SLAAEK6 June   2024 ULC1001 , ULC1001-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Acronyms
  5. 2Introduction
  6. 3Design Principles
    1. 3.1 Critical Acceleration
    2. 3.2 LCS Architecture
    3. 3.3 Design Procedure
    4. 3.4 Design of Components
      1. 3.4.1 Lens
      2. 3.4.2 Transducer
      3. 3.4.3 Thin Film
      4. 3.4.4 Glue Fixture
      5. 3.4.5 Housing
        1. 3.4.5.1 Housing Cap
        2. 3.4.5.2 Flexible Seal
        3. 3.4.5.3 Housing Base
  7. 4Fabrication Principles
    1. 4.1 Lens
    2. 4.2 Transducer
    3. 4.3 Thin Film
    4. 4.4 Glue Fixture
    5. 4.5 Housing
  8. 5Assembly Principles
    1. 5.1 Step 1: Gluing Components into Lens Cover
    2. 5.2 Step 2: Soldering of Lens Cover with Wires
    3. 5.3 Step 3: Assemble Lens Cover into Housing
  9. 6Example: CAD Drawings for Aperture = 15mm
  10. 7Resources

3.4.2 Transducer

The transducer acts as the actuator in the application.

Material: The recommended transducer material is PZT. TI uses PZT 8 in the prototypes considering the high mechanical quality factor. Other PZT materials such as PZT4 or PZT5 can be options as well.

Geometry: The transducer is a ring shape and is poled in the top/bottom direction. Figure 3-6 shows the top view, side view and isometric view of the transducer and also illustrates the dimensions of the transducer. T_ID, T_OD, and T_H represent the inner diameter, outer diameter and the height of the transducer, respectively.

Transducer: Top View, Side View and Isometric View Figure 3-6 Transducer: Top View, Side View and Isometric View

There are multiple resonant modes of the ring piezo. In this application, the radial mode is utilized for the cleaning modes and the resonant frequency can be estimated by the following equation:

Equation 3. f r a d i a l = 2 π ( T _ I D   + T _ O D ) ρ s 11 E

where ρ is the density of the material, and s 11 E is elastic compliance at constant electric field. This can be further simplified as

Equation 4. f r a d i a l = C ( T _ I D   + T _ O D )

where C is a constant, whose value is estimated to be about 2000 H z · m for PZT 8 material. Piezo suppliers have slightly different C values for the same type of the piezo material due to their recipe variances.

Radial Mode of Piezo for Water Cleaning Figure 3-7 Radial Mode of Piezo for Water Cleaning
Important:
  • The wall thickness ((T_OD-T_ID)/2) between the lens must be at least 3mm to maintain a large gluing area between the piezo and the lens.
  • The wall thickness ((T_OD-T_ID)/2) is typically more than 2 times the piezo thickness to be a ring-shaped piezo (thin and wide).