Specifications

dsPIC33F/PIC24H Family Reference Manual

43.6.5 Dead Time Ranges

The dead time duration provided by each dead time unit is set by specifying an unsigned value

in the DTRx and ALTDTRx registers. At maximum operating clock frequency with a 1.04 ns duty

cycle resolution, the dead time resolution is 1.04 ns. At the highest PWM resolution, the

maximum dead time value is 17.03

µs.

43.6.6 Dead Time Distortion

For duty cycle values near 0% or 100%, the PWM signal becomes nonlinear if dead time is

active. For any duty cycle value less than the dead time, the PWM output is zero. For duty

cycle values greater than (100% - dead time), the PWM output is same as if the duty cycle

is (100% - dead time).

43.6.7 Dead Time Resolution

At the highest clock rate, the dead time resolution is 1.04 ns under normal operating conditions.

However, there are some exceptions: For fault current-limit, or user override events, the highest

possible dead time resolution is 8.32 ns (bit 3 in the DTRx and ALTDTRx registers) at maximum

CPU speed and prescaler.

The configuration of PWM dead time control is shown in Example 43-15. The configuration of

PWM dead time initialization is shown in Example 43-16.

Example 43-15: PWM Dead Time Control

Example 43-16: PWM Dead Time Initialization

Note: When current-limit or fault override data is set to ‘0’, dead time is not applied, and

the “zero” override data is applied immediately.

Note: For duty cycle values greater than (100% - dead time), and the application

demands 100% duty cycle (that is, there is no dead time in the PWM output);

therefore, configure DTC = 2 in the PWMCONx register.

/* Select Dead Time control */

/* Choose one of these options */

PWMCON1bits.DTC = 0; /* Positive Dead Time applied for all modes */

PWMCON1bits.DTC = 1; /* Negative Dead Time applied for all modes */

/* Dead Time value for PWM generator */

/* Refer to Equation 43-7 */

DTR1 = 96; /* Dead Time value is 100 ns */

ALTDTR1 = 96; /* Alternate Dead time value is 100 ns */