Figure 3-4. Power Supply Block Diagram
USB
Target
MCU
Power source
Cut strap
Power consumer
P3V3
DEBUGGER
Power converter
DEBUGGER
Regulator
VUSB
Target
Regulator
Power
Supply
strap
Adjust
Level
shifter
VLVL
VREG
I/O
I/O
GPIO
straps
I/O
On/Off
Measure
On/Off
ID system
#VOFF
PTC
Fuse
Power protection
VBUS
Target
Power
strap
VTG
3.3.1
Target Regulator
The target voltage regulator is a MIC5353 variable output LDO. The on-board debugger can adjust the voltage output
supplied to the board target section by manipulating the MIC5353’s feedback voltage. The hardware implementation
is limited to an approximate voltage range from 1.7V to 5.1V. Additional output voltage limits are configured in the
debugger firmware to ensure that the output voltage never exceeds the hardware limits of the ATtiny3217
microcontroller. The voltage limits configured in the on-board debugger on ATtiny3217 Curiosity Nano are 1.8-5.5V.
Info:
The target voltage is set to 3.3V when the board is manufactured. It can be changed through
MPLAB X IDE project properties and in the Atmel Studio device programming dialog. Any change to the
target voltage is persistent, even through a power toggle. The resolution is less than 5 mV but may be
limited to 10 mV by the adjustment program.
Info:
Voltage settings that are set up in Atmel Studio/Microchip MPLAB
®
X IDE are not immediately
applied to the board. The new voltage setting is applied to the board when the debugger is accessed in
any way, like pushing the Refresh Debug Tool Status button in the project dashboard tab, or programming/
reading program memory.
Info:
There is a simple option to adjust the target voltage with a drag and drop command text file to the
board. This only supports settings of 0.0V, 3.3V, and 5.0V. See section
for
further details.
The MIC5353 supports a maximum current load of 500 mA. It is an LDO regulator in a small package, placed on a
small printed circuit board (PCB), and the thermal shutdown condition can be reached at lower loads than 500 mA.
The maximum current load depends on the input voltage, the selected output voltage, and the ambient temperature.
The figure below shows the safe operating area for the regulator, with an input voltage of 5.1V and an ambient
temperature of 23
°
C.
ATtiny3217
Curiosity Nano
©
2020 Microchip Technology Inc.
User Guide
DS40002193A-page 14
