JPS5936451B2 - integrated circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an integrated circuit device that reduces noise generated in the analog signal during switching in an integrated circuit device that includes a circuit that handles analog signals and an electronic switching circuit.

Conventionally, integrated circuit devices including electronic switching circuits that handle analog signals have been widely used as squelch circuits, various automatic switching circuits, and their display circuits.

However, in general, a large amount of noise is generated each time the switching circuit operates, deteriorating the quality of the analog signal.

Specifically, in the case of a circuit that handles audio signals, a harsh shock sound is output from a speaker or the like, which is not only unpleasant, but may even destroy the speaker.

In the case of television, the screen becomes blurred.

When we investigated the cause of this, we found that when the switching circuit directly intermittents the analog signal, the superimposed DC component also intermittents, resulting in a change in the DC component, which is differentiated by the coupling capacitor, and then amplified and output at the subsequent stage. It has been found that, for example, changes in the current flowing through the common wiring of a circuit can cause voltage changes in the wiring resistance or the internal resistance of the power supply, which can affect circuits that handle analog signals. Ta.

The present invention relates to the latter solution.

FIG. 1 is a block diagram of a conventional FM stereo broadcast multiplex demodulator.

A power supply 1 is applied to a power supply terminal 5 on the external shape (on the lead frame) of the integrated circuit device 4 via its internal resistance and resistance (equivalently indicated by 2) associated with wiring.

Also, the power supply 1 is bypassed with a capacitor 3 for the social gathering.

The voltage applied to the terminal 5 is applied to the lead-out terminal (bonding butt) 7 on the integrated circuit board through a minute resistance (equivalently indicated by 6) present in the lead wire etc. Supplied as block power.

Similarly, the ground terminal is grounded from the lead-out terminal 8 on the integrated circuit board through a resistance associated with wiring (equivalently indicated by 9) and a terminal 10 on the outside.

On the other hand, the FM detected signal 11 is passed through a coupling capacitor 12 to an input terminal 13 (correctly, this part can also be divided into a terminal on the outside and a terminal on the board, but since it is not directly related to the present invention, the latter is omitted.

) is applied to the emitter follower circuit 15 in the integrated circuit device, and its output is applied to the demodulation circuit 16 and the subcarrier regeneration circuit 23, respectively.The demodulation circuit 16 multiplies the regenerated subcarrier and the above signal, and A demodulated output is obtained at both ends of load resistors 19 and 21 via terminals 17 and 18.

Note that the capacitors 20 and 22 are for de-emphasis.

Here, the carrier wave regeneration circuit 23 doubles the pilot signal, but at that time, components 25, 27, which cannot be incorporated into the integrated circuit.
28, it has a path that is connected to the power source 1 or grounded without going through the power source and ground terminals 5 and 10.

29 has a pilot signal or manually controls the stereo
This is an electronic switching circuit for monaural switching and driving the display lamp 31.

33 and 34 are signal output terminals to the next stage.

Further, 14 is a voltage stabilizing circuit.

In such a circuit configuration, noise is generated every time the switching circuit 29 switches, and the noise is amplified in a subsequent stage (not shown), producing unpleasant sound from the speaker.

One of the reasons for this is that, due to the structure of the integrated circuit device, it is necessary to lead out the lead-out terminals 7 and 8 on the board to the terminals 5 and 10 on the outside using thin wires, which results in a slight resistance 6 and 9.
exists, and the subcarrier regeneration circuit 23. is connected from the power supply before and after switching. There is a difference in the DC component of the current supplied to the switching circuit 29 etc., and there is also a difference in the DC component of the current flowing through the terminals 24 and 26, which causes a difference in the DC component of the current flowing to the power supply terminal 5 and the ground terminal 10. This is because the voltage generated across the microresistances 2, 6.9, etc. fluctuates.

Now, assuming that the resistance value is 0.5Ω, it will be 10 to 100 before and after switching.
If there is a current change of mA, the number 1077LVI)p
This results in a voltage change of .

First, considering the influence of the minute resistance 9 on the ground side, the input signal is transmitted from the signal source 11 to the capacitor 12. It is added to the emitter follower circuit 15 via the terminal 13, and the lead-out terminal 8. Since the signal returns to the signal source 11 via the terminal 10 of the microresistance 9, the voltage change across the microresistance 9 on the ground side becomes equivalent to that applied in series to the input signal.

Also, considering the influence of minute resistance on the power supply side, the internal resistance of the power supply 2
The DC voltage between the terminals 33 and 34 and the ground directly changes due to the fluctuation in the voltage drop caused by the voltage drop.

This is because even if the voltage at the lead-out terminal 7 on the board fluctuates somewhat, the voltage stabilizing circuit 14 keeps the current flowing through the terminals 17 and 18 almost constant, so the voltage across the resistors 19 and 21 remains almost constant. Become.

In other words, the voltage change occurring in the internal resistance 2 of the power supply appears directly between the output terminals 33, 34 and ground.

The sum of these voltage changes is differentiated by a coupling capacitor, etc., and amplified by an amplifier circuit with a gain of <40 dB or more after terminals 33 and 34, so a voltage sufficient to produce an unpleasant sound is applied to the speaker. Become.

FIG. 2 is a block diagram of an FM stereo broadcast multiplex demodulator to which the present invention is applied, and FIG. 3 is a detailed circuit diagram thereof.

The same symbols indicate the same thing.

Elements 401 to 409 constitute the voltage stabilizing circuit 14 and keep the emitter voltages of the transistors 402 and 404 at a constant value.

410 to 415 constitute an emitter follower circuit 15, which impedance converts the input signal from the terminal 13 and supplies it to the demodulation circuit 16 and the subcarrier regeneration circuit 23.

467 is a terminal to which an external capacitor 468 is connected.

416 to 426 are elements constituting a switching type demodulation circuit 16 that is widely used in integrated circuits.

431 to 444 are elements constituting the subcarrier regeneration circuit 23. A transistor 439 amplifies the input signal, an external tuning circuit 25 selects a pilot signal, and the transistor 434,
It is class C amplified by 436, shaped by diodes 443 and 444, and doubled by 441 to obtain a reproduced subcarrier wave to an external 38 KHz tuning circuit 464.

A portion of the pilot signal is rectified by transistor 438 and applied to switching circuit 29 .

It is smoothed by a capacitor 466 connected to the terminal 465 (
Here is the manual stereo/mono switch 469
It is also a connection terminal.

) 449 to 453, and its output drives lamp drivers 454 to 456 to blink the lamp 31, and the transistor 4
46 to switch the subcarrier recovery circuit 23 into operation or non-operation.

There are two points that are different from the conventional one due to the present invention.
The point is on the ground side.

Signal input is a signal source 11, a capacitor 12. Terminal 13. Emitter follower circuit 15. Grounding terminal 308 (
The resistance (represented by 309) forms a closed circuit that returns to the signal source via the terminal 310, but the current flowing through the microresistance 309 does not practically change before and after switching between stereo and monaural. The voltage across such a resistor is constant and is not influenced by the switching circuit via the input.

Specifically, such a resistor is provided with a voltage stabilizing circuit 14. Emitter follower 15. Demodulation circuit 16. Only the currents flowing through the loads 319 and 321 and the emitter current of the first stage transistor 439 of the subcarrier regeneration circuit 23 are flowing, and neither of them changes due to the switching operation.

The remaining portion is grounded via the second grounding terminal 355 (equivalent resistance 356) and the external terminal 357, so the potential of the grounding terminal 355 changes every time the subcarrier regeneration circuit 23 and the switching circuit 29 are connected to form a closed circuit on the substrate, so the operation of this circuit does not depend on slight fluctuations in the potential.

The second point is the power supply. That is, since the bias of the output current of the demodulator 16 is stabilized by the voltage stabilizing circuit 14 as in the conventional case, the output current remains almost constant in both direct current and alternating current even if the power supply voltage fluctuates.

Since the diode 351 and the transistor 352 formed on the same substrate have a constant current amplification factor determined by the emitter area ratio, a voltage proportional to the output current of the demodulator 16 is generated in the load 319.

This is insensitive to fluctuations in power supply voltage. Therefore, even if the potentials of the terminal 5 and the lead-out terminal 7 change due to the internal resistance 2 and minute resistance 6 of the power supply 1 during switching, there is no change in the DC component of the voltage of the output terminals 33, 34 as in the conventional case.

Output terminals 320 and 322 on the outside are de-emphasis capacitors.

In this way, it was possible to reduce the noise generated during switching.

Note that the DC component of the output voltage has a slight dependence on the power supply voltage due to the dynamic resistance of the constant voltage element, etc. However, in reality, the fluctuation is about 1/30 of the power supply voltage fluctuation, so the voltage fluctuation that occurs in the internal resistance 2 of the power supply 1. 1/30 of this occurs in the output at the time of switching, but it is sufficiently small that it can be ignored.

The means for keeping the DC component of the output voltage constant is not limited to the one shown in FIG. 2; for example, as shown in FIG. Means (voltage stabilization means) 581
~ 583, or load resistance 19 as shown in the same figure.
, 20 may be differentially coupled to the next stage 535, 536 via terminals 533, 534.

Although it seems that the integrated circuit device to which the present invention is applied always requires one more terminal than the conventional one, as shown in FIG. 5, two grounding points (bands) 602.
03 and connect the leader lines 605 and 606 respectively,
If these are connected together to the terminal 608 on the same external shape (lead frame), there is no need to increase the number of external terminals.

Here, since the terminal 608 on the outside (lead frame) is large, its resistance is smaller than that of the lead wires 620, 621, etc., and even in this case, the effects of the present invention are not diminished.

Note that 604, 607, and 609 are other connection points for drawing out, drawing lines, and terminals on the external shape, respectively.

The present invention is not limited to FM stereo broadcast multiplex demodulation circuits, but can generally be applied to integrated circuits in which a circuit that handles analog signals and an electronic switching circuit are included on one substrate.

The important thing here is that the ground side of the wiring connected to the two electrodes of the power supply should be connected to the ground terminal of the analog signal system so that the current of the circuit (including the switching circuit itself) that causes a current change when switching does not flow through it. The remaining debris will flow to the second ground terminal),
On the non-grounded side of the power supply, it is sufficient to prevent the DC voltage of the analog signal output terminal from being affected by power supply voltage fluctuations by means such as those illustrated in Figures 3, 4, and 5. It is possible to create a circuit that is not affected by the internal resistance of the terminals or the battery.

Also, changes in the DC component during switching are a problem, and changes in the AC component are usually caused by the power supply's bypass capacitor (see Figures 1 and 3).
This is not a problem because it is absorbed by step 3) in the figure.

However, if a transient current flows during switching, for example when a capacitor is charged or discharged, a DC component will be generated transiently, so these currents should be passed through the ground lead wire of the analog signal system mentioned above. must not.

[Brief Description of the Drawings] Fig. 1 is an example of a block diagram of a conventional FM stereo broadcasting multiplex demodulator, and Fig. 2 is an example of a block diagram of a conventional FM stereo broadcasting multiplex demodulator.
An example of a block diagram of an M stereo broadcasting demodulator; FIG. 3 is an example of a detailed circuit diagram; FIG. 4 is another embodiment of the means for keeping the output DC voltage constant, which is part of the present invention; The figure shows another embodiment of the connection to the grounding lead terminal which is part of the present invention. Identical parts in each figure are given the same numbers. 1 is a power supply, 2 is an equivalent representation of its internal resistance, 4 is an integrated circuit device, 6 and 9 are equivalent representations of the resistance of the power supply and grounding wires, respectively, and 7 and 8 are the same as a board. Upper extraction terminal (bonding pad), 5 and 10 are terminals on the outer shape (on the lead frame), 14 is a voltage stabilization circuit, 15 is an emitter follower circuit,
16 is a demodulation circuit, 23 is a subcarrier regeneration circuit, 29 is a switching circuit, 20 and 22 are load resistors, 31 is a lamp, 33
and 34 are signal output terminals to the next stage.

Claims (1)

[Claims] 1. A signal processing circuit and an electronic switching circuit that changes the signal processing operation of the signal processing circuit to obtain different output signals, the electronic switching circuit changing the direct current flowing through it when switching. In an integrated circuit device in which an electronic switching circuit is integrated on one semiconductor substrate as an integrated circuit element, the signal processing circuit is operated by a voltage supplied separately from the electronic switching circuit from a voltage stabilizing circuit. The ground line of the signal processing circuit and the connection line of the electronic switching circuit are formed by separate wires within the integrated circuit element, and each wire is connected to two separate ground lines of the integrated circuit element. 1. An integrated circuit device characterized in that the two grounding lead-out terminals are respectively connected to different grounding external terminals via conductors. 2. The receiver for human input signals includes a signal processing circuit that generates a desired output signal and a switching circuit that changes the operation of at least a part of this signal processing circuit so that a different output signal is generated. In an integrated circuit device in which a switching circuit in which a flowing DC current component fluctuates is configured on one semiconductor substrate, the signal processing circuit is configured such that the DC current component of the signal processing circuit does not substantially change even when switching operations. is operated by voltage from a voltage stabilizing circuit configured on the semiconductor substrate, and the ground point of the signal processing circuit and the ground point of the switching circuit connect two independent wiring lines on the semiconductor substrate. An integrated circuit characterized in that the integrated circuit is connected to two grounding electrodes provided on the semiconductor substrate through the semiconductor substrate, and each of these two grounding electrodes is connected to a common external lead through a metal conductor. Device.