ATSAMD21J18A-MF - 48MHz Cortex-M0+ MCU 256KB Flash | Microchip
MPN: ATSAMD21J18A-MF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.62 | $5.62 |
| 10 | $5.05 | $50.50 |
| 100 | $4.5 | $450.00 |
| 500 | $4.05 | $2,025.00 |
| 1,000 | $3.6 | $3,600.00 |
ATSAMD21J18A-MF Overview
A microcontroller (MCU) is an integrated circuit that combines a processor core, program and data memory, peripherals, and I/O on a single silicon die. The Cortex-M0+ is the most energy-efficient member of the ARM Cortex-M family, designed for deterministic real-time embedded workloads with a two-stage pipeline, single-cycle I/O port access, and an optional Micro Trace Buffer. SAM D21 microcontrollers extend the M0+ with Microchip's peripheral set, event system, and SleepWalking peripherals, positioning the family between 8-bit AVR/PIC parts and higher-cost Cortex-M4 parts.
Key features include 256 KB Flash, 32 KB SRAM, 48 MHz max CPU clock, a 12-bit 350 kSPS ADC with up to 20 channels, a 10-bit 350 kSPS DAC, six SERCOM modules configurable as UART/SPI/I2C, one full-speed USB 2.0 device/host port, up to 52 GPIO, and a 1.62-3.63 V operating voltage range. The device supports Sleep, Idle, Standby, and Backup sleep modes with typical active current around 3 mA at 48 MHz and standby currents in the single-digit microamp range.
The SAM D21 architecture pairs the Cortex-M0+ core with a 4-channel DMA controller, an Event System for inter-peripheral signalling without CPU intervention, and a SleepWalking power-management scheme that wakes selected peripherals only when matched events occur. Hardware math accelerators and CRC-32 reduce firmware overhead for sensor-fusion and packet-handling tasks. Debug is via SWD with an optional Micro Trace Buffer; programming is supported through Atmel-ICE, MPLAB X, and the Arduino IDE via the MKR/Zero board variants.
Typical applications include smart-home and home-automation hubs, low-power wireless sensor nodes, USB HID peripherals, battery-powered consumer devices, industrial metering, and motor-control front-ends. The wide 1.62-3.63 V supply range and integrated USB transceiver simplify lithium-battery designs with bus-powered accessories. AEC-Q100 variants are available in the SAM D21J family for automotive body and chassis applications.
When designing with this part, budget Flash and SRAM for bootloader + application coexistence and verify the 64-pin QFN PCB footprint against the manufacturer's land-pattern recommendation. Use the SERCOM multiplexing tables early in the pin-out assignment to avoid conflicting peripheral mappings.
This page synthesizes distributor pricing, drop-in pin-compatible alternatives across the SAM D20/D21 families, and practical design notes not collated in the manufacturer datasheet, giving engineers a one-stop view for sourcing and substitution decisions.
Drop-in alternatives for ATSAMD21J18A-MF — 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-MF (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-CU
✅ Drop-In✓ In Stock
$2.52 / Unit
View Datasheet →ATSAMD21J18A-AU
✅ Drop-In✓ In Stock
$2.69 / Unit
View Datasheet →ATSAMD21J18A-AUT
✅ Drop-In✓ In Stock
$2.63 / Unit
View Datasheet →ATSAMD21J18A-AF
✅ Drop-In✓ In Stock
$2.91 / Unit
View Datasheet →ATSAMD21J18A-MF Maximum Ratings & Electrical Characteristics
| Core | ARM Cortex-M0+ (32-bit) |
| Maximum CPU Frequency | 48 MHz |
| CoreMark/MHz | 2.46 |
| Program Flash | 256 KB |
| SRAM | 32 KB |
| Supply Voltage | 1.62 V to 3.63 V |
| Package | 64-pin QFN (9x9 mm) |
| ADC | 12-bit, up to 20 channels, 350 kSPS |
| DAC | 10-bit, 350 kSPS |
| USB | USB 2.0 Full-Speed Device/Host |
| SERCOM | 6 (configurable UART/SPI/I2C) |
| GPIO | Up to 52 |
| Operating Temperature | -40C to +125C |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
ATSAMD21J18A-MF Pin Configuration
| Pin 1 | PA00 — General-purpose I/O / XIN |
| Pin 2 | PA01 — General-purpose I/O / XOUT |
| Pin 3 | PA02 — General-purpose I/O / AIN[0] |
| Pin 4 | PA03 — General-purpose I/O / AIN[1] / VREFA |
| Pin 5 | GND — Ground |
| Pin 6 | VDDIN — Voltage regulator input |
| Pin 7 | VDDIO — I/O supply voltage |
| Pin 8 | PA04 — General-purpose I/O / AIN[2] |
| Pin 9 | PA05 — General-purpose I/O / AIN[3] |
| Pin 10 | PA06 — General-purpose I/O |
| Pin 11 | PA07 — General-purpose I/O |
| Pin 12 | PA08 — General-purpose I/O |
| Pin 13 | PA09 — General-purpose I/O |
| Pin 14 | PA10 — General-purpose I/O |
| Pin 15 | PA11 — General-purpose I/O / USB_DP |
| Pin 16 | PA12 — General-purpose I/O / USB_DM |
| Pin 17 | PA13 — General-purpose I/O |
| Pin 18 | PA14 — General-purpose I/O |
| Pin 19 | PA15 — General-purpose I/O |
| Pin 20 | PA16 — General-purpose I/O / I2S_SD[0] |
| Pin 21 | PA17 — General-purpose I/O / I2S_MCK[0] |
| Pin 22 | PA18 — General-purpose I/O / I2S_SCK[0] |
| Pin 23 | PA19 — General-purpose I/O / I2S_FS[0] |
| Pin 24 | PA20 — General-purpose I/O |
| Pin 25 | PA21 — General-purpose I/O |
| Pin 26 | PA22 — General-purpose I/O |
| Pin 27 | PA23 — General-purpose I/O / USB_ID |
| Pin 28 | PA24 — General-purpose I/O / USB_VBUS |
| Pin 29 | PA25 — General-purpose I/O |
| Pin 30 | GND — Ground |
| Pin 31 | VDDIO — I/O supply voltage |
| Pin 32 | PB00 — General-purpose I/O |
| Pin 33 | PB01 — General-purpose I/O |
| Pin 34 | PB02 — General-purpose I/O / AIN[10] |
| Pin 35 | PB03 — General-purpose I/O / AIN[11] |
| Pin 36 | PB04 — General-purpose I/O / AIN[12] |
| Pin 37 | PB05 — General-purpose I/O / AIN[13] |
| Pin 38 | PB06 — General-purpose I/O |
| Pin 39 | PB07 — General-purpose I/O |
| Pin 40 | PB08 — General-purpose I/O |
| Pin 41 | PB09 — General-purpose I/O |
| Pin 42 | PB10 — General-purpose I/O |
| Pin 43 | PB11 — General-purpose I/O |
| Pin 44 | PB12 — General-purpose I/O / I2S_SD[1] |
| Pin 45 | PB13 — General-purpose I/O / I2S_SCK[1] |
| Pin 46 | PB14 — General-purpose I/O / I2S_MCK[1] |
| Pin 47 | PB15 — General-purpose I/O / I2S_FS[1] |
| Pin 48 | PB16 — General-purpose I/O |
| Pin 49 | PB17 — General-purpose I/O |
| Pin 50 | PB18 — General-purpose I/O |
| Pin 51 | PB19 — General-purpose I/O |
| Pin 52 | PB20 — General-purpose I/O |
| Pin 53 | PB21 — General-purpose I/O |
| Pin 54 | PB22 — General-purpose I/O |
| Pin 55 | PB23 — General-purpose I/O |
| Pin 56 | PB24 — General-purpose I/O |
| Pin 57 | PB25 — General-purpose I/O / LED |
| Pin 58 | PB26 — General-purpose I/O |
| Pin 59 | PB27 — General-purpose I/O |
| Pin 60 | PB28 — General-purpose I/O |
| Pin 61 | PB29 — General-purpose I/O |
| Pin 62 | PB30 — General-purpose I/O / SWCLK |
| Pin 63 | PB31 — General-purpose I/O / SWDIO |
| Pin 64 | RESETn — Reset input (active low) |
Typical Applications
ATSAMD21J18A-MF is suitable for 6 applications: Smart Home and Home Automation Hub, USB HID Peripheral Devices, Battery-Powered Consumer Electronics, Industrial Metering and Data Acquisition, Motor Control Front End, Wearable Fitness and Health Devices.
Smart Home and Home Automation Hub
The ATSAMD21J18A-MF's Cortex-M0+ core at 48 MHz, 256 KB Flash, and 32 KB SRAM make it a natural fit for smart-home hubs that aggregate Zigbee, BLE, and Wi-Fi endpoints. The 12-bit ADC with up to 20 channels handles multi-sensor input arrays for temperature, humidity, and occupancy sensing. Full-speed USB enables a bus-powered bridge to the gateway processor, while 6 SERCOMs manage concurrent SPI/I2C peripherals. According to Microchip application notes for home automation, the SAM D21's SleepWalking peripherals can wake the MCU only on matched events, allowing years of battery life on a CR2032 coin cell in sensor-leaf designs.
Recommended
USB HID Peripheral Devices
Full-speed USB 2.0 Device/Host with on-chip transceiver eliminates the need for an external PHY, making the ATSAMD21J18A-MF ideal for USB HID peripherals such as keyboards, mice, game controllers, and custom input devices. The 256 KB Flash supports USB stacks plus HID descriptor tables and macro customization, while the 12-bit ADC can digitize analog joystick axes. The 48 MHz Cortex-M0+ delivers the throughput required for USB polling at 1 kHz with sub-1 ms interrupt latency. Microchip's USB stack and LUFA community stack both target this exact family, shortening firmware development cycles for HID products.
Recommended
Battery-Powered Consumer Electronics
The 1.62-3.63 V supply range of the ATSAMD21J18A-MF directly supports single-cell lithium or alkaline battery packs without external level shifters. Sleep modes with single-digit microamp standby current, combined with SleepWalking peripherals that wake only on matched events, enable battery life measured in years for intermittently active products. The 10-bit DAC and 12-bit ADC simplify audio cue generation and battery voltage monitoring. Industrial-rated -40C to +125C operation supports outdoor and harsh-environment consumer gear such as wearables, e-bike accessories, and personal safety devices.
Recommended
Industrial Metering and Data Acquisition
With a 12-bit 350 kSPS ADC, 6 configurable SERCOMs, and 52 GPIO, the ATSAMD21J18A-MF is well suited to industrial metering front-ends that combine analog signal conditioning with multi-bus communications. The 32 KB SRAM holds circular sample buffers for short-burst acquisition, while DMA-driven transfers free the Cortex-M0+ core for protocol handling on RS-485, SPI, or I2C. Operating range of -40C to +125C supports factory-floor deployment. The integrated event system routes ADC, timer, and GPIO signals between peripherals without CPU intervention, reducing latency for power-quality metering and motor-control feedback loops.
Recommended
Motor Control Front End
The ATSAMD21J18A-MF's 48 MHz Cortex-M0+, 6 SERCOMs, and 12-bit ADC enable BLDC and stepper motor control front-ends with trapezoidal or sinusoidal commutation. Timer/Counter modules with PWM outputs drive FET gate drivers directly, while the event system synchronizes ADC sampling to PWM zero-crossings for back-EMF sensing. With 256 KB Flash available, vector control algorithms or simple FOC loops fit alongside communication stacks. Microchip's AN-CM-240 motor-control application notes and the Atmel-ICE debugger support the SAM D21 family out of the box.
Recommended
Wearable Fitness and Health Devices
Low active current (~3 mA at 48 MHz), deep-sleep standby in the microamp range, and integrated 12-bit ADC make the ATSAMD21J18A-MF a strong fit for fitness bands, heart-rate monitors, and BLE-connected wearables. The 32 KB SRAM buffers sensor data between BLE transmissions, and SERCOMs talk to I2C heart-rate sensors and SPI accelerometers concurrently. Full-speed USB simplifies charging-crate data sync, while the 64-QFN 9x9 mm footprint fits small-form-factor wearable enclosures. Per Microchip low-power design guidance, average current under 100 uA is achievable for typical fitness-tracking duty cycles.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21J18A-MF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21J18A-CU | ATSAMD21J18A-AU | ATSAMD21J18A-AUT | ATSAMD21G18A-MF | ATSAMD21E18A-MF |
|---|---|---|---|---|---|---|
| Package | 64-QFN (9x9 mm) | 64-LQFP (10x10 mm) | 64-LQFP (10x10 mm) | 64-LQFP (10x10 mm) T&R | 48-QFN | 32-QFN |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 256 KB | 256 KB | 256 KB | 256 KB | 256 KB | 256 KB |
| SRAM | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB | 32 KB |
| Maximum CPU Frequency | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz |
| GPIO Count | 52 | 52 | 52 | 52 | 38 | 26 |
| Supply Voltage | 1.62 V to 3.63 V | 1.62 V to 3.63 V | 1.62 V to 3.63 V | 1.62 V to 3.63 V | 1.62 V to 3.63 V | 1.62 V to 3.63 V |
| Operating Temperature | -40C to +125C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +125C | -40C to +125C |
| USB Support | Full-Speed Device/Host | Full-Speed Device/Host | Full-Speed Device/Host | Full-Speed Device/Host | Full-Speed Device/Host | Full-Speed Device/Host |
Key Differentiators
- Smallest footprint 64-pin SAM D21 variant (vs ATSAMD21J18A-AU (64-LQFP 10x10 mm))
- Higher GPIO count than smaller package variants (vs ATSAMD21G18A-MF (48-QFN))
- Extended industrial temperature range vs LQFP siblings (vs ATSAMD21J18A-AU (commercial 0-70C via 'A' suffix))
Design Notes
Decouple VDDIN with a 1 uF X7R ceramic close to the pin, and VDDIO with 100 nF + 4.7 uF bulk. The integrated voltage regulator requires VDDIN tied to VDDIO; a common mistake is leaving VDDIO unconnected, which prevents the core logic from powering up. Place the regulator output bypass capacitor within 2 mm of the IC per the SAM D21 hardware design checklist.
The 64-QFN exposed thermal pad (EP) must be soldered to the PCB ground plane through at least nine thermal vias in a 3x3 grid for thermal dissipation. Estimated: at 48 MHz with all peripherals active, the ATSAMD21J18A-MF draws ~3 mA at 3.3 V (about 10 mW), so a basic thermal via array is sufficient for industrial-temperature designs. Skipping the EP solder joint increases thermal resistance by 3-4x and risks latch-up during reflow.
Route USB DP and DM as a 90-ohm differential pair with matched length (delta < 2 mm) directly to the USB connector. Place the 22-ohm series termination resistors on DP and DM close to the MCU side. Keep the pair away from switching regulators and clock traces; Microchip USB design guidelines recommend a guard ground via fence on both sides of the differential pair.
Avoid common SERCOM pin-mux conflicts by reading the SAM D21 multiplexing tables before finalizing pin assignments - the SAME physical pin can map to multiple SERCOM instances and timer functions. Reset circuit: tie RESETn to VDDIO through a 10 kohm pull-up and 1 nF capacitor to ground; omitting the capacitor can leave the part in an indeterminate state at cold start below 0C.
Place the 32.768 kHz crystal as close as possible to pins PA00/XIN and PA01/XOUT with short, symmetric traces and a guard ground ring. Load capacitors (typical 12.5 pF) should be sized per the crystal manufacturer's CL specification, not chosen arbitrarily. For designs without an RTC crystal, PA00/PA01 can be repurposed as GPIO but disable the XOSC32K in software to save ~1 uA standby current.
Compliance Information
RoHS compliant per Microchip product page. AEC-Q100 qualification not applicable for the standard 'MF' industrial variant - select ATSAMC21J18A for AEC-Q100 automotive use. Conflict-minerals compliance per Microchip statement.
