Preliminary Technical Data

AD5801

Rev. 0 | Page 9 of 13

programme up to four transitions within the time set in the

PWMPERIOD Register (See Figure 4 for typical timing

diagrams, with outputs FC and FD as an example).

The number of PWMPERIOD periods is again set in the

AFSTEPS and ZSTEPS Registers. When the outputs are

disabled they can be set configured in a High Impedance, or

High or Low state.

PWMPERIOD

PWMAFCT1

PWMAFCT2

PWMAFDT1

PWMAFDT2

PWM

FC

PWM

FD

PWMAFCT3

PWMAFCT4

PWMAFDT4

PWMAFDT3

Figure 4. Timing Diagram for PWM Drivers.

Temperature Compensation of Drive Patterns

Because of the high temperature coefficients associated with

piezo elements fine tuning of the drive pattern and drive

frequencies are required to ensure the device operates over its

intended temperature range.

In all drive modes it is possible to specify different timing

parameters

for

three

different

temperature

areas..

If

Temperature compensation mode is selected by programming

the appropriate bit to the DRIVEMODE register, the PTAT

temperature is checked at the beginning of the new ACTIVE

move command and depending on the Temperature recorded

the timing data for the move is read from the appropriate

timing register, HOT, COLD or NOMINAL.

The timing registers for all the driver outputs FA-ZD are

duplicated for Hot and Cold operation and the relevant timing

information for the Hot and Cold bands of operation are

programmed in these Registers.

PWM Slope Mode

A piezo element is a block of ceramic material and is basically a

moving capacitor. The electrical energy of the drive patterns are

converted into mechanical reaction energy inside the piezo

element, and the resulting deformation in the material is used

to produce forces to move the lens assembly in an optical

module.

Driving a capacitive element with digital patterns may produce

large surges in power because power is only consumed during

transients and the impedance of the piezo motor can be very

small on the rising and falling edges of a pulse.

TheAD5801 has an alternative driving scheme called the PWM

Slope Mode which can be employed on Channels FA and FB.

The Slope Mode allows the user to control the rise and fall

times of the drive waveform by taking advantage of the energy

storage properties of the series inductor and the resultant LC