal of the power-on reset circuit, the second terminal being connected to a ground line, and the third terminal being connected to the control terminal, and allows current to flow between the second terminal and the third terminal when the output of the power-on reset circuit is the first output level, and prevents current from flowing between the second terminal and the third terminal when the output of the power-on reset circuit is the second output level.

7. The semiconductor integrated circuit of claim 6, wherein

the switching device is a MOS transistor.

8. The semiconductor integrated circuit of claim 6, wherein the power-on reset circuit includes:

a second capacitor connected at one end to the ground line;

an inverter device whose output is the first output level from after the rectifier circuit starts outputting the DC power until the second capacitor has been charged and is the second output level after the second capacitor has been charged.

9. The semiconductor integrated circuit of claim 8, wherein the power-on reset circuit further includes:

an impedance device connected at one end to a node disposed between the second capacitor and an input terminal of the inverter device and connected at another end to an output terminal of the rectifier circuit that outputs the DC power;

a switching device connected at one end to a node disposed between the second capacitor and an input terminal of the inverter device and allows current to flow through itself when the rectifier circuit stops outputting the DC power, allowing the second capacitor to discharge.

10. The semiconductor integrated circuit of claim 1 further comprising:

a differentiating circuit which differentiates an output from an output terminal of the regulator circuit and outputs a differential signal; and

a detecting means which detects a change in a voltage value of the DC power in accordance with the differential signal.

11. The semiconductor integrated circuit of claim 1, wherein

the rectifier circuit is a two-voltage rectifier circuit which outputs two DC power supplies with different voltage values in parallel.

12. The semiconductor integrated circuit of claim 11, wherein

the input terminal receives a DC power supply with a higher voltage value out of the two DC power supplies output from the two-voltage rectifier circuit.

13. A contactless information medium comprising:

a power generation circuit which receives an ASK-modulated carrier from outside the contactless information medium and generates AC power;

a rectifier circuit which rectifies the AC power generated by the power generation circuit to DC power;

a reference voltage generation circuit which outputs a reference voltage;

a regulator circuit which includes an input terminal for receiving the DC power, a control terminal, and an output terminal, regulates the DC power so as not to exceed a voltage value determined from a voltage value received by the control terminal, and outputs the regulated DC power from the output terminal; and

a reference voltage changing circuit which changes the reference voltage in correspondence to voltage change of the DC power, the changed reference being input to the control terminal.

14. The contactless information medium of claim 13 further comprising:

a differentiating circuit which differentiates an output from the output terminal; and

a detecting circuit which detects a change in a voltage value of the DC power output from the differentiating circuit.

15. The contactless information medium of claim 14, wherein

the rectifier circuit is a two-voltage rectifier circuit which rectifies the AC power and outputs two DC power supplies with different voltage values in parallel.

16. The contactless information medium of claim 14 used as a contactless IC card which receives an ASK-modulated carrier from a power supply source.

17. A method for driving a semiconductor integrated circuit which includes a regulator circuit for outputting DC power so as not to exceed a voltage value determined from a voltage value received by a control terminal, the method comprising:

a reception step in which a carrier having been ASK-modulated by digital data is received by an antenna coil;

a rectification step in which the carrier is received and AC power which is generated at two ends of the antenna coil is rectified; and

a value discrimination step in which the digital data piggybacked on the carrier is discriminated by inputting the DC power into the regulator circuit and latching a pulse signal which is obtained by differentiating an output of the regulator circuit, wherein

a value of a voltage input into the control terminal is changed in correspondence to voltage change of the DC power.