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2016-04-28 - Giant Gecko Family - d0053_Rev1.20
537
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The PWM frequency is given by Equation 20.7 (p. 535) :
TIMER 2x Mode PWM Frequency Equation( Up/Down-count)
f
PWM
2xmode
= f
HFPERCLK
/ TOP
(20.13)
The high duty cycle is given by Equation 20.14 (p. 537)
TIMER 2x Mode Duty Cycle Equation
DS
2xmode
= CCVx/TOP
(20.14)
20.3.3 Dead-Time Insertion Unit (TIMER0 only)
The Dead-Time Insertion Unit aims to make control of BLDC motors safer and more efficient
by introducing complementary PWM outputs with dead-time insertion and fault handling, see
Figure 20.22 (p. 537) .
Figure 20.22. TIMER Dead-Time Insertion Unit Overview
Dead t im e
insert ion
Original PWM (TIM0_CCx _pre)
Fault
handling
Prim ary out put (TIM0_CCx )
Com plem ent ary out put (TIM0_CDTIx )
Fault sources
When used for motor control, the PWM outputs TIM0_CC0, TIM0_CC1 and TIM0_CC2 are often
connected to the high-side transistors of a triple half-bridge setup (UH, VH and WH), and the
complementary outputs connected to the respective low-side transistors (UL, VL, WL shown in
Figure 20.23 (p. 537) ). Transistors used in such a bridge often do not open/close instantaneously, and
using the exact complementary inputs for the high and low side of a half-bridge may result in situations
where both gates are open. This can give unnecessary current-draw and short circuit the power supply.
The DTI unit provides dead-time insertion to deal with this problem.
Figure 20.23. TIMER Triple Half-Bridge
UH
VH
WH
WL
VL
UL
W
V
U
For each of the 3 compare-match outputs of TIMER0, an additional complementary output is provided by
the DTI unit. These outputs, named TIM0_CDTI0, TIM0_CDTI1 and TIM0_CDTI2 are provided to make
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