ATSAMD21J16B-MU - 64KB Flash Cortex-M0+ MCU | Microchip 64-QFN
MPN: ATSAMD21J16B-MU β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.42 | $3.42 |
| 10 | $3.07 | $30.70 |
| 100 | $2.74 | $274.00 |
| 500 | $2.45 | $1,225.00 |
| 1,000 | $2.18 | $2,180.00 |
ATSAMD21J16B-MU Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, program memory (Flash), data memory (SRAM), and a rich set of peripherals such as timers, ADCs, communication interfaces, and GPIO. The ARM Cortex-M0+ is the smallest and most energy-efficient ARM processor core, designed for embedded applications that prioritize low power consumption and deterministic real-time response. Within the broader taxonomy, the SAM D21 sits at the intersection of MCU -> 32-bit MCU -> ARM Cortex-M MCU -> low-power MCU -> Microchip SAM D family, and the ATSAMD21J16B is the 64KB Flash variant within the SAM D21J 64-pin sub-family.
Key features include the Cortex-M0+ core delivering 2.46 CoreMark/MHz, full-speed USB 2.0 device/host support, a 12-bit 1 MSPS ADC, two I2C, up to six SERCOM (configurable serial communication), and advanced low-power Idle/Standby sleep modes with SleepWalking peripherals. The device also integrates a 12-channel DMAC, a 12-channel Event System, and a 48MHz DFLL locked to a 32.768kHz crystal for accurate USB timing. The 64-QFN package with EPAD provides a low-thermal-resistance path to the PCB copper pour, enabling sustained 48MHz operation in thermally constrained industrial enclosures.
The SAM D21 family is drop-in compatible with the SAM D20 family, simplifying migration from lower-pin-count or smaller-Flash designs. The 64KB Flash variant (J16) is positioned for cost-sensitive connected designs that need USB, more serial channels, or a richer analog front end than the J15 (32KB) variant. With its combination of low power, USB, and Cortex-M0+ performance, the ATSAMD21J16B-MU targets IoT sensor nodes, consumer USB peripherals, and industrial control modules.
Drop-in alternatives for ATSAMD21J16B-MU 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 ATSAMD21J16B-MU (same form factor and footprint) β differing in ADC, Package, USB, DAC, Timers/Counters.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATSAMD21J15B-MU
β Drop-Inβ In Stock
$1.74 / Unit
View Datasheet βATSAMD21J17B-MU
β Drop-Inπ Reference alternative (not in catalog)
ATSAMD21J18B-MU
β Drop-Inπ Reference alternative (not in catalog)
ATSAMD21J16B-MU Maximum Ratings & Electrical Characteristics
| Core Architecture | ARM Cortex-M0+ (32-bit) |
| Maximum CPU Frequency | 48 MHz |
| CoreMark/MHz | 2.46 CoreMark/MHz |
| Flash Memory | 64 KB |
| SRAM | 8 KB |
| Package | 64-QFN (9x9 mm) with EPAD |
| Operating Voltage (VDDIN) | 1.62 V to 3.63 V |
| Operating Temperature | -40C to +85C (industrial) |
| USB | USB 2.0 Full-Speed Device + Host |
| ADC | 12-bit, up to 1 MSPS, 20 channels |
| SERCOM | 6 configurable serial interfaces |
| DMAC Channels | 12 |
| Event System Channels | 12 |
| Timer/Counters (TC) | Multiple 16-bit and 8-bit TC |
| GPIO (max) | 52 |
| Debug Interface | Serial Wire Debug (SWD), 2-pin |
| Low-Power Modes | Idle, Standby, Backup, SleepWalking peripherals |
| RoHS Status | Compliant (Green) |
ATSAMD21J16B-MU Pin Configuration
| Pin 1 | PA00 β GPIO / XIN32 (32.768kHz crystal input) |
| Pin 2 | PA01 β GPIO / XOUT32 (32.768kHz crystal output) |
| Pin 3 | PA02 β GPIO / AIN0 (ADC analog input 0) |
| Pin 4 | PA03 β GPIO / AIN1 / VREFA / REFADC |
| Pin 5 | GND β Ground |
| Pin 6 | VDD β Digital supply voltage (1.62V to 3.63V) |
| 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 SCK |
| Pin 12 | PA09 β GPIO / AIN7 / I2S FS |
| Pin 13 | PA10 β GPIO / AIN8 / I2S MCK |
| Pin 14 | PA11 β GPIO / AIN9 / I2S SDO |
| Pin 15 | VDDIO β I/O supply voltage |
| Pin 16 | GND β Ground |
| Pin 17 | PA12 β GPIO / AIN10 / SDI |
| Pin 18 | PA13 β GPIO / AIN11 / SDO |
| Pin 19 | PA14 β GPIO / AIN12 / SCK |
| Pin 20 | PA15 β GPIO / AIN13 / CS |
| Pin 21 | PA16 β GPIO / I2C SDA (SERCOM) |
| Pin 22 | PA17 β GPIO / I2C SCL (SERCOM) |
| Pin 23 | PA18 β GPIO / USB DM (USB D-) |
| Pin 24 | PA19 β GPIO / USB DP (USB D+) |
| Pin 25 | PA20 β GPIO / TCC0 |
| Pin 26 | PA21 β GPIO / TCC0 |
| Pin 27 | PA22 β GPIO / TCC0 |
| Pin 28 | PA23 β GPIO / TCC0 |
| Pin 29 | PA24 β GPIO / USB Host enable |
| Pin 30 | PA25 β GPIO / USB VBUS sense |
| Pin 31 | GND β Ground |
| Pin 32 | VDDIN β Voltage regulator input supply |
| Pin 33 | PA27 β GPIO |
| Pin 34 | PA28 β GPIO / RESET (alternate function) |
| Pin 35 | PA29 β GPIO / SWDIO |
| Pin 36 | PA30 β GPIO / SWCLK |
| Pin 37 | PA31 β GPIO |
| Pin 38 | PB00 β GPIO / AIN14 |
| Pin 39 | PB01 β GPIO / AIN15 |
| Pin 40 | PB02 β GPIO / AIN16 |
| Pin 41 | PB03 β GPIO / AIN17 |
| Pin 42 | PB04 β GPIO / AIN18 |
| Pin 43 | PB05 β GPIO / AIN19 |
| Pin 44 | PB06 β GPIO |
| Pin 45 | PB07 β GPIO |
| Pin 46 | PB08 β GPIO / I2C SDA (alt SERCOM) |
| Pin 47 | PB09 β GPIO / I2C SCL (alt SERCOM) |
| Pin 48 | PB10 β GPIO |
| Pin 49 | PB11 β GPIO |
| Pin 50 | PB12 β GPIO |
| Pin 51 | PB13 β GPIO |
| Pin 52 | PB14 β GPIO |
| Pin 53 | PB15 β GPIO |
| Pin 54 | PB16 β GPIO |
| Pin 55 | PB17 β GPIO |
| Pin 56 | PB18 β GPIO |
| Pin 57 | PB19 β GPIO |
| Pin 58 | PB20 β GPIO |
| Pin 59 | PB21 β GPIO |
| Pin 60 | PB22 β GPIO |
| Pin 61 | PB23 β GPIO |
| Pin 62 | PB24 β GPIO |
| Pin 63 | PB25 β GPIO |
| Pin 64 | EPAD β Exposed thermal pad - connect to GND |
Typical Applications
ATSAMD21J16B-MU is suitable for 7 applications: USB HID Consumer Devices, Industrial Sensor Hubs, Battery-Powered IoT Nodes, Home Automation Controllers, Wearables and Fitness Devices, Automotive Body Electronics (Non-Safety), Smart Agriculture Sensor Nodes.
USB HID Consumer Devices
The ATSAMD21J16B-MU's integrated USB 2.0 Full-Speed controller with device and host modes makes it a strong fit for USB HID peripherals such as keyboards, mice, game controllers, and custom HID devices. The Cortex-M0+ core at 48MHz delivers enough throughput for complex HID descriptors and on-device firmware updates, while 64KB Flash accommodates USB stacks plus application code. The on-chip transceiver eliminates external USB PHY components, reducing BOM and PCB area, and the SERCOM peripherals provide flexible GPIO-to-USB bridging for legacy peripherals.
Recommended
Industrial Sensor Hubs
The ATSAMD21J16B-MU's 12-bit 1 MSPS ADC with up to 20 channels, combined with 6 SERCOM interfaces and a 12-channel Event System, suits industrial sensor hub designs aggregating analog and digital sensors over I2C, SPI, and UART. The industrial -40C to +85C temperature rating supports factory-floor deployment. The 64KB Flash and 8KB SRAM are sufficient for Modbus or CANopen firmware stacks plus sensor calibration tables, and the Event System enables deterministic, low-latency sensor sampling without CPU intervention.
Recommended
Battery-Powered IoT Nodes
The ATSAMD21J16B-MU's Idle, Standby, and Backup sleep modes plus SleepWalking peripherals enable multi-year battery life in IoT sensor nodes. The Event System can autonomously wake the ADC, compare a reading against a threshold, and only invoke the CPU when action is required, keeping average current in the single-digit microamp range. The 48MHz performance headroom supports burst-mode LoRa, BLE, or sub-GHz radio packet handling, while 64KB Flash accommodates OTA update staging buffers for future-proof firmware management.
Recommended
Home Automation Controllers
The ATSAMD21J16B-MU integrates the peripherals needed for home automation gateways: USB for Wi-Fi/BLE module attachment, multiple SERCOM for sensor buses (I2C, SPI), timers for HVAC control loops, and ADC for analog sensor inputs. The 64-QFN (9x9 mm) package with EPAD allows compact gateway PCB layouts, and the 8KB SRAM comfortably supports small TCP/IP stacks over an external Wi-Fi module. Cortex-M0+ simplicity also keeps firmware development straightforward on the Microchip Studio/MPLAB X platform.
Recommended
Wearables and Fitness Devices
The ATSAMD21J16B-MU's low-power Standby mode (single-digit microamp with RTC) combined with a 48MHz burst-mode Cortex-M0+ is well suited to battery-powered wearables such as fitness bands, heart-rate monitors, and BLE beacons. The 12-bit ADC supports bio-impedance and optical heart-rate sensor front ends, while SERCOM enables I2C/SPI connections to accelerometers and BLE modules. The 9x9 mm QFN footprint leaves room for small, curved wearable PCBs, and Microchip's ASF/START driver library accelerates time-to-market.
Recommended
Automotive Body Electronics (Non-Safety)
The ATSAMD21J16B-MU's industrial -40C to +85C rating, CAN-friendly SERCOM (via external transceiver), and 64KB Flash suit non-safety automotive body applications such as HVAC controls, seat controllers, lighting modules, and infotainment secondary displays. The integrated USB enables media player and smartphone interface connectivity, while the Event System guarantees deterministic response times for body-control tasks. For ASIL-rated safety functions, designers should use Microchip's dedicated automotive-qualified SAM D20/D21 variants instead of the industrial-grade J16B-MU.
Recommended
Smart Agriculture Sensor Nodes
The ATSAMD21J16B-MU combines low-power operation with sufficient peripherals for smart agriculture applications including soil moisture sensing, environmental monitoring, and irrigation valve control. The 12-bit ADC digitizes multiple analog sensors, the RTC with Standby mode enables scheduled wake cycles for years of battery life, and the SERCOM interfaces support LoRa, NB-IoT, or Sub-GHz radio modules for field-area-network connectivity. The wide operating temperature range supports harsh outdoor deployment in agricultural environments.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21J16B-MU β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21J15B-MU | ATSAMD21J17B-MU | ATSAMD21J18B-MU |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 64-QFN (9x9 mm) | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same |
| Core | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ |
| Maximum CPU Frequency | 48 MHz | 48 MHz | 48 MHz | 48 MHz |
| Flash Memory | 64 KB | 32 KB (-50%) | 128 KB (+100%) | 256 KB (+300%) |
| SRAM | 8 KB | 4 KB (-50%) | 16 KB (+100%) | 32 KB (+300%) |
| USB | USB 2.0 FS Device + Host | USB 2.0 FS Device + Host | USB 2.0 FS Device + Host | USB 2.0 FS Device + Host |
| ADC Resolution | 12-bit / 1 MSPS | 12-bit / 1 MSPS | 12-bit / 1 MSPS | 12-bit / 1 MSPS |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
Key Differentiators
- Balanced Flash/RAM in the SAM D21J family at lowest price point (vs ATSAMD21J15B-MU)
- Half the Flash capacity of the J17, identical silicon for cost savings (vs ATSAMD21J17B-MU)
- Industrial temperature rated, full SAM D21 feature set in 64-QFN (vs ATSAMD20J16A-MU)
Design Notes
The SAM D21 family operates from a single 1.62V to 3.63V rail on VDDIN; the internal voltage regulator generates the 1.2V core supply from VDDIN. Place a 1uF X7R decoupling capacitor as close as possible to each VDD/VDDIO pin pair. For USB applications, VDDIN must be at least 3.0V for reliable USB signaling, and a 10uF bulk capacitor on VBUS is recommended when powering from USB. Avoid switching the main supply below the BOD threshold without proper reset handling.
The 64-QFN package with EPAD provides the primary heat-dissipation path; solder the EPAD to a continuous ground copper pour of at least 25 mm^2 for best thermal performance. At 48MHz the SAM D21 typically dissipates under 30 mW, so the EPAD copper is more for electrical grounding than thermal relief, but it must not be left floating - an ungrounded EPAD can cause latch-up and erratic behavior under temperature stress.
Place the 32.768kHz crystal and its load capacitors within 5 mm of the XIN32/XOUT32 pins (PA00/PA01). Use short, symmetric traces and a ground guard ring for low-jitter RTC operation. The DFLL48M locking to this crystal provides USB-accurate 48MHz; long, asymmetric traces will increase cycle-to-cycle jitter and degrade USB compliance margins. Keep the 32kHz traces away from switching signals and DC-DC inductors.
Do not confuse the SAM D21J16B-MU (industrial temp, 64-QFN, Green/RoHS-compliant) with the J16B-AU (64-TQFP) or the J16A revision (earlier silicon with errata). The 'B' revision is required for the latest USB and SERCOM fixes. Also note that the SAMD21 SERCOM peripheral requires explicit pin-mux configuration in firmware - the default port pin assignments are NOT the same as the GPIO port letter; consult the SAM D21 datasheet pin-mux tables before assigning I2C or SPI signals.
Compliance Information
Green-compliant per Microchip product page; industrial temperature grade only (not AEC-Q100 qualified for automotive). Lead-free finish. RoHS and REACH compliant.
