105
ATtiny25/45/85 [DATASHEET]
2586Q–AVR–08/2013
14. 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 Generator 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 adjustable and the
PWM output and it’s complementary output are adjusted separately, and independently for both PWM outputs.
Figure 14-1. 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 con-
trolled by two control bits DTPS1[1:0] 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 comparator is used to com-
pare 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 14-2. Dead Time Generator
The length of the counting period is user adjustable by selecting the dead time prescaler setting in 0x23 register,
and selecting then the dead time value in I/O register DT1x. The DT1x register consists of two 4-bit fields, DT1xH
and DT1xL that control the dead time periods of the PWM output and its’ complementary output separately. Thus
TIMER/COUNTER1
OC1A
OC1B
DEAD TIME GENERATOR
PWM GENERATOR
PCKE
T15M
PCK
CK
DT1AH
DT1BH
DEAD TIME GENERATOR
PWM1B
PWM1A
DT1AL
DT1BL
CLOCK CONTROL
OC1x
T/C1 CLOCK
PWM1x
4-BIT COUNTER
COMPARATOR
DT1xL
DT1xH
DT1x
I/O REGISTER
DEAD TIME
PRESCALER
DTPS1[1:0]