JPH04349720A - A/d converter - Google Patents

Abstract

PURPOSE:To quicken the operating speed of the A/D converter by devising the A/D converter such that a digital signal whose speed is twice the speed of each A/D converter circuit. CONSTITUTION:An analog signal (a) inputted to an A/D converter circuit (1)2 is converted by using a sampling clock (b) from an input terminal 4 into a digital signal (d). On the other hand, the analog signal (a) inputted to an A/D converter circuit (2)3 is converted by using an inverted sampling clock (c) into a digital signal (e). The digital signals d, e are inputted to a multiplexer circuit 5, in which they are subjected to time division multiplex. Since the multiplexed digital signal (f) has two sampling values for one sampling period, the signal is digitized at a double speed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an A/D converter, and more particularly to increasing the speed of an A/D converter used in a PCM encoder using a sampling clock.

0002

[Prior Art] Conventionally, this type of A/D converter inputs analog signals such as audio and video, samples them using a sampling clock, and then converts them into digital signals through processing steps such as level comparison, quantization, compression, and encoding. It is converted into a signal and output. This A/D converter is usually composed of one circuit and is integrated into an LSI, either exclusively or mixed with other circuits.

0003

[Problem to be solved by the invention] The conventional A described above
When converting a high-speed analog signal such as a video into a digital signal, a /D converter needs to speed up each processing step, but there are technical difficulties due to the large number of processing steps, so speeding up was difficult.

0004

[Means for Solving the Problems] The A/D converter of the present invention includes a first A/D conversion circuit that converts an analog signal into a digital signal using a sampling clock, and a first A/D conversion circuit that inverts the phase of the sampling clock. a phase inversion circuit;
a second A/D conversion circuit that converts the analog signal into a digital signal using the output of the phase inversion circuit; and a second A/D conversion circuit that converts each output of the first A/D conversion circuit and the second A/D conversion circuit. and a multiplexing circuit that performs multiplexing using the sampling clock.

Alternatively, the analog signal is input to an A/D converter having an A/D conversion circuit that samples the analog signal using a sampling clock and then converts the signal into a digital signal. Multiplexing in which another A/D conversion circuit using a sampling clock with the phase of the sampling clock inverted is added, and the outputs of the two A/D conversion circuits are multiplexed using the sampling clock and output as a digital signal. It consists of a circuit.

[0006]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the circuit configuration of this embodiment. Analog signal a from input terminal 1 is input to A/D conversion circuit (1) 2 and A/D conversion circuit (2) 3. A
In the /D conversion circuit (1) 2, the input analog signal a is sampled by the high level of the sampling clock b from the input terminal 4, and is converted into a digital signal d through processing steps such as quantization, compression, and encoding. Become. , On the other hand, in the A/D conversion circuit (2) 3, the analog signal a is similarly converted into the digital signal e, but the sampling clock passes through the phase inversion circuit 6 and uses the sampling clock c whose phase has been inverted. Therefore, the digital signal e is delayed by 180° in phase from the digital signal d.

Digital signals d and e are input to a multiplexing circuit 5, are alternately selected by a sampling clock b, and are time-division multiplexed. The multiplexed digital signal f is
Since there are two sampling values in one sampling period, the data is converted into a digital signal at twice the speed.

FIG. 2 is a timing chart explaining the operation of this embodiment. The input analog signal a is converted into digital signals d and e with a phase difference of 180° by sampling clocks b and c whose phases are inverted, respectively.
Both signals are time-division multiplexed into a digital signal f at twice the speed.
becomes.

[0009] In a D/A converter corresponding to the present A/D converter, the conversion process described above is reversed.

0010

Effects of the Invention As explained above, the present invention has a phase difference of 1
Since the outputs of two A/D converter circuits having an angle of 80° are multiplexed, a digital signal with twice the speed of the output of each A/D converter circuit can be obtained, and the high speed of the A/D converter can be obtained. It is effective for

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of this embodiment.

FIG. 2 is a timing chart illustrating the operation of this embodiment.

[Explanation of symbols]

1 Input terminal 2 A/D conversion circuit (1) 3 A/D conversion circuit {2) 4 Input terminal 5 Multiplex circuit 6 Phase inversion circuit 7 Output terminal

Claims (2)

[Claims] 1. A first A/D conversion circuit that converts an analog signal into a digital signal using a sampling clock, a phase inversion circuit that inverts the phase of the sampling clock, and an output of the phase inversion circuit that converts the a second A/D conversion circuit that converts an analog signal into a digital signal; the first A/D conversion circuit; and the second A/D conversion circuit;
An A/D converter comprising a multiplexing circuit that multiplexes outputs of the conversion circuit using the sampling clock. 2. An A/D converter having an A/D conversion circuit that inputs an analog signal, samples the analog signal using a sampling clock, and then converts and outputs the digital signal. Adding another A/D conversion circuit using a sampling clock with the phase of the sampling clock inverted,
An A/D converter that multiplexes the outputs of two A/D conversion circuits using the sampling clock and outputs the resultant signal as a digital signal.