DSPIC30F3011 Microchip Technology Inc., DSPIC30F3011 Datasheet - Page 98

• Manufacturer Part Number: DSPIC30F3011
• Description: Dspic30f3010/3011 Enhanced Flash 16-bit Digital Signal Controller
• Manufacturer: Microchip Technology Inc.

dsPIC30F3010/3011
When the PWM time base is in the Up/Down Counting
mode with double updates, new duty cycle values are
updated when the value of the PTMR register is zero,
and when the value of the PTMR register matches the
value in the PTPER register. The contents of the duty
cycle buffers are automatically loaded into the duty
cycle registers when the PWM time base is disabled
(PTEN = 0).
15.6
In the Complementary mode of operation, each pair of
PWM outputs is obtained by a complementary PWM
signal. A dead time may be optionally inserted during
device switching, when both outputs are inactive for a
short period (Refer to Section 15.7).
In Complementary mode, the duty cycle comparison
units are assigned to the PWM outputs as follows:
• PDC1 register controls PWM1H/PWM1L outputs
• PDC2 register controls PWM2H/PWM2L outputs
• PDC3 register controls PWM3H/PWM3L outputs
The Complementary mode is selected for each PWM
I/O pin pair by clearing the appropriate PMODx bit in the
PWMCON1 SFR. The PWM I/O pins are set to
Complementary mode by default upon a device Reset.
15.7
Dead-time generation may be provided when any of
the PWM I/O pin pairs are operating in the Comple-
mentary Output mode. The PWM outputs use Push-
Pull drive circuits. Due to the inability of the power out-
put devices to switch instantaneously, some amount of
time must be provided between the turn-off event of
one PWM output in a complementary pair and the turn-
on event of the other transistor.
The PWM module allows two different dead times to be
programmed. These two dead times may be used in
one of two methods described below to increase user
flexibility:
• The PWM output signals can be optimized for
• The two dead times can be assigned to individual
DS70141D-page 96
different turn-off times in the high side and low
side transistors in a complementary pair of
transistors. The first dead time is inserted
between the turn-off event of the lower transistor
of the complementary pair and the turn-on event
of the upper transistor. The second dead time is
inserted between the turn-off event of the upper
transistor and the turn-on event of the lower
transistor.
PWM I/O pin pairs. This Operating mode allows
the PWM module to drive different transistor/load
combinations with each complementary PWM I/O
pin pair.
Complementary PWM Operation
Dead-Time Generators
Confidential
15.7.1
Each complementary output pair for the PWM module
has a 6-bit down counter that is used to produce the
dead-time insertion. As shown in Figure 15-4, each
dead-time unit has a rising and falling edge detector
connected to the duty cycle comparison output.
15.7.2
The amount of dead time provided by the dead-time
unit is selected by specifying the input clock prescaler
value and a 6-bit unsigned value.
Four input clock prescaler selections have been pro-
vided to allow a suitable range of dead time, based on
the device operating frequency. The dead-time clock
prescaler values are selected using the DTAPS<1:0>
control bits in the DTCON1 SFR. One of four clock
prescaler options (T
selected.
After the prescaler value is selected, the dead time is
adjusted by loading 6-bit unsigned values into the
DTCON1 SFR.
The dead-time unit prescaler is cleared on the following
events:
• On a load of the down timer due to a duty cycle
• On a write to the DTCON1 register.
• On any device Reset.
comparison edge event.
Note:
DEAD-TIME GENERATORS
DEAD-TIME RANGES
The user should not modify the DTCON1
value while the PWM module is operating
(PTEN = 1). Unexpected results may
occur.
CY
, 2T
© 2007 Microchip Technology Inc.
CY
, 4T
CY
or 8T
CY
) may be