AN2524 Freescale Semiconductor / Motorola, AN2524 Datasheet - Page 6

• Manufacturer Part Number: AN2524
• Description: DC Motor with Dead-Time Correction TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

AN2524/D
Detailed Function Description
DC Motor with Dead-
Time Correction
(DCmDt)
6
voltage
motor
SW1
SW2
SW3
SW4
DT
DT
PWM period
dc = - 0.5
center-time
DC Motor with Dead-Time Correction TPU Function Set (DCmDt)
The DCmDt TPU function generates a 4-channel, 2-phase unipolar-switched
center-aligned PWM signal, with dead-time between the top and bottom
channels. In order to charge the bootstrap transistors, the PWM signals start to
run 1.6ms after their initialization (at 20MHz TCR1 clock). The functions
generate signals corresponding to value 0 in duty-cycle ratio dc until the first dc
value is processed, or for at least one PWM period.
The CPU controls the PWM output by setting the TPU parameters. The duty-
cycle ratio dc, PWM period T and current can be adjusted during run time.
Conversely, dead-time (DT) and minimum pulse width (MPW) are not
supposed to be changed during run time. The duty-cycle ratio dc can gain a
value in the range (–1, 1). The sign controls the motion system direction, while
the absolute value controls the amplitude of the applied voltage.
The following figures show the input dc value and corresponding output PWM
signals (valid for positive motor current):
DT
Freescale Semiconductor, Inc.
For More Information On This Product,
DT
Figure 3. Unipolar switching
Go to: www.freescale.com
DT
DT
PWM period
center-time
dc = 0
DT
DT
DT
DT
PWM period
center-time
dc = 0.5
DT
MOTOROLA
DT