JP2005333313A - Semiconductor integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a semiconductor integrated circuit by reducing the number of inductors by sharing the inductors at a plurality of circuits in the semiconductor integrated circuit which duplexes the plurality of the circuits by time sharing. <P>SOLUTION: The semiconductor integrated circuit includes a plurality of circuits which are operated by time sharing, an inductor which a plurality of circuits share, and a switch for switching the connection of the plurality of the circuits and the inductor. The number of the inductors is reduced by connecting the operating circuits of the plurality of the circuits and the inductor by the switch, and the semiconductor integrated circuit is miniaturized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor integrated circuit having an inductor, and more particularly to a semiconductor integrated circuit suitable for a transmission / reception circuit that is used in a communication system that performs transmission and reception in a time division manner and that has an inductor in both a transmission unit and a reception unit.

  With the spread of PHS and mobile phones, technological development in the field of wireless communication using semiconductor integrated circuits is rapidly progressing. Among them, miniaturization of circuits and reduction of power consumption are particularly desired from the market, and various efforts such as miniaturization of transistors and ingenuity of circuit configurations have been made.

  FIG. 3 shows a general wireless transmission / reception circuit 100. The radio transmission / reception circuit 100 includes an antenna 101, a reception unit 102, and a transmission unit 103. A transmission / reception switching function called duplex is provided between the reception unit 102 and the transmission unit 103 so that both signals do not interfere with each other. ing.

  Duplex methods include time division duplex and frequency duplex, and FIG. 3 shows an example of time division duplex. In the time division duplex, the reception unit 102 and the transmission unit 103 are switched by the switch 104, and the same frequency band is used for each half time. Since the switch 104 is switched at a very high speed, the communicator does not notice that the switch is being performed. On the other hand, the frequency duplex uses different frequencies for transmission and reception, and the transmission frequency and the reception frequency are separated by a band-pass filter. Which duplex method is used is determined by the wireless standard. For example, the Digital European Cordless Telephone (DECT) standard employs a time division duplex method.

  With the increase in the frequency of communication circuits and the miniaturization of transistors, many inductor elements 105 have been used in individual circuits in the receiving unit 102 and the transmitting unit 103 (for example, Patent Document 1). 4 and 5 show typical amplifier circuits and oscillation circuits, respectively.

  FIG. 4 shows a differential amplifier 110 in which two transistors 115a and 115b are connected to load inductors 117a and 117b with a current source 118 as the center, and there are two types of matching inductors 116a and 116b and load inductors 117a and 117b. An inductor is used. Matching inductors 116a and 116b have come to be used with higher frequency circuits, and are generally used in a frequency band of about several GHz. The load inductors 117a and 117b are used as the power supply voltage of the circuit is reduced, and the center voltage of the output terminals 114a and 114b becomes a positive power supply voltage. Can do.

  FIG. 5 shows a cross-coupled oscillator 120 in which two transistors 124a and 124b are connected to each other around a current source 128, and further connected to two resonators 125a and 125b, respectively. The resonators 125a and 125b are LC resonators in which inductors 126a and 126b and capacitors 127a and 127b are connected in parallel. The cross-coupled oscillator 120 oscillates at the resonance frequency of the resonator.

  In the receiving unit 102 shown in FIG. 3, an amplifier based on the differential amplifier shown in FIG. 4 such as an LNA or LO buffer is often used, and the cross-cup oscillator shown in FIG. 5 is basically used as an oscillator for LO. An oscillator is used. Similarly, the transmitter 103 uses an amplifier based on the differential amplifier of FIG. 4 such as a buffer amplifier or a power amplifier, and an oscillator based on the cross-cup oscillator of FIG. 5 is used for generating a modulation signal. .

In the frequency band of several GHz, a spiral inductor is used as the inductor element.
JP 2003-283263 A

  Incidentally, the spiral inductor requires a very large area on the semiconductor substrate as compared with the transistor element. For this reason, if many inductors are used as described above, the chip area increases, which hinders miniaturization of the circuit. The present invention reduces the number of inductors in a semiconductor integrated circuit in which a plurality of circuit units are duplexed in a time division manner, such as a receiving unit and a transmitting unit, by sharing the inductors among the plurality of circuit units. The purpose is to reduce the size.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a semiconductor integrated circuit including a plurality of circuits each operating in a time division manner, an inductor shared by the plurality of circuits, the plurality of circuits, and the inductor. And the inductor is connected to the operating circuit of the plurality of circuits by the switch.

  According to a second aspect of the present invention, in the semiconductor integrated circuit according to the first aspect, the plurality of circuits operating in time division are a reception circuit and a transmission circuit.

  According to a third aspect of the present invention, in the semiconductor integrated circuit according to the first or second aspect, the shared inductor selects a different inductance value and is connected to an operating circuit among the plurality of circuits. It has the switch to switch, It is characterized by the above-mentioned.

  According to the present invention, in a semiconductor integrated circuit in which a plurality of circuit units are duplexed in a time-sharing manner, the number of inductors can be reduced and the semiconductor integrated circuit can be reduced in size by sharing the inductors. In particular, in the transmission / reception circuit that time-divides the transmission circuit and the reception circuit, the area occupied by the inductor is large, and the effect of downsizing the semiconductor integrated circuit by reducing the number of shared inductors is great. If an inductor whose inductance value can be varied is used as the inductor, a desired inductance value can be set, and the characteristics of the semiconductor integrated circuit can be improved.

  In the present invention, a plurality of circuits that operate by dividing time and an inductor are switched by a switch and the inductor is shared. Examples of the present invention will be described below.

  FIG. 1 is an explanatory diagram of a wireless transmission / reception circuit according to an embodiment of the present invention. The wireless transmission / reception circuit 1 of the present invention includes an antenna 2, a receiving unit 3, a transmitting unit 4, inductors 9a and 9b shared by the receiving unit 3 and the transmitting unit 4, and switches 5, 6a, 6b, 7a, 7b, 8a, 8b. It consists of The receiving unit 3 and the transmitting unit 4 are duplexed in a time division manner, and switching is performed by the switch 5. When the switch 5 is connected to the receiving unit 3 side, the switches 6a and 6b are connected to the receiving unit 3 side in synchronization therewith, the switches 7a and 7b are turned on, and the switches 8a and 8b are turned off. As a result, the inductors 9a and 9b are connected to the receiving unit 3 and operate as inductors on the receiving unit 3 side. Conversely, when the switch 5 is connected to the transmission unit 4 side, the switches 6a and 6b are connected to the transmission unit 4 side in synchronization therewith, the switches 7a and 7b are in the OFF state, and the switches 8a and 8b are in the ON state. Become. As a result, the inductors 9a and 9b are connected to the transmission unit 4 and operate as inductors on the transmission unit 4 side. Since the reception unit 3 and the transmission unit 4 are time-shared, no interference occurs due to the sharing of the inductors 9a and 9b. Although FIG. 1 shows the case where the number of shared inductors is two, the number of inductors may be one or more.

  In the wireless transmission / reception circuit shown in FIG. 1, the inductance value of the inductor 9 is made different between the receiving unit 3 side and the transmitting unit 4 side. FIG. 2 shows an example of an inductor 9 that can vary the inductance value. The inductor 9 capable of varying the inductance value is composed of, for example, a spiral first wiring layer 10, lead wiring second wiring layers 11 a and 11 b, and a switch 12 on a semiconductor substrate. The two lead wires formed by the layers 11a and 11b are connected to the terminal 13a (corresponding to 7a and 7b in FIG. 1) and the terminal 13b (corresponding to 8a and 8b in FIG. 1) of the switch 12, respectively. Further, the first wiring layer 10 and the second wiring layers 11 a and 11 b are connected by a through hole 14. By switching the terminals 13a and 13b with the switch 12, the inductance value of the inductor 9 can be changed. In the example of FIG. 2, since the number of turns of the spiral conductor is about 2.5 turns, when the switch 12 is switched to the terminal 13a, an inductor of about 2.5 turns is obtained. When the switch 12 is switched to the terminal 13b, the one-turn portion located almost on the inner peripheral side can be invalidated and used as an inductor of about 1.5 turns as a whole. As described above, the inductance value can be changed by switching the switch 12.

  If an inductor capable of setting a desired inductance value is used in this way, the inductance value of the inductor connected to the receiving unit 3 and the inductance value of the inductor connected to the transmitting unit 4 can be individually set. The characteristics can be improved. It goes without saying that inductors having the same inductance value may be switched and connected.

It is the figure which showed the structure of the radio | wireless transmission / reception circuit based on the Example of this invention. It is explanatory drawing of an inductance variable element. It is the figure which showed the structure of the conventional radio | wireless transmission / reception circuit. It is a figure which shows the typical example of the amplifier using an inductor. It is a figure which shows the typical example of the oscillator which uses an inductor.

Explanation of symbols

1: wireless transmission / reception circuit, 2: antenna, 3: reception unit, 4: transmission unit, 5, 6, 8: switch, 9: inductor, 10: first wiring layer, 11: second wiring layer, 12: Switch: 13: Terminal, 14: Through-hole, 100: Radio transceiver circuit, 101: Antenna, 102: Receiver, 103: Transmitter, 104: Switch, 105: Inductance element, 110: Differential amplifier, 111: Positive Power supply, 112: Negative power supply, 113: Input terminal, 114: Output terminal, 115: Transistor, 116: Inductor for matching, 117: Load inductor, 120: Cross-coupled oscillator, 121: Positive power supply, 122: Negative power supply, 123 : Output terminal, 124: transistor, 125: resonator, 126: inductor, 127: capacitor

Claims (3)

  A semiconductor integrated circuit, comprising: a plurality of circuits each operating in a time-sharing manner; an inductor shared by the plurality of circuits; a switch for switching the connection between the plurality of circuits and the inductor; A semiconductor integrated circuit, wherein an operating circuit and the inductor are connected by the switch.   2. The semiconductor integrated circuit according to claim 1, wherein the plurality of circuits operating in time division are a receiving circuit and a transmitting circuit. 3. The semiconductor integrated circuit according to claim 1, wherein the shared inductor includes a switch that selects a different inductance value and switches a connection to an operating circuit among the plurality of circuits. A semiconductor integrated circuit.

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