ATtiny45 datasheet(93/196 Pages) ATMEL

93 / 196 page

7598H–AVR–07/09

ATtiny25/45/85

15. Dead Time Generator

The Dead Time Generator is provided for the Timer/Counter1 PWM output pairs to allow driving

external power control switches safely. The Dead Time Generator is a separate block that can

be connected to Timer/Counter1 and it is used to insert dead times (non-overlapping times) for

the Timer/Counter1 complementary output pairs (OC1A-OC1A and OC1B-OC1B). The sharing

of tasks is as follows: the timer/counter generates the PWM output and the Dead Time Genera-

tor generates the non-overlapping PWM output pair from the timer/counter PWM signal. Two

Dead Time Generators are provided, one for each PWM output. The non-overlap time is adjust-

able and the PWM output and it’s complementary output are adjusted separately, and

independently for both PWM outputs.

Figure 15-1. Timer/Counter1 & Dead Time Generators

The dead time generation is based on the 4-bit down counters that count the dead time, as

shown in Figure 46. There is a dedicated prescaler in front of the Dead Time Generator that can

divide the Timer/Counter1 clock (PCK or CK) by 1, 2, 4 or 8. This provides for large range of

dead times that can be generated. The prescaler is controlled by two control bits DTPS11..10

from the I/O register at address 0x23. The block has also a rising and falling edge detector that

is used to start the dead time counting period. Depending on the edge, one of the transitions on

the rising edges, OC1x or

OC1x is delayed until the counter has counted to zero. The compara-

tor is used to compare the counter with zero and stop the dead time insertion when zero has

been reached. The counter is loaded with a 4-bit DT1xH or DT1xL value from DT1x I/O register,

depending on the edge of the PWM generator output when the dead time insertion is started.

Figure 15-2. Dead Time Generator

TIMER/COUNTER1

OC1A

OC1B

DEAD TIME GENERATOR

PWM GENERATOR

PCKE

T15M

PCK

DT1AH

DT1BH

DEAD TIME GENERATOR

PWM1B

PWM1A

DT1AL

DT1BL

CLOCK CONTROL

OC1x

T/C1 CLOCK

PWM1x

4-BIT COUNTER

COMPARATOR

DT1x

I/O REGISTER

DEAD TIME

PRESCALER

DTPS11..10

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