Rainbow Electronics ATtiny43U - Manual (Page 39)

39
8048B–AVR–03/09
Figure 8-4. Input and Output Voltages of Boost Converter.
When input voltage V
BAT
falls below V
STOP
the converter enters Stop Mode and output voltage
V
CC
begins to fall. When converter output voltage, i.e. the supply voltage of the microcontroller,
falls below V
POT
the MCU will go into reset.
Figure 8-5 illustrates how the boost converter output changes with load current. As converter
output voltage rises above the power-on threshold the microcontroller is brought on-line and cur-
rent consumption steps up to a level sufficiently high for the converter to remain in Active
Regulated Mode of operation.
Figure 8-5. Output Voltage vs. Load Current of Boost Converter.
Note: The figure is not to scale. Typically, the switching time (rising voltage) is measured in hundreds of
microseconds and idle time (falling voltage) is measured in seconds.
V
CC
t
V
POT
V
START
V
BOOST
V
STOP
V
BAT
STOP STOP ACTIVE
RESET ACTIVE RESET
CONVERTER:
MCU CORE:
V
CC
t
I
LOAD
V/A
V
CCMIN
V
CCMAX
LOW CURRENT MODE ACTIVE, REGULATED MODE:
V
CCNOM
I
MS
REGULATED