JPH03112220A - A/d converter - Google Patents

Abstract

PURPOSE: To facilitate adjustment of an analog input level by outputting an additional signal, which indicates that a digital signal is within a specific range, together with the digital signal to which an analog signal is converted. CONSTITUTION: An A/D conversion part 14 converts an analog signal into a PCM digital code. The output of the A/D conversion part 14 is processed in an additional code generation part 9, a full-scale detection part 1, and a full- scale switching part 10a. The additional code generation part 9 generates an additional code, which indicates that the output is within a preliminarily determined range, in accordance with upper 12 bits (A8 to A19) out of 20 bits of output data of the A/D conversion part 14 and an output T2 of the full-scale detection part 10. Next, 16-bit output data and the 3-bit additional code are latched in an output register 11 and are outputted serially by a serial out clock 12 or are outputted in parallel by a parallel out clock 13. The analog input level is most suitably set from this 3-bit information of the additional code.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention samples analog electrical signals commonly used in the fields of so-called digital audio and measurement, and converts them into PCM (pulse This relates to a so-called to/D converter that converts the code into a digital code such as code modulation and outputs it.

[Prior art]

When the digital codes converted and output by the A/D converter are arranged chronologically in the order in which they were sampled, the digital signals are compared to the analog signals before conversion.
Alternatively, it is called a discrete value signal.

In conventional D/D converters, there are positive and negative full scales (maximum and minimum values) as individually determined conversion standards, and the value when sampling the analog signal input manually (Nth place) If the sampled value (bell) is within the positive and negative full scales, it will be converted to the corresponding digital code and output; however, if the sampled value is outside the positive and negative full scales, it will be output as a positive or negative full scale. It outputs each full scale value. For example, in a 16-bit precision linear A/D converter, if the reference positive and negative full scale values are +3. OV and -3,Ov
In this case, the maximum amplitude of the manually input analog signal is ±3. If it is within Ov, the output digital code will definitely be one of 216 types of data within the positive and negative full scale, and the obtained result will be an accurate digital signal (see Figure 1-a). .

[Problem to be solved by the invention] However, in the above-mentioned conventional D/D converter, if the maximum amplitude value of the manually input analog signal is ±3
．． +3 if it exceeds Ov. Ov or more or
It is necessary to convert the potential below -3.0V, and there is no corresponding P C,M code, so +3. If greater than or equal to OV, a positive full scale value (e.g. +32
767, or %·218 t), and if below 3.0V, a negative full scale value (e.g. -327
68) will be output as is (rounded), resulting in an inaccurate digital signal, a signal with so-called overscale distortion, and the waveform after D/A conversion is as shown in Figure 1-C. As shown in Figure 1-b, the signal is greatly different from the original analog signal in Figure 1-b.

When using such an A/D converter in the fields of digital audio and measuring instruments, manual input is required to make maximum use of its finite resolution (for example, the limit for 16 bits is approximately 98 dB). It is necessary to adjust the amplitude level of the analog signal to be as large as possible and to avoid overscale distortion. However, as mentioned above, conventional A/D converters cannot provide the user with information corresponding to when the full scale is exceeded. , or from the output digital signal,
The only way to do this was to detect and adjust the positive or negative full scale using a number of gating methods. In the former case, the resolution capability of the original D/D converter is often reduced by about 10 dB, and in the latter method, not only many gate means are required, but even if the full scale value is Even if it is detected, it is possible to distinguish whether the input is a true full scale value or an overscale value, and to obtain information such as the extent of the overscale (how many dB it exceeded). It is impossible to do so, resulting in the user wasting a great deal of time and effort in optimally adjusting the analog human power level.

An object of the present invention is to provide an A/D converter that solves the above problems.

[Means for Solving the Problems] The present invention provides a device that converts an analog signal into a digital signal and outputs the digital signal, a so-called A/D converter, which converts the digital signal into is included in a specific range (in the above example, a range of ten or more dB in the vicinity of full school).

[Function] According to the present invention, with the above-mentioned configuration, it becomes possible to easily determine whether or not the human input analog signal is within the full scale by using the additional code.

〔Example〕

In FIG. 2, 14 is an A/D converter, which converts an analog signal into a PCM digital code.

Reference numeral 7 denotes a so-called delta-sigma type A/D converter, which samples, or oversamples, a manually input analog signal at high speed and outputs a 1-bit delta-sigma modulated digital signal. This 1-bit digital signal is converted into a 16-bit PGM signal at a low speed (that is, the target sampling speed) by digital filtering processing in eight digital calculation units. At this time, the input analog signal is
In order to accurately convert bit PCM data up to positive and negative full scale, both the delta-sigma/D converter 7 and the digital calculation unit 8 can handle input voltages that are higher than positive and negative full scale. It is made with sufficient margin to allow for For example, when the positive and negative full scales of the output digital signal are set to ±3V, the delta-sigma/D converter 7 can convert up to ±5.5V, and the calculation in the digital calculation unit 8 Since the capacity is set to 20 bits, and the output is 4 bits more than the original 16 bits, the output is 20 bits (see 0 to 19).

Therefore, the A/D converter 14 converts even an overscaled input analog signal as shown in FIG. 1-b.
The calculated results are accurately converted, including data of 16 bits full scale or higher.

An additional code generating unit generates the upper 12 bits (A8 to A19) of the 20 bits of output data from the A/D converter 14.
) and the output T2 of the full-scale detection unit 10, which will be described later, an additional code indicating that it is within a predetermined range is generated by, for example, an AND gate or an OR gate (Tl, TO). IO is a full scale detection unit, which detects whether or not the output data of the D/D conversion unit 14 is overscaled based on, for example, a 16-bit standard, using the upper 5 bits (A19.818 to A15 (MSB+
4 bits)) using, for example, an OR gate.

The output of the full scale detector 10 becomes an additional code (Tl) indicating over scale, and at the same time is inputted to the full scale switching section 10a, and serves as a switching signal. If the output data of the A/D converter 14 is within a 16-bit range (within full scale), the full scale switching section 10a discards the upper 4 bits (A15 to A181) according to the switching signal from the full scale detection section 10. Then, the lower 15 bits (80 to A14) and the MSB (A19) are output as they are (80 to B15), and in the case of over scale, they are switched to a full scale value of 16 bits depending on the sign and output.

Reference numeral 11 denotes an output register, which in the conventional to/D converter had only 18 bits, but here it has a 19-bit configuration with an extra 3 bits as an additional sign bit. The calculation result of the digital calculation unit 8 is sent to the additional code generation unit 9. Full scale detector 10. After going through the necessary processing in the full scale switching unit 10a, it is latched into this output register 11 as 16-bit output data and 3 additional bits of code, and is output in series from there by the serial out clock (12). Or they are output in parallel by the parallel out clock (13). As an example of serial output when the additional code is 3 bits, the frame structure is shown in FIGS. 3-a to 3-c. Here, B
15 to Bφ represent A/D converted 16-bit digital output data, and 3 bits T2 to Tφ each represent an additional code. When the order of output data is that 815 is output first, Fig. 3-a shows the case where additional codes 12 to Tφ are outputted after the data bit, and the third
Figure 3-b shows the case where additional codes 12 to Tφ are output to the head of the data bit, and Figure 3-c shows T2 to Tφ as DI5 and 8.
The cases in which the output is placed between 14 and 14 are shown respectively.

As an example of the specific range indicated by the 3 bits of the additional code, it is set as shown in ■.

Additional sign values (Tl), (Tl), (To)
/ Range indicated by the additional sign (assuming the full scale value is 100% or OdB): 1.1,1 / Dog from 137.5%, 1.1,0 /
Dog than 125%, 137.5% or less, 1.0,1
/ Greater than 112.5%, less than 125%, 1.0.0
/ Greater than 100%, 112.5% or less, 0.1
,1/OdB or less, greater than -1dB, 0.1.0
/-1dB or less, greater than -3dB, 0.0,1 /
-3dB or less, -6dB or more, dog, 0.0,0/-8
Less than dB.

The user of the wooden A/D converter should check the 3 values of T2 to Tφ.
The analog human power level can be easily set optimally from bit information. That is, Tl-1 indicates that the human power level is overscale, and furthermore, from T1 and TI, the full scale reference value is 11.
You can see which level is up to 25%, 125%, 137.5%, and above, and accordingly,
It would be better to lower the level of manpower. Conversely, if T2=φ,
It was found that no overscale distortion occurred, and T
I, TI below 6dB from full scale, −
6dB to -3dB, -3dB to -1dB, -1
Level information such as full scale can be obtained from dB, and based on this information, the human power level can be increased to make more effective use of the resolution of the D/D converter.

In the above embodiment, an example of application to a delta-sigma type to/D converter and a to/D converter having a digital arithmetic unit was specifically described. It is also possible to output additional codes by improving various conventional D/D converters such as the flash type, integral type, etc.

In addition, in the above embodiment, the specific range indicated by the additional code is a range of ten or more dB with full scale as a reference, but the reference position may be set as follows depending on the purpose of the user. I can do it.

(1) A specific range of 10 dB inward from full scale.

(2) Specify range from full scale to outside by 10%, 20
%, 30% or more range.

(3) At least one range in which the specific range is divided into predetermined intervals within the full scale range, for example, one range divided into 10.

Further, in the case of the delta-sigma type/D converter in the above embodiment, additional code generation section 9.degree. full scale detection section 10. The full scale switching unit 10a is configured to use part of the functions of the multiplier and accumulator in the digital calculation unit 8 in a time-sharing manner during the original digital filtering process, and when included in the digital calculation unit 8. It's also possible.

Furthermore, in the embodiment, the additional code is 3 bits, but it is set to 1 bit, and only the overscaled or within the range of the output digital signal is turned on and off. It goes without saying that you can make it known.

[Effects of the Invention] According to the present invention, in addition to the digital output signal originally converted by the A/D converter, an additional code is provided to indicate that this digital output data is within a specific range near full scale. It is possible to simultaneously output and use this additional code to simplify the adjustment of the analog human power level. Furthermore, in fields such as digital audio, it is also possible to use the additional code as is as data for a level indicator; in that case,
It is possible to obtain accurate information at full scale over, which could not be read from 16-bit data with a conventional A/D converter.

[Brief explanation of drawings]

Figures 1a to 1d show the analog human input signal and digital output signal from the A/D converter, as well as the waveforms of the signal when the digital output signal is converted back into an analog signal by the D/8 converter. Figure 1a shows ±3. Figure 1b shows an analog human input signal within a reference potential range of Ov and a digital output signal. Analog human signal that exceeds OV,
Figure 1c is a diagram showing the analog waveform without overscale distortion after D/A conversion of the digital output in Figure 1a, Figure 1d is the digital output in Figure 1b. Figure 2 shows an analog waveform in which overscale distortion occurs after converting the D/8 to D/8. FIGS. 3a to 3C are block diagrams showing an embodiment applied to an A/D converter having an A/D converter. FIG. 3 is a diagram showing an example of a frame configuration when outputting. In the drawings, 1... Analog input type within full scale, 2...
(1) is the digital signal after A/D conversion, 3... overscaled analog human waveform, 4... (3) is the digital signal after A/D conversion, 5...
...(2) is the reproduced analog waveform after D/A conversion, 6...
・(4) is the reproduced analog waveform after D/A conversion, 7...
Delta-sigma type A/D conversion section, 8... Digital operation section, 9... Additional code generation section, 10... Full scale detection section, 10a... Full scale switching section, 11... - Output register, 12... Serial output clock, 13... Parallel output clock, 14... To/D conversion unit.

Claims (1)

[Claims] 1) In an A/D converter that converts an analog signal into a digital signal and outputs the digital signal, an additional signal indicating that the digital signal is within a specific range is output together with the digital signal. An A/D converter characterized by having a means for