R5F72115D160FPV datasheet(512/1228 Pages) RENESAS

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Section 10 Multi-Function Timer Pulse Unit 2 (MTU2)

Rev. 2.00 May. 08, 2008 Page 488 of 1200

REJ09B0344-0200

(j)

Complementary PWM Mode PWM Output Generation Method

In complementary PWM mode, 3-phase output is performed of PWM waveforms with a non-

overlap time between the positive and negative phases. This non-overlap time is called the dead

time.

A PWM waveform is generated by output of the output level selected in the timer output control

counting, data register and temporary register values are simultaneously compared to create

consecutive PWM pulses from 0 to 100%. The relative timing of on and off compare-match

occurrence may vary, but the compare-match that turns off each phase takes precedence to secure

the dead time and ensure that the positive phase and negative phase on times do not overlap.

Figures 10.46 to 10.48 show examples of waveform generation in complementary PWM mode.

The positive phase/negative phase off timing is generated by a compare-match with the solid-line

counter, and the on timing by a compare-match with the dotted-line counter operating with a delay

of the dead time behind the solid-line counter. In the T1 period, compare-match a that turns off the

negative phase has the highest priority, and compare-matches occurring prior to a are ignored. In

the T2 period, compare-match c that turns off the positive phase has the highest priority, and

compare-matches occurring prior to c are ignored.

In normal cases, compare-matches occur in the order a

→ b → c → d (or c → d → a' → b'), as

shown in figure 10.46.

If compare-matches deviate from the a

→ b → c → d order, since the time for which the negative

phase is off is less than twice the dead time, the figure shows the positive phase is not being turned

on. If compare-matches deviate from the c

→ d → a' → b' order, since the time for which the

positive phase is off is less than twice the dead time, the figure shows the negative phase is not

being turned on.

If compare-match c occurs first following compare-match a, as shown in figure 10.47, compare-

match b is ignored, and the negative phase is turned off by compare-match d. This is because

turning off of the positive phase has priority due to the occurrence of compare-match c (positive

phase off timing) before compare-match b (positive phase on timing) (consequently, the waveform

does not change since the positive phase goes from off to off).

Similarly, in the example in figure 10.48, compare-match a' with the new data in the temporary

off the positive phase, are ignored. As a result, the negative phase is not turned on.

Thus, in complementary PWM mode, compare-matches at turn-off timings take precedence, and

turn-on timing compare-matches that occur before a turn-off timing compare-match are ignored.

R5F72115D160FPV Datasheet(PDF) 512 Page - Renesas Technology Corp