AN2527 Freescale Semiconductor / Motorola, AN2527 Datasheet - Page 6

• Manufacturer Part Number: AN2527
• Description: DC Motor with Dead-Time Correction - XOR version TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

AN2527/D
Detailed Function Description
DC Motor with Dead-
Time Correction –
XOR version – C
channels
(DCmDtXor_C) and
DC Motor with Dead-
Time Correction –
XOR version – T
channels
(DCmDtXor_T)
6
voltage
motor
SW1
SW2
SW3
SW4
DT
DC Motor with Dead-Time Correction – XOR version TPU Function Set (DCmDtXor) MOTOROLA
DT
PWM period
dc = - 0.5
center-time
The DCmDtXor_C and DCmDtXor_T TPU functions work together to generate
4 pairs of XOR gate inputs. The XOR gate outputs then produce a 4-channel
2-phase 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 a 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) is 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 XOR gate
outputs (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
DT