JPH02280532A - Signal attenuator - Google Patents

Abstract

PURPOSE:To reduce the number of analog switches by adopting a constitution such that attenuation is applied to both a digital signal and an analog signal respectively. CONSTITUTION:A multiplier 21 applies multiplication between a digital input signal DIN inputted to each input terminal with a digital attenuation control signal DATC. A D/A converter 3 converts a 16-bit digital signal from a digital signal attenuation circuit 2 into a corresponding analog signal. When an analog signal being a half the digital input signal DIN is desired, bits of the attenuation control signal ATC are selected as [A11, A10, A9, A8]=0001, and [A7, A6,-, A1, A0]=10000000. The digital signal attenuation circuit 2 attenuates the signal into 1/2, the resulting signal is outputted as it is without being attenuated by an analog signal attenuation circuit 4 and in total a half of the analog signal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Minute Hand] The present invention relates to a signal attenuation device, and more particularly to a signal attenuation device that converts a digital signal into an analog signal attenuated by an arbitrary level.

[Conventional technology]

Conventionally, this type of signal attenuation device has a configuration as shown in FIGS. 5 and 6.

The former is a digital signal attenuation circuit 2AK equipped with a multiplier 21, which multiplies the digital input signal DIN and an attenuation amount control signal ATC1 to attenuate the digital input signal DIN, and then converts the digital input signal DIN to an analog signal by a D-A converter 3. Signal (A
The latter converts the digital input signal DIN into an analog signal using the %DA converter 38, and then outputs the attenuation amount control signal A'l to the four analog signal attenuation circuits. 'D-A converter 3 according to C2. It is configured to attenuate the output signal of.

The analog signal attenuation circuit 4A, as shown in FIG.
- a resistor R1 connected in series to the output signal 1 of the large converter 3B;
Analog switch Sll that divides the voltage with 1-RIN and turns on/off this divided signal with the attenuation amount control signal ATC2.
"" It is designed to select and output by SIN.

[Problem to be solved by the invention]

The above-mentioned conventional signal attenuation device has a digital input signal D.
Since the configuration is such that IN is attenuated and then converted to an analog signal, or the digital input signal DIN is converted to an analog signal and then attenuated, in the former case, multiplier 2
Since the bit precision of the digital input signal DIH is reduced by 1 µm, the so-called "quantization distortion" increases as the amount of attenuation increases.

For example, if this signal attenuation device is applied to adjust the volume of a sound source with 16-bit accuracy such as a compact disc player, the sound quality will deteriorate as the volume is lowered. The practically applicable range is said to be the attenuation amount up to a point where the bit precision is reduced by about 2 bits, and the attenuation amount at this time is only 12-0, which is not practical for volume adjustment.

In the latter case, the signal attenuation processing is performed after converting it to an analog signal, so there is no drawback like the former, but increasing the number of attenuation levels requires many analog switches and resistors. Therefore, the number of these circuit elements increases,
There is a drawback that the chip size increases when integrated circuits are implemented.

Generally, in the case of volume adjustment, at least 64 variable levels are required, so the circuit shown in FIG. 7 requires 64 analog switches and 64 resistors each. Furthermore, transmission gates are generally used as analog switches, but in order to pass large-amplitude signals, the transistor size of the transmission gate must be increased, and the chip size becomes larger.

An object of the present invention is to provide a signal attenuation device that can reduce the chip size by reducing the number of analog switches without increasing quantization distortion, and can cover a sufficient attenuation range. Ru.

(Means for Solving Problem III) The signal attenuation device of the present invention includes a control signal conversion circuit that converts an attenuation amount control signal into a digital attenuation amount control signal and an analog attenuation amount control signal, and a control signal conversion circuit that converts the value of the digital input signal into the A digital signal attenuation circuit that reduces and outputs the signal according to the digital attenuation amount control signal, a D-A converter that converts the output signal of this digital signal attenuation circuit into an analog signal, and a D-A converter that converts the output signal of this D-A converter into an analog signal. and an analog signal attenuation circuit that attenuates according to the analog attenuation amount control signal.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In this embodiment, the 12-bit attenuation control signal ATC is
It is equipped with a control signal conversion circuit 1 and a multiplier 21 for converting a 16-bit digital attenuation control signal DATC and a 4-bit analog attenuation control signal AATCK, and converts the value of a 16-bit digital input signal L'IN into a digital attenuation control signal. 1) A digital signal attenuation circuit 2 that reduces and outputs according to A'l'e, and 1) -A converter 3 that converts the output signal of this digital signal attenuation circuit 2 into an analog signal.
The configuration includes an analog signal attenuation circuit 4 that attenuates the output signal of the L)-A converter 3 in accordance with an analog attenuation amount control signal AATC.

Next, the operation of this embodiment will be explained.

The multiplier 21 multiplies the value of the digital input signal DIN input to each input terminal by the value of the digital attenuation amount control signal DATC. However, the value of the digital attenuation amount control signal DATC is always below the decimal point. It is a numerical value.

In other words, the digital attenuation control signal 1) has a weight of 110.5 (most significant bit of ATC), and the next bit is α
25. The next bit is Q, 125. Similarly, the least significant bit has a weight of 0.00390625. Therefore, when all bits are @1'', the total weight is 0.
9961 can be considered to be approximately 1.0.

The DA converter 3 converts the 16-bit digital signal r from the digital signal attenuation circuit 2 into a corresponding analog signal K.
f exchange.

The analog signal attenuation circuit 4 has a configuration as shown in FIG. Becomes conductive.

In this analog signal attenuation circuit 4, when the most significant bit AAo of the analog attenuation amount control signal AATC is 1#, the output signal of the D-A converter remains unchanged, AAg is "0", and AAI
When is “1”, %, AA6, AAI is “0”, A
When A2 is “1”, 1/16, AA6 = AA4 is 0
”, when AA3 is 1#, it becomes 1/64.

As shown in FIG. 3, the control signal conversion circuit 1 simply separates the 12-bit attenuation control signal ATC into an 8-bit digital attenuation control signal DATC and a 4-bit analog attenuation control signal AATC. It is.

Now, if you want to obtain an analog signal that is 0.5 times the value of the digital input signal L'IN, change each bit of the attenuation control signal ATC to (A11 + AI O + A9 + A8) = 0.
001 + (A7.A6.-, At, Ao) = 1000
It may be set to 0000.

By doing this, the digital signal attenuation circuit 2
The signal is attenuated to 2, and the analog signal attenuation circuit 4 outputs that 1 without attenuation, resulting in a total of 0.5 times the analog signal.

Similarly, if you want to obtain a 0.25x analog signal,
(A11, A1 o, Ag, 4) = Q QQ
l, (A7, A6.~At, Ao'1=0100
If it's 0000 then yes.

Next, when you want to obtain an analog signal of 0.25 times to 0.0625 times, (All, Alg, Ag, A4) = QQIQ (A?
*A6+~+AI+AO) = 11111111? That's good.

tb, (At t, A11), Ag, A4)
Id is fixed, [A7゜A6. ~． A□, A6) is
The value of the attenuation amount control signal A'I' C1 of the conventional signal attenuation device shown in FIG. 5 may be shifted by two bits in the upper direction. In this case, the analog signal attenuation circuit 4
The signal is attenuated to 1/4 by the digital signal attenuation circuit 1, and is attenuated by 0.99609375 times to 0.25 times by the digital signal attenuation circuit l.

The attenuation range and the value of the attenuation control signal TC
Shown in the table.

The 8-bit attenuation control signal ATC is converted into an 8-bit digital attenuation control signal DAT.
C and a 4-bit analog attenuation control signal AATC and outputs it.

The shifter 41 receives an analog attenuation amount control signal AATC(
The attenuation amount control signal ATC (Ao, ~, A7] is shifted according to the value of AA g, =, AA3), and the digital attenuation amount control signal DATC (DAo, ~, DA
, ). (Ao.

= +At) and (AA6, -, AA3)
Table 2 shows the relationship between the shift operation and the shift operation.

As can be seen from Table 1, digital signal attenuation circuit 1
The attenuation is in the range of 1 to α25 to suppress quantization distortion.

Further, only four analog switches 81 to 84 are required, and a wide attenuation range can be covered.

FIG. 4 is a circuit diagram showing another example of the control signal conversion circuit.

This control signal conversion circuit consists of an inverter l to 16,
Shifter 41. By configuring the OR gates 01 to G4 and the AND control signal conversion circuit LM in this manner, there is an advantage that the number of bits of the attenuation amount control signal A'l'C can be reduced.

〔Effect of the invention〕

As explained above, the present invention has a structure in which attenuation is performed for both digital signals and analog signals, and the number of analog switches can be reduced, thereby reducing the chip size. This has the effect of suppressing quantization distortion and covering a sufficiently wide attenuation range.

FIG. 2 is a circuit diagram showing a specific example of an analog signal attenuation circuit of the signal attenuation device.

1.1 person...control signal conversion circuit s 2+2A...
Digital signal attenuation circuit, 3.3mm y3B...D-A
Converter, 4°4A...analog signal attenuation circuit, 21,
21A... Multiplier.

41...C7ri, G, -04...0 Gate, 05
~G7...AND gate, I, -I,...inverter, R1-R4* RtIA-HrsNo"Jk anti, 8
1-84 + 811~S IN "'Analog switch.

Agent: Patent Attorney Susumu Uchihara

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a circuit diagram showing a specific example of the analog signal attenuation circuit of the embodiment shown in FIG. 1, and FIGS. 3 and 4 are circuit diagrams of the control signal conversion circuit of the embodiment shown in FIG. 5 and 6 are block diagrams showing first and second examples of conventional signal attenuation devices, respectively, and FIG. 7 is a circuit diagram showing a specific example. 2 Figure M 4 Concave

Claims (1)

[Claims] a control signal conversion circuit that converts an attenuation amount control signal into a digital attenuation amount control signal and an analog attenuation amount control signal; and a digital signal attenuation circuit that reduces the value of a digital input signal according to the digital attenuation amount control signal and outputs it. , a D-A converter that converts the output signal of this digital signal attenuation circuit into an analog signal, and an analog signal attenuation circuit that attenuates the output signal of this D-A converter according to the analog attenuation amount control signal. A signal attenuation device characterized by: