JP3182908B2 - Semiconductor sensor circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MRE (magnetoresistive element) type vehicle speed sensor which is integrated, for example, and more particularly to a comparator to which an output signal from a bridge-connected sensor circuit is supplied. The present invention relates to a semiconductor sensor circuit device for stabilizing the operation of a semiconductor device.

[0002]

2. Description of the Related Art For example, in a vehicle speed sensor, a rotating body having magnetic poles magnetized at equal intervals is provided on an outer peripheral portion, and a magnetic sensor is installed near the peripheral portion of the rotating body. It is configured to magnetically detect a state in which each magnetic pole of the rotating body that rotates together with the wheel passes close to the magnetic sensor, and a sine wave detection signal is detected and output corresponding to each magnetic pole. I have to. An output signal from such a magnetic sensor is supplied to a comparator so that a detection signal that changes to a high level and a low level whose cycle is set according to the wheel speed is output.

FIG. 3A shows an example of a sensor circuit to which an output signal from such a magnetic sensor is supplied.
Bridge circuit (magnetic sensor) composed of MR elements
Are supplied to a negative input terminal and a positive input terminal of a comparator 31, respectively, so that a pulse-like output signal which changes to a high level and a low level is obtained from the comparator 31. I have to.

In the sensor circuit configured as described above,
A hysteresis circuit 32 is provided to prevent a malfunction of the comparator 31, and the operation of the comparator 31 is stabilized by the hysteresis circuit 32.

The hysteresis circuit 32 is connected, for example, to a power supply V
The resistors R1 and R2 connected to B and the comparator
The transistor Q whose conduction is controlled in response to the output from 31
The transistor Q1 is turned on when the output of the comparator 31 is at a high level,
The hysteresis voltage set by the resistors R1 and R2 is fed back to the negative input of the comparator 31.

In this case, the resistors R1 and R2 are:
Particularly, high precision and high resistance are required. For this reason, a hybrid type resistance element using a thick film resistor is adopted. As a countermeasure against external noise, a capacitor C1 is connected to the positive and negative input portions of the comparator 31.

FIG. 3B shows a sensor circuit in the case of integration. A hysteresis voltage V10 is generated by a constant current measured by transistors Q2 and Q3 and resistors R4 and R5. The voltage V10 is supplied to the negative input V- of the comparator 31. in this case,
When the transistor Q4 is turned off, the hysteresis operation may be delayed, and it may be difficult to stabilize the operation of the comparator 31, resulting in a malfunction. For this reason, a capacitor C2 is added to the output terminal to prevent this malfunction. Therefore, in such a sensor circuit device as shown in FIG. 3, it is difficult to sufficiently reduce the size, and the cost is further increased.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and particularly focuses on the operation speed of a hysteresis circuit, and effectively feeds back a system having a high operation speed. A semiconductor-type sensor circuit device that enables the operational stability of the comparator section to be effectively maintained, enables easy integration, and eliminates the use of capacitors. It is something to offer.

[0009]

In order to achieve the above object, the present invention has first and second output terminals.
At least the first and second terminals connected to the first and second output terminals
A sensor bridge circuit comprising a second resistor, the first及
And two output signals from the second output terminal are inverted input,
A comparator respectively input to the non-inverting input, a constant current source that can supply a predetermined current to the first and second resistors of the sensor bridge circuit via the first and second output terminals , A first transistor and a second transistor that are connected to a constant current source and that are conductively controlled in response to an output signal from the comparator; The conduction states are inverted with each other in response to a signal, and in accordance with the conduction states of the first and second transistors, the first and second resistors of the sensor bridge circuit are supplied from the constant current source to the first and second resistors . The predetermined current supply path is switched, and the predetermined current and the first and second resistors cause the hysteresis voltage to change between the two outputs from the sensor bridge circuit. The signals are applied to the respective signals.

[0010]

In the semiconductor sensor circuit device thus configured, two systems of hysteresis circuits are formed by the first and second transistors. When the output of the comparator is at a high level and at a low level, respectively. The second or first transistor is turned on, and the constant current hysteresis voltage is fed back to the input of the comparator via the respective diode. As a result, the hysteresis voltage is operated earlier than the output of the comparator, and the malfunction of the comparator is reliably prevented.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit configuration of this device, which is used, for example, as a vehicle speed sensor and has a magnetoresistive element R11.
R14 to the sensor circuit 11 of a bridge circuit constituted by R14. For example, a power supply VB is connected to one side of the bridge circuit constituting the sensor mechanism 11, and the other end is grounded. The output V- is connected to the negative input of the comparator 12, and the output V + is connected to the positive side. Connected to input.

A hysteresis circuit 13 is connected to the comparator 12, and includes, for example, a constant current circuit composed of a resistor R10 connected to a power supply VB and a transistor Q10. First and second transistors Q11 and Q12 are provided so that the constant current from the constant current circuit is connected to the collector, respectively. The output Vo of the comparator 12 is provided at the base of the transistor Q11 by an inverter In or the like. Inverted and supplied, the transistor Q12
The output Vo of the comparator 12 is supplied as it is to the base of.

The output from the collector of the transistor Q11 is supplied to the input V- of the comparator 12 through the diode D1.
The output from the collector of the transistor Q12 is supplied to the input V + of the comparator 12 through the diode D2.
To be supplied to And the comparator 12
Q11 and Q12 controlled by the output of
To form a two-system hysteresis circuit.

The principle of operation of generating hysteresis in the circuit thus constructed is that the hysteresis current I1 is determined, for example, by the power supply voltage VB and the resistor R10, and the path through which the hysteresis current I1 flows is determined by the transistor Q11
And Q12.

The operation of the transistors Q11 and Q12 is governed by the output of the comparator 12,
When the output Vo of the comparator 12 is at a high level (in the state indicated by A in FIG. 2A), the transistor Q12 is turned on, and the transistor Q11 is set to the off state. As a result, the hysteresis current I1 flows to the ground. When the output of the comparator 12 is low (in the state indicated by B in FIG. 2A), the transistor Q11 is turned on and the transistor Q12 is turned off, and the hysteresis current I1 is passed through the turned on transistor Q11. Flow to ground.

Looking further at the transient operation, for example, when the output of the comparator 12 is at a high level, the transistor Q12
Is turned on and the transistor Q11 is turned off, the hysteresis voltage is generated at the input V-.

Here, when the input to the comparator 12 changes with time and the output of the comparator 12 changes to a low level, the transistor Q12 changes from on to off, the transistor Q11 changes from off to on, and the input V -The hysteresis voltage from ON to OFF, and the input V
Attempts to change the + hysteresis voltage from off to on.

Focusing on the operation speed when the hysteresis voltage is turned on and off, first considering the case where the hysteresis voltage is turned off, the reason why the hysteresis voltage is turned off is that the transistor Q11 or Q12 is turned on from the off state. It is time to become. The operation speed t1 when this transistor is turned on from off is "t1 = C
Where R is the junction capacitance between the collector and the emitter of the transistor, and R is the on-resistance between the collector and the emitter of the transistor, which is a very small resistance value. It can be understood that the operation speed t1 at which is turned on is very fast.

Next, when the hysteresis voltage is turned on, the hysteresis voltage is turned on when the transistor changes from on to off.
The operation speed t2 is represented by "t2 = CV / I1". Here, V is (the voltage of the input V-, V +) + (the forward voltage of the diodes D1, D2). Since I1 is a hysteresis current and becomes a relatively small current, the transistor is turned off. The operating speed t2 is inevitably slower than t1.

Therefore, in order to operate the hysteresis circuit earlier than the output of the comparator 12, a state in which the hysteresis circuit operates at high speed, that is, a characteristic in which the hysteresis voltage is changed from on to off is used. Also, to select this, the output from comparator 12
The operation of the transistors Q11 and Q12 is selected.

In order to integrate such a circuit device in one chip, it is necessary to set the hysteresis voltage to a constant voltage. At this time, the diodes D1 and D2 are provided to prevent the backflow of the hysteresis current. However, when the hysteresis voltage changes from on to off by the diodes D1 and D2, that is, the hysteresis current is connected to the ground. When the current flows, the potential on the anode side of the diode (the voltages of the inputs V- and V +) + (the forward voltage of the diodes D1 and D2) instantaneously becomes the ground potential.

Therefore, the cathode of the diodes D 1 and D 2, that is, the input of the comparator 12,
1, AC coupled by the P / n junction capacitance of D2, a spike waveform larger than the hysteresis voltage is generated for several nanoseconds as shown in FIG. 2B, and the hysteresis effect is further enhanced. .

[0023]

As described above, according to the semiconductor sensor circuit device of the present invention, two systems of the constant current type hysteresis circuit are provided, and the middle point of the bridge circuit constituting the sensor mechanism, that is, the input of the comparator. This is feedback, and two hysteresis circuits are selected by the comparator output. Also,
The feedback circuits of the two systems of hysteresis circuits are each provided with a diode for preventing backflow, and a spike waveform that further enhances the hysteresis effect in a region where hysteresis works most effectively due to the P / n junction capacitance of the diode. Is generated, the sensor circuit device can be easily integrated and configured, and the operation of the comparator is sufficiently stabilized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a semiconductor sensor circuit device according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams illustrating an input voltage corresponding to an operation of a comparator for describing the embodiment.

FIGS. 3A and 3B are diagrams showing examples of a conventional sensor circuit, respectively.

[Explanation of symbols]

11: sensor mechanism, 12: comparator, 13: hysteresis circuit, R11 to R14: magnetoresistive element, R10: resistance, Q10 to
Q12: Transistor, D1, D2: Diode.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H03K 5/08 (58) Fields investigated (Int.Cl. ⁷ , DB name) H03K 3/023 G01D 5/245 G01P 3/481 H01L 27/04 H03K 5/08

Claims (2)

(57) [Claims] A first output terminal connected to the first output terminal and a second output terminal connected to the first output terminal;
At least first and second terminals connected to the first and second output terminals
A sensor bridge circuit comprising a resistor, wherein the first and
A comparator in which two output signals from a second output terminal are input to an inverting input and a non-inverting input, respectively; and a predetermined current is applied to the first of the sensor bridge circuits via the first and second output terminals . And a constant current source that can be supplied to the second resistor, and first and second transistors connected to the constant current source and controlled to conduct in response to an output signal from the comparator, The conduction state of the first transistor and the second transistor is reversed according to the output signal from the comparator. According to the conduction state of the first and second transistors,
A supply path of a predetermined current from the constant current source to the first and second resistors of the sensor bridge circuit is switched, and the predetermined current and the first and second resistances are switched . No
As the hysteresis voltage by the antibodies are applied to each of the two output signals from the sensor bridge circuit
A semiconductor sensor circuit configured as described above . 2. The sensor bridge circuit according to claim 2, wherein
Between the first and second output terminals and the constant current source,
It is equipped with a diode for backflow prevention.
2. The semiconductor sensor circuit according to claim 1, wherein