Datasheet

Chapter 11 Pulse Width Modulator with Fault Protection (PMF15B6C) Module
MC9S12E256 Data Sheet, Rev. 1.10
370 Freescale Semiconductor
Figure 11-56. Output Voltage Waveforms
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.
Table 11-40. 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
DEADTIME
PWM TO TOP
POSITIVE
NEGATIVE
PWM TO BOTTOM
LOAD VOLTAGE WITH
LOAD VOLTAGE WITH
TRANSISTOR
TRANSISTOR
HIGH POSITIVE CURRENT
LOW POSITIVE CURRENT
CURRENT
CURRENT
LOAD VOLTAGE WITH
HIGH NEGATIVE CURRENT
LOAD VOLTAGE WITH
NEGATIVE CURRENT
TBTB
T = DEADTIME INTERVAL BEFORE ASSERTION OF TOP PWM
B = DEADTIME INTERVAL BEFORE ASSERTION OF BOTTOM PWM
V+