JPH0364207A - Pulse generating circuit - Google Patents

Abstract

PURPOSE:To control only the position of a pulse having the stable width with use of a single pin by externally controlling the charging start potential of an internal capacitor which decides the pulse position. CONSTITUTION:When an input trigger pulse 1 is supplied, a transistor switch 10 is turned on and the charging terminal potential of a capacitor C is equal to the output DC potential VB of a buffer 9. When the pulse 1 is turned off, a constant current set by a constant current source 2 flows to the capacitor C. Then the capacitor terminal potential VC increases linearly. The reference potentials of comparators 3 and 4 are set at Vref and Vref+IR respectively. A logic processing circuit 6 outputs the output pulses only for a time when the potential charged to the capacitor C crosses the IR. In such a case, the position of the output pulse can be linearly controlled to an input trigger by controlling the charging start potential of the capacitor C via an external terminal 8. As a result, a terminal of just a single pin suffices and at the same time the position of the terminal is variable to the input trigger only. Then the pulse width is constant regardless of the pulse position and has the stable accuracy.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a pulse generating circuit.

[Conventional technology]

Figure 3 is a circuit diagram of a conventional pulse generation circuit, in which an MMV (monostable multivibrator) which is triggered by an input pulse and begins to decay with the time constant of an external CRal) +12
It consists of 11 pieces. FIG. 5 is a timing chart showing the pulse generation operation of the circuit of FIG. 3. Inside MMV (2), there is a thread voltage (V+) as shown in the waveform diagram.
) and a threshold 2 (Vz) are provided, and the potential that begins to decay with a time constant triggered by the rise of the input a outputs a pulse as shown in waveform diagram C only while passing between these V + and V . The width t of the output pulse is determined by setting the potential vl and level 2, and the width t from the input trigger pulse is determined by setting the level 1. is adjusted by varying τ.

Figure 4 is a circuit diagram of another conventional pulse generation circuit,
FIG. 6 is a timing chart showing the pulse generation operation of the pulse generation circuit of FIG. When the input trigger shown in the waveform diagram a is input, the terminal voltage of MMVI (Li5 starts to attenuate with a time constant of 1 from the rising edge of the input trigger.From the position of the internal threshold V shown in the waveform diagram), τ A trigger is applied to MMV2 (2) with a time constant of , and it outputs a pulse up to the threshold voltage of potential v2 shown in waveform diagram C.The position t4 from the input trigger of the output pulse is τ, and the output pulse width is Since t. is adjusted by τ2, the position and width of each pulse can be adjusted independently.

FIG. 1 is a circuit diagram of another conventional pulse generating circuit. The internal capacitor C is charged with a constant current using a variable bias current from the external terminal, and the two comparators (31
This is a pulse generation circuit in which the threshold potential difference of 14) is made variable so as to increase in proportion to the slope of the constant current charging straight line, and the width of the output pulse is always constant without being affected by the position from the input trigger. .

Time from trigger pulse a is td+ Output pulse width is t
. Then, 1, = (1) ■ ■■ = CR−−−−−−−−−−−−−−−−−(2), the pulse width is determined by the externally variable current I. Takes a constant value regardless.

In this way, since the difference between the reference voltages of the comparator [31, (4)] is used as the potential difference between the resistor R and the bias current (2), only the pulse position is variable.

[Problem to be solved by the invention]

The conventional pulse generating circuit was constructed as described above, so in the conventional circuit shown in Fig. 3, the circuit format is easy and the pulse position can be varied using l adjustment pins, but the internal thresholds V, , V, Since it is fixed, there is a drawback that when changing the time constant, the output pulse width also changes at the same time.
In addition, in the case of Figure 4, each MMV is provided for adjusting the position and width of the output pulse, so it is possible to make independent adjustments, and although the problem shown in Figure 3 does not occur, the circuit configuration becomes larger. However, there was a major drawback in that two terminals were required. In addition, in the case of Figure 7, the terminal L pin is used and the circuit configuration is simple, and the pulse width basically remains unchanged even if the output pulse position changes, but in reality, the position from the input trigger is far away. As the voltage rises, the slope of the starting potential for constant current charging to the capacitor becomes smaller, and at the same time the internal threshold potential difference tends to narrow, which has the disadvantage that the accuracy and stability of the pulse width fluctuate depending on the position from the trigger.

This invention was made to solve the above-mentioned drawbacks; the circuit configuration is simple, only one pin is required, and only the position from the input trigger is variable, and the pulse width is constant regardless of the position. The purpose of this invention is to obtain a pulse generation circuit with stable accuracy.

[Means to solve the problem]

The pulse generating circuit according to the present invention is provided with a potential variable circuit that can control the constant current charging start potential to the internal capacitor from an external terminal with respect to an internal fixed range aldo potential.

[Effect]

The charging start potential variable circuit according to the present invention always outputs a stable pulse with a constant width regardless of the position of the output pulse.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a circuit diagram of a pulse generation circuit that is an embodiment of the present invention. In the figure, (11 is an input trigger pulse, (2) is an internally determined constant current source, (3) and (4) are comparators. and the reference potential vr*r+51 and VF*f+I Rf, respectively.
5) is connected to the internal power supply with threshold. (
6) is a logic processing circuit that generates an output pulse at the output terminal (7). (8) is an external terminal that determines the charging start potential of the capacitor, and (9) is a buffer AmP.

Next, the operation will be explained.

When an input trigger is applied, the transistor SW is turned on, and the charging terminal potential of the capacitor C becomes the buffer output DC potential V. After trigger pulse fl+ turns off, transistor SW
is turned OFF, a constant current determined by an internally fixed constant current source (2) flows through the internal capacitor C, and charge begins to accumulate.As a result, the capacitor terminal potential vc changes over time as shown in the waveform in Figure 2. , linearly increasing comparator (3
), the reference potential of the comparator (4) is set to the base potential of (5) vref, V, □+IH, respectively, and logic processing is performed such that it outputs only the time when the charging potential to the capacitor C crosses this IR. If the circuit (6) is installed, an output pulse as shown in waveform C in FIG. 2 can be obtained from the output terminal (7).

Since the two reference potentials V1.1 and vrot + I R are fixed values determined internally, the position of the output pulse from the input trigger is determined by the capacitor C connected to the external terminal (8).
By adjusting the charging start potential of I! 11m is possible. In addition, the threshold voltage IR is constant,
Since the charge to the capacitor C is always constant, the accuracy of the pulse width is constant regardless of the position.

The position from the trigger pulse is 14, and the pulse width is t.

Then, 1, = (3) ■ 1 1 Therefore, the output pulse width is determined internally by CR
is a constant value, and the position from the input trigger can be adjusted by externally controlled V.

In addition, in the above embodiment, the case of a pulse generation circuit in which the pulse width is constant compared to the input trigger pulse and only the position is variable was explained, but this pulse generation circuit requires that the pulse width is independent of the position in addition to the burst gate pulse. It is also applicable to all sampling pulse circuits.

〔Effect of the invention〕

As described above, according to the present invention, since the charging start potential of the internal capacitor that determines the pulse position can be controlled from the outside, a pulse generation circuit that can only adjust the position of a pulse with a stable width using one pin can be created. There is an effect that can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a pulse generation circuit showing an embodiment of the present invention, FIG. 2 is a waveform diagram of the circuit of FIG. 1, and FIGS.
Figure 7 is a circuit diagram of a conventional pulse generation circuit, respectively.
5, 6, and 8 are waveform diagrams of the circuits of FIGS. 3, 4, and 7, respectively. (1) --- input trigger pulse, (2) --- current source, +31. (4)--Comparator, (5)--Reference potential, 16+--Logic processing circuit, (7)--Output terminal, (8)--External control voltage terminal, (91- Bath sofa AmP, O-to transistor switch. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] The capacitor voltage that performs constant current charging is input to the first and second comparators whose threshold voltages are the first reference voltage and the second reference voltage obtained by adding a bias power supply that determines the output pulse width to this reference voltage. In the pulse generation circuit, the charging start voltage of the capacitor can be controlled by an external variable power supply, and after an input trigger pulse, a pulse is generated only between the two threshold voltages. A pulse generation circuit characterized by changing only the position from .