JPS6398872A - Analog/digital ic - Google Patents

Abstract

PURPOSE:To operate an analog circuit and a digital circuit properly against the change of a power supply system by providing a potential setting terminal corresponding to the change of a single power supply or a bipolar power supply and using a reference potential for the analog circuit and the digital circuit individually. CONSTITUTION:An IC2 is a recording/reproducing IC is for a VTR and provided with an analog circuit 4 amplifying an audio signal and a digital circuit 8 receiving a control signal from a system controller 6 to apply switching control. The analog circuit 4 is provided with a highest potential terminal 32, a reference potential terminal 34 and a minimum potential terminal 36 so as to cope with a single power supply and a bipolar power supply, a reference potential terminal 39 is provided to the digital circuit 8 in addition to a reference potential terminal 32 of the analog circuit 4 to use the reference potential individually for the analog circuit 4 and the digital circuit 8. Thus, the digital circuit 8 is operated properly by using a control signal from the system controller 6 independently of the change in the power system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an analog/digital IC that includes an analog circuit and a digital circuit.

[Conventional technology]

BACKGROUND ART Conventionally, various ICs have been put into practical use that are packaged with analog circuits and digital circuits.

For example, the I
There is C (recording/playback IC), but this recording/playback I
In C, the analog signal processing system amplifies the audio signal in recording or playback mode, and the analog signal processing system receives digital signals from a system controller such as a microcomputer installed externally, and switches the operating mode of the analog signal processing system (recording/playback mode). It is equipped with a digital control system that performs playback, mute, equalizer operation, and input or output switch switching.

[Problem that the invention seeks to solve]

By the way, one of the aims of converting electronic circuits to ICs is to make the circuits more compact by integrating a large number of discrete elements onto a single substrate. However, in audio systems, there are elements that cannot be integrated into ICs, so there are There is a capacitor used for coupling.

Such a capacitor is externally attached by providing a connection terminal to I'C, but this increases the number of parts and impairs the merits of IC implementation.

Therefore, in order to reduce the number of such capacitors, instead of using a single power supply with a positive voltage or a negative voltage with zero potential as the reference potential, a positive and negative power supply (commonly known as ±2 power source) is used.

However, conventional analog/digital ICs such as recording/reproducing ICs are set to be used exclusively for a single power supply, or exclusively for positive and negative power supplies. Furthermore, in order to reduce the number of terminals, the analog circuit and digital circuit share a common reference potential terminal.

For this reason, if an IC for a single power supply is driven by a positive and negative power supply, or an IC for a positive and negative power supply is driven by a single power supply, there will be no problem on the analog circuit side, but on the digital circuit side, the threshold voltage value will change. This will cause a mismatch with the control voltage from the system controller, making it impossible to perform proper switching control. Therefore, it is necessary to shift the control voltage from the system controller/troller to an appropriate voltage value using a level shift circuit. Is required. therefore,
In exchange for omitting the capacitor due to changing the power supply type, a level shift circuit or the like must be installed, which has the disadvantage that the circuit becomes more complicated.

Therefore, the present invention provides an analog/digital IC that allows digital circuits to operate properly together with analog circuits without adding a level shift circuit when changing the power supply system of a single power supply or a positive/negative power supply. It provides:

Means for Solving Problem C] The analog/digital IC of the present invention is an IC in which a digital circuit 8 is installed together with an analog circuit 4, as shown in FIGS. Potential setting terminals (highest potential terminal 32, reference potential terminal 34, 39, lowest potential terminal 3) corresponding to changing the power supply format of positive and negative power supplies
6), and the reference potentials of the analog circuit 4 and the digital circuit 8 are made individual.

[For production]

In this invention, signal processing is possible in response to the selection of a single power supply or positive and negative power supplies, and the reference potential on the digital circuit 8 side can be set separately from that on the analog circuit 4 side, so that the system controller 6, etc. Appropriate control can be performed in response to control signals (voltage, etc.) from.

〔Example〕

1 and 2 show embodiments of an analog/digital IC according to the present invention. The embodiment in FIG. 1 shows a case using a single power supply, and FIG. 2 shows a case using a positive and negative power supply.

In FIGS. 1 and 2, IC2 is a recording/playback IC for a VTR, which is an example of an analog/digital IC, and is connected to an analog circuit 4 for amplifying audio signals, and a system controller 1 to a roller 6. A digital circuit 8 is also provided which performs switching in response to a control signal; till:1'J.

The analog circuit 4 connects the magnetic head 1 which is a signal source during reproduction.
When the reproduction signal from 0 is DC cut through the capacitor 12 and applied to the terminal 14, the reproduction signal is amplified by the reproduction amplifier 40, and the amplified output is applied to the line amplifier 41 through the switch circuit 80 for amplification.
It is taken out as playback output from terminal 16, and when recording,
The audio signal applied to the input terminal 18 is applied to the line amplifier 41 through the switch circuit 80, amplified by the line amplifier 41, and then applied to the recording amplifier 42 through the switch circuit 81 for amplification, and the amplified output is sent to the output terminal. 20 to the magnetic head 10 through the capacitor 22#3 and the resistor 24.

A specific AC bias signal is applied to the magnetic herad 10 from an AC bias oscillator 28 through a variable resistor 26 .

On the other hand, the digital circuit 8, as a control means, receives a control signal from the system controller 6 at a terminal 30.31 and applies it to a logic circuit 82.83, and uses the logic output of the logic circuit 82 to switch the switch circuit 80 to the recording side (R). Playback side (P
), and at the same time, the switch circuit 81 is switched to the conductive state (R) during recording and to the cutoff state B (P) during reproduction according to the logical output of the logic circuit 83.

In the IC 2 in which the digital circuit 8 is installed together with the analog circuit 4, the highest potential terminal 32 is used as a potential setting terminal for setting a specific potential on the analog circuit 4 side.
A reference potential terminal 34 and a lowest potential terminal 3G that determine the operating point of the analog circuit 4 are provided, and the lowest potential terminal 36 is connected to the IC2.
connected to the board. A resistor 43 is installed between the highest potential terminal 32 and the reference potential terminal 34, and a resistor 44 is installed between the reference potential terminal 34 and the lowest potential terminal 36. amplifier 40
．． The reference voltage applied to 41.42 as a driving voltage and set on the reference potential terminal 34 side becomes a bias voltage for each amplifier 40.41.42 through a buffer circuit 45 functioning as an impedance converter.

By the way, since FIG. 1 shows a case using a single power supply, a positive voltage VCC is applied to the highest potential terminal 32 from a power supply 37 constituting the single power supply, and a reference potential terminal for setting the operating point voltage of the analog circuit 4 is applied. A capacitor 38 is connected to the resistor 43 for stabilization against power supply ripple, etc.
．． A voltage (Vcc/2) which is half of the voltage Vcc is set by the voltage dividing circuit 44, and the lowest potential terminal 36
is grounded.

On the digital circuit 8 side, each logic circuit 82.8
A voltage source 84 for setting a threshold voltage for the analog circuit 3 is provided, and a reference potential terminal 39 for setting a reference potential that is individualized from the analog circuit 4 is provided. Here, the individualized reference potential refers to a voltage source 8 that does not depend on the power supply voltage in order to eliminate the effects caused by changes in the power supply format.
4, and a base independent from the analog circuit 4 side! The $ potential terminal 39 is installed to set an independent reference potential, and in the embodiment, it is grounded to set the reference potential.

In addition, when inputting and outputting signals in an analog circuit, a coupling capacitor (capacitor 12. shown in FIG. 1) is used.
In the case of positive/negative power supply drive where step 22) can be omitted,
As shown in FIG. 2, the first power supply 37A has the reference potential terminal 34 grounded and the highest potential 6::5 terminal 32 side set to a positive voltage between the reference potential terminal 34 and the highest potential 5:iiIC3. , a second power supply 37B with a positive voltage on the reference potential terminal 34 side between the reference potential terminal 34 and the lowest potential terminal 36.
For example, +5V is connected to the highest potential terminal 32 as a voltage CC, and - is connected to the lowest potential terminal 36 as a voltage Vl).
5) Set.

In the IC 2 in which the analog circuit 4 and the digital circuit 8 are installed in this way, the highest potential terminal 32, the base 1 (potential terminal 34 and the lowest potential terminal 36) are installed on the analog circuit 4 side, and a single power supply and positive and negative power supplies are connected. In addition, a reference potential terminal 39 is installed on the digital circuit 8 side separately from the reference potential terminal 34 of the analog circuit 4, and each reference potential of the analog circuit 41. and digital circuit 8 is made individual. Irrespective of changes in the power supply format of the positive and negative power supplies, the digital circuit 8 can be caused to perform appropriate logical operations by the control signals from the system controller 6. That is, in the IC 2 of the embodiment, the control signals from the system controller 6 Digital circuit 8
The analog circuit 4 is operated to set the recording or playback mode to the analog circuit 4.

Although the embodiment has been described using a positive power supply as a single power supply, the analog/digital IC of this invention has a negative power supply.
This can also be applied when using a quasi-source.

〔Effect of the invention〕

As explained above, according to the present invention, potential setting terminals corresponding to changes in the 4j, - power supply or positive and negative power supplies are installed, and reference potentials for analog circuits and digital circuits are separated, so that a single power supply or Proper operating conditions can be obtained regardless of changes in the power supply format of the positive and negative power supplies, and there is no need for a level shift circuit or the like on the digital circuit side to accommodate changes in the power supply format, and control signals can be easily transmitted from control means such as a system controller. can be added directly to perform the desired operation.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing an embodiment of an analog/digital IC according to the present invention. 2...IC 4...Analog circuit 8...Digital circuit 32...Highest potential terminal 34...Reference potential terminal 36...Lowest potential terminal 37.37A, 37B...Power supply 39...・Reference potential terminal

Claims (1)

[Claims] It is an IC that has a digital circuit as well as an analog circuit, and is equipped with a potential setting terminal that corresponds to a change in the power supply type of a single power supply or positive/negative power supply, and has an analog/digital IC that has separate reference potentials for the analog circuit and digital circuit. I.C.