Delta Tau Turbo PMAC Clipper, Hardware Reference Manual

Page: 46 / 84

Turbo PMAC Clipper Hardware Reference Manual
Drive – Motor Setup 46
Filtered PWM Output (Analog ±10V)
In this mode, the ±10V analog output is obtained by passing the digital PWM signal through a 10 KHz
low pass filter. This technique, although not as performing as a true digital to analog converter, is more
than adequate for most servo applications.
The duty cycle of the PWM signal controls the magnitude of the voltage output. This is handled internally
by the PMAC, the user needs not to change any settings.
However, the frequency of the PWM signal determines the output resolution and ripple magnitude
(disturbance). The trade-off is as follows:
The higher the PWM frequency, the lower is the resolution with a low-ripple signal output.
The lower the PWM frequency, the higher is the resolution with a high-ripple signal output.
Note
Some amplifiers operate in the ±5V range; this can be regulated
using the motor command output limit, parameter Ixx69.
Both the resolution and the frequency of the Filtered PWM outputs are configured in software on the
Turbo PMAC Clipper through the variable
I7000 . This variable also effects the phase and servo
interrupts. Therefore as we change I7000 we will also have to change I7001 (phase clock divider), I7002
(servo clock divider), and I10 (servo interrupt time). These four variables are all related and must be
understood before adjusting parameters. The detailed information for these parameters can be found in
the
Turbo Software Reference Manual .
Note

Filtered PWM Output Configuration sets the Max PWM
frequency very high (29KHz). This setting can be problematic
with Direct PWM commutation on the same servo IC.

The ACC-28A and ACC-28B cannot be used on the same servo
IC since the PWM frequency settings are out of range for these
products.
PWM Frequency
Resolution Ripple