ZHCS408C August 2011 – June 2015 DRV201
PRODUCTION DATA.
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The DRV201 device is a voice coil motor driver designed for camera auto focus control. The device allows for a highly efficient PWM current control for VCM, while reducing lens ringing in order to significantly lower the time needed for the lens to auto focus. The following design is a common application of the DRV201 device.
Ringing compensation is dependent on the VCM resonance frequency, and this can be controlled through the VCM_FREQ register (07h) from 50 Hz up to 150 Hz. VCM mechanical ringing frequency for the ringing compensation can be selected using Equation 3. The formula gives the VCM_FREQ[7:0] register value in decimal which should be rounded to the nearest integer.
Default VCM mechanical ringing frequency is 76.4 Hz.
DESIGN PARAMETER | REFERENCE | EXAMPLE VALUE |
---|---|---|
Supply voltage | Vin | 3.7 |
Motor Winding Resistance | RL | 15 Ω |
Motor Winding Inductance | IL | 100 µH |
Actuator Size | 8.5 x 8.5 x 3.4 (mm) | |
Lens in the VCM | M6 (Pitch: 0.35) | |
Weight of VCM | 75 mg | |
TTL | 4.2 mm | |
FB | 1.1 mm |
In Figure 21, lens settling time and settling window shows how lens control is defined. Below is an example case how the lens is controlled and what settling time is achieved:
Measured VCM resonance frequency = 100 Hz
VCM resonance frequency, fVCM, variation is within ±10% (minimum 90 Hz, maximum 110 Hz)
Stepping the lens by 50 µm
If the case is otherwise exactly the same, but VCM resonance frequency cannot be guaranteed to stay at more than ±30% variation, slower ringing compensation should be used:
Measured VCM resonance frequency = 100 Hz
VCM resonance frequency, fVCM, variation is within ±30% (minimum 70 Hz, maximum 130 Hz)
Stepping the lens by 50 µm