Datasheet

Chapter 11 Pulse Width Modulator with Fault Protection (PMF15B6CV2)

MC9S12E128 Data Sheet, Rev. 1.07

Freescale Semiconductor 365

For a given PWM pair, whether the odd or even PMFVAL register is active depends on either:

• The state of the current status pin, ISx, for that driver

• The state of the odd/even correction bit, IPOLx, for that driver

To correct deadtime distortion, software can decrease or increase the value in the appropriate PMFVAL

• In edge-aligned operation, decreasing or increasing the PWM value by a correction value equal to

the deadtime typically compensates for deadtime distortion.

• In center-aligned operation, decreasing or increasing the PWM value by a correction value equal

to one-half the deadtime typically compensates for deadtime distortion.

In the complementary channel operation, ISENS selects one of three correction methods:

• Manual correction

• Automatic current status correction during deadtime

• Automatic current status correction when the PWM counter value equals the value in the PWM

counter modulus registers

NOTE

Assume the user will provide current status sensing circuitry causing the

voltage at the corresponding input pin to be low for positive current and high

for negative current. In addition, it assumes the top PWMs are PWM 0, 2,

and 4 while the bottom PWMS are PWM 1, 3, and 5.

Table 11-47. Correction Method Selection

ISENS Correction Method

00 No correction

The current status pins can be used as general purpose input/output ports.

01 Manual correction

10 Current status sample correction on pins

IS0, IS1, and IS2 during deadtime

The polarity of the ISx pin is latched when both the top and bottom PWMs are off. At the 0%

and 100% duty cycle boundaries, there is no deadtime, so no new current value is sensed.

11 Current status sample on pins

IS0, IS1, and IS2

At the half cycle in center-aligned operation

At the end of the cycle in edge-aligned operation

Current is sensed even with 0% or 100% duty cycle.