BU64241GWZ Datasheet, PDF (12/24 Pages) Rohm – Linear Constant Current VCM Driver

BU64241GWZ
Datasheet
・Step A2 – Selecting the Autofocus Algorithm’s Target DAC Codes
The ISRC algorithm is a proprietary technology developed to limit the ringing of an actuator by predicting the magnitude
of ringing created by an actuator and intelligently controlling the output signal of the driver to minimize the ringing effect.
Due to the ringing control behavior of ISRC, it is unable to operate properly unless the lens is floating (lens lifted off of the
mechanical end of the actuator). As such the ringing control behavior is broken into three separate operational areas in
order to provide the most optimally controlled autofocus algorithm.
Direct Mode
Step Mode
ISRC Mode
C
Displacement
(µm)
B
A
0
A: lens displacement = 0 µm
B: all lenses floating
C: final lens position
Figure 15. Lens Displacement vs. DAC Code
DAC code
Figure 15 illustrates the different operational modes that control the autofocus algorithm. Due to ISRC requiring a
floating lens, points A and B need to bet set in order to create a floating condition. Point A corresponds to the maximum
amount of current that can be applied to all VCM units without floating the lens. Point B corresponds to the minimum
amount of current that can be applied to the VCM so that all actuator units are floating. It should be noted that the target
DAC codes could vary between different actuator units and that sufficient evaluation should be performed before
selecting the point A and B target DAC codes. Point C is the final lens target position determined by the level of focus
required for the image capture.
The actuator manufacturer should be able to provide the required current for points A and B, however it is possible to test
these points by slowly increasing the 10 bit value of C_DAC[9:0] and measuring the lens movement using a laser
displacement meter or some other device to measure lens displacement.
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TSZ22111・15・001
12/20
TSZ02201-0H2H0B600460-1-2
01. Jul. 2013 Rev.004