ATMEGA406_0607 datasheet(5/263 Pages) ATMEL

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2548E–AVR–07/06

ATmega406

2.2

Pin Descriptions

2.2.1

VFET

High voltage supply pin. This pin is used as supply for the internal voltage regulator, described in

”Voltage Regulator” on page 114. In addition the voltage level on this pin is monitored by the bat-

tery protection circuit, for deep-under-voltage protection. For details, see ”Battery Protection” on

page 125.

2.2.2

VCC

Digital supply voltage. Normally connected to VREG.

2.2.3

VREG

Output from the internal Voltage Regulator. Used for external decoupling to ensure stable regu-

lator operation. For details, see ”Voltage Regulator” on page 114.

2.2.4

VREF

Internal Voltage Reference for external decoupling. For details, see ”Voltage Reference and

Temperature Sensor” on page 121.

2.2.5

VREFGND

Ground for decoupling of Internal Voltage Reference. For details, see ”Voltage Reference and

Temperature Sensor” on page 121.

2.2.6

GND

Ground

2.2.7

SGND

Signal ground pin, used as reference for Voltage-ADC conversions. For details, see ”Voltage

ADC – 10-channel General Purpose 12-bit Sigma-Delta ADC” on page 116.

2.2.8

Port A (PA7:PA0)

PA3:PA0 serves as the analog inputs to the Voltage A/D Converter.

Port A also serves as a low-voltage 8-bit bi-directional I/O port with internal pull-up resistors

(selected for each bit). As inputs, Port A pins that are externally pulled low will source current if

the pull-up resistors are activated. The Port A pins are tri-stated when a reset condition becomes

active, even if the clock is not running.

Port A also serves the functions of various special features of the ATmega406 as listed in ”Alter-

nate Functions of Port A” on page 68.

2.2.9

Port B (PB7:PB0)

Port B is a low-voltage 8-bit bi-directional I/O port with internal pull-up resistors (selected for

each bit). As inputs, Port B pins that are externally pulled low will source current if the pull-up

resistors are activated. The Port B pins are tri-stated when a reset condition becomes active,

even if the clock is not running.

Port B also serves the functions of various special features of the ATmega406 as listed in ”Alter-

nate Functions of Port B” on page 70.

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