ATMEGA161L-4AI - 16KB AVR MCU 4MHz TQFP-44 | Microchip
MPN: ATMEGA161L-4AI β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.95 | $8.95 |
| 10 | $8.1 | $81.00 |
| 100 | $7.25 | $725.00 |
| 500 | $6.6 | $3,300.00 |
| 1,000 | $5.95 | $5,950.00 |
ATMEGA161L-4AI Overview
A microcontroller is a single-chip computer that integrates a processor core, program memory, data memory, and peripherals such as timers, UARTs, and SPI interfaces into one integrated circuit. Within the semiconductor hierarchy, the ATmega161L sits in the 8-bit MCU class, within the AVR ATmega family, itself part of Microchip's embedded portfolio of power management and embedded control solutions. 8-bit MCUs remain dominant in cost-sensitive, low-power embedded designs where simple deterministic control outperforms larger 32-bit parts.
Key features include the advanced AVR RISC architecture with 130 powerful instructions, most executing in a single clock cycle, delivering up to 4 MIPS throughput at 4MHz. The 16KB self-programmable FLASH supports in-system programming via SPI, while 512 bytes of EEPROM retain non-volatile parameters. The L suffix denotes the low-voltage grade, operating from 2.7V to 5.5V, and the I suffix guarantees operation across the industrial -40C to +85C temperature range. Peripherals include two 8-bit timers, one 16-bit timer, UART, SPI, and 10-bit analog features per the AVR ATmega161 family.
The AVR Harvard architecture fetches instructions and data over separate buses, allowing single-cycle execution of most instructions and fast register-file access with 32 general-purpose working registers. External oscillator support provides flexible clocking; at 4MHz the device balances throughput against the low power consumption required for battery-operated equipment.
Typical applications include industrial control panels, metering and instrumentation front ends, legacy embedded system maintenance, and serial communication bridges using the UART and SPI ports. Its 35 I/O lines support keypads, displays, and relay drivers in compact boards.
Designers should note that this 4MHz speed grade is at the lower end of the family; system timing budgets must be confirmed before substituting faster variants, and the 1KB SRAM constrains large buffering designs.
This page synthesizes distributor availability, drop-in same-family alternatives, and practical design guidance not found in a single manufacturer datasheet.
Drop-in alternatives for ATMEGA161L-4AI β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with ATMEGA161L-4AI (same form factor and footprint) β differing in Operating Temperature, Program Memory Size, Mounting Type, Number of I/O, Program Memory Type.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATMEGA161L-4AU
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA161L-4PI
β Drop-Inβ In Stock
$6.35 / Unit
View Datasheet βATMEGA161-16AI
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA161-16AC
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
ATMEGA162-16AU
β Drop-In β οΈ εζ°εΎ ιͺθ―β In Stock
$2.45 / Unit
View Datasheet βATMEGA8535L-8MI
β Drop-Inπ Reference alternative (not in catalog)
ATMEGA161L-4AI Maximum Ratings & Electrical Characteristics
| Core Processor | AVR 8-bit RISC |
| Core Size | 8-bit |
| Speed | 4MHz |
| Program Memory Size | 16KB (8K x 16) |
| Program Memory Type | FLASH |
| RAM Size | 1K x 8 |
| Number of I/O | 35 |
| Connectivity | SPI, UART/USART |
| Oscillator Type | External |
| Operating Temperature | -40C to +85C |
| Voltage Supply Range | 2.7V to 5.5V (L grade) |
| Package / Case | 44-TQFP (10x10 mm) |
| Mounting Type | Surface Mount |
| Packaging | Tray |
| Series | AVR ATmega161 |
| Architecture | Harvard RISC, 130 instructions |
ATMEGA161L-4AI 44-tqfp (10x10 mm) Pin Configuration Guide
Pin configuration for ATMEGA161L-4AI (44-tqfp (10x10 mm) package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for ATMEGA161L-4AI.
Refer to the datasheet for full pin configuration.
Typical Applications
ATMEGA161L-4AI is suitable for 6 applications: Industrial Control Panels, Legacy Embedded System Maintenance, Serial Communication Bridges, Metering and Instrumentation Front Ends, Battery-Powered Portable Equipment, Security and Access Control Systems.
Industrial Control Panels
The ATMEGA161L-4AI fits industrial control panel designs that need deterministic 8-bit control, 35 I/O lines, and an industrial -40C to +85C temperature rating. Its 4MHz external-clock operation yields approximately 4 MIPS of single-cycle AVR throughput, adequate for relay sequencing, keypad scanning, and status LED management without software complexity of a 32-bit core. The L-grade 2.7V to 5.5V supply tolerance absorbs noisy industrial power rails, and the UART supports field configuration links. Placed on a 5V rail with the SPI port driving peripheral ICs, the MCU's 16KB FLASH accommodates full control firmware plus a bootloader for in-field updates via the in-system programming interface.
Recommended
Legacy Embedded System Maintenance
Sustaining engineering teams maintaining boards designed around the Atmel ATmega161 depend on the ATMEGA161L-4AI as the exact-fit source: identical die, 44-TQFP footprint, 4MHz speed grade, and L-grade voltage rating preserve board timing and power assumptions with zero redesign. Because the part is EOL, this application prioritizes authentic, verified stock and drop-in substitutes such as ATMEGA161L-4AU (lead-free TQFP) or ATMEGA162-16AU for firmware-portable upgrades. Existing binaries recompile on the AVR toolchain, and the SPI ISP interface keeps production programming flows unchanged. The 1KB SRAM and 16KB FLASH constraints match the original design envelope, avoiding unexpected behavioral drift in fielded systems.
Recommended
Serial Communication Bridges
The ATMEGA161L-4AI's UART/USART and SPI ports make it effective as a protocol bridge between legacy serial equipment and modern peripherals: the UART handles RS-232 or RS-485 links while SPI drives EEPROMs, ADCs, and display controllers at multi-hundred-kilobit rates. At 4MHz, the AVR core sustains full-duplex UART traffic with interrupt-driven buffering in the 1KB SRAM, and the double-buffered receive path reduces overrun risk. The L-grade supply suits 3.3V-side logic translation designs, and the industrial temperature range covers outdoor or cabinet installations. The external oscillator allows precision baud-rate crystals, keeping framing error rates low across the -40C to +85C range required in harsh deployments.
Recommended
Metering and Instrumentation Front Ends
Utility meters and bench instruments benefit from the ATMEGA161L-4AI's deterministic single-cycle instruction execution, EEPROM for calibration constants, and SPI connectivity to precision converters. The 16KB FLASH stores metrology firmware plus compensation tables, while 512 bytes of EEPROM retains tamper flags and calibration data through power loss. The L-grade 2.7V operation supports battery-backed meter variants, and the -40C to +85C I-grade rating meets outdoor metering environments. The two 8-bit timers and one 16-bit timer generate measurement gates and pulse outputs; the external oscillator interface accepts a crystal stabilized to the accuracy class required by the metering standard the product targets.
Recommended
Battery-Powered Portable Equipment
The ATMEGA161L-4AI's L-grade 2.7V supply floor enables direct operation from two lithium cells or three NiMH cells without a boost converter, reducing cost and quiescent losses in portable equipment. At 4MHz, dynamic current is modest by AVR standards, and the external oscillator allows designers to drop clock frequency further in standby states. The 35 I/O lines with per-pin drive capability interface keypads, LCDs, and buzzers directly, while the UART provides a service port. The 44-TQFP 10x10 mm footprint fits compact two-layer boards, and the industrial temperature grade supports outdoor portable instruments that must operate from -40C to +85C in logistics and field-service environments.
Recommended
Security and Access Control Systems
Door controllers, keypad readers, and small alarm panels use the ATMEGA161L-4AI's combination of 35 I/O lines, UART for host communication, and EEPROM for access credentials. The 16KB FLASH stores Wiegand or clock-and-data decoding routines plus a local authorization table in the 1KB SRAM, while the 512-byte EEPROM persists PINs and configuration through power cycles. Timers generate watchdog intervals and tamper pulse-width measurement; the -40C to +85C rating covers unheated gate and garage installations. The L-grade supply tolerates backup-battery sag down to 2.7V, keeping the controller alive during mains loss, and the SPI ISP interface enables secure field firmware updates with a locked bootloader region.
Recommended
Recommended Products Summary
Engineering reference data for ATMEGA161L-4AI β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATMEGA161L-4AU | ATMEGA161-16AI | ATMEGA162-16AU | ATMEGA8535L-8MI |
|---|---|---|---|---|---|
| Package | 44-TQFP (10x10 mm) | 44-TQFP (10x10 mm) - same | 44-TQFP (10x10 mm) - same | 44-TQFP (10x10 mm) - same | 44-TQFP (10x10 mm) - same family pinout |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Max Clock Speed | 4MHz | 4MHz | 16MHz | 16MHz | 8MHz |
| Program Memory (FLASH) | 16KB (8K x 16) | 16KB (8K x 16) | 16KB (8K x 16) | 16KB | 8KB |
| Supply Voltage Range | 2.7V to 5.5V (L grade) | 2.7V to 5.5V | 4.5V to 5.5V | 4.5V to 5.5V at 16MHz | 2.7V to 5.5V (L grade) |
| Operating Temperature | -40C to +85C (I grade) | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| Lifecycle Status | EOL (legacy stock) | EOL (legacy stock) | EOL (legacy stock) | Active successor part | Mature / verify availability |
Key Differentiators
- True 4MHz low-voltage speed grade (vs ATMEGA161-16AI)
- Industrial temperature coverage (vs ATMEGA161-16AC)
- Maximum FLASH in the direct family (vs ATMEGA8535L-8MI)
- Exact legacy die vs successor (vs ATMEGA162-16AU)
Design Notes
The L grade of the ATmega161 operates from 2.7V to 5.5V, but maximum clock frequency derates with supply voltage per the AVR datasheet; at 4MHz the part is safe across the full L-grade range, so confirm your rail regulation stays above 2.7V including battery sag and brownout. Add 100nF ceramic decoupling on VCC pins plus 10uF bulk capacitance. If brownout detection matters, note the ATmega161 relies on external supervisor circuits since it lacks a modern internal BOD typical of newer AVR parts.
This device uses an external oscillator; the clock source fuse settings determine whether an external crystal, resonator, or clock signal is expected, and mis-set fuses are a classic cause of 'dead' boards. When migrating firmware from an ATmega161L-4AI to the ATMEGA162-16AU, review register differences - the successor adds peripherals and changes some register addresses, so recompile from source and re-verify timing rather than flashing the original binary.
The 44-TQFP 10x10 mm lead pitch of 0.8 mm is easy to rework with a standard iron, making legacy-board maintenance practical. Route the RESET trace short and add a 10k pull-up plus optional ISP header (MOSI, MISO, SCK, RESET, VCC, GND) so in-system programming via SPI remains possible in the enclosure. Keep the external oscillator crystal with load capacitors placed close to the XTAL pins with a guard ground to minimize jitter on UART baud generation.
With 35 I/O lines at up to 5V CMOS levels, limit simultaneous switching loads: drive relay coils or LED strings through transistor drivers rather than direct port pins, and add series resistors on long ribbon-cable lines to control ringing. The UART benefits from a 0.1uF to 10uF local reservoir near the supply pin when long cable transceivers (e.g., MAX232-class) switch on the same rail, preventing reset-inducing rail droop on transmit bursts.
Compliance Information
Compliance status for this specific AI suffix was not stated in the retrieved web data; the related ATMEGA161L-4AU variant was introduced in the lead-free TQFP flow and is the safer RoHS sourcing choice. Verify with Microchip certificate of conformance.
