CN107076807B

CN107076807B - Hall sensor chip with time sequence control

Info

Publication number: CN107076807B
Application number: CN201580059568.3A
Authority: CN
Inventors: 杨文佳; K·塔帕; 卓英堂; C-Y·蔡; R·鲁滨逊
Original assignee: Dahl Technology Co ltd
Current assignee: Dahl Technology Co ltd
Priority date: 2015-10-30
Filing date: 2015-11-19
Publication date: 2021-01-22
Anticipated expiration: 2035-11-19
Also published as: CN107076807A

Abstract

A sensor device comprising: a sensor element for measuring a stimulus and generating a corresponding signal; an ADC for converting the signal to a multi-bit digital signal; a memory unit for storing the digital signal; and a timing unit for switching off the sensor element while the ADC is converting the signal and for switching off the ADC after storing the digital signal in the memory.

Description

Hall sensor chip with time sequence control

Background

Modern sensor systems, when subjected to an external stimulus, produce a signal that can be read directly at the output of the sensor system or further processed and then directed to downstream systems. A variety of stimulus modem sensor systems are designed to sense sound, temperature, weight, position, current and voltage, light, color, speed of motion, magnetic fields, pressure, and two and three dimensional geometries, foreign objects in a solution (e.g., blood, urine, etc.). Among modern sensors, hall effect sensors (hall sensors) are designed to sense the presence of a magnetic field and measure the strength of the magnetic field or other measurable quantity that can be converted into a magnetic field.

One type of known hall sensor system continuously measures the magnetic field and continuously outputs the measured data. With this type of hall sensor, the sensing portion (e.g., hall plate) and the data processing portion of the sensor system are continuously energized to maintain continuous measurements and outputs. Most linear hall sensors are of this type.

Known hall sensor systems of the second type measure the magnetic field sporadically or periodically. In contrast to linear hall sensors, this second type of hall sensor is suitable for applications in which only occasional readings of the magnetic field are required. Hall sensors of this type typically remain de-energized except during short periods when measurements need to be taken. During these short periods, both the sensing portion and the data processing portion of the sensor are energized, thereby taking measurements and processing and displaying the measurement data. Outside the periodic window, no measurements are made and no measured information can be collected from the system.

Disclosure of Invention

The applicant has studied said existing hall sensors and has noticed that they all have serious drawbacks. The first type of hall sensor (i.e., a linear hall sensor) is very power inefficient. While data output can be readily obtained from this type of sensor, which is desirable for certain applications, high power consumption makes this type of hall sensor a poor choice for many battery-powered applications.

The second type of hall sensor has limited data availability. Although this type of hall sensor is more power efficient because the system is not constantly powered on, during the power down time, no data is available externally and this makes the sensor unsuitable for many applications.

The inventors have noted that these drawbacks affect not only magnetic sensor systems, but also many other sensor systems. To improve both power efficiency and data availability, the inventors invented a new sensor system in which power consumption remains extremely low and the measured data remains accessible before the next measurement is made. These benefits are achieved by intelligent management of power into the different functional blocks of the sensor system.

The invention can be understood with the aid of an exemplary hall sensor system, but is applicable to many other sensor systems mentioned in the background section. The new sensor system includes a number of functional blocks including a power supply block and a measurement and data processing block that draws power at different levels from the power supply block.

The new hall sensor system has a hall plate, which is a semiconductor device that measures a magnetic field and converts the magnetic field into a voltage signal. The signal from the hall plate is typically analog after amplification. To process the signals via modern electronics, the sensor system includes an analog-to-digital converter (ADC) block that acquires an analog signal and converts the analog signal to a digital format. In addition, the system has a memory unit. The memory block follows the ADC and includes a register that holds digital data from the converter output.

Further processing of the digital data may be required. For example, for some applications, the digital signal may need to be reverted to analog form. This can be done using a digital-to-analog converter (DAC) block that follows the ADC and memory cells.

In this exemplary sensor system, the hall plate is turned off after the magnetic field is measured and after the voltage signal is amplified and locked into the ADC. Thus, the hall plate will no longer consume power when processing the voltage signal in the ADC block.

The ADC may then be turned off after the signal conversion is completed and the digital data is stored in the memory block for direct output or further processing in the DAC block. The new system consumes less than a fraction of the power compared to a conventional linear hall. And the new system provides information of the measured magnetic field continuously without interruption, compared to a conventional hall switch.

Drawings

FIG. 1 is a block diagram of a sensor system embodying the present invention.

FIG. 2 is a schematic timing diagram showing operation of the sensor system of FIG. 1.

Detailed Description

Definition of terms

Within the context of the present invention, the terms used in this disclosure generally have their ordinary meaning in the art. Certain terms are discussed below to provide additional guidance to the practitioner regarding the description of the invention. It will be understood that the same may be expressed in more than one way. Thus, alternative languages and synonyms may be used.

A sensor element in the context of the present invention means a component of a system or apparatus whose purpose is to detect an event or change in the environment and provide a corresponding output or signal. The sensor elements typically provide an electrical signal or visual indicia in response to a sensed event. Some sensor elements require power to operate, for example: a thermocouple that generates a known voltage in response to temperature; a CCD that generates a known voltage in response to light; and a hall sensor that generates a known voltage in response to a magnetic field. Other sensor elements may not require power to operate, such as a mercury glass thermometer, the human eye, and a compass.

Instrumentation amplifiers in the context of the present invention mean a type of differential amplifier suitable for use in measurement and test equipment. Which is typically a type of differential amplifier equipped with an input buffer amplifier that eliminates the need for input impedance matching. Additional characteristics include very low DC offset, low drift, low noise, very high open loop gain, very high common mode rejection ratio, and very high input impedance. Instrumentation amplifiers are used in situations where great accuracy and stability of the circuit is required. This type of amplifier is commonly used in hall plate sensors.

An analog signal is in the context of the present invention a continuous signal for which the temporal variation of the signal represents some other temporal variation.

A digital signal is a type of persistent signal that represents a series of discrete values (quantized signal). A digital signal is generally synonymous with a logic signal, which is a digital signal having discrete values with two possible logic values.

An external stimulus means in the context of the present invention an environment external to the sensor device that can be sensed or measured by the sensor elements to generate a signal corresponding to the measured value. Examples of measurable stimuli include sound, temperature, weight, position, current and voltage, light, color, speed of motion, magnetic field, pressure, and foreign objects in two-and three-dimensional geometries, blood and urine, and the like.

A signal converter means in the context of the present invention a device that can convert a characteristic of a signal from one representation to a different representation. Among the electronic signal converter technologies, the most well-known types of signal converters are analog-to-digital converters (ADCs) and digital-to-analog converters (DACs).

A power supply means in the context of the present invention an electronic device that supplies AC or DC power to a load. The power supply may draw its power from a generator, a battery, a solar cell, or the like. In most electronic devices, the supplied power is DC power in the form of a fixed voltage at varying current or a fixed current at varying voltage.

Memory elements in the context of the present invention include electronic memories such as: volatile memory, such as DRAM; or non-volatile memory such as logic latches or flash memory.

A clock is in the context of the present invention an electronic device that generates a periodic clock signal. The clock signal has a frequency defined in clock cycles or cycles per second. The clock signal is typically represented by a square wave, with a portion of the clock cycle being on-time states and the remainder of the cycle being off-time states. The duty cycle of a clock is defined as the ratio of the on-time to the period.

Activating a device from a deactivated state means in the context of the present invention that the device is ready to perform its designed function in the system. This may be accomplished by raising the power supply voltage to the device from a reduced level to a preset level.

Deactivating a device means in the context of this disclosure temporarily pausing the device for its designed function for the purpose of, for example, saving power. This may be accomplished by reducing the power supply voltage to the device below a preset level. In some cases, the preset level is zero.

Sampling (sampling or sampling) means in the context of the present invention that the sensor element measures the stimulus. The sampling can include measuring a magnitude (e.g., temperature) of the stimulus; or the sampling may comprise measuring a magnitude plus a direction, such as a velocity or a polarity (e.g., a magnetic field, a voltage, or a current). Sampling is typically controlled by a clock (i.e., a sampling clock). The sampling rate is a determining factor of the resolution of the measurement.

Exemplary embodiments

Example a magnetic field sensor System

FIG. 1 depicts an exemplary sensor system 100 embodying certain aspects of the present invention. The sensor system includes an Integrated Circuit (IC) chip 101 containing a sensor element 102 having a hall effect sensor for measuring a magnetic field. In this system, the hall effect sensor is an integrated component in the IC chip 101; in other systems, the hall effect sensor may be a stand-alone chip. When current flows through the hall effect sensor and the magnetic field is perpendicular to the current path, the current will deflect according to the right hand rule and a voltage will be generated in the sensor. The magnitude of the generated voltage and its polarity are a function of the magnitude and direction of the current flow and the magnetic field.

In integrated circuits, hall effect sensors are miniaturized and the generated voltage signals are typically small, so it may be desirable to incorporate an instrumentation amplifier 103 into the sensing element 102 to increase the signal level.

In this example, the voltage signal generated in 102 is an analog signal. As depicted in fig. 1, this signal is passed to an analog-to-digital converter (ADC) 104. The resolution of the ADC 104 is expressed in the number of bits at its output and may range from 1 bit to 12 bits or even higher; in this example, the resolution is chosen to be 8 bits for illustration purposes.

Following the ADC is a memory element 106, which stores the output of the ADC 104. The memory is preferably non-volatile, such as a latch or EEPROM, but volatile memory, such as DRAM, may also be used. In some applications, the digital information stored in memory 104 is the final output of sensor system 100 at output 30. In other applications, when an analog output of the measured magnetic field is desired, the system optionally may incorporate a digital-to-analog converter (DAC)108 that receives its input from memory and converts the input to analog form at another output 20.

The system also has a timing controller element 110 that receives an enable signal external to the sensor system 101 at EN pin 10 when a measurement of the magnetic field is required. The timing controller element 110 has an on/off control unit 1102 that controls power delivered from the power supply 105 and a clock 1104 that clocks on/off actions. The timely turning on and off of the various components in the sensor system 101 makes the system more power efficient than sensing systems within the known art. The function of the timing control unit 110 will be explained in the following example.

Example timing control of a two-magnetic sensor System

Timing control to enable the sensor system to achieve very high power efficiency is depicted in fig. 2 and incorporated in the exemplary magnetic sensor system 100 depicted in fig. 1. System activity begins with Enabling (EN) clock 201. The frequency of the clock 201 is determined by the frequency at which the magnetic field needs to be measured. In this example, the rising edge of the clock 201 triggers the sensor element 102 to measure the magnetic field and present the measured information in the form of an analog voltage signal at the output of the sensor element. It is also possible to use the falling edge of the clock 201 as a trigger instead.

Upon receiving the trigger signal, the timing controller 110 generates a clock signal 203 in the clock generator 1104. The rising edge of the clock signal 203 activates the sensor element 102 to sample the magnetic field. And the duration of clock pulse 2031 is determined by the amount of time necessary for sensor element 102 to: taking one or more samples of the magnetic field, amplifying the resulting voltage signal in an amplifier (if needed), and delivering the amplified signal to an ADC 104 that follows the sensor element 102.

In this exemplary system, the current from the power supply 105 to the sensor element 102 is about 2.7mA, which includes the bias of the Hall sensor and powers the amplifier. At the end of the clock pulse 2031, while the ADC 102 is converting the analog signal from the sensor element, a signal from the on/off controller 1102 in the timing controller 110 turns off the switch 1021 and cuts off the power supplied from the power supply 105 to the sensor element 102. The switch 1021 remains open during the pulse length 2032 and very little power is consumed in the sensor element 102.

Clock generator 1104 further generates second clock signal 205 to activate ADC 104 and place ADC 104 in an active mode during pulse period 2051. The ADC 104 remains active to convert the analog signals from the sensor elements 102 to digital signals and deliver the digital data to the memory 106. In this exemplary system 100, the current to maintain the ADC in active mode is 0.3 mA. When data is stored in the memory 104, the on/off controller 1102 sends a signal to turn off the switch 1041 at the falling edge of the pulse 2051 to cut off power supplied from the power supply 105 to the ADC 104. During the pulse length 2052, the switch 1041 remains open and very little power is consumed in the ADC 104.

The memory 106 now contains information of the measurement of the magnetic field and is ready to deliver the data outside the sensor system 100. Since modern memory devices are extremely power efficient, the memory can remain in an active mode, so that the data can be obtained without interruption.

The optional DAC 108 that converts digital data from the memory 106 to an analog signal also consumes little power, thus in this exemplary system 100, the DAC 108 remains in an active mode. The total power consumed by both the memory 106 and the DAC 108 is only 8 μ Α. This is negligible compared to other components of the system. By keeping both the memory 106 and the DAC 108 active, the system can provide digital and analog data of the measured magnetic field.

Claims

1. A sensor system, comprising:

a sensor element configured to generate a signal in response to an external stimulus;

a first signal converter configured to receive the signal from the sensor element and convert the signal to a multi-bit digital signal;

a power supply configured to sequentially supply power to the sensor element and the first signal converter; and

a timing unit configured to generate an active mode of the sensor system with a first clock pulse having a first clock edge to activate the sensor element and a second clock edge adjacent the first clock edge to deactivate the sensor element after the sensor element delivers the signal to the first signal converter to reduce the supplied power to the sensor element;

the timing unit is further configured to generate a second clock pulse that overlaps the first clock pulse, the second clock pulse having a first clock edge to activate the first signal converter to receive the signal from the sensor element and a second adjacent clock edge to deactivate the first signal converter; and

the timing unit is further configured to maintain an activated state of the first signal converter after the sensor element delivers the signal to the first signal converter.

2. The sensor system of claim 1, further comprising a memory cell configured to store the multi-bit digital signal.

3. The sensor system of claim 2, further comprising a second clock configured to trigger a switch to cut off power from the power supply to the first signal converter after the memory cell stores the multi-bit digital signal.

4. The sensor system of claim 3, wherein the sensor element comprises a Hall sensor and an amplifier.

5. The sensor system of claim 4, wherein the Hall sensor, the amplifier, the first signal converter, the memory unit are part of an integrated circuit chip.

6. The sensor system of claim 5, further comprising a second signal converter configured to convert the multi-bit digital signal to an analog signal.

7. The sensor system of claim 6, further comprising a first output terminal coupled to the memory cell and a second output terminal coupled to the second signal converter.

8. The sensor system of claim 7, further comprising an enable clock configured to activate the sensor element.

9. A method of operating a sensor system, comprising

Subjecting the sensor element to an external stimulus;

initiating an active mode of the sensor system with a first clock edge of a first clock pulse;

generating a signal in the sensor element in response to the external stimulus;

activating a signal converter with a first clock edge of a second clock pulse, the second clock pulse overlapping the first clock pulse;

converting the signal to a multi-bit digital signal;

after the sensor element delivers the signal to the signal converter, deactivating the sensor element with an adjacent clock edge of the first clock pulse, ending the active mode; and

maintaining a converted signal in the sensor system after ending the active mode.

10. The method of claim 9, wherein the step of deactivating the sensor element comprises cutting power to the sensor element.

11. The method of claim 9, further comprising storing the multi-bit digital signal in a memory cell.

12. The method of claim 11, further comprising cutting power to the signal converter after storing the multi-bit digital signal in the memory cell.

13. The method of claim 9, wherein the sensor elements comprise hall sensors and amplifiers.

14. The method of claim 13, wherein the step of generating a signal and the step of converting to a multi-bit digital signal are both performed in one integrated circuit chip.