Analog Devices SHARC ADSP-214 Series

ADSP-214xx SHARC Processor Hardware Reference 7-17
Pulse Width Modulation
Output Control Feature Precedence
The order in which output control features are applied to the PWM signal
is significant and important. The following lists the order in which the
signal features are applied to the PWM output signal.
1. Duty Cycle Generation
2. Crossover
3. Output Enable
Figure 7-4. Normal Modulation to Full ON to Full OFF Transition
............................................
PWMPERIOD PWMPERIOD
PWMPERIOD
1
2
+
0
PWMPERIOD
1
2
PWMTM
2
2
+
PWM_AH
PWM_AL
PWM_AH
PWM_AL
............................................
FULL OFF
FULL ON
2xPWMDT
PWMCHA
1
EMERGENCY DEAD TIME
INSERTED BY PWM CONTROLLER
2xPWMDT
(a) TRANSITION FROM NORMAL MODULATION TO FULL-ON, AT HALF-CYCLE BOUNDARY IN DOUBLE UPDATE MODE,
WHERE NO ADDITIONAL DEAD TIME IS NEEDED.
(b) TRANSITION FROM NORMAL MODULATION TO FULL-OFF, AT HALF-CYCLE BOUNDARY IN DOUBLE UPDATE MODE,
WHERE ADDITIONAL DEAD TIME IS INSERTED BY THE PWM CONTROLLER
(a)
(b)
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