SEMICONDUCTOR DEVICE

Abstract

There is provided a semiconductor device capable of supplying an analog input signal higher than or equal to an operating power supply voltage. An electrostatic discharge protection circuit corresponding to the analog input signal is provided for an external terminal that is supplied with an analog input signal generated with a first power supply voltage. A voltage divider resistor divides the analog input signal passing through the electrostatic discharge protection circuit into a voltage corresponding to a second power supply voltage lower that the first power supply voltage. An input circuit operating on the second power supply voltage receives the analog input signal divided by the voltage divider resistor to form an internal analog signal. There are provided first and second unidirectional elements. The first unidirectional element passes current from the input circuit's input terminal to the second power supply voltage. The second unidirectional element passes current from a circuit ground potential to a first circuit's input terminal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing an embodiment of an analog input circuit according to the invention;

FIG. 2 is a circuit diagram showing another embodiment of the analog input circuit according to the invention;

FIG. 3 is a circuit diagram showing yet another embodiment of the analog input circuit according to the invention;

FIG. 4 is an overall block diagram showing an embodiment of a DVD recording/reproducing apparatus using the analog input circuit according to the invention;

FIG. 5 is a block diagram showing an embodiment of a DSP unit in FIG. 4;

FIG. 6 is a detailed block diagram showing an embodiment of an interface IF in FIG. 5;

FIG. 7 is a circuit diagram showing still yet another embodiment of the analog input circuit according to the invention;

FIG. 8 is a flowchart describing servo control of the DVD recording/reproducing apparatus according to the invention;

FIG. 9 is an explanatory diagram of servo signal operation for the DVD recording/reproducing apparatus according to the invention;

FIG. 10 is an output waveform diagram for OEIC and FMD in the DVD recording/reproducing apparatus according to the invention;

FIG. 11 is an explanatory diagram of servo phase difference detection in the DVD recording/reproducing apparatus according to the invention;

FIG. 12 is an explanatory diagram of defect detection in the DVD recording/reproducing apparatus according to the invention;

FIG. 13 is an explanatory diagram of wobble detection operation in the DVD recording/reproducing apparatus according to the invention;

FIG. 14 is an explanatory diagram for wobble computation construction of the DVD recording/reproducing apparatus according to the invention;

FIG. 15 is a waveform diagram for describing power control by an FMD of the DVD recording/reproducing apparatus according to the invention; and

FIG. 16 is a circuit diagram showing an embodiment of another interface provided for a signal processing unit according to the invention.

Claims

1. A semiconductor device comprising: a first input circuit unit,wherein the first input circuit unit includes: a first external terminal supplied with a first analog input signal generated in a first external circuit operating on a first power supply voltage;a first electrostatic discharge protection circuit corresponding to the first analog input signal;a first voltage divider resistor for dividing the first analog input signal passing through the first electrostatic discharge protection circuit into a voltage corresponding to a second power supply voltage lower than the first power supply voltage;a first input circuit that operates on the second power supply voltage and receives a first analog input signal divided by the first voltage divider resistor to generate an internal analog signal;a first unidirectional element for passing current from an input terminal of the first input circuit to the second power supply voltage; anda second unidirectional element for passing current from a circuit ground potential to an input terminal of the first input circuit.

2. The semiconductor device according to claim 1, wherein the first electrostatic discharge protection circuit includes: a plurality of serially connected diodes that are provided between the first external terminal and a power supply conductor supplied with the second power supply voltage and do not operate on a maximum value for the first analog signal; anda diode that is provided between the first external terminal and a grounding conductor supplied with a circuit ground potential and passes current from a ground potential side to the first external input terminal.

3. The semiconductor device according to claim 2 further comprising: a MOSFET that is provided between one terminal of the voltage divider resistor and a circuit ground potential and has its gate supplied with a control signal for allowing the internal analog signal to be a specified voltage.

4. The semiconductor device according to claim 3, wherein the first input circuit unit further comprises: resistor means for transmitting the analog input signal passing through the first electrostatic discharge protection circuit;a second input circuit that operates on the second power supply voltage and receives the first analog input signal passing through the resistor means to generate an internal analog signal;a third unidirectional element for passing current from an input terminal of the second input circuit to the second power supply voltage; anda fourth unidirectional element for passing current from a circuit ground potential to an input terminal of the second input circuit.

5. The semiconductor device according to claim 4, wherein the first input circuit unit further comprises: a second external terminal supplied with a second analog input signal formed in the external circuit;a second electrostatic discharge protection circuit corresponding to the second analog input signal;a second voltage divider resistor for dividing the second analog input signal passing through the second electrostatic discharge protection circuit into a voltage corresponding to the second power supply voltage;a third input circuit that operates on the second power supply voltage and receives a second analog input signal divided by the second voltage divider resistor to generate an internal analog signal;a fifth unidirectional element for passing current from an input terminal of the third input circuit to the second power supply voltage; anda sixth unidirectional element for passing current from a circuit ground potential to an input terminal of the third input circuit.

6. The semiconductor device according to claim 5, wherein the first voltage divider resistor, the second voltage divider resistor, and the resistor means use polysilicon resistors.

7. The semiconductor device according to claim 6, wherein the first, second, and third input circuits each include a source follower MOSFET with its gate connected to an input terminal and a power supply source connected to the source.

8. The semiconductor device according to claim 7 further comprising: a second input circuit unit,wherein the second input circuit unit includes: a third external terminal supplied with a third input signal generated in a second external circuit operating on the second power supply voltage;a third electrostatic discharge protection circuit corresponding to the third input signal; anda fourth input circuit that operates on the second power supply voltage and receives the third input signal to generate an internal signal.

9. The semiconductor device according to claim 8, wherein the first external circuit is a DVD optical pickup circuit, andwherein the semiconductor device is mounted with a DVD signal processing circuit including a DVD analog front-end.

10. The semiconductor device according to claim 9, wherein an internal analog signal passing through the first input circuit is used for detecting a servo level, wobble, and LPP,wherein an internal analog signal passing through the second input circuit is used for detecting a servo phase difference, defect, unsuccessful recording, and RF signal, andwherein an internal analog signal passing through the third input circuit is used for power control.

11. The semiconductor device according to claim 10, wherein the semiconductor device includes: a first chip mounted with the DVD signal processing circuit; anda second chip mounted with the SDRAM, andwherein signals corresponding to the first and second chips are connected with each other and are contained in one package.