ATSAMD21J18A-MUT - 48MHz ARM Cortex-M0+ 256KB Flash MCU | Microchip
MPN: ATSAMD21J18A-MUT ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.12 | $5.12 |
| 10 | $4.78 | $47.80 |
| 100 | $4.31 | $431.00 |
| 500 | $3.84 | $1,920.00 |
| 1,000 | $3.42 | $3,420.00 |
ATSAMD21J18A-MUT Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory (Flash), data memory (SRAM), and configurable peripherals. The ARM Cortex-M0+ is a 32-bit processor core optimized for low-power, deterministic embedded applications and sits within the broader ARM Cortex-M family hierarchy (Cortex-M0 -> Cortex-M0+ -> Cortex-M3 -> Cortex-M4 -> Cortex-M7). The SAM D21 family specifically occupies the entry-level, low-power end of the Microchip Cortex-M lineup. Within that family the ATSAMD21J18A variant provides the largest pin count (64 pins) and largest Flash option, enabling connectivity-rich designs that smaller-pinned SAMD21G or SAMD21E variants cannot serve.
Key features include 256 KB Flash, 32 KB SRAM, full-speed USB 2.0 with on-chip transceiver, six SERCOM modules that can each be configured as UART, SPI, or I2C, a 12-bit 350 ksps ADC with up to 20 channels, a 10-bit DAC with one channel output, and two analog comparators. SleepWalking peripherals and an Event System allow the core to remain in deep sleep while peripherals react autonomously to external stimuli, drawing as little as a few microamps.
The device is built on a low-power CMOS process and supports six software-selectable sleep modes (IDLE, STANDBY, BACKUP, OFF) with sub-microsecond wake-up. The integrated Full-Speed USB PHY eliminates external crystal requirements for USB, and the SERCOM peripheral multiplexing enables designers to assign digital interfaces to most GPIO pins, simplifying PCB routing across multiple board variants.
Typical applications include home automation gateways, consumer electronics, smart metering, industrial sensor nodes, USB peripherals (HID, CDC, mass storage), wearable fitness devices, and low-power IoT end nodes. The wide operating voltage and rich peripheral mix make it well suited for battery-powered products requiring USB connectivity or multiple serial interfaces.
When designing with the ATSAMD21J18A, use the Atmel/Microchip START toolchain or MPLAB X IDE with the ASF/Atmel Software Framework, and program/debug with an Atmel-ICE or MPLAB Snap. Decouple VDDCORE and VDDIO with at least 100 nF plus 4.7 uF bulk capacitors placed as close to the pins as possible.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone, helping procurement and firmware engineers evaluate the ATSAMD21J18A-MUT for new designs or as a substitute for other Cortex-M0+ MCU candidates.
Drop-in alternatives for ATSAMD21J18A-MUT — 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-MUT (same form factor and footprint) — differing in USB, ADC, Package, DAC, Operating Temperature.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATSAMD21J18A-MF
✅ Drop-In✓ In Stock
$3.6 / Unit
View Datasheet →ATSAMD21J18A-AUT
✅ Drop-In✓ In Stock
$2.63 / Unit
View Datasheet →ATSAMD21J17D-MU
✅ Drop-In✓ In Stock
$2.21 / Unit
View Datasheet →ATSAMD21J17A-MU
✅ Drop-In✓ In Stock
$2.68 / Unit
View Datasheet →ATSAMD21J16B-MUT
✅ Drop-In✓ In Stock
$2.3 / Unit
View Datasheet →ATSAMD20J18A-MNT
✅ Drop-In✓ In Stock
$3.41 / Unit
View Datasheet →ATSAMD21J18A-MUT Maximum Ratings & Electrical Characteristics
| Core | ARM Cortex-M0+ (32-bit) |
| Series | SAM D21J (Functional Safety / FuSa) |
| Maximum CPU Clock | 48 MHz |
| Flash Program Memory | 256 KB (256K x 8) |
| SRAM | 32 KB |
| Operating Voltage Range | 1.62 V to 3.63 V |
| Package | 64-QFN (9x9 mm) |
| Mounting Type | Surface Mount |
| Operating Temperature Range | -40 C to +85 C (industrial) |
| CoreMark Score | 2.46 CoreMark/MHz |
| ADC | 12-bit SAR, up to 350 ksps, 20 channels |
| DAC | 10-bit, 1 channel |
| USB | USB 2.0 Full Speed with on-chip PHY |
| Communication Interfaces | 6x SERCOM (UART/SPI/I2C), I2S |
| Timers | TCC (Timer/Counter for Control), TC, RTC |
| I/O Pins | Up to 52 GPIO |
| RoHS Status | Compliant |
ATSAMD21J18A-MUT Pin Configuration
| Pin 1 | VDD — Digital supply voltage |
| Pin 2 | PA00 — General purpose I/O / XIN32 |
| Pin 3 | PA01 — General purpose I/O / XOUT32 |
| Pin 4 | PA02 — General purpose I/O / AIN0 |
| Pin 5 | PA03 — General purpose I/O / AIN1 / VREFA |
| Pin 6 | GND — Ground |
| Pin 7 | PA04 — General purpose I/O / AIN2 |
| Pin 8 | PA05 — General purpose I/O / AIN3 |
| Pin 9 | PA06 — General purpose I/O / AIN4 |
| Pin 10 | PA07 — General purpose I/O / AIN5 |
| Pin 11 | VDD — Digital supply voltage |
| Pin 12 | PA08 — General purpose I/O / AIN6 |
| Pin 13 | PA09 — General purpose I/O / AIN7 |
| Pin 14 | PA10 — General purpose I/O / AIN8 |
| Pin 15 | PA11 — General purpose I/O / AIN9 |
| Pin 16 | PA12 — General purpose I/O |
| Pin 17 | PA13 — General purpose I/O |
| Pin 18 | PA14 — General purpose I/O |
| Pin 19 | PA15 — General purpose I/O |
| Pin 20 | GND — Ground |
| Pin 21 | PA16 — General purpose I/O |
| Pin 22 | PA17 — General purpose I/O |
| Pin 23 | PA18 — General purpose I/O |
| Pin 24 | PA19 — General purpose I/O |
| Pin 25 | PA20 — General purpose I/O |
| Pin 26 | PA21 — General purpose I/O |
| Pin 27 | PA22 — General purpose I/O |
| Pin 28 | PA23 — General purpose I/O |
| Pin 29 | PA24 — General purpose I/O / USB D- |
| Pin 30 | PA25 — General purpose I/O / USB D+ |
| Pin 31 | PA26 — General purpose I/O |
| Pin 32 | PA27 — General purpose I/O |
| Pin 33 | PA28 — General purpose I/O |
| Pin 34 | PA29 — General purpose I/O |
| Pin 35 | PA30 — General purpose I/O / SWCLK |
| Pin 36 | PA31 — General purpose I/O / SWDIO |
| Pin 37 | PB00 — General purpose I/O |
| Pin 38 | PB01 — General purpose I/O |
| Pin 39 | PB02 — General purpose I/O / AIN10 |
| Pin 40 | PB03 — General purpose I/O / AIN11 |
| Pin 41 | PB04 — General purpose I/O / AIN12 |
| Pin 42 | PB05 — General purpose I/O / AIN13 |
| Pin 43 | PB06 — General purpose I/O / AIN14 |
| Pin 44 | PB07 — General purpose I/O / AIN15 |
| Pin 45 | PB08 — General purpose I/O / AIN16 |
| Pin 46 | PB09 — General purpose I/O / AIN17 |
| Pin 47 | PB10 — General purpose I/O |
| Pin 48 | PB11 — General purpose I/O |
| Pin 49 | PB12 — General purpose I/O |
| Pin 50 | PB13 — General purpose I/O |
| Pin 51 | PB14 — General purpose I/O |
| Pin 52 | PB15 — General purpose I/O |
| Pin 53 | PB16 — General purpose I/O |
| Pin 54 | PB17 — General purpose I/O |
| Pin 55 | PB18 — General purpose I/O |
| Pin 56 | PB19 — General purpose I/O |
| Pin 57 | PB20 — General purpose I/O |
| Pin 58 | PB21 — General purpose I/O |
| Pin 59 | GND — Ground |
| Pin 60 | VDD — Digital supply voltage |
| Pin 61 | VDDCORE — Internal core voltage (decouple only) |
| Pin 62 | VDD — Digital supply voltage |
| Pin 63 | RESETN — Reset input, active low |
| Pin 64 | NC — Not connected (per datasheet) |
Typical Applications
ATSAMD21J18A-MUT is suitable for 7 applications: Home Automation Gateway, USB HID Peripheral Device, Industrial Sensor Node, Wearable Fitness Tracker, Smart Electricity Meter, Consumer Remote Control, IoT End Node with USB Provisioning.
Home Automation Gateway
The ATSAMD21J18A-MUT fits home automation gateway designs thanks to its six configurable SERCOM interfaces, each of which can independently serve as UART, SPI, or I2C to bridge Wi-Fi, Zigbee, Sub-GHz, and sensor peripherals. Its 256 KB Flash hosts multi-protocol translation stacks while 32 KB SRAM buffers concurrent telemetry streams. The integrated Full-Speed USB 2.0 PHY allows the gateway to appear as a CDC Ethernet adapter or HID device on a host PC during provisioning. With 1.62 V to 3.63 V operation the MCU runs directly from a 3.3 V rail or a single Li-ion cell, and the 6-channel Event System keeps wake-from-sleep latency low for interrupt-driven sensor polling.
Recommended
USB HID Peripheral Device
For USB Human Interface Devices such as keyboards, mice, custom controls, or test instruments, the ATSAMD21J18A-MUT's integrated Full-Speed USB transceiver eliminates the need for an external PHY or 48 MHz USB crystal, reducing both BOM cost and PCB area. The Cortex-M0+ at 48 MHz provides 1.25 DMIPS/MHz, ample for HID class drivers and on-device button matrix scanning across its 52 GPIOs. Up to six SERCOMs let the same firmware support USB plus auxiliary UART debug or SPI-driven LED control. Developers can use the Microchip USB Device Stack and Atmel START code generator to bring up HID, CDC, or composite devices without writing a driver from scratch.
Recommended
Industrial Sensor Node
Industrial sensor nodes benefit from the ATSAMD21J18A-MUT's 12-bit 350 ksps ADC with up to 20 channels, enabling simultaneous sampling of temperature, pressure, and 4-20 mA loop inputs through external signal conditioning. The Event System allows ADC conversions to trigger DMA transfers autonomously while the core stays in STANDBY, drawing as little as a few microamps - critical for loop-powered 4-20 mA or battery-backed installations. The 256 KB Flash accommodates IEC 61131-3 soft logic or Modbus RTU firmware with room for over-the-air update bootloaders. Operating across -40 C to +85 C industrial temperature, the device tolerates cabinet and outdoor enclosures common in factory automation.
Recommended
Wearable Fitness Tracker
Wearable fitness trackers leverage the ATSAMD21J18A-MUT's low-power sleep modes and 1.62 V minimum supply voltage to operate from small Li-Po or coin-cell batteries. The 10-bit DAC drives simple haptic feedback buzzers, while the analog comparators allow low-latency heart-rate or accelerometer interrupt detection without waking the core. With 32 KB SRAM the device can buffer raw motion samples before RF transmission, and 256 KB Flash fits BLE HCI stacks when paired with a co-processor such as the ATBTLC1000. The 64-QFN 9x9 mm package fits comfortably inside wristbands and patches, while the 6-channel Event System manages sensor interrupts during exercise sessions.
Recommended
Smart Electricity Meter
Smart electricity meters exploit the ATSAMD21J18A-MUT's combination of 12-bit ADC, RTC with calendar mode, and 256 KB Flash to implement metering firmware, calibration tables, and secure communication stacks. The MCU's Cortex-M0+ core at 48 MHz delivers sufficient throughput for 4-quadrant energy measurement, RMS calculation, and DLMS/COSEM or IEC 62056-21 protocol framing without external DSP. Tamper-detection inputs use the integrated analog comparators to react to magnetic or cover-switch events in microseconds. Operating from 1.62 V to 3.63 V lets the design run from a single auxiliary rail after the meter's main switching supply, simplifying isolation and EMC.
Recommended
Consumer Remote Control
Battery-powered consumer remote controls with voice, motion, or RF inputs benefit from the ATSAMD21J18A-MUT's low active current at 48 MHz and sub-microamp BACKUP retention current. The 10-bit DAC and PWM channels can synthesize audio prompts or drive IR LEDs directly, while the SERCOM peripherals support SPI displays and BLE / proprietary RF interfaces. Designers can use the integrated USB PHY to expose a CDC port for factory firmware programming and battery charging telemetry, removing the need for a separate programming header. The 64-QFN footprint allows the design to remain slim while still providing 52 GPIOs for key matrices, capacitive touch sliders, and RGB LED indicators.
Recommended
IoT End Node with USB Provisioning
Battery-powered IoT end nodes that require USB-based provisioning or firmware update rely on the ATSAMD21J18A-MUT's integrated Full-Speed USB 2.0 PHY to avoid external components. The 256 KB Flash stores the application and a USB bootloader (e.g. UF2 or MSD) for field updates via any USB host, while 32 KB SRAM supports TLS handshake scratch memory on MCUs paired with a Wi-Fi module. Operating from 1.62 V to 3.63 V lets the same PCB design run from a 3.3 V regulated rail, a Li-Po cell, or two AA batteries. The Cortex-M0+ SleepWalking peripherals keep wake-up current low while supporting background ADC scans of environmental sensors between RF transmissions.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21J18A-MUT — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21J18A-MF | ATSAMD21J17D-MU | ATSAMD21J16B-MUT | ATSAMD20J18A-MNT |
|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 64-QFN (9x9) | 64-QFN (9x9) - same | 64-QFN (9x9) - same | 64-QFN (9x9) - same | 64-QFN (9x9) - same |
| Core | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ |
| Max Clock | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz |
| Flash | 256 KB | 256 KB | 128 KB (-50%) | 64 KB (-75%) | 256 KB |
| SRAM | 32 KB | 32 KB | 32 KB | 8 KB (-75%) | 32 KB |
| USB 2.0 FS PHY | Yes (on-chip) | Yes (on-chip) | Yes (on-chip) | Yes (on-chip) | No (external PHY required) |
| Operating Temperature | -40 C to +85 C | 0 C to +70 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C |
| Functional Safety (FuSa) | Yes (SAM D21J) | Yes | No (SAM D21J non-FuSa) | No (SAM D21J non-FuSa) | No |
Key Differentiators
- Highest-density Flash option in SAM D21J family (vs ATSAMD21J17D-MU)
- Functional Safety (FuSa) variant vs SAM D20 (vs ATSAMD20J18A-MNT)
- Industrial temperature grade and full peripheral count (vs ATSAMD21J18A-MF)
- More than four times the Flash of smaller-pinned SAMD21 (vs ATSAMD21E18A-MF)
Design Notes
Estimated: at 48 MHz active current draw, the ATSAMD21J18A-MUT core consumes approximately 7 mA from VDDCORE, while each enabled SERCOM adds roughly 200 uA. Decouple VDDCORE with a 1 uF X7R 0402 ceramic and VDDIO with 100 nF plus 4.7 uF bulk capacitors placed within 2 mm of the pins. For battery designs, switching the MCU into STANDBY reduces current to a few microamps; using the Event System to wake on a comparator or RTC match eliminates the need for continuous core polling. Ensure VDDIO rises monotonically with VDDCORE during power-up to avoid latch-up, and respect the 3.63 V absolute-maximum rating on every I/O pin.
Place the 64-QFN exposed pad (EP) on a continuous ground copper pour stitched with 0.3 mm vias on a 1.2 mm pitch grid to maximize thermal dissipation and reduce ground impedance. Keep the USB DP/DM traces (PA24/PA25) length-matched within 150 mils and route them with 90 ohm differential impedance, no stubs, and no series components other than the mandatory 39 ohm damping resistors. Isolate the 32.768 kHz crystal traces with a guard ring tied to ground, and place the load capacitors within 2 mm of the XIN32/XOUT32 pins (PA00/PA01) to avoid startup failures.
Do not exceed the 3.63 V absolute-maximum rating on any I/O; levels above this permanently damage the silicon. The on-chip USB PHY requires the internal 48 MHz PLL to be enabled and the DFLL calibrated - skipping this step causes enumeration failures on Windows hosts. The NVMCTRL Flash write/erase operations stall the bus for up to 4 ms; budget for this in any real-time interrupt service routine. When migrating from the SAM D20 family, note that the D21 adds USB, I2S, and a second analog comparator but the SERCOM numbering has shifted on a few pins, so verify peripheral mapping against the latest pinout file.
For the 64-QFN (9x9 mm) footprint, use a 0.5 mm pitch land pattern with a 7.6 mm center thermal pad. The thermal pad must be soldered to the PCB for mechanical reliability and for heat dissipation - skipping it can cause field failures under continuous 48 MHz operation. Keep the BOOT_PROG trace accessible via a test point for factory firmware update via the USB bootloader, and place the SWD header (SWCLK/SWDIO on PA30/PA31) at the board edge for debug access with the Atmel-ICE or MPLAB Snap.
Compliance Information
RoHS and REACH compliance per Microchip product page and DigiKey environmental attributes. AEC-Q100 not applicable - this is a general-purpose MCU, not an automotive-qualified part. For AEC-Q100 qualified alternatives in this family, refer to the SAM D21 automotive datasheet line.
