Two solutions of ultrasonic sensor chip

Ultrasonic sensing must be familiar to everyone. This ultrasonic based sensing method is widely used and plays a role in many fields of life. Ultrasonic sensor is manufactured according to some characteristics of ultrasonic. The internal energy conversion chip vibrates under the excitation of voltage to produce ultrasonic, and then completes the transmission and reception of ultrasonic.

The composition of the ultrasonic sensor is not so complex. The transmitter and transducer constitute the transmitting part, the amplification circuit and transducer constitute the receiving part, and then the general function of the sensor can be completed by combining the control part and the power supply part. In these components, the ultrasonic control can be realized with high-grade single chip microcomputer. In the acoustic generator, the single chip microcomputer operates as the main control chip of the whole circuit, and cooperates with D / a converter and IGBT power module to realize pulse width modulation. It can be seen that the ordinary single chip microcomputer can basically complete the ultrasonic control. This is only the basic realization of control. For some high-frequency circuit requirements, the processing speed of ordinary single chip microcomputer will still be a little slow.

MSP430 series integrated solutions

Since ordinary MCU can not fully meet the requirements, what should we do? Let's take a look at ti's MSP430 series, which is specially strengthened for ultrasonic applications. MSP430 Series MCU, especially msp430fr604x and msp430fr504x series, provides a low-cost single-chip solution for ultrasonic sensing. This series has an integrated ultrasonic sensing analog front end, which is easy to use and flexible for developing various applications. Its unique waveform capture technology and high-speed ADC can realize low-power and high-precision measurement.

（TI）

Taking msp430fr5043 as an example, the device is specially designed for ultrasonic water meter, calorimeter and gas meter. The ultrasonic sensing solution (uss_a) module is integrated into the whole device for ultrasonic applications, which can provide high-precision measurement for a variety of flow rates. USS_ A is highly integrated and requires few external components, which helps to achieve ultra-low power metering and reduce system cost.

USS_ Module a includes programmable pulse generator (PPG) and physical interface (PHY) with low impedance output driver to achieve the best sensor excitation and accurate impedance matching effect as far as possible, so as to achieve the best in zero flow drift (zfd).

In order to achieve accurate signal acquisition, USS_ Programmable gain amplifier (PGA) and high-speed 12 bit 8msps are also integrated in module a Σ-Δ  ADC。 In the environment of water as medium, the accuracy of differential flight time of the device is ± 12.5ps and ± 1% in the wide dynamic range of 500:1. In gas medium, the accuracy of differential flight time is ± 250ps, and the accuracy of ± 1% can be achieved under the condition of flow rate up to 12000l / h, with a wide dynamic range of 200:1.

Msp430fr5043 device adopts low-power accelerator (LEA) to realize signal acquisition and subsequent optimized digital signal processing based on high-speed ADC, which provides an ultra-low power consumption and high-precision measurement solution application for battery powered measurement. This MSP system architecture with ultra-low overall power consumption can reduce the energy consumption and improve the performance of the whole ultrasonic sensor system.

ADI special split solution

ADI does not integrate the whole controller function for ultrasonic application like ti, and adopts a separate solution. Although not packaged into a chip, each device is powerful for every application.

（ADI）

From the transmitting end, ADI gives a four channel scheme based on ad9106. Through this four channel, 180msps 12 bit arbitrary waveform generator, the transmitted signal is accurately controlled to enhance the performance of the flowmeter. At the same time, this configuration can also save a lot of flowmeter space.

On the receiving front end, AFE selects the highly integrated eight channel ad9670, which can greatly improve the performance. There are ad3388 and ad8332 options on VGA. The first can provide the highest dynamic range, and the second can achieve the lowest noise. It can be selected according to the actual needs.

On the DAC, ad5681r, a single channel 12 bit precision DAC, is selected. The DAC integrates the reference voltage and is a good small-size scheme. The common fully integrated digital temperature sensor is selected as the temperature sensor, which is simple and accurate, and can not be used for temperature compensation.

The processor uses 400MHz ads9-bf70x. The DSP is equipped with 1MB SRAM and built-in encryption accelerator. It is a processor supporting a variety of industrial interfaces. Another consideration given to this scheme should be to focus on the power consumption of the DSP less than 100MW at 400MHz, reduce the power consumption from the inside of the sensor and reduce the self heating of the flowmeter.

From the matching of these discrete devices, it is not difficult to see that ADI attaches great importance to low power consumption for ultrasonic applications, as well as the strict control of space. In the selection of each device, we not only consider the high precision, but also subtract the size as much as possible.

Summary

Whether it is a fully integrated chip solution or a discrete solution, we should do it with low power consumption and low cost as far as possible. Although ADI does not integrate these discrete devices into SOC, it can also see the development direction of miniaturization of ultrasonic sensor chip from the practice of reducing the size as much as possible.

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Keyword：Ultrasonic sensor   chip   MCU   accelerator   controller   signal acquisition   digital signal   transmitter   Commax-Tech Electronic