MC68HC708MP16 Datasheet, PDF (151/398 Pages) Freescale Semiconductor, Inc – Microcontrollers

Pulse Width Modulator for Motor Control (PWMMC)
To correct deadtime distortion, software can decrease or increase the
value in the appropriate PWMVAL register.
• In edge-aligned operation, decreasing or increasing the PWM
value by a correction value equal to the deadtime compensates for
deadtime distortion.
• In center aligned operation, decreasing or increasing the PWM
value by a correction value equal to one-half the deadtime
compensates for deadtime distortion.
In complementary channel operation, the ISENS1–3 bits in PWM control
register 1 select one of three correction methods:
• Manual correction
• Automatic current-sensing correction during deadtime
• Automatic current sensing correction when the PWM counter
value equals the value in the PWM counter modulus registers.
Table 9-4. Correction Method Selection
ISENS[1:0]
Correction method
0X
Manual correction with IPOL1–IPOL3 bits; or for no correction
Automatic current-sensing correction on pins IS1, IS2, and IS3
10
during deadtime⁽¹⁾
Automatic current-sensing correction on pins IS1, IS2, and IS3⁽²⁾
11
At the half cycle in center-aligned operation
At the end of the cycle in edge-aligned operation
1. 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.
2. Current is sensed even with 0% or 100% duty cycle.
NOTE: The ISENSx bits are not buffered; therefore, changing the current
sensing method can affect the present PWM cycle.
MC68HC708MP16 — Rev. 3.1
Freescale Semiconductor Pulse Width Modulator for Motor Control (PWMMC)
Technical Data
151