Microchip Technology dsPIC30F - Page 337

© 2004 Microchip Technology Inc. DS70062C-page 15-27
Section 15. Motor Control PWM
Motor Control
PWM
15
15.6.2 Dead Time Assignment
The DTCON2 register contains control bits that allow the two programmable dead times to be
assigned to each of the complementary outputs. There are two dead time assignment control
bits for each of the complementary outputs. For example, the DTS1A and DTS1I control bits
select the dead times to be used for the PWM1H/PWM1L complementary output pair. The pair
of dead time selection control bits are referred to as the ‘dead-time-select-active’ and
‘dead-time-select-inactive’ control bits, respectively. The function of each bit in a pair is as
follows:
• The DTSxA control bit selects the dead time that is to be inserted before the high-side
output is driven active.
• The DTSxI control bit selects the dead time that is to be inserted before the low-side PWM
active is driven active.
Table 15-3 summarizes the function of each dead time selection control bit.
Table 15-3: Dead Time Selection Bits
15.6.3 Dead Time Ranges
Dead time A and dead time B are set by selecting an input clock prescaler value and a 6-bit
unsigned dead time count value.
Four input clock prescaler selections have been provided to allow a suitable range of dead
times based on the device operating frequency. The clock prescaler option may be selected
independently for each of the two dead time values. The dead time clock prescaler values are
selected using the DTAPS<1:0> and DTBPS<1:0> control bits in the DTCON1 SFR. The
following clock prescaler options may be selected for each of the dead time values:
•T
CY
•2 TCY
•4 TCY
•8 TCY
Equation 15-3: Dead Time Calculation
Note: The dead time assignment logic is only applicable to dsPIC variants that contain the
8-output PWM module. The 6-output PWM module uses dead time A only.
Bit Function
DTS1A Selects PWM1H/PWM1L dead time inserted before PWM1H is driven active.
DTS1I Selects PWM1H/PWM1L dead time inserted before PWM1L is driven active.
DTS2A Selects PWM1H/PWM1L dead time inserted before PWM2H is driven active.
DTS2I Selects PWM1H/PWM1L dead time inserted before PWM2L is driven active.
DTS3A Selects PWM1H/PWM1L dead time inserted before PWM3H is driven active.
DTS3I Selects PWM1H/PWM1L dead time inserted before PWM3L is driven active.
DTS4A Selects PWM1H/PWM1L dead time inserted before PWM4H is driven active.
DTS4I Selects PWM1H/PWM1L dead time inserted before PWM4L is driven active.
Dead Time
Prescale Value • T
CY
Note: DT (Dead Time) is the DTA<5:0> or DTB<5:0> register value.
DT =