Semiconductor integrated circuit device for non-contact type IC card

• US 6,343,022 B1
• Filed: 03/24/2000
• Issued: 01/29/2002
• Est. Priority Date: 10/01/1999
• Status: Expired due to Term

• Current Assignee: Socionext Inc.
• Original Assignee: Fujitsu Limited
• Inventors: Naruse, Tomomi
• Primary Examiner(s): Patel, Rajnikant B.
• Application Number:
  US09/534,227
• Time in Patent Office: 676 Days
• Field of Search: 363/16, 363/17, 363/20, 363/71, 363/28, 363/89, 323/264, 323/347, 235/380, 320/106, 320/117, 320/118, 340/531
• US Class Current: 363/16
• 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

Abstract

A semiconductor integrated circuit device for a non-contact type IC card equipped with a rectifying circuit rectifying a received signal and thus producing a power supply voltage is disclosed. A shunt regulator is connected between a power supply voltage and ground, and controls a shunt resistance. A control circuit controls the shunt regulator as follows. The shunt resistance gradually decreases when the power supply voltage becomes higher than an upper limit of a reference voltage range, and gradually increases when the power supply voltage becomes lower than a lower limit thereof. The shunt resistance remains constant when the power supply voltage falls within the reference voltage range.

Claims

1. A semiconductor integrated circuit device for a non-contact type IC card equipped with a rectifying circuit rectifying a received signal and thus producing a power supply voltage, said device comprising:

a shunt regulator which is connected between a power supply voltage and ground and controls a shunt resistance; and

a control circuit which controls the shunt regulator so that;

the shunt resistance gradually decreases when the power supply voltage becomes higher than an upper limit of a reference voltage range, and gradually increases when the power supply voltage becomes lower than a lower limit thereof; and

the shunt resistance remains constant when the power supply voltage falls within the reference voltage range.

2. The semiconductor integrated circuit device as claimed in claim 1, wherein the shunt regulator comprises first through (n+1)th unit shunt regulators connected in parallel, each of the first through (n+1)th unit shunt regulators comprising a shunt resistor and a connection switch circuit connected in series.

3. The semiconductor integrated circuit device as claimed in claim 2, wherein a kth unit shunt regulator (k=1, 2, . . . , n+1) has a resistance value of (a constant value)×

2<sup>n+1−

k</sup>.

4. The semiconductor integrated circuit device as claimed in claim 3, wherein the connection switch circuit provided in each of the unit shunt regulators comprises a connection switch connected in series to the shunt resistor, and a delay circuit supplying a control signal from the control circuit to the connection switch, the delay circuit being configured so that a delay time of an edge which turns ON the connection switch is longer than that of another edge which turns OFF the connection switch.

5. The semiconductor integrated circuit device as claimed in claim 3, wherein said control circuit comprises:

a voltage detection circuit which detects a voltage value of the power supply voltage;

an N-bit overflow up/down counter; and

a counter control circuit which instructs the counter to operate as a down counter when the voltage detection circuit detects that the power supply voltage is higher than the reference voltage range and instructs the counter to operate as an up counter when the voltage detection circuit detects that the power supply voltage is lower than the reference voltage range and which instructs the counter to be in a hold state when the voltage detection circuit detects that the power supply voltage falls within the reference voltage range,

connection switch circuits of the first through (n+1)th unit shunt regulators being supplied with output signals D0 (LSB), D1, . . . , Dn (MSB) of the counter.

6. The semiconductor integrated circuit device as claimed in claim 3, further comprising a block generator generating clocks of different frequencies, and a clock selection circuit which selects one of the clocks of a higher frequency as a difference between the voltage value of the power supply voltage and the reference voltage range increases, wherein the counter counts said one of the clocks.

7. The semiconductor integrated circuit device as claimed in claim 1, further comprising a load switch modulation circuit that superimposes modulated transmission data onto the power supply voltage, said load switch modulation circuit being controlled by a switch control signal output by said control circuit and used to control the shunt regulator.

8. The semiconductor integrated circuit device as claimed in claim 7, wherein said load switch modulation circuit comprises first through (n+1)th unit load switch modulation circuits connected in parallel, each including a load resistor and a connection switch circuit connected in series, the connection switch circuits being controlled by the switch control signal supplied from the control circuit.

9. The semiconductor integrated circuit device as claimed in claim 8, wherein the load resistor of a kth unit shunt regulator (k=1, 2, . . . , n+1) has a resistance of (constant value)×

2<sup>n+1−

k</sup>.

10. The semiconductor integrated circuit device as claimed in claim 9, wherein the connection switch circuit provided in each of the unit shunt regulators comprises a connection switch connected in series to the shunt resistor, and a delay circuit supplying the switch control signal from the control circuit to the connection switch, the delay circuit being configured so that a delay time of an edge which turns ON the connection switch is longer than that of another edge which turns OFF the connection switch.

11. The semiconductor integrated circuit device as claimed in claim 5, further comprising a load switch modulation circuit that superimposes modulated transmission data onto the power supply voltage, said load switch modulation circuit being controlled by a switch control signal output by said control circuit and used to control the shunt regulator, wherein:

said load switch modulation circuit comprises first through (n+1)th unit load switch modulation circuits connected in parallel, each including a load resistor and a connection switch circuit connected in series, the connection switch circuits being controlled by the switch control signal supplied from the control circuit; and

the output signals D0, D1, . . . , Dn are applied, as switch control signals, to the connection switch circuits of the first through (n+1)th unit load switch modulation circuit.

12. The semiconductor integrated circuit device as claimed in claim 1, further comprising a controller, and a switch circuit which selects one of the control circuit and the controller in order to control the shunt regulator.

13. The semiconductor integrated circuit device as claimed in claim 12, wherein the controller starts to control the shunt regulator after stabilization of the power supply voltage by the control circuit is completed.

14. The semiconductor integrated circuit device as claimed in claim 1, further comprising:

a plurality of shunt regulators respectively provided to individual circuits which use the power supply voltage, each of the plurality of shunt regulators causing a shunt current equal to or approximately equal to a current flowing in a corresponding one of the individual circuits to flow therein; and

a controller controlling the plurality of shunt regulators.

15. The semiconductor integrated circuit device as claimed in claim 14, wherein the controller starts to control the shunt regulator after stabilization of the power supply voltage by the control circuit is completed.

16. A non-contact type IC card comprising:

a rectifying circuit rectifying a received signal via an antenna and thus producing a power supply voltage; and

a semiconductor integrated circuit device comprising;

a shunt regulator which is connected between a power supply voltage and ground and controls a shunt resistance; and

a control circuit which controls the shunt regulator so that;

the shunt resistance gradually decreases when the power supply voltage becomes higher than an upper limit of a reference voltage range, and gradually increases when the power supply voltage becomes lower than a lower limit thereof; and

the shunt resistance remains constant when the power supply voltage falls within the reference voltage range.