JPH01217611A - Constant voltage generating circuit - Google Patents

Abstract

PURPOSE:To set the output voltage at a desired level with control applied to the voltage after its generation by connecting one of two ends of each of plural switch elements with which the switching actions are programmable to each connection point of a MOS transistor TR together with the other end of the switch element short-circuited with each other to obtain the constant voltage output at said short circuit part. CONSTITUTION:When a current is supplied from a power supply 1 via a high resistance 2, this current energizes a series circuit containing eight MOS TR7-14 via the programmable elements 15 and 19. Then the voltage of (8XVt) is obtained at an output terminal 20 when the threshold voltage of each MOS TR is set at Vt. If said obtained voltage is lower than a prescribed level, the fuse of the element 19 is cut by a laser trimming device for acquisition of the (9XVt) output. Furthermore the (10XVt) output is obtained with cut of the fuse of the element 18. As a result, the output voltage can be controlled within a range of (8XVt)-(12XVt).

Description

Detailed Description of the Invention (a) Industrial Application Field This invention relates to constant voltage generation circuits configured inside semiconductor devices such as ICs, Is, and SIs, and is mainly used to compare constant voltage sources and input levels. It is used as a reference voltage generation source.

(B) Prior art In this type of conventional constant voltage generation circuit, MOS transistors 103 to 112 are connected in series as shown in FIG. The MOS transistors 103 to 112 (
In this case, when each threshold voltage of 10 threshold voltages is Vt,
The voltage of toxvt is obtained from the output terminal 113.

(c) Problems to be Solved by the Invention However, since the threshold voltages of MOS transistors vary individually and do not necessarily match the design value, it is necessary to accurately output a desired constant voltage from this constant voltage generation circuit. The problem was that it was difficult to do so.

This invention was made in consideration of these circumstances,
The present invention provides a constant voltage generation circuit capable of correcting individual variations in MoS transistors after manufacturing and obtaining a highly accurate constant voltage.

(d) Means for Solving the Problems The present invention is configured such that a series circuit of a plurality of MOS transistors is connected to a DC power supply via a high resistance, and a constant voltage is obtained from the voltage drop occurring across the series circuit. The constant voltage generating circuit is equipped with a plurality of switching elements whose opening/closing operations can be programmed, and one end of each switching element is connected to each connection point of a MOS transistor, and the other ends are mutually short-circuited. This is a constant voltage generation circuit characterized by obtaining a constant voltage output.

(e) By measuring the output voltage after manufacturing the working circuit and programming the opening/closing operation of the switching element according to the excess or deficiency of the output voltage, the number of MOS transistors to be energized can be adjusted, so the desired output voltage can be adjusted. can be obtained with high precision.

(f) Examples The present invention will now be described in detail based on examples shown in the drawings. This invention is not limited by this.

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.
1 is a power supply, 2 is a high resistance, and 3 to 14 are MOs connected in series.
S transistor! 5~! 9 is a programmable element whose one end is connected to each of the MOS transistors 3 to 7 and the other end is connected to the output terminal 20. In this case, this programming element! 5 to 19 use polysilicon fuses that can be cut by a laser trimming device after the circuit is manufactured.

In such a configuration, when a current is supplied from the power supply l through the high resistance 2, the current flows through the programmable elements 15 and 19 to the MOS transistors 7 to 14 (8).
If the threshold voltage of each MOS transistor is Vt, then the output terminal 20 has a voltage of 5xvt.
voltage can be obtained. If this value is lower than the desired value, the fuse of programmable element 19 may be blown using a laser trimming device to obtain an output of 9xVt. Furthermore, if the fuse of programmable element 18 is blown, the output becomes toxvt.

In this way, by sequentially blowing the fuses of programmable elements 19 to 15 while actually measuring the output voltage, the output voltage can be adjusted within the range of Bxvt to 12xVL, and the output voltage is the closest to the desired value. Can be set.

FIG. 2 is an electric circuit diagram showing another embodiment of Hara's invention, in which numeral 31 is a power supply, 32 is a high resistance, 33 to 44 are MoS transistors connected in series, and 45 to 48 are MoS transistors 33 to 48 connected at one end, respectively. transfer gates 49 to 52 connected to 36 and the other end connected to output terminal 60;
are gate signal lines to transfer gates 45 to 48, 53 to 56 are EEFROM (or EPROM), 5
7 is a write signal line, 58 is a clear signal line, 5
9 is a write signal line 57 and a clear signal line 5
This is a control circuit that outputs to 8.

In such a configuration, E E P RO? 1/I
When transfer gates 53 to 56 receive a write signal from signal line 57 and transfer gates 45 to 48 are all in the ON state, MOS transistors 36 to 44 (91 ml) are energized from power supply 31 via resistor 32. Assuming that each threshold voltage of the Mo9 transistors 33 to 44 is Vt, an output of 9XVt is obtained from the terminal 60. here,
If this output voltage has not reached the desired value, the control circuit 59 clears the EEF ROM 56 and turns off the transfer gate 48.
The output voltage from terminal 60 will be 10xVt. In this way, the output voltage is
By sequentially turning off 4B-40, 9XVt~12
Adjustment is possible within a range up to xVt, and the output voltage closest to the desired value can be set after manufacturing. The output voltage of the embodiment shown in FIG. 1 is mainly adjusted by the manufacturer, but the output voltage of the embodiment shown in FIG. 2 can also be easily adjusted by the user.

(G) Effects of the Invention According to the present invention, it is possible to adjust the output voltage of the constant voltage generation circuit after manufacture and set it to a desired value.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram showing one embodiment of the present invention, FIG. 2 is an electrical circuit diagram showing another embodiment of the invention, and FIG. 3 is an electrical circuit diagram showing a conventional example. l...Power supply, 2...High resistance, 3~I4
...MOS transistor, 15-19...
...Programmable element, 20...Output terminal. Figure 1

Claims (1)

[Claims] 1. In a constant voltage generation circuit configured to connect a series circuit of a plurality of MOS transistors to a DC power supply via a high resistance, and obtain a constant voltage from a voltage drop occurring across the series circuit. , comprising a plurality of switching elements whose opening/closing operations can be programmed, one end of the switching element being connected to each connection point of the MOS transistor, and the other ends thereof being short-circuited to each other,
A constant voltage generation circuit characterized in that a constant voltage output is obtained from the short circuit part.