ATtiny261A datasheet(94/292 Pages) ATMEL

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8197A–AVR–10/09

ATtiny261A/461A/861A

12.6 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 used to insert dead times (non-overlapping times) for the Timer/Counter1 complementary

output pairs OC1x and OC1x when the PWM mode is enabled and the COM1x1:0 bits are set to

“01”. See Figure 12-7 below.

Figure 12-7. Block Diagram of Waveform Generator and Dead Time Generator.

The tasks are shared as follows: the Waveform Generator generates the output (OCW1x) and

the Dead Time Generator generates the non-overlapping PWM output pair from the output.

Three 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.

The Dead Time Generation is based on 4-bit down counters that count the dead time, as shown

in Figure 12-8.

Figure 12-8. Dead Time Generator

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. 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 compare the counter with zero

and stop the dead time insertion when zero has been reached. The counter is loaded with a 4-bit

DT1H or DT1L value from DT1 I/O register, depending on the edge of the Waveform Output

(OCW1x) when the dead time insertion is started. The Output Compare Output are delayed by

one timer clock cycle at minimum from the Waveform Output when the Dead Time is adjusted to

OCnx

WGM10

Waveform Generator

top

FOCn

COMnx

bottom

PWMnx

OCWnx

Dead Time Generator

OCnx

DTnH

DTnL

DTPSn

CK OR PCK

CLOCK

OCnx

CLOCK CONTROL

OCnx

CK OR PCK

CLOCK

OCWnx

4-BIT COUNTER

COMPARATOR

DEAD TIME

PRE-SCALER

DTn I/O REGISTER

DATA BUS (8-bit)

TCCRnB REGISTER

PWM1X

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