ATSAMD21G18A-AF - 48MHz Cortex-M0+ MCU 256KB Flash | Microchip
MPN: ATSAMD21G18A-AF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.58 | $5.58 |
| 10 | $5.02 | $50.20 |
| 100 | $4.46 | $446.00 |
| 500 | $3.95 | $1,975.00 |
| 1,000 | $3.49 | $3,490.00 |
ATSAMD21G18A-AF Overview
What is a Cortex-M0+ microcontroller? A Cortex-M0+ microcontroller is an ARM-based 32-bit processor core designed for energy-efficient embedded computing. It belongs to the Cortex-M family of microcontrollers, which sit within the broader category of microcontrollers and, at the top level, integrated circuits. The Cortex-M0+ uses a 2-stage pipeline with a Thumb/Thumb-2 instruction subset, delivers deterministic interrupt response, and offers significantly higher DMIPS/mW than 8-bit AVR or 8051 alternatives, making it ideal for battery-powered IoT nodes and portable consumer products.
Key features of the ATSAMD21G18A-AF include a full-speed USB 2.0 device with on-the-go (OTG) support, a 12-bit 350 ksps ADC, a 10-bit 350 ksps DAC, up to six SERCOM channels, and up to five 16-bit Timer/Counters. The device also integrates a 12-channel DMA controller, a 12-channel Event System, and two-pin Serial Wire Debug (SWD) for programming and boundary-scan. It supports SleepWalking peripherals, idle and standby sleep modes, and is pin-compatible with the SAM D20 family for simple migration.
The ATSAMD21G18A-AF uses a single 1.62V to 3.63V supply rail and offers multiple low-power modes that drop quiescent current to a few microamps in standby. The integrated full-speed USB PHY eliminates the need for an external transceiver, simplifying USB-enabled designs. The peripheral Event System and DMAC allow data movement without CPU intervention, enabling deterministic response and freeing the core for application logic.
Typical applications include smart-home sensor hubs, IoT edge nodes, industrial HMI panels, low-power wireless sensor platforms, and battery-powered consumer devices such as fitness wearables. The device is also widely used in maker and education platforms, including Arduino-compatible boards that leverage its native USB, capacitive touch, and PWM peripherals.
When designing with the ATSAMD21G18A-AF, ensure the VDD decoupling network includes a 100 nF capacitor close to each supply pin and a bulk 4.7 uF capacitor to handle USB inrush current. Plan the boot loader pin (BOOTPROT) configuration early if field firmware updates are required, and reserve a dedicated SWD header for in-circuit debugging.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for ATSAMD21G18A-AF — 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 ATSAMD21G18A-AF (same form factor and footprint) — differing in ADC, Operating Temperature, Package, USB, RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATSAMD21G18A-AFT
✅ Drop-In✓ In Stock
$2.69 / Unit
View Datasheet →ATSAMD21G18A-AU
✅ Drop-In✓ In Stock
$1.74 / Unit
View Datasheet →ATSAMD21G18A-AUT
✅ Drop-In📋 Reference alternative (not in catalog)
ATSAMD21G17A-AF
✅ Drop-In✓ In Stock
$2.15 / Unit
View Datasheet →ATSAMD21G17A-AFT
✅ Drop-In✓ In Stock
$3.7 / Unit
View Datasheet →ATSAMD21G18A-MUT
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$3.37 / Unit
View Datasheet →ATSAMD21G18A-AF Maximum Ratings & Electrical Characteristics
| Core | ARM Cortex-M0+ (SAM D21) |
| Core Architecture | 32-bit RISC, Thumb/Thumb-2 instruction set |
| Maximum CPU Clock | 48 MHz |
| Flash Memory | 256 KB |
| SRAM | 32 KB |
| Supply Voltage (VDD) | 1.62 V to 3.63 V |
| Package | 48-pin TQFP (7x7 mm) |
| Mounting Type | Surface Mount |
| ADC | 12-bit, up to 350 ksps |
| DAC | 10-bit, 350 ksps |
| USB | Full-speed USB 2.0 device with on-the-go (OTG) |
| SERCOM Channels | Up to 6 (configurable as I2C/SPI/UART) |
| Timers | Up to 5 x 16-bit Timer/Counters (TC) |
| DMA Channels | 12-channel DMAC |
| Event System | 12-channel inter-peripheral |
| Debug Interface | Two-pin Serial Wire Debug (SWD) |
| Operating Temperature | -40C to +85C |
| RoHS Status | Compliant |
ATSAMD21G18A-AF Pin Configuration
| Pin 1 | PA00 — GPIO / XIN32 (external 32 kHz crystal input) |
| Pin 2 | PA01 — GPIO / XOUT32 (external 32 kHz crystal output) |
| Pin 3 | PA02 — GPIO / AIN0 (ADC input) |
| Pin 4 | PA03 — GPIO / AIN1 (ADC input) / VREFA reference voltage |
| Pin 5 | GND — Ground |
| Pin 6 | VDD — Digital supply voltage 1.62 V to 3.63 V |
| Pin 7 | PA04 — GPIO / AIN2 / VREFB |
| Pin 8 | PA05 — GPIO / AIN3 |
| Pin 9 | PA06 — GPIO / AIN4 |
| Pin 10 | PA07 — GPIO / AIN5 |
| Pin 11 | PA08 — GPIO / AIN6 / SERCOM0 PAD0 / I2S SD0 |
| Pin 12 | PA09 — GPIO / AIN7 / SERCOM0 PAD1 / I2S MCK0 |
| Pin 13 | PA10 — GPIO / AIN8 / SERCOM0 PAD2 / I2S SCK0 |
| Pin 14 | PA11 — GPIO / AIN9 / SERCOM0 PAD3 / I2S FS0 |
| Pin 15 | VDD — Digital supply voltage |
| Pin 16 | GND — Ground |
| Pin 17 | PA12 — GPIO / SERCOM2 PAD0 / USB D- |
| Pin 18 | PA13 — GPIO / SERCOM2 PAD1 / USB D+ |
| Pin 19 | PA14 — GPIO / SERCOM2 PAD2 / XIN (main crystal input) |
| Pin 20 | PA15 — GPIO / SERCOM2 PAD3 / XOUT (main crystal output) |
| Pin 21 | PA16 — GPIO / SERCOM1 PAD0 / I2S SD1 |
| Pin 22 | PA17 — GPIO / SERCOM1 PAD1 / I2S MCK1 |
| Pin 23 | PA18 — GPIO / SERCOM1 PAD2 / I2S SCK1 |
| Pin 24 | PA19 — GPIO / SERCOM1 PAD3 / I2S FS1 |
| Pin 25 | PA20 — GPIO / SERCOM5 PAD2 / TCC0 channel 6 |
| Pin 26 | PA21 — GPIO / SERCOM5 PAD3 / TCC0 channel 7 |
| Pin 27 | PA22 — GPIO / SERCOM3 PAD0 / TCC1 channel 4 |
| Pin 28 | PA23 — GPIO / SERCOM3 PAD1 / TCC1 channel 5 |
| Pin 29 | PA24 — GPIO / SERCOM3 PAD2 / USB ID |
| Pin 30 | PA25 — GPIO / SERCOM3 PAD3 / USB VBUS detect |
| Pin 31 | GND — Ground |
| Pin 32 | VDD — Digital supply voltage |
| Pin 33 | PA26 — GPIO / DAC0 output |
| Pin 34 | PA27 — GPIO / DAC1 output |
| Pin 35 | PA28 — GPIO / RESETN (external reset, active low) |
| Pin 36 | PA29 — GPIO / SWDIO (Serial Wire Debug data) |
| Pin 37 | PA30 — GPIO / SWCLK (Serial Wire Debug clock) |
| Pin 38 | PA31 — GPIO / BOOTPROT / SERCOM5 PAD1 |
| Pin 39 | PB00 — GPIO / SERCOM5 PAD2 |
| Pin 40 | PB01 — GPIO / SERCOM5 PAD3 |
| Pin 41 | PB02 — GPIO / SERCOM5 PAD0 / TCC0 channel 0 |
| Pin 42 | PB03 — GPIO / SERCOM5 PAD1 / TCC0 channel 1 |
| Pin 43 | PB04 — GPIO / SERCOM3 PAD0 |
| Pin 44 | PB05 — GPIO / SERCOM3 PAD1 |
| Pin 45 | PB06 — GPIO / SERCOM3 PAD2 |
| Pin 46 | PB07 — GPIO / SERCOM3 PAD3 |
| Pin 47 | PB08 — GPIO / SERCOM4 PAD0 / TCC1 channel 0 |
| Pin 48 | PB09 — GPIO / SERCOM4 PAD1 / TCC1 channel 1 |
Typical Applications
ATSAMD21G18A-AF is suitable for 6 applications: Smart Home Sensor Hubs, USB HID Devices and Wearables, Industrial Sensor Front-Ends, Low-Power Wireless IoT Nodes, Battery-Powered Metering, Consumer HMI and Maker Platforms.
Smart Home Sensor Hubs
The ATSAMD21G18A-AF's 256 KB Flash holds Zigbee or Thread application stacks plus room for application logic, while its six SERCOM channels let the same MCU drive multiple I2C sensors, an SPI display, and a UART radio concurrently. The 48 MHz Cortex-M0+ runs sensor-fusion loops comfortably and the 12-bit ADC at 350 ksps supports simultaneous temperature, humidity, and light sampling. Dropping into standby between events drops quiescent current to single-digit microamps, suiting coin-cell and energy-harvesting deployments.
Recommended
USB HID Devices and Wearables
Integrated full-speed USB 2.0 with on-the-go support removes the need for an external PHY, making the ATSAMD21G18A-AF ideal for USB HID peripherals such as keyboards, mice, audio interfaces, and MIDI controllers. The 48-pin TQFP gives designers 38 GPIO pins for capacitive touch or rotary encoder matrices, and the 10-bit DAC at 350 ksps can drive simple audio cue tones. SleepWalking peripherals let the device wake on USB activity without CPU intervention, preserving battery life in portable accessories.
Recommended
Industrial Sensor Front-Ends
In industrial 4-20 mA loop-powered transmitters and machine-vibration monitors, the ATSAMD21G18A-AF delivers the deterministic response of a Cortex-M0+ while consuming under 10 uA in standby. The 12-bit ADC and the integrated op-amp support ratiometric RTD and strain-gauge measurement, while the Event System guarantees that timing-critical interrupts are never blocked by DMA transfers. The wide 1.62 V to 3.63 V supply range tolerates noisy 24 V-derived rails after regulation.
Recommended
Low-Power Wireless IoT Nodes
For battery-powered LoRa, BLE, or sub-GHz sensor nodes, the ATSAMD21G18A-AF pairs with modules such as the RN2483 or nRF52832 over UART or SPI. The 256 KB Flash is enough to hold LoRaWAN stacks and user application firmware concurrently, while the 32 KB SRAM buffers radio packet payloads. Standby current around 2-5 uA allows multi-year operation from a pair of AA cells when wake-up duty cycles are kept low.
Recommended
Battery-Powered Metering
Utility meters for water, gas, and electricity benefit from the ATSAMD21G18A-AF's combination of precise 12-bit ADC channels, low standby current, and the integrated RTC plus sleep modes. The Event System can trigger ADC conversions from timer events without waking the CPU, enabling tamper detection and pulse counting at single-digit microamp currents. The 48-pin TQFP leaves enough GPIO to drive e-paper or segmented LCD interfaces through inexpensive external drivers.
Recommended
Consumer HMI and Maker Platforms
Arduino-compatible boards such as the Adafruit Feather M0 and the Arduino Zero use the ATSAMD21G18A-AF because its native USB, capacitive touch I/O, and PWM peripherals cover the full maker-feature list. The 48 MHz core drives small TFT displays over SPI, the 10-bit DAC generates simple audio cues, and the SWD interface lets students debug firmware using free MPLAB X tools. The 256 KB Flash comfortably hosts CircuitPython and Arduino libraries.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21G18A-AF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21G18A-AFT | ATSAMD21G18A-AU | ATSAMD21G18A-AUT | ATSAMD21G17A-AF | ATSAMD21G17A-AFT | ATSAMD21G18A-MUT |
|---|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 48-pin TQFP (7x7 mm) | 48-pin TQFP (7x7 mm) | 48-pin TQFP (7x7 mm) | 48-pin TQFP (7x7 mm) | 48-pin TQFP (7x7 mm) | 48-pin TQFP (7x7 mm) | 48-pin QFN (7x7 mm) |
| Core | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ |
| Max CPU Clock | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz |
| Flash Memory | 256 KB | 256 KB | 256 KB | 256 KB | 128 KB | 128 KB | 256 KB |
| SRAM | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB |
| USB Support | USB 2.0 FS with OTG | USB 2.0 FS with OTG | USB 2.0 FS with OTG | USB 2.0 FS with OTG | USB 2.0 FS with OTG | USB 2.0 FS with OTG | USB 2.0 FS with OTG |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
Key Differentiators
- Native full-speed USB 2.0 with OTG integrated (vs ATSAMD20G18A-AU)
- Larger Flash in the same TQFP-48 package (vs ATSAMD21G17A-AF)
- TQFP-48 footprint eases hand soldering vs QFN (vs ATSAMD21G18A-MUT)
Design Notes
Place a 100 nF decoupling capacitor within 3 mm of every VDD pin (pins 6, 15, 32) and a bulk 4.7 uF capacitor near the regulator output to handle USB inrush current. The SAM D21 internal regulator derives the USB 3.3 V from VDDIN, so VDDIN must be at least 3.0 V whenever the USB transceiver is enabled.
Route the two SWD pins (SWDIO on PA29, SWCLK on PA30) away from switching signals and provide a dedicated 2x5 or 1x6 header for in-circuit programming. If using the external main crystal on PA14/PA15, keep the traces short, symmetrical, and guarded by a ground plane; failure to do so can corrupt the high-speed USB reference clock.
Do not leave the BOOTPROT pin (PA31) floating in production firmware; tie it through a 10 kOhm resistor to VDD or GND per the bootloader configuration to avoid accidental bootloader entry. The 32 kHz crystal pins (PA00/PA01) must use a crystal with load capacitance matched to the on-chip load configuration, or RTC accuracy will suffer.
When using the integrated USB peripheral, the D-/D+ pair (PA12/PA13) must be routed as a 90 ohm differential pair on the top layer with no splits and an uninterrupted ground reference beneath. Place the USB connector's shield-decoupling capacitor within 10 mm of the connector shell to ensure EMI compliance.
Compliance Information
RoHS and REACH compliance stated on the Microchip product page. Not AEC-Q100 qualified; consider ATSAMx automotive variants for automotive deployments.
