JP3228165B2 - Trimming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trimming method , and more particularly to a trimming method which is suitably used for realizing a highly accurate analog semiconductor integrated circuit.

[0002]

2. Description of the Related Art In order to realize a highly accurate analog semiconductor integrated circuit, a method of adjusting on-chip trimming called "Zener zap trimming" is widely used as a means for correcting variations caused in a manufacturing process after manufacturing. . This is equivalent to the fact that a Zener diode does not exist in a circuit in a bias state below its breakdown voltage. On the other hand, when a voltage higher than the breakdown is externally applied to the Zener diode and a large current flows, the diode is destroyed ( This utilizes the property of being zapped and permanently short-circuited. Then, several such zener diodes are arranged in the circuit in advance, and when zapping is not performed, the diodes do not conduct in the forward direction, and under a bias condition that a voltage higher than the zener voltage is not applied in the reverse direction. In trimming, zapping is performed by deciding a designated portion while looking at a circuit error, and only a few appropriate combinations are short-circuited to reduce the total error.

FIG. 5 shows an example of a conventional trimming circuit. Referring to FIG. 5, this circuit includes transistors Q1,
A current mirror circuit is constituted by Q2 and the resistors R1 to R7, and by changing the resistance ratio of the resistor R1 connected to the emitter of the transistor Q1 and R2 to R7 connected in series to the emitter of the transistor Q2. The relationship between the current input to the input terminal and the current output from the output terminal can be changed.

[0004] First, the Zap terminals P1 to P6 are all opened, and the output current of the output terminal when a predetermined input current is applied to the input terminal is measured.
Is short-circuited, and the output current is measured in the same manner as described above. Thereafter, the combination of zap terminals is sequentially short-circuited to determine which Zener diode short-circuits to obtain a desired output current.

When a zener diode to be zapped is determined, a voltage equal to or higher than the breakdown voltage of the zener diode is externally applied between zap terminals at both ends of the zener diode. The resistance connected in parallel with the resistor becomes almost zero ohm, and the zener zap trimming is completed.

In the conventional trimming circuit shown in FIG.
Although the output current of the current mirror circuit is trimmed to a desired value, when the current mirror circuit is used in combination with another circuit block whose characteristics can be controlled by the output current value of the current mirror circuit, Zener zap trimming is performed in the same procedure as above while measuring specific characteristics.

However, the conventional trimming circuit shown in FIG. 5 requires a large number of zap terminals for performing zener zap trimming, and these zap terminals are useless in terms of circuitry after trimming is completed, and are economical. Loss.

In particular, when high precision is required, trimming is necessary including the piezo effect by the resin at the time of molding, and it is necessary to draw out the zap terminals as package terminals so that the trimming can be performed after molding.
This increases the number of package terminals.

On the other hand, for the purpose of reducing the number of package terminals, for example, Japanese Unexamined Patent Publication No. Hei 6-140512 discloses a method in which a decoder circuit is used to selectively apply a breakdown voltage to a Zener diode by a switch circuit. Trimming circuits have been proposed.

[0010]

However, in the trimming circuit proposed in JP-A-6-140512, the Zener diode can be selectively destroyed, but the Zener diode is tested beforehand and externally short-circuited. It is not possible to determine the optimum combination of the Zener diodes to be destroyed. Also, as the number of bits for trimming increases, the number of terminals of the decoder input terminals for controlling the decoder circuit also increases.

As described above, the conventional trimming circuit has the following problems.

(1) The first problem is that it is necessary to prepare a large number of zap terminals in the conventional trimming circuit.

The reason is that it is necessary to arrange zap terminals at both ends of each of a plurality of zener diodes for trimming.

(2) The second problem is that when trying to reduce the number of zap terminals, it is not possible to measure the optimum combination of zener diodes to be destroyed before destroying the zener diode.

The reason is that there is no terminal for short-circuiting the Zener diode from the outside.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and has as its object to reduce the number of zap terminals required for zener zap trimming and to reduce the number of terminals of a semiconductor integrated circuit. Using a circuit
It is to provide a trimming method . Another object of the present invention is to provide a trimming method using a trimming circuit that can determine an optimum Zener diode to be destroyed before destroying the Zener diode even if the number of zap terminals required for Zener zap trimming is reduced. Is to provide.

[0017]

Means for Solving the Problems The present invention to achieve the object, derived via the switches corresponding respectively from one electrode of the plurality of Zener diodes to a common 1 becomes conductive <br/> voltage application terminal from the terminal And a selection circuit for selecting an on or off state of each switch of the switch circuit based on an input voltage of a control terminal, and selectively destroying any of the plurality of zener diodes to obtain desired characteristics. A trimming method in a trimming circuit, wherein the switches of the switch circuit are sequentially turned on according to the voltage applied to the control terminal, and the electrodes of the respective Zener diodes corresponding to the switches are connected via the voltage application terminal. Are sequentially short-circuited to determine in advance the Zener diode to be destroyed, and connect a Zener diode to the voltage application terminal. To be a breakdown voltage is applied destroy the Zener diode to be the breakdown, characterized in that.

According to the present invention constructed as described above, first, a common potential (ground potential) is applied to a voltage application terminal, and an input voltage of a control terminal is sequentially applied in a stepwise manner. By sequentially switching the switches that turn on the circuit, it is possible to short-circuit the Zener diode and measure it.After the measurement is completed, the input voltage at the control terminal that turns on the switch that gives the optimum characteristics is applied. Then, if a voltage that destroys the Zener diode is applied to the voltage application terminal, the trimming is completed.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention. Referring to FIG. 1, transistors Q11, Q1
2. A current mirror circuit is formed by the resistors R11 and R12, and the input current input from the input terminal 10 is output as an output current from the output terminal 11 with a predetermined current ratio.

On the output side of the current mirror circuit, transistors Q11, Q12 and bases are commonly connected and transistors Q12 and Q13 are connected in common to the collector.
Q17, and the emitters of the transistors Q13 to Q17 have resistors R13 to R17 and zener diodes ZD11 to ZD, respectively.
D15 are respectively connected in series, and resistors R11, R12,
The anodes of the Zener diodes ZD11 to ZD15 are commonly connected and connected to a lower power supply (ground terminal). The cathodes of the Zener diodes ZD11 to ZD15 are connected to the switches SW1 to SW5 of the switch circuit 12, and the switches SW1 to SW5. Is turned on and off by the selection circuit 13 and is connected to the power supply terminal 14.

The switches SW1 to SW5 of the switch circuit 12
Is off, the Zener diodes ZD11 to ZD15 are all off, so that the output of the current mirror circuit for correcting these output currents is not operating, and the output terminal 11 is connected to the transistor Q12 and the resistor R12. Only the output current flows.

When the control voltage applied to the control terminal 15 is at the ground potential, the selection circuit 13
The operation is performed so that all of W1 to SW5 are turned off.

Next, when the control voltage applied to the control terminal 15 of the selection circuit 13 is gradually increased,
Turns on SW1 (others are off) of the switches of the switch circuit 12, and when the control voltage is further increased, the switch SW2 is turned on (others are off). Thereafter, the switches SW1 to SW5 are alternately turned on in order. To go.

At this time, if the ground potential is applied to the voltage application terminal of the switch circuit 12, the Zener diodes ZD11 to ZD15 are alternately short-circuited by the switches SW1 to SW5, and the Zener diodes ZD11 to ZD
15 can be realized as a trial, and any one of the Zener diodes ZD11 to ZD15 is short-circuited, so that the output section of the current mirror circuit for correcting the output current operates. The output current increases.

By measuring the output current of the output terminal 11 at the point where each Zener diode is short-circuited, it is possible to determine which Zener diode should be destroyed to obtain the best characteristics.

After the zener diode to be destroyed is determined by the above procedure, a control voltage set so that the target zener diode is short-circuited is applied to the control terminal of the selection circuit 13, and the target diode is applied to the switch circuit 12. Is turned on, and a voltage that destroys the Zener diode is applied to the voltage application terminal 14 of the switch circuit 12, a breakdown current flows only in the target Zener diode, and the Zener diode is destroyed and trimming is completed. I do.

When the semiconductor integrated circuit is mounted on a set after the trimming is completed, the control terminal 15 of the selection circuit 13 may be connected to the ground potential, and the voltage application terminal 14 of the switch circuit 12 may be left open.

[0029]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

FIG. 2 is a diagram showing an example of the configuration of the switch circuit 12 in the trimming circuit shown in FIG. 1 as one embodiment of the present invention. Referring to FIG. 2, the switch SW1 shown in FIG. 1 uses a transistor switch in which a transistor Q21 and a transistor Q22 are connected in parallel with their collector and emitter connected in opposite directions. Here, the two transistors are connected in parallel with their collector-emitters connected in the opposite direction when a ground potential is applied to the voltage application terminal 14 of the switch circuit 12 and when a voltage that destroys the Zener diode ZD11 is applied. This reverses the direction of the current. The common base of the transistors Q21 and Q22, the internal terminal 16 ₁ is connected, the transistors Q21, the base current of the transistor Q22 is if it is supplied to the internal terminal 16 _1, the transistor Q21 or transistor Q22 is turned on, the switch SW1 is It is turned on. Switches SW2 to SW
5 has the same configuration as the switch SW1.

FIG. 3 is a diagram showing an example of the configuration of the selection circuit 13 in the trimming circuit shown in FIG. 1 as one embodiment of the present invention.

Referring to FIG. 3, five pairs of differential pairs are formed by PNP transistors whose emitters are commonly connected (Q31 and Q32, Q33 and Q34, Q35 and Q36, Q37 and Q38,
The bases of one of the transistors constituting each differential pair are divided by resistors R31 to R36 and weighted at respective division points (divided values of the power supply voltage). ) Are sequentially connected, and the bases of the other transistors constituting each differential pair are connected in common and connected to the control terminal 15.

The operating current of the differential pair Q31, Q32 in which the base of one transistor is connected to the lowest voltage divider point is such that the base of one transistor is connected to the second lowest voltage resistor divider point. differential pair Q33, is supplied from Q34, the following are sequentially similarly connected according to the potential relationship, one of the base with the highest voltage resistance division point connected to differential pair Q39, Q40 operating current than the constant current I ₀ Supplied.

Here, the voltage applied to the control terminal 15 is
First, in the case of the ground potential, the transistors Q32, Q3
4, Q36, Q38, Q40 are turned on, the constant current I ₀ flows to the ground potential from the collector of the transistor Q32 via these on to that transistor, in any current is also the internal terminal 17 ₁ to 17 ₅ Not supplied.

Next, when the voltage applied to the control terminal 15 is gradually increased, the transistors Q31 and Q
The base potential of 32 reverses, transistor Q31 turns on,
The transistor Q32 turns off. As a result, the constant current I
₀ is supplied to the internal terminal 17 ₁ .

When the voltage applied to the control terminal 15 is further increased, the transistors Q33 and Q
The base potential of 34 reverses, turning on transistor Q33 and turning off transistor Q34. As a result, the constant current I
₀ is supplied to the internal terminal 17 _2, the transistor Q34 is turned off, the transistor Q31 and the transistor Q32
For the differential pair of operating current not supplied, the constant current I ₀ not flow through the internal terminal 17 _1.

When the voltage applied to the control terminal 15 is sequentially increased from the ground potential by the same operation, the following six states can be realized.

[0038] (1) internal terminal 17 ₁ to 17 ₅ constant current I ₀ into all is not supplied.

(2) The constant current I ₀ is supplied only to the internal terminal 17 ₁ .

[0040] (3) the internal terminal 17 ₂ only to the constant current I ₀ is supplied.

[0041] (4) a constant current I ₀ is supplied only to the internal terminal 17 _3.

[0042] (5) a constant current I ₀ is supplied only to the internal terminal 17 _4.

[0043] (6) a constant current I ₀ is supplied only to the internal terminal 17 _5.

From the above operation, the internal terminals 17 ₁ to 17 _{1 in} FIG.
17 _5, by connecting the terminals of the same number of internal terminals 16 ₁ to 16 ₅ in FIG. 2 (subscript), so that can be realized the embodiment shown in FIG.

FIG. 4 is a diagram showing the overall circuit configuration of the switch circuit and the selection circuit according to one embodiment of the present invention, which are internally connected to each other. In FIG. 4, the same elements as those in FIGS. 1 to 3 are denoted by the same reference numerals.

[0046]

As described above, according to the present invention, the following effects can be obtained.

(1) The first effect of the present invention is that the number of zap terminals required for zener zap trimming can be reduced.

The reason is that in the present invention, it is possible to realize all the steps of zener zap trimming with only two terminals, the control terminal and the voltage application terminal.

(2) The second effect of the present invention is that, even if the number of zap terminals required for zener zap trimming is reduced, an optimum zener diode to be destroyed can be determined before the zener diode is destroyed. That is.

The reason is that, in the present invention, the characteristics can be measured by sequentially short-circuiting the Zener diodes in a trial manner with a combination of the voltage applied to the control terminal and the voltage application terminal.

[Brief description of the drawings]

FIG. 1 is a diagram for describing an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a circuit configuration of a switch circuit as one embodiment of the present invention.

FIG. 3 is a diagram showing an example of a circuit configuration of a selection circuit as one embodiment of the present invention.

FIG. 4 is a diagram showing an entire circuit configuration of an embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a configuration of a conventional trimming circuit.

[Description of Signs] 10 input terminal 11 output terminal 12 switch circuit 13 selection circuit 14 voltage application terminal 15 control terminal 16, 17 internal terminal Q11 to Q17 NPN transistor Q31 to Q40 PNP transistor I ₀ constant current source R11 to R17, R31 to R36 resistor ZD11 ~ ZD17 Zener diode SW1 ~ SW5 switch

Claims (2)

(57) [Claims] 1. A common terminal from one electrode of a plurality of Zener diodes via a corresponding switch.
And a selection circuit for selecting an on or off state of each switch of the switch circuit by an input voltage of a control terminal, and selectively selecting any one of the plurality of zener diodes. A trimming method for a trimming circuit that obtains desired characteristics by destruction, wherein a switch of the switch circuit is sequentially turned on in accordance with a voltage applied to the control terminal, and the switch is connected to the switch via the voltage application terminal. By sequentially shorting the electrodes of each Zener diode, the Zener diode to be destroyed is determined in advance, and the Zener diode to be destroyed is destroyed by applying a Zener diode breakdown voltage to the voltage application terminal. Characteristic trimming method. 2. A Zener diode to be destroyed by applying a ground potential to the other electrode of the plurality of Zener diodes and sequentially turning on the switches of the switch circuit while applying a ground potential to the voltage application terminal. 2. The trimming method according to claim 1, further comprising: applying a breakdown voltage of a Zener diode to the voltage application terminal to destroy the Zener diode to be destroyed.