JP3138565B2 - Semiconductor integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit, and more particularly to a semiconductor integrated circuit having a circuit which requires external adjustment after the manufacture of the semiconductor integrated circuit, such as a voltage controlled oscillator (VCO) and a filter circuit. .

[0002]

2. Description of the Related Art Referring to FIG. 3, which shows a conventional monitoring method in a circuit requiring external adjustment after manufacturing a semiconductor integrated circuit, a circuit 3 requiring adjustment by an external element 1 of the semiconductor integrated circuit, and a monitor External draw-out terminal 7
And an external lead-out terminal 2, and outputs 12 a to 12 a of an adjustment monitor of the circuit 3 requiring the adjustment.
12d is a corresponding monitor external lead-out terminal 7
Connected to.

[0003]

In the conventional monitoring method described above, one monitor external lead-out terminal is provided for one circuit requiring adjustment, and there are a plurality of circuits requiring adjustment. However, there is a disadvantage in that the number of external lead-out terminals for monitoring is required by that number, and the number of external lead-out terminals of the semiconductor integrated circuit increases.

[0004]

SUMMARY OF THE INVENTION A semiconductor integrated circuit according to the present invention incorporates a large number of circuits that require external adjustment after the semiconductor integrated circuit is manufactured, and the number of monitor outputs for adjustment of the circuit that requires the adjustment. A switch circuit having the same number of inputs and one output is provided, each of the adjustment monitor outputs is connected to a corresponding input of the switch circuit, and an output of the switch circuit is connected to a monitor external lead-out terminal. A semiconductor integrated circuit provided with a control external lead-out terminal for controlling the switch circuit, further comprising a cutoff switch circuit interlocked with the switch circuit, wherein the adjustment monitor output is supplied to the switch circuit via the cutoff switch circuit. Is connected to the input of

[0005]

FIG. 1 is a block diagram showing an example showing the prior art of the present invention .
And a switch circuit 4 having a control external lead-out terminal 9 and a monitor external lead-out terminal 7. The adjustment monitor outputs 12a to 12d are:
Each of the switches 5 is connected to the corresponding input 5a to 5d, and the only output 6 of the switch circuit 4 is connected to the monitor external lead-out terminal 7.

By switching the switch circuit 5 having the same number of inputs and one output as the number of the circuits 3 requiring adjustment by the external control lead terminal 9, the monitor outputs 12a to 12d for adjustment are provided. Is output to the monitor external lead-out terminal 7, and the output signal is easily measured by the measuring device 8. The electrical characteristics of the circuit 3 requiring the adjustment are determined by selecting a plurality of monitor signals 12a to 12d by the control external lead-out terminal 7 as described above.
It functions as a semiconductor integrated circuit that outputs a target adjustment monitor signal to the external lead-out terminal 7.

Referring to the block diagram of FIG. 2 showing an embodiment of the present invention, this embodiment is provided with a monitor output 12a for adjustment of a circuit 11 which constantly oscillates and needs adjustment, such as a VCO.
Immediately after this, a switching circuit 10 for shutoff is provided. The output of the circuit 11 requiring the adjustment is connected to the input 5a of the switch circuit 4 via the switch circuit 10 for shutoff. Here, the switching circuit 10 and the switch circuit 4 are linked to each other, so that the input 5a of the switching circuit 4 is selected, so that the switching circuit 10 is turned on.

As described above, the provision of the switching circuit 10 has an effect of preventing influence on other circuits .

[0009]

As described above, the present invention provides a semiconductor integrated circuit in which a single external lead-out terminal is used as a monitor external lead-out terminal for an integrated circuit having a large number of circuits requiring external adjustment. By reducing the number of external lead-out terminals of the circuit and providing an interrupting switch circuit immediately after the adjustment monitor output in an oscillation circuit or the like that oscillates constantly, the influence on other circuits can be prevented.

According to the present invention, since the number of external monitor terminals is one, the connection between the external monitor terminal and the measuring device can be fixed at the time of adjustment, and the number of man-hours at the time of adjustment can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a prior art example of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional semiconductor integrated circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 External element for adjustment of semiconductor integrated circuit 2 External lead-out terminal for adjustment of semiconductor integrated circuit 3 Circuit which requires external adjustment after manufacture of semiconductor integrated circuit 4 Switch circuit 5a-5d Input of switch circuit 6 Output of switch circuit 7 External read-out terminal for adjustment 8 Measurement device 9 External lead-out terminal for control 10 Switch circuit for cut-off 11 Circuit that constantly oscillates and requires adjustment of semiconductor integrated circuit 12a to 12d Monitor output for adjustment

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 27/00 H01L 27/04 H01L 21/882

Claims (1)

(57) [Claims] A semiconductor integrated circuit includes a large number of circuits that require external adjustment after manufacturing, and has the same number of inputs and one output as the number of monitor outputs for adjustment of the circuit requiring adjustment. A switch circuit is provided, wherein each of the adjustment monitor outputs is connected to a corresponding input of the switch circuit, and an output of the switch circuit is connected to a monitor external lead terminal, and a control external lead terminal for controlling the switch circuit. A semiconductor integrated circuit having a switch circuit interlocked with the switch circuit, wherein the monitor output for adjustment is connected to an input of the switch circuit via the switch circuit for cutoff. Integrated circuit.