DSPIC30F2010 datasheet(100/236 Pages) MICROCHIP

100 / 236 page

dsPIC30F6010A/6015

DS70150C-page 98

15.6

Complementary PWM Operation

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 “Dead-Time

Generators”).

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

• PDC4 register controls PWM4H/PWM4L 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 Generators

Dead-time generation may be provided when any of

the

PWM

I/O

pairs

are

operating

the

Complementary Output mode. The PWM outputs use

Push-Pull drive circuits. Due to the inability of the

power output 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

different turn off times in the high side and low

side transistors in a complementary pair of tran-

sistors. 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.

• The two dead times can be assigned to individual

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.

15.7.1

DEAD-TIME GENERATORS

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

DEAD-TIME ASSIGNMENT

The DTCON2 SFR contains control bits that allow the

dead times to be assigned to each of the complemen-

tary outputs. Table 15-1 summarizes the function of

each dead-time selection control bit.

TABLE 15-1:

DEAD-TIME SELECTION BITS

15.7.3

DEAD-TIME RANGES

The amount of dead time provided by each dead-time

unit is selected by specifying the input clock prescaler

value and a 6-bit unsigned value. The amount of dead

time provided by each unit may be set independently.

Four input clock prescaler selections have been pro-

vided 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. One of

four clock prescaler options (TCY, 2 TCY, 4 TCY or 8 TCY)

may be selected for each of the dead-time values.

After the prescaler values are selected, the dead time

for each unit is adjusted by loading two 6-bit unsigned

values into the DTCON1 SFR.

The dead-time unit prescalers are cleared on the

following events:

• On a load of the down timer due to a duty cycle

comparison edge event.

• On a write to the DTCON1 or DTCON2 registers.

• On any device Reset.

Bit

Function

DTS1A

Selects PWM1L/PWM1H active edge dead time.

DTS1I

Selects PWM1L/PWM1H inactive edge

dead time.

DTS2A

Selects PWM2L/PWM2H active edge dead time.

DTS2I

Selects PWM2L/PWM2H inactive edge

dead time.

DTS3A

Selects PWM3L/PWM3H active edge dead time.

DTS3I

Selects PWM3L/PWM3H inactive edge

dead time.

DTS4A

Selects PWM4L/PWM4H active edge dead time.

DTS4I

Selects PWM4L/PWM4H inactive edge

dead time.

Note:

The user should not modify the DTCON1

or DTCON2 values while the PWM mod-

ule is operating (PTEN = 1). Unexpected

results may occur.

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