JP2751357B2 - Trimming code setting circuit - Google Patents

Description

The present invention relates to a trimming code setting circuit, and more particularly to a trimming code setting circuit for setting a trimming code for a trimming circuit of a semiconductor integrated circuit device.

[Conventional technology]

In a semiconductor integrated circuit device, especially the setting of a reference voltage value and the setting of a circuit current value of an analog circuit or the like have strict catalog standards, and require a trimming circuit to drive the voltage value and the current value into the catalog standard. .

For setting the trimming code for this trimming circuit, for example, a trimming code setting circuit as shown in FIG. 2 has been used.

This trimming code setting circuit shows an example where the trimming code is 3 bits.

This circuit includes a P-channel MOS transistor M having a source connected to a first power supply terminal (power supply voltage V _DD = 5 V).
10 and one end connected to the drain and gate of the transistor M10 and the other end connected to a second power supply terminal (power supply voltage V _SS =
-5V) and a constant current circuit 51 having a constant current source 51 for supplying a predetermined current to the transistor M10, and a plurality of thin film resistors R1 each having one end connected to a second power supply terminal ( _VSS ).
To R3 and the source are connected to the first power supply terminal (V _DD ), the drains are respectively connected to the other ends of the thin film resistors R1 to R3, and the gates are both transistors of the constant current circuit 5.
P-channel MOS connected to the drain and gate of M10 and forming a current mirror circuit together with the constant current circuit 5
And a code setting unit 4 having inverters 41a to 41c that connect the input terminals of the transistors M7 to M9 corresponding to the drains of the transistors M7 to M9 and output trimming codes. I was

Before the trimming code is set, all thin film resistors R1
Since R3 is not disconnected and the transistors M7 to M9 form a current mirror circuit together with the constant current circuit 5, current flows through the thin film resistors R1 to R3 with a predetermined ON resistance. At this time, the thin film resistor
Since the resistance value of R1~R3 usually sufficiently smaller than the ON resistance of the transistor M7～M9, the level of the input end of the inverter 41 _A to 41 _C is low, so that all levels of the trimming code CD1~CD3 is "1" I have.

When the trimming codes CD1 to CD3 are set to, for example, "101", the thin film resistor R2 is cut as shown in FIG. Since the thin film resistor R2 is cut level of the input terminal of the inverter 41 _B is climb may be trimming code CD2 is "0", the trimming code CD1~CD3 "101".

The cutting of the thin-film resistors R1 to R3 is performed by cutting the normal thin-film resistors R1 to R3.
A pad made of aluminum or the like is taken out from each of the nodes of the transistors M7 to M9 and a voltage is applied to the thin film resistors (R1 to R3) to be cut in a wafer inspection process using a tester or the like and a current is applied to blow out, Then, only the desired thin film resistors (R1 to R3) are cut by a laser.

[Problems to be solved by the invention]

The above-described conventional trimming code setting circuit has a configuration in which the trimming code is set by cutting off a desired thin film resistor (R1 to R3). It must not change permanently while the semiconductor integrated circuit device used is operating, and requires high reliability, but the cutting state of the thin film resistors (R1 to R3) is incomplete. Since it is difficult to completely remove the trimming code, the trimming code may change due to a change over time during use, resulting in a failure.

That is, assuming that the current flowing through the transistors M7 to M9 forming the ratio circuit with the thin film resistors R1 to R3 is, for example, 10 μA,
If the leakage current at the cut portion of the incompletely cut thin film resistor (R1 to R3) is slightly smaller than 10 μA, the product becomes a good product. But then, the output of the inverter (41 _A ~41 _C) as soon as the current leakage in the aging exceeds slightly increased to 10μA becomes the changed defect.

Thus, in the conventional trimming code setting circuit,
Since the incompletely cut part cannot be completely removed as a defect, the reliability of the semiconductor integrated circuit device incorporating the trimming code setting circuit has been significantly reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a trimming code setting circuit that can reliably remove an incompletely cut thin film resistor as a defect.

[Means for solving the problem]

In the trimming code setting circuit according to the present invention, the source is set to the first
A first transistor connected to a power supply terminal of the first transistor, one end connected to a drain and a gate of the first transistor, and the other end connected to a second power supply terminal to supply a predetermined current to the first transistor. A first constant current circuit having a first constant current source flowing therein, a second transistor having a source connected to the first power supply terminal, and one end connected to a drain and a gate of the second transistor; Connect the other end to the second
The second transistor is connected to a power supply terminal of the second transistor so that a predetermined current smaller than the first transistor flows through the second transistor.
A first constant current circuit having a constant current source, and first and second input terminals connected to the drain and gate of the first and second transistors, respectively, so that a control signal is supplied to the first and second transistors.
And a switching circuit for connecting the first input terminal to the output terminal at the second level and the second input terminal to the output terminal at the second level, and one end to the second power supply terminal. A plurality of thin film resistors and a source are respectively connected to the first power supply terminal, drains are respectively connected to the other ends of the thin film resistors, and gates are both connected to output terminals of the switching circuit. A code setting unit including a plurality of third transistors each forming a current mirror circuit together with the second constant current circuit.

〔Example〕

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

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

The first constant current circuit 1 includes a first transistor having a source connected to a first power supply terminal (power supply voltage V _DD = + 5 V).
M1 and one end connected to the drain and gate of the first transistor M1 and the other end connected to a second power supply terminal (power supply voltage V _SS =
-5V) and a predetermined current I is supplied to the first transistor M1.
₁ and a first constant current power supply 11 for flowing 1.

The second constant current circuit 2 includes a second transistor M2 having a source connected to the first power supply terminal (V _DD ), one end connected to the drain and gate of the second transistor M2, and the other end connected to the second transistor M2. and a second constant current source 21 supplying a current I ₂ of the power supply terminal (V _SS) and connected first to the second transistor M2 to the transistor M1 smaller predetermined.

Switching circuit 3, the transistors M3, M4 and M5, two transfer gates consisting of M6 and two inverters 31 _A, 31 _B
And the first and second input terminals are connected to the drain and gate of the first and second transformers M1 and M2, respectively, so that the control signal A () is at a high (low) level in actual use. When the first input terminal is connected to the output terminal at the time of (low) in the test
At the level, the second input terminal is connected to the output terminal.

Code setting unit 4, a plurality of thin film resistors R1~R3 respectively connecting one end to the second power supply terminal (V _SS),
The source is connected to the first power supply terminal (V _DD ), the drain is connected to the other end of each of the thin film resistors R1 to R3, and the gate is connected to the output terminal of the switching circuit 3 to connect the first and second terminals. And a plurality of third transformers M7-M9 forming current mirror circuits together with the constant current circuits 1 and 2, respectively, and input terminals connected to drains of the transformers M7-M9 to output trimming codes CD1-CD3. Multiple inverters
41 _{A to} 41 _C are provided.

By the way, the object of the present invention is that a non-defective product becomes a good product at the time of a test, and the leakage current of the cut portion of the thin film resistors R1 to R3 increases with the lapse of time during use, resulting in a failure. Is to remove those that have potential during the test.

As a method, the current flowing through the transistors M7 to M9 during the test is made smaller than the current flowing during actual use.

That is, the current determined by the constant current circuit 2 is set sufficiently smaller than the current determined by the constant current circuit 1.

For example, the current at the time of test is 1/10 of the current at the time of actual use.
Set to. Here, assuming that the current in actual use is 10 μA, it is set to 1 μA in the test.

By doing so, a non-defective product will not be obtained unless the leakage current of the thin film resistors (R1 to R3) cut during the test is less than 1 μA. Also, in actual use, if the leakage current does not increase by 10 μA or more, it will not be a defective product and the margin will be significantly increased compared to the conventional trimming code setting circuit, and if the cutting is incomplete, ensure that it is incomplete. Can be removed as defective.

〔The invention's effect〕

As described above, according to the present invention, the cut-off state of the thin-film resistor can be detected with a sufficient margin by making the current at the time of the test flowing through the code setting unit sufficiently smaller than the current at the time of actual use. Therefore, the incomplete cutting of the thin film resistor can be reliably removed as a defect,
There is an effect that the reliability of a semiconductor integrated circuit to which this circuit is applied can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are circuit diagrams showing a conventional trimming code setting circuit, respectively, and related parts when a trimming code is set by the trimming code setting circuit. FIG. 1,2 constant current circuit, 3 switching circuit, 4 code setting section, 5 constant current circuit, 11, 21 constant current source, 31 _A , 3
1 _B , 41 _{A to} 41 _C ... Inverter, 51 ... Constant current source, M1 to M10
...... Transistors, R1 to R3 ... Thin film resistors.

Claims (1)

(57) [Claims] A first transistor having a source connected to a first power supply terminal, one end connected to a drain and a gate of the first transistor, and the other end connected to a second power supply terminal. A first constant current circuit having a first constant current source for supplying a predetermined current to the first transistor; a second transistor having a source connected to the first power supply terminal; A second constant current source connected to the drain and the gate of the transistor and having the other end connected to the second power supply terminal and flowing a predetermined current to the second transistor smaller than the first transistor. A second constant current circuit, and first and second input terminals respectively connected to drains and gates of the first and second transistors, respectively, and when the control signal is at a first level, the first constant current circuit is connected to the first and second input terminals. Connect input end to output end A switching circuit for connecting the second input terminal to the output terminal at the second level; and a plurality of thin film resistors each having one end connected to the second power supply terminal and a source connected to the first power supply. And a drain connected to the other end of each of the thin-film resistors, and a gate connected to the output end of the switching circuit to form a current mirror circuit together with the first and second constant current circuits. And a code setting unit including a plurality of third transistors.