TDK CH101 Mechanical Integration Manual
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TDK CH101 Mechanical Integration Manual

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CH101 and ICU-10201 Mechanical Integration
Chirp Microsystems reserves the right to change
specifications and information herein without notice.
Guide
InvenSense, a TDK Group Company
2560 Ninth Street, Ste 220, Berkeley, CA 94710 U.S.A
+1(510) 640–8155
www.chirpmicro.com
AN-000158
Document Number: AN-000158
Revision: 1.2
Release Date: 10/06/2021

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  • Page 1 AN-000158 CH101 and ICU-10201 Mechanical Integration Guide InvenSense, a TDK Group Company Document Number: AN-000158 Chirp Microsystems reserves the right to change 2560 Ninth Street, Ste 220, Berkeley, CA 94710 U.S.A Revision: 1.2 specifications and information herein without notice. +1(510) 640–8155 Release Date: 10/06/2021 www.chirpmicro.com...

  • Page 2: Introduction

    AN-000158 1 INTRODUCTION The purpose of this document is to provide recommendations and guidance on the mechanical integration of Chirp CH101 and ICU- 10201 ultrasonic sensors in device enclosures. This document will cover the mechanical design, geometry, part and assembly tolerances, material considerations, testing, and best practices for mechanical integration.

  • Page 3: Acronyms And Abbreviations

    AN-000158 2 ACRONYMS AND ABBREVIATIONS Some commonly used acronyms and abbreviations in this document are listed in Table 1. Acronyms and Abbreviations Definition ASIC Application-specific integrated circuit Field-of-View Flexible printed circuit FWHM Full-width half-maximum Integrated circuit Infrared Least significant bits (ADC counts) MEMS Micro-electro-mechanical systems Pressure-sensitive adhesive...

  • Page 4: Table Of Contents

    MPACT AND NSERTION OSSES PIF P ..................................14 LACEMENT PIF I ............................15 NTEGRATION AND PTIMIZATION ASSEMBLY GUIDELINES, TOLERANCES AND REQUIREMENTS ....................16 CH101 ICU-10201 M ............................16 OUNTING ....................16 ECOMMENDED ETHOD FOR ENSOR SSEMBLY AND TTACHMENT ............................16...

  • Page 5: Overview

    (343 m/s at room temperature), the system can determine the distance to the object. Unlike other types of ToF rangefinders, such as infrared (IR) sensors, the CH101 and ICU-10201 sensors are not affected by the color or transparency of objects and works in all lighting conditions. It also uses significantly less power than comparable IR sensors and the sensor’s Field-of-View (FoV) can be customized by using different acoustic housings.

  • Page 6: Sensor Configurations

    SENSOR CONFIGURATIONS As ultrasonic transceivers, the CH101 and ICU-10201 are capable of measuring distances to objects just by themselves. However, a network of sensors can be used together for additional functionality such as 2D and 3D location identification. The most common sensor configurations are detailed below.
  • Page 7 AN-000158 Figure 4. Ultrasonic transceiver sensors operating in Pitch-Catch configuration. One sensor is set to transmit, with all remaining sensors set to receive only. The transmitting sensor can still measure the ToF of its own ultrasonic signal. Page 7 of 22 Document Number: AN-000158 Revision: 1.2...

  • Page 8: Acoustic Interfaces

    TUBES Tubes are holes of a specific length and diameter. For the CH101, the optimal tube length is 0.475 mm with a diameter of 0.7 mm. A straight tube is the Acoustic Interface of choice for applications that require the smallest opening possible. Straight tubes are always omnidirectional (~180 degree FoV).
  • Page 9 Field-of-View (Vertical) (Degrees) On-Axis Pulse-Echo 4.5x Amplitude (Typ. Relative to AH-180180) Comments Omnidirectional Narrow FoV Narrow FoV, Module Asymmetric FoV retrofit Table 2. Summary of common CH101 and ICU-10201 Acoustic Interfaces Page 9 of 22 Document Number: AN-000158 Revision: 1.2...

  • Page 10: Definition Of Field-Of-View

    DEFINITION OF FIELD-OF-VIEW The FoV of the CH101 and ICU-10201 can be set to meet the application requirements by designing the appropriate Acoustic Interface. It should be noted that, unlike the FoV of IR sensors, it is still possible to detect objects beyond the acoustic FoV. This is because the acoustic FoV is defined as the full-width half-maximum (FWHM) of the round-trip beam pattern.

  • Page 11: Angled/Curved Device Enclosure Exterior Surface

    MATERIALS Any material that does not absorb ultrasound (~175 kHz for CH101 and ICU-10201) is suitable for use as the Acoustic Interface. This includes most plastics (PC, ABS, Delrin, etc.), metals, and composite materials. Materials NOT recommended for use include all foams, fabrics, and textiles.
  • Page 12 AN-000158 • Layer thickness of 0.025 mm (0.001”) For critical dimensions, the tolerance of printed samples should be within 0.1 mm of nominal. Chirp DOES NOT recommend using FDM (filament based) 3D printers for making horn Acoustic Interfaces. FDM 3D printing does not have the required resolution, accuracy, and surface finish to produce Acoustic Interfaces with good acoustic performance.

  • Page 13: Particle Ingress Filters

    Using a protective covering or Particle Ingress Filter (PIF) over the sensor is recommended if dust, liquid or other contaminants are present in the application environment. For the CH101 and ICU-10201, the currently supported PIF material is SAATI Acoustex B042HY. The B042HY has been tested by Chirp to provide a dust protection rating of IP5X. Due to the small size of the sensor, it is not feasible to test for IP6X, because negative pressure cannot be applied to the part.

  • Page 14: Pif Acoustic Performance Impact And Insertion Losses

    PIF PLACEMENT For the CH101 and ICU-10201, the PIF must be placed in a specific position in the acoustic path between the sensor PMUT and the air. Chirp’s testing has shown that PIFs placed directly on top of the sensor package and right over the port hole generally significantly decrease acoustic performance.

  • Page 15: Pif Integration And Optimization

    AN-000158 In some instances when using a straight tube Acoustic Interface, designers may want to have the PIF invisible for industrial design reasons. In this case, the PIF can be obscured by placing an additional straight tube on top of the inner tube Acoustic Interface. The outermost tube will need to have a 0.9 mm diameter and 0.9 mm thickness.

  • Page 16: Assembly Guidelines, Tolerances And Requirements

    CH101 AND ICU-10201 MOUNTING The recommended method of placing the CH101 or ICU-10201 in a device is to mount and solder it on its own PCB (FPC, rigid flex or rigid PCB). This PCBA makes it much easier to control the mounting and assembly of the sensor onto the Acoustic Interface, thereby decreasing the chances of poor assembly accuracy and reduced acoustic performance.

  • Page 17: Sensor-To-Acoustic Interface Assembly Tolerances

    AN-000158 Sensor Configuration Max Assembly Force (grams-force) Max Allowable Frequency Shift Due to Assembly (Hz) Pulse-Catch Pitch-Echo 1500 Table 6. Summary of maximum allowable residual assembly force. The easiest way to detect when this force is exceeded is to measure the frequency shift from before and after assembly. One method of holding the module against the device enclosure while avoiding applying excessive force on the module is to use a backplate to transfer the force applied to the module to the Acoustic Interface instead of the sensor (see Figure 16).

  • Page 18: Acoustic Interface-To-Device Enclosure Assembly Tolerances

    AN-000158 Figure 18. Examples of what good and bad assembly of the Acoustic Interface look like. There must be no gap between the Acoustic Interface and the sensor for optimal acoustic performance. ACOUSTIC INTERFACE-TO-DEVICE ENCLOSURE ASSEMBLY TOLERANCES For applications using a separate Acoustic Interface from the overall device enclosure, there are additional considerations for the assembly and associated tolerances of the Acoustic Interface to the device enclosure.

  • Page 19: Assembly Inspection And Quality Control Checklist

    AN-000158 Figure 21. The Acoustic Interface should be mounted flush to the device enclosure to within 0.2 mm. There should also be minimal diametrical/clearance gap between the Acoustic Interface and the device enclosure. Chirp recommends no more than 0.1 mm clearance gap between the device enclosure and Acoustic interface. Figure 22.

  • Page 20: Summary

    AN-000158 7 SUMMARY DESIGN TRADEOFF CONSIDERATIONS As with any engineering design, there are always design tradeoffs. When integrating the CH101 or ICU-10201, the top tradeoff considerations are: • FoV vs max range: The amount of energy being emitted from the PMUT is finite. To focus the ultrasound beam in a narrow FoV requires taking energy from the sides of the beam pattern.

  • Page 21: Mechanical Design And Integration Steps Checklist

    AN-000158 MECHANICAL DESIGN AND INTEGRATION STEPS CHECKLIST 1. Estimate the maximum range (distance) required in your application to detect objects of interest. The Acoustic Interface (Step 2) and PIF (Step 5) will affect your range from the baseline case. 2. Estimate the FoV needed for your application. Note that Chirp defines the FoV of a sensor at FWHM, essentially the width of the beam pattern at half amplitude.

  • Page 22: Revision History

    ©2021 Chirp Microsystems. All rights reserved. InvenSense, MotionTracking, MotionProcessing, MotionProcessor, MotionFusion, MotionApps, DMP, AAR, and the InvenSense logo are trademarks of InvenSense, Inc. The TDK logo is a trademark of TDK Corporation. Other company and product names may be trademarks of the respective companies with which they are associated.

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Icu-10201

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