MC9S12E64CFUE Datasheet, PDF (368/606 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 11 Pulse Width Modulator with Fault Protection (PMF15B6CV2)
11.4.5.3 Current-Sensing Correction
A current sense pin, ISx, for a PWM pair selects either the odd or the even PWM value registers to use in
the next PWM cycle. The selection is based on user-provided current sense circuitry driving the ISx pin
high for negative current and low for positive current.
Table 11-49. Top/Bottom Current-Sense Correction
Pin
Logic State
0
IS0
1
0
IS1
1
0
IS2
1
Output Control
PMFVAL0 controls PWM0/PWM1 pair
PMFVAL1 controls PWM0/PWM1 pair
PMFVAL2 controls PWM2/PWM3 pair
PMFVAL3 controls PWM2/PWM3 pair
PMFVAL4 controls PWM4/PWM5 pair
PMFVAL5 controls PWM4/PWM5 pair
Previously shown, the current direction can be determined by the output voltage during deadtime. Thus, a
simple external voltage sensor can be used when current status is completed during deadtime, ISENS = 10.
Deadtime does not exists at the 100 percent and zero percent duty cycle boundaries. Therefore, the second
automatic mode must be used for correction, ISENS = 11, where current status is sampled at the half cycle
in center-aligned operation and at the end of cycle in edge-aligned operation. Using this mode requires
external circuitry. It actually senses current direction.
PWM CONTROLLED BY
ODD PWMVAL REGISTER
PWM CONTROLLED BY
EVEN PWMVAL REGISTER
INITIAL VALUE = 0
A
B
A/B
DEADTIME
GENERATOR
ISx PIN
IN DEADTIME
D
Q
CLK
D
Q
CLK
TOP PWM
BOTTOM PWM
PWM CYCLE START
Figure 11-57. Internal Correction Logic when ISENS = 10
PWM CONTROLLED BY
ODD PWMVAL REGISTER
PWM CONTROLLED BY
EVEN PWMVAL REGISTER
INITIAL VALUE = 0
A
B
A/B
DEADTIME
GENERATOR
ISx PIN
PMFCNT = PMFMOD
D
Q
CLK
D
Q
CLK
TOP PWM
BOTTOM PWM
PWM CYCLE START
Figure 11-58. Internal Correction Logic when ISENS = 11
MC9S12E128 Data Sheet, Rev. 1.07
368
Freescale Semiconductor