ATSAMD21J18A-AU - ARM Cortex-M0+ MCU 256KB Flash | Microchip
MPN: ATSAMD21J18A-AU β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.3 | $4.30 |
| 10 | $3.87 | $38.70 |
| 100 | $3.45 | $345.00 |
| 500 | $3.05 | $1,525.00 |
| 1,000 | $2.69 | $2,690.00 |
ATSAMD21J18A-AU Overview
A microcontroller (MCU) is an integrated circuit that combines a CPU core, memory (Flash for code and SRAM for data), and a rich set of peripherals on a single silicon die. ARM Cortex-M0+ cores are the smallest and most energy-efficient members of the ARM Cortex-M family, optimized for deterministic embedded control and ultra-low-power operation. The SAM D21 family specifically targets battery-powered and always-on IoT, consumer, and industrial applications where low active current, deep-sleep retention, and integrated analog peripherals reduce bill-of-materials cost.
Key features include a full-speed USB 2.0 device/host interface, up to six SERCOM configurable serial communication modules, a 12-bit 350 ksps ADC with up to 20 channels, two 12-bit DACs, three analog comparators, up to 52 GPIO pins with interrupt capability, and a powerful peripheral event system for inter-peripheral signaling without CPU intervention. Hardware touch support, a CRC engine, and a true random number generator (TRNG) are also integrated.
The ATSAMD21J18A-AU is built on a low-leakage process and features an advanced peripheral touch controller, two 24-bit timers, RTC, and a 16-bit PWM with dead-time generators suitable for motor and power control. Its bootloader is pre-loaded in ROM, enabling in-system programming over USB or UART without external programmer hardware.
Typical applications include home automation gateways, smart metering, industrial sensor nodes, USB HID input devices, LED lighting controllers, wearable fitness bands, and consumer electronics with capacitive touch user interfaces. The wide 1.62β3.6V supply range and integrated USB PHY simplify designs that previously required an external voltage regulator.
When designing with the ATSAMD21J18A-AU, consider the thermal envelope of the TQFP-64 package, ensure proper decoupling with 100 nF + 4.7 uF bulk capacitors near each supply pin, and follow the trace-impedance recommendations for the USB differential pair (D+/D-) to maintain USB compliance.
This page synthesizes live distributor pricing, drop-in SAMD21J18A family variants, and practical design notes that are not present in the manufacturer datasheet PDF, helping engineers select the right SAMD21 member for production.
Drop-in alternatives for ATSAMD21J18A-AU 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 ATSAMD21J18A-AU (same form factor and footprint) β differing in USB, Operating Temperature, ADC, DAC, Package.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATSAMD21J18A-AUT
β Drop-Inβ In Stock
$2.63 / Unit
View Datasheet βATSAMD21J18A-AF
β Drop-Inβ In Stock
$2.91 / Unit
View Datasheet βATSAMD21J17A-AUT
β Drop-Inβ In Stock
$3.3 / Unit
View Datasheet βATSAMD21J17D-AUT
β Drop-Inβ In Stock
$2.05 / Unit
View Datasheet βATSAMD21J16B-AU
β Drop-Inβ In Stock
$2.75 / Unit
View Datasheet βATSAMD21G18A-AU
β Drop-In β οΈ εζ°εΎ ιͺθ―β In Stock
$1.74 / Unit
View Datasheet βATSAMD21J18A-AU Maximum Ratings & Electrical Characteristics
| Core | ARM Cortex-M0+ (32-bit) |
| Family | SAM D21J |
| Maximum Clock Frequency | 48 MHz |
| Flash Memory | 256 KB |
| SRAM | 32 KB |
| Supply Voltage Range | 1.62 V to 3.6 V |
| GPIO Count | 52 (maximum) |
| Package | 64-pin TQFP (10x10 mm) |
| Operating Temperature Range | -40C to +85C (industrial) |
| ADC | 12-bit, up to 20 channels, 350 ksps |
| DAC | 2x 12-bit |
| USB | Full-Speed USB 2.0 Device & Host |
| SERCOM Modules | 6 (configurable UART/SPI/I2C) |
| CoreMark/MHz | 2.46 |
| RoHS Status | Compliant |
| Lead-Free | Yes |
| Carrier Type (suffix AU) | Tray |
ATSAMD21J18A-AU Pin Configuration
| Pin 1 | PA00 β GPIO / XIN32 (external 32.768 kHz crystal input) |
| Pin 2 | PA01 β GPIO / XOUT32 (external 32.768 kHz crystal output) |
| Pin 3 | PA02 β GPIO / AIN0 (ADC input channel 0) |
| Pin 4 | PA03 β GPIO / AIN1 / VREFA |
| Pin 5 | GND β Ground |
| Pin 6 | VDDIO β I/O supply voltage |
| Pin 7 | PA04 β GPIO / AIN2 / VREFB |
| Pin 8 | PA05 β GPIO / AIN3 |
| Pin 9 | PA06 β GPIO / AIN4 |
| Pin 10 | PA07 β GPIO / AIN5 |
| Pin 11 | PA08 β GPIO / AIN6 / I2S MCK1 |
| Pin 12 | PA09 β GPIO / AIN7 |
| Pin 13 | PA10 β GPIO / AIN8 |
| Pin 14 | PA11 β GPIO / AIN9 |
| Pin 15 | VDDANA β Analog supply voltage |
| Pin 16 | GND β Ground |
| Pin 17 | PA12 β GPIO / AIN10 |
| Pin 18 | PA13 β GPIO / AIN11 |
| Pin 19 | PA14 β GPIO / AIN12 |
| Pin 20 | PA15 β GPIO / AIN13 |
| Pin 21 | PA16 β GPIO / AIN14 / I2S SD1 |
| Pin 22 | PA17 β GPIO / AIN15 / I2S SCK1 |
| Pin 23 | PA18 β GPIO / AIN16 / I2S FS1 |
| Pin 24 | PA19 β GPIO / AIN17 |
| Pin 25 | PA20 β GPIO / AIN18 |
| Pin 26 | PA21 β GPIO / AIN19 |
| Pin 27 | PA22 β GPIO |
| Pin 28 | PA23 β GPIO / USB D- |
| Pin 29 | PA24 β GPIO / USB D+ |
| Pin 30 | PA25 β GPIO / NRESET (external reset input) |
| Pin 31 | PA27 β GPIO |
| Pin 32 | GND β Ground |
| Pin 33 | VDDIO β I/O supply voltage |
| Pin 34 | PA28 β GPIO |
| Pin 35 | PB00 β GPIO |
| Pin 36 | PB01 β GPIO |
| Pin 37 | PB02 β GPIO / ADC AIN4 alt |
| Pin 38 | PB03 β GPIO |
| Pin 39 | PB04 β GPIO |
| Pin 40 | PB05 β GPIO |
| Pin 41 | PB06 β GPIO |
| Pin 42 | PB07 β GPIO |
| Pin 43 | PB08 β GPIO / I2S MCK0 |
| Pin 44 | PB09 β GPIO / I2S SCK0 |
| Pin 45 | PB10 β GPIO / I2S MCK1 |
| Pin 46 | PB11 β GPIO / I2S SD0 |
| Pin 47 | PB12 β GPIO / I2S SCK1 alt |
| Pin 48 | PB13 β GPIO / I2S FS0 |
| Pin 49 | PB14 β GPIO |
| Pin 50 | PB15 β GPIO |
| Pin 51 | PB16 β GPIO |
| Pin 52 | PB17 β GPIO |
| Pin 53 | PB18 β GPIO |
| Pin 54 | PB19 β GPIO |
| Pin 55 | PB20 β GPIO |
| Pin 56 | PB21 β GPIO |
| Pin 57 | PB22 β GPIO |
| Pin 58 | PB23 β GPIO |
| Pin 59 | PB24 β GPIO |
| Pin 60 | PB25 β GPIO |
| Pin 61 | PB26 β GPIO |
| Pin 62 | PB27 β GPIO |
| Pin 63 | PB28 β GPIO |
| Pin 64 | PB29 β GPIO |
Typical Applications
ATSAMD21J18A-AU is suitable for 6 applications: Home Automation Hubs, Smart Electricity Metering, Industrial Sensor Nodes, USB Human Interface Devices, LED Lighting Controllers, Wearable Fitness Bands.
Home Automation Hubs
The ATSAMD21J18A-AU fits home automation hub designs because its integrated full-speed USB 2.0 device/host port simplifies gateway connectivity to Wi-Fi or Ethernet companion modules, while the 256 KB Flash and 32 KB SRAM comfortably run MQTT-SN or Thread stacks alongside Zigbee/BLE radio drivers. The 1.62β3.6 V supply accepts a single Li-ion cell directly, removing the external LDO and shrinking BOM cost. The 6 SERCOM modules allow simultaneous UART to a smart-meter modem, SPI to an OLED display, and I2C to environmental sensors. Low-power sleep modes drop quiescent current below 10 uA with RTC retention, so battery-backed sensors last over a year on a coin cell. AEC-Q100 qualification is not required for indoor residential gateways, but the part is automotive-grade silicon by process, giving designers long-term supply stability.
Recommended
Smart Electricity Metering
The ATSAMD21J18A-AU is a strong fit for smart electricity metering because its 12-bit 350 ksps ADC with up to 20 channels simultaneously samples voltage and current waveforms for accurate true-RMS power calculation. The Cortex-M0+ runs at 48 MHz (2.46 CoreMark/MHz), so meter math, anti-tamper detection, and DLMS/COSEM protocol stack coexist without performance headroom loss. Hardware CRC32 accelerates secure message authentication, while the integrated USB enables firmware updates and factory calibration without an external programmer. Industrial -40 to +85 C operation handles outdoor meter cabinet environments. Two 12-bit DACs are useful for analog test-tone generation during factory calibration. The 256 KB Flash supports OTA-capable bootloader plus application image simultaneously.
Recommended
Industrial Sensor Nodes
Industrial 4-20 mA sensor nodes benefit from the ATSAMD21J18A-AU because its 52 GPIO pins accept multiple digital inputs, status LEDs, and a local HMI without external I/O expanders. The 1.62β3.6 V supply tolerates 24 V loop power through a wide-Vin LDO, and the SERCOM peripherals drive RS-485 transceivers for Modbus RTU. Hardware peripheral-event system lets ADC conversions trigger DMA transfers without CPU wake-ups, dropping average current below 2 mA for battery-powered field sensors. The robust -40 to +85 C industrial temperature grade handles factory-floor thermal stress. On-chip comparators also implement window-watchdog supervisor behavior. The deviceβs 256 KB Flash stores IEC 61131-3 runtime libraries plus customer application code.
Recommended
USB Human Interface Devices
The ATSAMD21J18A-AU is ideal for USB HID devices such as keyboards, mice, game controllers, and barcode scanners because its integrated full-speed USB 2.0 device PHY eliminates the external USB chip. The bootloader in ROM supports USB-DFU firmware upgrades, so end users can reflash the device over USB without a JTAG programmer. Up to 52 GPIO scan a 26-key matrix plus status LEDs with zero ghosting, while six SERCOM modules drive SPI displays, I2C sensors, and a UART debug port simultaneously. Hardware CRC and TRNG modules provide cryptographic primitives for authenticated accessories. The 256 KB Flash stores HID report descriptors, vendor-specific reports, and dual-bank OTA images for failsafe upgrades.
Recommended
LED Lighting Controllers
The ATSAMD21J18A-AU drives intelligent LED lighting controllers because its 16-bit PWM with dead-time generators can produce high-resolution dimming at 16-bit, while hardware peripheral-event system synchronizes PWM updates to ADC zero-crossing detection for AC-line phase-cut dimming. The Cortex-M0+ runs DMX-512 or DALI protocol stacks on top of lighting effects with ample CPU headroom. Six SERCOM modules support multiple SPI-driven LED strips (APA102, SK9822), and the 1.62β3.6 V supply is compatible with single-cell Li-ion or USB-powered fixtures. Industrial temperature grade ensures reliability in enclosed luminaires. Two 12-bit DACs output 0-10 V analog dimming for legacy dimmers, while the integrated USB enables field firmware updates over a phone charger.
Recommended
Wearable Fitness Bands
Wearable fitness bands benefit from the ATSAMD21J18A-AU because its integrated peripheral touch controller (PTC) supports up to 256 capacitive touch channels for swipe gestures on a small wearable display, and its low-power sleep modes drop quiescent current below 5 uA in standby while RTC and SRAM retention keep BLE bonding state. The 32 KB SRAM buffers raw accelerometer/gyroscope data before BLE transmission, while six SERCOM interfaces drive the BLE module, SPI OLED, and I2C heart-rate sensor simultaneously. USB-charging is supported natively, and the 1.62β3.6 V supply works with a single-cell Li-Po. Industrial temperature grade handles body-temperature swings during workouts. The 256 KB Flash stores Bluetooth stacks, sensor-fusion algorithms, and OTA firmware.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21J18A-AU β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21J18A-AUT | ATSAMD21J18A-AF | ATSAMD21J17A-AU | ATSAMD21J17D-AU | ATSAMD21J16B-AU |
|---|---|---|---|---|---|---|
| Package | 64-pin TQFP (10x10 mm) | 64-pin TQFP (10x10 mm) - same | 64-pin TQFP (10x10 mm) - same | 64-pin TQFP (10x10 mm) - same | 64-pin TQFP (10x10 mm) - same | 64-pin TQFP (10x10 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Flash Memory | 256 KB | 256 KB | 256 KB | 128 KB | 128 KB | 64 KB |
| SRAM | 32 KB | 32 KB | 32 KB | 16 KB | 16 KB | 8 KB |
| Maximum Clock | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz |
| USB | Full-Speed USB 2.0 | Full-Speed USB 2.0 | Full-Speed USB 2.0 | Full-Speed USB 2.0 | Full-Speed USB 2.0 | Full-Speed USB 2.0 |
| GPIO Count | Up to 52 | Up to 52 | Up to 52 | Up to 52 | Up to 52 | Up to 52 |
| Supply Voltage | 1.62 V to 3.6 V | 1.62 V to 3.6 V | 1.62 V to 3.6 V | 1.62 V to 3.6 V | 1.62 V to 3.6 V | 1.62 V to 3.6 V |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
Key Differentiators
- Maximum Flash density in the SAM D21J family (vs ATSAMD21J17A-AU)
- Includes USB, DACs, and I2S not present on the SAM D20 (vs ATSAMD20J18A-AU)
- Highest GPIO count in the SAMD21 family at 64-pin TQFP (vs ATSAMD21G18A-AU)
Design Notes
Decouple each VDDIO and VDDANA pin with a 100 nF ceramic capacitor placed within 3 mm of the pin, plus a shared 4.7 uF bulk capacitor. Use separate analog and digital ground planes tied together at a single point under the IC to prevent ADC reference noise from corrupting USB signal integrity. Place a ferrite bead between VDDIO and VDDANA on mixed-supply designs.
Route the USB D+ / D- pair as a 90-ohm differential with maximum length matching within 150 mil. Keep the pair away from switching regulator inductors and high-speed clock traces. Add a 15 kohm pull-down on D+ and 15 kohm pull-up on D- (or vice versa for host) only if not relying on the internal PHY pull resistors. The 32 kHz crystal traces must be short (<5 mm) and guarded by ground.
The 64-pin TQFP-10x10 package has a theta_JA of approximately 60 C/W on a standard 4-layer JEDEC test PCB. Estimated: at 50 MHz, 3.3 V, with all peripherals active, total power dissipation stays below 100 mW, keeping junction temperature rise under 6 C above ambient. No external heatsink is required for typical IoT applications.
Do not enable the DFLL48M open-loop mode without calibrating against the 32 kHz crystal or USB SOF frame, or the core will run at the wrong frequency and USB will fail compliance. Do not leave the NRESET pin floating - either drive it from a supervisor or pull it up with a 10 kohm resistor and a 100 nF cap for manual reset. Ensure SWDIO/SWCLK are accessible for production programming.
Compliance Information
RoHS and REACH compliant per Microchip product page. Not AEC-Q100 qualified; the SAM D21 family is industrial-grade (-40C to +85C). For automotive designs choose the SAM V71/VE family or SAM C20/C21 AEC-Q100 variants.
