DRV201A

SLVSBN6 – JUNE 2013

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VCM DRIVER OUTPUT STAGE OPERATION

Current in the VCM can be controlled with a linear or PWM mode output stage. Output stage is enabled in

ACTIVE mode which can be controlled through VCM_CURRENT control register and the output stage mode is

selected from MODE register bit PWM/LIN.

In linear mode the output PMOS is configured to a high side current source and current can be controlled from a

VCM_CURRENT registers.

In PWM control the VCM is driven with a half bridge driver. With PWM control the VCM current is increased by

mode through the sense resistor and low side NMOS. Current in the VCM is sensed with a 1-

Ω sense resistor

which is connected into an error amplifier input where the other input is controlled by the 10-bit DAC output.

PWM mode switching frequency can be selected from 0.5 MHz up to 4 MHz through a CONTROL register. PWM

or linear mode can be selected with the PWM/LIN bit in the MODE register.

RINGING COMPENSATION

spring which causes a dampened ringing in the lens position when current is changed. This mechanical ringing is

compensated internally by generating an optimized ramp whenever the current value in the VCM_CURRENT

register is changed. This enables a fast auto focus algorithm and pleasant user experience.

Ringing compensation is dependent on the VCM resonance frequency and this can be controlled via

VCM_FREQ register (07h) from 50 Hz up 150 Hz. Table 1 shows the VCM_FREQ register setting for each

resonance frequency in 1-Hz steps. If more accurate resonance frequency is available, the control value can be

calculated with Equation 1.

Ringing compensation is designed in a way that it can tolerate ±30% frequency variation in the VCM resonance

VCM is needed in production.

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