ATmega328 / ATmega328P / ATmega168 / ATmega8 connection guide

ATmega328 / ATmega328P / ATmega168 / ATmega8 TQFP-32 wiring guide with power, signal assignments, and bench checks.

TQFP-32

32 contacts Current package

QFN-28 29 contacts

QFN-32 33 contacts

PDIP-28 28 contacts

Microchip Technology · 32 numbered contacts. See the individual package drawings for footprint dimensions.

32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +105 °C

Power and reset

Required

Use a current-limited supply at a voltage permitted by the order code and system clock. Tie the listed supply pins to that rail. Fit one 100 nF ceramic capacitor close to each supply-and-ground pair. Use a 10 kΩ reset pull-up for this bench circuit.

Target rail
- Bench supply positive
- VCC (4)
- VCC (6)
- AVCC (18)
Ground
- Bench supply return
- GND (3)
- GND (5)
- GND (21)
Reset
- PC6 (29)

Bench checks

With power off, check for a short across the supply. Power on and measure voltage at every supply pin and at reset.
Check the clock source configured by CKSEL. If a used part expects an external clock, provide it before attempting serial programming.

AN2519 §§2–3 and DS40002061B · Pin descriptions and clock source

Connection scenarios

Program and read the signature over ISP

Start from the power and reset circuit. Attach a voltage-compatible AVR in-system programmer and use the target voltage as its reference. Connect reset, serial data in/out, and SCK as shown.

Target voltage sense
- Programmer VTG
- VCC (4)
- VCC (6)
Common ground
- Programmer GND
- GND (3)
- GND (5)
- GND (21)
Reset assertion
- Programmer RESET
- PC6 (29)
Serial data into target
- Programmer MOSI
- PB3 (15)
Serial data out of target
- Programmer MISO
- PB4 (16)
Programming clock
- Programmer SCK
- PB5 (17)

Bench checks

Read the device signature before writing flash or fuses. If it fails, verify target power, the clock source, programmer direction, and the selected device.
If the programmer offers an adjustable SCK, start below one quarter of the target clock and check the data sheet’s SCK high and low timing. Disconnect or isolate other peripherals that drive the programming lines.
Disable power output on the programmer if the target has its own bench supply. Confirm the programmer’s VTG behavior in its manual.

AN2519 §4.1 and DS40002061B · Serial Programming Pin Mapping

TQFP-32 wiring map

Highlighted contacts are used in the required step or selected circuit. Select a contact to inspect it.

TQFP-32

Top view · Pin 1 at the upper left · Schematic outline Scroll the map to reach all contacts.

Selected pin details

9 · PD5

Bidirectional · GPIO

General-purpose digital I/O. Alternate assignments: T (TC1), OCB (TC0), PCINT21 (EXINT).

After reset · GPIO driver is high impedance during reset. Clock, debug, and alternate-function use depend on fuse and peripheral configuration.

DS40002061B · Pinout and peripheral signal descriptions

Electrical limits · Pin in the reference

Models and documents

Each package lists the documented order codes and variants covered by this map. Select the marked model to see its peripheral assignments and memory. Check the exact order code and datasheet revision before laying out a PCB.

ATmega328: 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM. Choose the marked order code for voltage, clock, and temperature.
ATmega328-AU: 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +85 °C
ATmega328-AUR: 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +85 °C
ATmega328P: 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM. Choose the marked order code for voltage, clock, and temperature.
ATmega328P-AU: 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +85 °C
ATmega328P-AUR: 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +85 °C
ATmega328P-AN: 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +105 °C
ATmega328P-ANR: 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +105 °C
ATmega168: 16 KiB flash · 1 KiB SRAM · 512 B EEPROM. Choose the marked order code for voltage, clock, and temperature.
ATmega168V-10AU: 16 KiB flash · 1 KiB SRAM · 512 B EEPROM · 1.8–5.5 V · 10 MHz maximum · -40 to +85 °C
ATmega168V-10AUR: 16 KiB flash · 1 KiB SRAM · 512 B EEPROM · 1.8–5.5 V · 10 MHz maximum · -40 to +85 °C
ATmega168-20AU: 16 KiB flash · 1 KiB SRAM · 512 B EEPROM · 2.7–5.5 V · 20 MHz maximum · -40 to +85 °C
ATmega168-20AUR: 16 KiB flash · 1 KiB SRAM · 512 B EEPROM · 2.7–5.5 V · 20 MHz maximum · -40 to +85 °C
ATmega8: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM. Choose the marked order code for voltage, clock, and temperature.
ATmega8L-8AU: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM · 2.7–5.5 V · 8 MHz maximum · -40 to +85 °C
ATmega8L-8AUR: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM · 2.7–5.5 V · 8 MHz maximum · -40 to +85 °C
ATmega8-16AU: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM · 4.5–5.5 V · 16 MHz maximum · -40 to +85 °C
ATmega8-16AUR: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM · 4.5–5.5 V · 16 MHz maximum · -40 to +85 °C
ATmega8L-8AN: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM · 2.7–5.5 V · 8 MHz maximum · -40 to +105 °C
ATmega8L-8ANR: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM · 2.7–5.5 V · 8 MHz maximum · -40 to +105 °C
ATmega8-16AN: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM · 4.5–5.5 V · 16 MHz maximum · -40 to +105 °C
ATmega8-16ANR: 8 KiB flash · 1 KiB SRAM · 512 B EEPROM · 4.5–5.5 V · 16 MHz maximum · -40 to +105 °C

ATmega328/ATmega328P data sheet· DS40002061B · Pin configuration, electrical characteristics, ordering table and serial programming.
ATmega168 data sheet· 2545W · Pin configuration, electrical characteristics, ordering table and serial programming.
ATmega8 data sheet· 2486AA · Pin configuration, electrical characteristics, ordering table and serial programming.
ATmega_DFP Device Family Pack· Machine-readable device definition: package contacts, peripheral routes, and memory sizes.
AVR Microcontroller Hardware Design Considerations· Power supply, reset network, and programmer connection guidance.
ATmega328 documentation and errata· Check current manufacturer documentation, ordering status and silicon revision applicability.
ATmega328P documentation and errata· Check current manufacturer documentation, ordering status and silicon revision applicability.
ATmega168 documentation and errata· Check current manufacturer documentation, ordering status and silicon revision applicability.
ATmega8 documentation and errata· Check current manufacturer documentation, ordering status and silicon revision applicability.
AVR source register· Source identifiers, applicability, retrieval dates, and SHA-256 digests.