Power-on reset circuit and IC card

• US 6,737,884 B2
• Filed: 07/30/2002
• Issued: 05/18/2004
• Est. Priority Date: 07/30/2001
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Nakao, Yoshihiro, Shigemasa, Haruhiko
• Primary Examiner(s): LE, DON P
• Application Number:
  US10/207,187
• Publication Number:
  US 20030020525A1
• Time in Patent Office: 658 Days
• Field of Search: 326/37, 326/38, 326/82, 327/142, 327/143
• US Class Current: 326/38
• CPC Class Codes: G06F 1/24 Resetting means
• 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: H03K 17/22 Modifications for ensuring a predetermined initial state when the supply voltage has been applied bi-stable generators H03K3/12

Abstract

A power-on reset circuit includes a first reset circuit, a second reset circuit, and an NOR circuit. The first reset circuit detects VCC2V supplied to a logic section so as to produce a first reset signal RST1, and the second reset circuit detects REGIN voltage, which is an output voltage of a rectifying circuit that rectifies power voltage obtained from an external power supply source, so as to produce a second reset signal RST2. The NOR circuit outputs either the RST1 or the RST2 as a reset signal P-RST. The above arrangement can provide the power-on reset circuit which outputs a reliable and effective reset signal even in case where the rising of power obtained from the external power supply source varies.

Claims

1. A power-on reset circuit, provided in a system in which a power voltage is obtained from an external power supply source without contacting by electromagnetic induction, a power voltage thus obtained is converted into a predetermined voltage and supplied to a logic section which performs a logic operation, which produces a reset signal for controlling a reset state of the system,

the power-on reset circuit, comprising:

a first reset circuit for detecting a voltage supplied to the logic section so as to produce a first reset signal;

a second reset circuit for detecting an output voltage of a rectifying circuit which rectifies a power voltage thus obtained from the external power supply source so as to produce a second reset signal; and

a reset signal outputting circuit for outputting as the reset signal either the first reset signal or the second reset signal.

2. The power-on reset circuit according to claim 1, wherein the first reset circuit includes a comparator circuit for comparing the voltage supplied to the logic section and a reference voltage which is used in a regulator circuit for converting the output voltage of the rectifying circuit which rectifies the power voltage into a predetermined voltage, and produces the first reset signal in response to the comparator circuit.

3. The power-on reset circuit according to claim 2, wherein the voltage supplied to the logic section is supplied to the comparator circuit via a delay circuit.

4. The power-on reset circuit according to claim 3, wherein the delay circuit includes a resistor and a capacitor.

5. The power-on reset circuit according to claim 1, wherein the second reset circuit includes a comparator circuit for comparing the output voltage of the rectifying circuit and a reference voltage which is used in a regulator circuit for converting into a predetermined voltage the output voltage of the rectifying circuit which rectifies the power voltage, and produces the second reset signal in response to the comparator circuit.

6. The power-on reset circuit according to claim 5, wherein the output voltage of the rectifying circuit is supplied to the comparator circuit via a delay circuit.

7. The power-on reset circuit according to claim 6, wherein the delay circuit includes a resistor and a capacitor.

8. The power-on reset circuit according to claim 1, wherein the reset signal outputting circuit outputs the reset signal for releasing the reset state of the system when both the first and second reset signals become signals for releasing the reset state.

9. The power-on reset circuit according to claim 8, wherein the reset signal outputting circuit conducts a logical NOR operation with respect to the first and second reset signals so as to output the reset signal.

10. The power-on reset circuit according to claim 1, wherein the second reset circuit has a hysteresis characteristic with respect to variation in the output voltage of the rectifying circuit.

11. The power-on reset circuit according to claim 1, wherein the system also performs a contact-type power supply from the external power supply source, the reset signal outputting circuit outputs as the reset signal one of the first reset signal, the second reset signal, and a third reset signal supplied along with the contact-type power supply.

12. The power-on reset circuit according to claim 11, wherein the reset signal outputting circuit gives top priority outputting of the third reset signal as the reset signal when the third reset signal is supplied.

13. An IC apparatus, comprising:

(a) a power source obtaining section for obtaining a power voltage from an external power supply source without contacting by electromagnetic induction;

(b) a voltage control circuit for converting a power voltage thus obtained from the power source obtaining section into a predetermined voltage;

(c) a logic section for being supplied voltage from the voltage control circuit and for conducting a logical operation; and

(d) a power-on reset circuit for producing a reset signal for controlling a reset state of the logic section,

wherein the power-on reset circuit includes;

a first reset circuit for detecting a voltage supplied to the logic section so as to produce a first reset signal;

a second reset circuit for detecting an output voltage of a rectifying circuit which rectifies a power voltage thus obtained from the external power supply source so as to produce a second reset signal; and

a reset signal outputting circuit for outputting as the reset signal either the first reset signal or the second reset signal.

14. The IC apparatus according to claim 13, further comprising a nonvolatile memory to and from which the logic section can write and read information.

15. The IC apparatus according to claim 13, wherein the power source obtaining section demodulates data superposed by electromagnetic waves transmitted from the external power supply source, and modulates data transmitted from the logic section to transmit electromagnetic waves toward outside.

16. The IC apparatus according to claim 13, wherein the power source obtaining section extracts a clock signal superposed by electromagnetic waves transmitted from the external power supply source, and transmits a clock signal thus extracted to the logic section.

17. The IC apparatus according to claim 13, wherein the power source obtaining section, the voltage control circuit, the logic section, and the power-on reset circuit are included inside a card object.

18. The IC apparatus according to claim 13, wherein the power source obtaining section is also arranged so as to perform a contact-type power supply from the external power supply source.