Dead Time Generator - Atmel ATtiny25 Manual

15. Dead Time Generator

7598H–AVR–07/09
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
PCKE
T15M
CK
PCK
DT1AH
DT1AL
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
DTPS11..10
T/C1 CLOCK
DEAD TIME
PRESCALER
PWM1x
TIMER/COUNTER1
PWM GENERATOR
PWM1A
DEAD TIME GENERATOR
OC1A OC1A
COMPARATOR
CLOCK CONTROL
4-BIT COUNTER
DT1x
I/O REGISTER
ATtiny25/45/85
PWM1B
DT1BH
DEAD TIME GENERATOR
DT1BL
OC1B
OC1B
OC1x
OC1x
93