2 switching to full duty cycle mode of operation, 6 component selection, 1 inductor – Rainbow Electronics ATtiny43U User Manual
Page 43
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8048B–AVR–03/09
To stop the boost converter, follow the below procedure:
1.
Write 110x xxxx to the Power Reduction Register, PRR
2.
Within 3 clock cycles of the above, write 10xx xxxx to PRR
3.
Within 4 clock cycles of the first step, write 01xx xxxx to PRR
8.5.2
Switching to Full Duty Cycle Mode of Operation
When duty cycle control is disabled the output voltage of the boost converter will rise as fast as
possible, resulting in a minimum switching time and a maximum idle time for the converter.
To turn on Full Duty Cycle (FDC) mode, follow the below procedure:
1.
Write 110x xxxx to the Power Reduction Register, PRR
2.
Within 3 clock cycles of the above, write 10xx xxxx to PRR
3.
Within 4 clock cycles of the first step, write 111x xxxx to PRR
8.5.3
Switching to Normal (Variable Duty Cycle) Mode of Operation
To return duty cycle control to the boost converter, follow the below procedure:
1.
Write 111x xxxx to the Power Reduction Register, PRR
8.6
Component Selection
for component placement and numbering.
8.6.1
Inductor
Low inductance increases peak currents of the inductor, creating more interference noise and
lowering the overall efficiency of the converter. Too high inductance values force the converter
into non-stable operation. The boost converter has been optimized for a certain size inductance,
L, and may not work reliably if other inductance values are used. See
.
The inductor must be able to tolerate the following input current:
... where
η
is the efficiency of the converter at given voltages and load current. See
verter Efficiency vs. Load Current and VBAT Voltage” on page 166
.
The inductor must also be able to tolerate short peak currents. At steady state, i.e. when the
converter has stabilised after a constant load current has been introduced, the peak current is
calculated as follows:
I
IN
V
CC
I
LOAD
×
V
BAT
η
×
--------------------------------
=
I
PEAK
V
BAT
T
S
D
Ч
Ч
L
------------------------------------
=