BU64241GWZ Datasheet, PDF (13/24 Pages) Rohm – Linear Constant Current VCM Driver

BU64241GWZ
Datasheet
●Controlling the Driver
After following steps A1 and A2 to characterize the VCM performance, the following steps should be followed in order to
properly control the driver settings for optimized autofocus performance.
・Step B1 – Setting Point A, B, and C DAC Codes
Points A, B, and C are defined by 10 bit DAC codes set with the following registers:
Location
Point C
Point A
Point B
W2W1W0 Register
000b
010b
011b
DAC Code Location
C_DAC[9:0]
A_DAC[9:0]
B_DAC[9:0]
Description
Final lens position before image capture
Maximum output current without floating the lens
Minimum output current required to float the lens
・Step B2 – Controlling Direct Mode
Direct mode is when the driver outputs the desired amount of output current with no output current control. The time in
which the lens reaches the position that corresponds to the amount of output current set by the 10 bit DAC code is ideally
instant, ignoring the ringing effects. If the driver is set so that the lens is moved from a resting position to point C with
direct mode, ringing and settling time will be at a maximum.
Direct mode is used either when M = 0 or when M = 1 and the present DAC code is less than the DAC code of point A.
M = 0 = ISRC mode disabled
When ISRC mode is disabled by setting the M bit equal to 0, the lens will traverse to the DAC code set for point C when
the EN bit is set equal to 1.
M = 1 = ISRC mode enabled
The driver automatically uses direct mode if the present DAC code is less than the target DAC code corresponding to
point A. Therefore during ISRC operation when the autofocus sequence has been started by setting the EN bit equal to
1, the driver will automatically decide to use direct mode to output current up to point A and then switch to step mode
before continuing the autofocus sequence.
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TSZ22111・15・001
13/20
TSZ02201-0H2H0B600460-1-2
01. Jul. 2013 Rev.004