Datasheet

Chapter 11 Pulse Width Modulator with Fault Protection (PMF15B6CV2)
MC9S12E128 Data Sheet, Rev. 1.07
368 Freescale Semiconductor
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.
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.
Figure 11-57. Internal Correction Logic when ISENS = 10
Figure 11-58. Internal Correction Logic when ISENS = 11
Table 11-49. Top/Bottom Current-Sense Correction
Pin Logic State Output Control
IS0
0 PMFVAL0 controls PWM0/PWM1 pair
1 PMFVAL1 controls PWM0/PWM1 pair
IS1
0 PMFVAL2 controls PWM2/PWM3 pair
1 PMFVAL3 controls PWM2/PWM3 pair
IS2
0 PMFVAL4 controls PWM4/PWM5 pair
1 PMFVAL5 controls PWM4/PWM5 pair
DQ
CLK
PWM CONTROLLED BY
PWM CONTROLLED BY
DEADTIME
GENERATOR
DQ
CLK
ISx PIN
A/B
A
B
PWM CYCLE START
TOP PWM
BOTTOM PWM
INITIAL VALUE = 0
ODD PWMVAL REGISTER
EVEN PWMVAL REGISTER
IN DEADTIME
DQ
CLK
PWM CONTROLLED BY
PWM CONTROLLED BY
DEADTIME
GENERATOR
DQ
CLK
ISx PIN
A/B
A
B
PWM CYCLE START
TOP PWM
BOTTOM PWM
INITIAL VALUE = 0
ODD PWMVAL REGISTER
EVEN PWMVAL REGISTER
PMFCNT = PMFMOD