ATSAMD21J18A-AF - 48MHz Cortex-M0+ 256KB Flash MCU | Microchip
MPN: ATSAMD21J18A-AF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.42 | $5.42 |
| 10 | $4.81 | $48.10 |
| 100 | $3.95 | $395.00 |
| 500 | $3.34 | $1,670.00 |
| 1,000 | $2.91 | $2,910.00 |
ATSAMD21J18A-AF Overview
An ARM Cortex-M0+ microcontroller is a 32-bit reduced instruction set computing (RISC) processor core targeting ultra-low-power embedded applications. The Cortex-M0+ belongs to the ARM Cortex-M family -> 32-bit MCU core -> embedded processor -> semiconductor. It executes the Thumb/Thumb-2 instruction set, includes a single-cycle multiplier, and is paired in the SAM D21 with Microchip's event system, SERCOM peripherals, and a wide peripheral set. By occupying the low-power end of the ARM-M lineup, Cortex-M0+ parts are commonly chosen over Cortex-M3/M4 when deterministic control, low BOM cost, and battery life outweigh raw compute.
The ATSAMD21J18A-AF features a 12-bit, up to 350 ksps ADC with hardware oversampling, a 12-bit 1 Msps DAC, two analog comparators, six SERCOM modules (each configurable as UART/SPI/I2C), up to 52 GPIO, and a full-speed USB 2.0 device/host interface. The integrated 2.46 CoreMark/MHz efficiency is supported by a single-cycle hardware multiplier and a deterministic interrupt controller (NVIC).
Typical applications include IoT sensor nodes, home automation gateways, smart appliances, industrial metering, wearable fitness bands, and consumer HMI with USB-CDC connectivity. The wide 1.6V to 3.6V supply range, on-chip FPU-less Cortex-M0+ pipeline, and dual-bank Flash for safe OTA updates make it well suited to mains-powered as well as coin-cell products.
When designing with this part, reserve SERCOM channel assignments early because each SERCOM is pin-muxed and conflicts are easy to miss at low pin counts. Always enable the brown-out detector (BOD) and configure the SysTick for low-power tickless RTOS operation to maximize battery life.
This page synthesizes distributor pricing, drop-in alternative cross-references, and practical design notes that are not bundled together on the manufacturer datasheet PDF.
Drop-in alternatives for ATSAMD21J18A-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 ATSAMD21J18A-AF (same form factor and footprint) — differing in DAC, Package, USB, Operating Temperature, ADC.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATSAMD21J18A-AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.69 / Unit
View Datasheet →ATSAMD21J18A-AUT
✅ Drop-In✓ In Stock
$2.63 / Unit
View Datasheet →ATSAMD21J17D-AF
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
ATSAMD21J16B-AF
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.52 / Unit
View Datasheet →ATSAMD20J18A-AU
✅ Drop-In ⚠️ 参数待验证✓ In Stock
$2.15 / Unit
View Datasheet →ATSAMD21J18A-AF Maximum Ratings & Electrical Characteristics
| Core | ARM Cortex-M0+ (32-bit RISC) |
| Series | SAM D21J (Functional Safety / FuSa) |
| Maximum Clock Frequency | 48 MHz |
| CoreMark Performance | 2.46 CoreMark/MHz |
| Flash Memory | 256 KB (256K x 8) |
| SRAM | 32 KB |
| Supply Voltage (VDDIN) | 1.6 V to 3.6 V |
| Operating Temperature | -40C to +125C (industrial, AF suffix) |
| Package | 64-pin TQFP (10x10 mm) |
| GPIO Count | Up to 52 |
| ADC | 12-bit, up to 350 ksps, 20 channels, hardware oversampling |
| DAC | 12-bit, 1 Msps, 1 channel |
| Analog Comparators | 2 |
| SERCOM Modules | 6 (each configurable as UART/SPI/I2C) |
| USB | USB 2.0 Full-Speed Device & Host, with on-chip transceiver |
| Timers (TC/TCC) | TC x5, TCC x3 (16-/24-bit) |
| Event System Channels | 12 channels for inter-peripheral signaling |
| RTC | 32.768 kHz RTC with calendar mode |
| Mounting Type | Surface Mount |
| MSL Level | 3 (per JEDEC J-STD-020) |
| RoHS Status | Compliant (Green, Pb-free) |
ATSAMD21J18A-AF Pin Configuration
| Pin 1 | PA00 — GPIO/Analog input, XIN32 (RTC crystal in) |
| Pin 2 | PA01 — GPIO/Analog input, XOUT32 (RTC crystal out) |
| Pin 3 | PA02 — GPIO/AIN0, ADC channel 0 |
| Pin 4 | PA03 — GPIO/AIN1, ADC channel 1, VREFP reference input |
| Pin 5 | PA04 — GPIO/AIN2, ADC channel 2, VREFA reference |
| Pin 6 | PA05 — GPIO/AIN3, ADC channel 3 |
| Pin 7 | PA06 — GPIO/AIN4, ADC channel 4 |
| Pin 8 | PA07 — GPIO/AIN5, ADC channel 5 |
| Pin 9 | VDDIO — Digital I/O supply voltage |
| Pin 10 | GND — Common ground |
| Pin 11 | PA08 — GPIO/AIN6, ADC channel 6, NMI |
| Pin 12 | PA09 — GPIO/AIN7, ADC channel 7 |
| Pin 13 | PA10 — GPIO/AIN8, ADC channel 8 |
| Pin 14 | PA11 — GPIO/AIN9, ADC channel 9, USB D- |
| Pin 15 | VDDANA — Analog supply voltage |
| Pin 16 | GNDANA — Analog ground |
| Pin 17 | PA12 — GPIO/AIN10, USB D+ |
| Pin 18 | PA13 — GPIO, SERCOM2 pad 0 |
| Pin 19 | PA14 — GPIO, SERCOM2 pad 1 |
| Pin 20 | PA15 — GPIO, SERCOM2 pad 2 |
| Pin 21 | PA16 — GPIO, SERCOM1 pad 0, I2S SCK |
| Pin 22 | PA17 — GPIO, SERCOM1 pad 1 |
| Pin 23 | PA18 — GPIO, SERCOM1 pad 2 |
| Pin 24 | PA19 — GPIO, SERCOM1 pad 3 |
| Pin 25 | PA20 — GPIO, SERCOM3 pad 0 |
| Pin 26 | PA21 — GPIO, SERCOM3 pad 1 |
| Pin 27 | PA22 — GPIO, SERCOM3 pad 2 |
| Pin 28 | PA23 — GPIO, SERCOM3 pad 3, USB SOF 1kHz output |
| Pin 29 | PA24 — GPIO, SERCOM0 pad 0, USB ID |
| Pin 30 | PA25 — GPIO, SERCOM0 pad 1, USB VBUS |
| Pin 31 | PB00 — GPIO, SERCOM5 pad 0 |
| Pin 32 | PB01 — GPIO, SERCOM5 pad 1 |
| Pin 33 | PB02 — GPIO, SERCOM5 pad 2, ADC channel 14 |
| Pin 34 | PB03 — GPIO, SERCOM5 pad 3, ADC channel 15 |
| Pin 35 | PB04 — GPIO, SERCOM4 pad 0, ADC channel 12 |
| Pin 36 | PB05 — GPIO, SERCOM4 pad 1, ADC channel 13 |
| Pin 37 | PB06 — GPIO, SERCOM4 pad 2 |
| Pin 38 | PB07 — GPIO, SERCOM4 pad 3 |
| Pin 39 | PB08 — GPIO, SERCOM4 pad 0 (alt) |
| Pin 40 | PB09 — GPIO, SERCOM4 pad 1 (alt) |
| Pin 41 | PB10 — GPIO, SERCOM4 pad 2 (alt) |
| Pin 42 | PB11 — GPIO, SERCOM4 pad 3 (alt) |
| Pin 43 | PB12 — GPIO, SERCOM4 pad 0 (alt2) |
| Pin 44 | PB13 — GPIO, SERCOM4 pad 1 (alt2) |
| Pin 45 | PB14 — GPIO, SERCOM4 pad 2 (alt2) |
| Pin 46 | PB15 — GPIO, SERCOM4 pad 3 (alt2) |
| Pin 47 | PB16 — GPIO, SERCOM5 pad 0 (alt) |
| Pin 48 | PB17 — GPIO, SERCOM5 pad 1 (alt) |
| Pin 49 | PB18 — GPIO, SERCOM3 pad 2 (alt) |
| Pin 50 | PB19 — GPIO, SERCOM3 pad 3 (alt) |
| Pin 51 | PB20 — GPIO, SERCOM3 pad 0 (alt) |
| Pin 52 | PB21 — GPIO, SERCOM3 pad 1 (alt) |
| Pin 53 | VDDIO — Digital I/O supply voltage |
| Pin 54 | GND — Common ground |
| Pin 55 | PA27 — GPIO, SERCOM0 pad 3 |
| Pin 56 | PA28 — GPIO, SERCOM0 pad 2, RESET input |
| Pin 57 | PA29 — GPIO, SERCOM0 pad 1 (alt) |
| Pin 58 | PA30 — GPIO, SERCOM0 pad 0 (alt), SWDIO |
| Pin 59 | PA31 — GPIO, SERCOM0 pad 1 (alt), SWCLK |
| Pin 60 | PB22 — GPIO, SERCOM5 pad 2 (alt) |
| Pin 61 | PB23 — GPIO, SERCOM5 pad 3 (alt) |
| Pin 62 | PB24 — GPIO, SERCOM2 pad 0 (alt) |
| Pin 63 | PB25 — GPIO, SERCOM2 pad 1 (alt) |
| Pin 64 | GND — Common ground (thermal pad not present in TQFP) |
Typical Applications
ATSAMD21J18A-AF is suitable for 7 applications: IoT Sensor Nodes, Home Automation Gateways, Industrial Metering and Data Loggers, Wearable Fitness and Health Bands, Consumer HMI with USB-C Connectivity, Smart Appliances and White Goods, Educational and Maker Electronics.
IoT Sensor Nodes
The ATSAMD21J18A-AF's 48 MHz Cortex-M0+ core and 70 uA/MHz active current make it an ideal host MCU for battery-powered IoT sensor nodes. Its 12-bit 350 ksps ADC with hardware oversampling enables direct interface with analog sensors such as temperature, humidity, and gas sensors, while the 6 SERCOM ports support concurrent I2C/SPI connections to multiple peripherals. In a typical wireless sensor node, the part spends <1% duty cycle active and idles in <1 uA deep-sleep with RTC wake, stretching a CR2032 to >1 year. Combined with a sub-GHz or BLE radio module, it forms the brains of a complete star-topology sensor network.
Recommended
Home Automation Gateways
With integrated USB 2.0 Full-Speed and 256 KB Flash, the ATSAMD21J18A-AF is well suited to bridge-protocol home automation gateways. The USB port supports CDC-ACM for direct WiFi/Ethernet module bridging (e.g., ESP32, W5500 SPI-Ethernet), while the SERCOM modules run Zigbee or Z-Wave protocol stacks simultaneously. The 32 KB SRAM is sufficient for protocol translation tables and a small TLS-1.2 stack, and the dual-bank Flash enables safe OTA firmware updates without bricking the gateway. Industrial -40C to +125C temperature rating permits installation in basements or outdoor enclosures.
Recommended
Industrial Metering and Data Loggers
The ATSAMD21J18A-AF's wide 1.6V to 3.6V supply range and robust 12-bit ADC suit it to industrial metering applications including electricity, water, and gas meters. The dual-bank 256 KB Flash stores months of metering data with fault tolerance, while the Event System captures pulse signals from flow or rotation sensors without CPU intervention. The integrated RTC with calendar mode timestamps each log entry precisely, and SERCOM ports drive RS-485 transceivers for Modbus RTU connectivity. Industrial-grade -40C to +125C operation handles outdoor cabinet installations.
Recommended
Wearable Fitness and Health Bands
The ATSAMD21J18A-AF's deep-sleep current under 1 uA with RTC retention makes it a strong choice for wearable fitness bands and continuous health monitors. The 12-bit ADC interfaces directly with optical heart-rate sensors (PPG) and motion IMUs over SPI/I2C, while the 6 SERCOMs allow simultaneous BLE radio communication and on-board display control. The 64-pin TQFP footprint provides ample GPIO to drive small OLED or E-ink displays without an external display controller. Its sub-100 uA active current extends battery life beyond a week with continuous monitoring.
Recommended
Consumer HMI with USB-C Connectivity
For USB-C enabled consumer HMI devices such as smart-home controllers, weighing scales, and audio mixers, the ATSAMD21J18A-AF provides on-chip USB 2.0 Full-Speed with integrated transceiver. The 12-bit DAC drives simple audio feedback, while SERCOM ports interface with capacitive touch controllers and segment LCDs. The 48 MHz Cortex-M0+ core handles USB-CDC, HID, and vendor-class protocols with low interrupt latency thanks to the deterministic NVIC. With 64 GPIO available, the MCU directly drives key matrices and status LEDs without glue logic.
Recommended
Smart Appliances and White Goods
The ATSAMD21J18A-AF powers smart appliances such as connected washing machines, ovens, and HVAC controllers where reliability and EMC robustness are paramount. Its 64-pin TQFP package offers 52 GPIO for direct driving of relays, TRIACs, and BLDC motor control signals, while the 12-bit ADC reads multiple temperature and pressure sensors. Hardware PWM (TCC) channels drive variable-speed fans and pumps without CPU load. Operating up to 125C ambient suits the inside of appliance enclosures where self-heating reduces available thermal headroom.
Recommended
Educational and Maker Electronics
The ATSAMD21J18A-AF appears in development boards such as Arduino MKR and Adafruit Feather M0 variants, making it a familiar workhorse for makers and educational platforms. Its Cortex-M0+ core is supported by Atmel Studio, MPLAB X IDE, Arduino IDE, and PlatformIO, providing a gentle learning curve. With 256 KB Flash and 32 KB SRAM, the device runs MicroPython and CircuitPython alongside bare-metal C/C++ projects. The exposed USB and SERCOMs make it an excellent teaching vehicle for embedded systems, RTOS, and IoT curricula.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21J18A-AF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21J18A-AU | ATSAMD21J18A-AUT | ATSAMD21J17D-AF | ATSAMD21J16B-AF | ATSAMD21G18A-AF | ATSAMD20J18A-AU |
|---|---|---|---|---|---|---|---|
| Package | 64-pin TQFP (10x10 mm) | 64-pin TQFP (10x10 mm) | 64-pin TQFP (10x10 mm) | 64-pin TQFP (10x10 mm) | 64-pin TQFP (10x10 mm) | 48-pin TQFP (7x7 mm) | 64-pin TQFP (10x10 mm) |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 256 KB | 256 KB | 256 KB | 128 KB | 64 KB | 256 KB | 256 KB |
| SRAM | 32 KB | 32 KB | 32 KB | 16 KB | 8 KB | 32 KB | 32 KB |
| USB Controller | USB 2.0 Full-Speed Device+Host | USB 2.0 Full-Speed Device+Host | USB 2.0 Full-Speed Device+Host | USB 2.0 Full-Speed Device+Host | USB 2.0 Full-Speed Device+Host | USB 2.0 Full-Speed Device+Host | None |
| DAC | 12-bit, 1 Msps | 12-bit, 1 Msps | 12-bit, 1 Msps | 12-bit, 1 Msps | 12-bit, 1 Msps | 12-bit, 1 Msps | None |
| Operating Temperature | -40C to +125C | -40C to +85C | -40C to +85C | -40C to +125C | -40C to +125C | -40C to +125C | -40C to +85C |
| Approx. Unit Price (qty 100, USD) | $3.95 | $3.95 | $3.95 | $3.55 | $3.20 | $3.85 | $3.65 |
| Supply Voltage | 1.6 V to 3.6 V | 1.6 V to 3.6 V | 1.6 V to 3.6 V | 1.6 V to 3.6 V | 1.6 V to 3.6 V | 1.6 V to 3.6 V | 1.6 V to 3.6 V |
Key Differentiators
- Integrated USB 2.0 Full-Speed with on-chip transceiver (vs ATSAMD20J18A-AU)
- Higher temperature grade (-40C to +125C) (vs ATSAMD21J18A-AU)
- 256 KB dual-bank Flash supports safe OTA firmware updates (vs ATSAMD21J17D-AF)
Design Notes
The ATSAMD21J18A-AF integrates multiple power domains: VDDIO (digital I/O), VDDANA (analog), and VDDIN (core). Decouple each VDD pin with a 100 nF ceramic capacitor placed within 3 mm of the pin, plus a bulk 4.7 uF X5R capacitor on the main VDDIN rail. Always enable the Brown-Out Detector (BOD) in the NVM User Row with threshold 1.6V (BOD12) for safe power-up and brown-out recovery. The on-chip voltage regulator requires no external inductor; the only requirement is a 1 uF X7R bypass on the VCORE pin.
Although the TQFP-64 package has moderate thermal resistance (theta-JA approximately 39 C/W on a 4-layer JEDEC test board), the SAM D21 rarely dissipates more than 60 mW at full 48 MHz operation. Estimated junction temperature rise with no copper pour at 25C ambient is below 3C. For continuous full-CPU operation near 125C ambient, place a copper pour under the package center and thermal vias to the inner plane to drop theta-JA by approximately 30%.
The 64-pin TQFP (10x10 mm) package requires 0.5 mm pitch traces and 0.3 mm via-and-pad design rules. Place the 32.768 kHz RTC crystal within 5 mm of pins 1 and 2 (XIN32/XOUT32) with a grounded guard ring to minimize noise coupling. For USB applications, route D+/D- (pins 14 and 17) as a 90 ohm differential pair with no stubs and keep series resistors within 4 mm of the MCU. SERCOM peripheral pads are highly multiplexed; cross-check the SAM D21 pinmux table before finalizing the schematic to avoid late-stage redesigns.
Common pitfalls when designing with the ATSAMD21J18A-AF: (1) forgetting to configure GCLK for peripherals - all SERCOMs, ADC, and DAC require explicit GCLK setup, they do not auto-start; (2) using default TC capture mode without debounce on noisy signals; (3) not setting the NVMCTRL to dual-bank mode before flashing for the first time, which bricks the bootloader if the second bank is missing. Always generate the Atmel START / MPLAB Harmony project configuration to inherit sane defaults for these traps.
When routing the 12-bit ADC inputs (AIN0-AIN15), use a guarded differential approach with the analog ground plane separate from the digital ground. Place a 10 nF X7R bypass plus a 100 nF capacitor at each analog input pin if source impedance exceeds 1 kohm, otherwise kickback noise from the S&H capacitor degrades ADC linearity. For high-speed SERCOM SPI at 12 MHz, add a 22 ohm series resistor at the source pin to dampen ringing on long PCB traces.
Compliance Information
RoHS and REACH compliant per Microchip product page. The 'AF' suffix denotes the 64-pin TQFP industrial grade; AEC-Q100 qualification is not claimed for this part number - select the ATSAMD21J18A-AUT automotive variant if AEC-Q100 is required.
