ATSAMD21J15B-MU - 32KB Flash Cortex-M0+ MCU | Microchip
MPN: ATSAMD21J15B-MU ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.1 | $3.10 |
| 10 | $2.86 | $28.60 |
| 100 | $2.41 | $241.00 |
| 500 | $2.05 | $1,025.00 |
| 1,000 | $1.74 | $1,740.00 |
ATSAMD21J15B-MU Overview
A microcontroller (MCU) is a single-chip computer that combines a processor core, program memory (Flash), data memory (SRAM), and configurable peripherals on one die. Cortex-M0+ cores are the smallest, most energy-efficient members of the ARMv6-M family, positioned below Cortex-M4 in the ARM Cortex taxonomy (Cortex-M -> Cortex-M0/M0+ -> general-purpose MCU). MCUs hierarchically belong to: MCU -> microcontroller -> embedded processor -> semiconductor. The SAMD21J further extends this with Microchip's sleepwalking peripherals and SERCOM (Serial Communication Interface) modules that can run independently of the core.
Key features include up to six SERCOM interfaces for I2C/SPI/UART, a 12-bit 350 ksps ADC with up to 14 channels, a 10-bit 350 ksps DAC, three 24-bit timers/counters, two I2S interfaces, and a full-speed USB 2.0 device/host with on-chip transceiver. The device integrates a 48 MHz Digital Frequency Locked Loop (DFLL48M) and a 32.768 kHz low-power oscillator that can serve as reference for fractional PLLs (FDPLL) generating 48 MHz to 96 MHz. Power-on reset, brown-out detection, and an External Interrupt Controller with 16 channels and one non-maskable interrupt round out the housekeeping features.
Architecturally, the ATSAMD21J15B implements the Cortex-M0+ core with single-cycle multiplier, NVIC, and Microchip's standard SAM peripheral set including Event System for hardware-triggered peripheral-to-peripheral signaling without CPU intervention. The 32KB Flash variant is the smallest in the J-pin (64-pin) family, with code-compatible migration paths to J16/J17/J18 (64KB/128KB/256KB Flash). The 'B' silicon revision and 'F' revision designation denote incremental fixes that the SAM D21 family datasheet (DS40001882) documents.
Typical applications include IoT sensor nodes, USB HID/CDC devices, low-power wireless sensor hubs, industrial HMI panels, home automation controllers, and battery-powered wearables. The combination of Cortex-M0+ efficiency, USB, and rich analog makes the part especially attractive for any 64-pin industrial design that needs both USB device and precision ADC sampling in a single chip.
When designing with this part, choose the QFN package (-MU suffix) when PCB real-estate is critical and thermal performance via the exposed pad is acceptable; choose the TQFP (-AU) for hand-prototyping or where thermal vias or heat-sinking are impractical. Always enable the brown-out detector (BOD) at the lowest threshold the application tolerates and use the 32.768 kHz crystal with the FDPLL for jitter-sensitive USB or I2S streams.
This page synthesizes distributor pricing, parametric data, drop-in same-footprint alternatives, and design notes from the Microchip SAM D21/DA1 Family datasheet that are not assembled in one place in the manufacturer datasheet.
Drop-in alternatives for ATSAMD21J15B-MU — 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 ATSAMD21J15B-MU (same form factor and footprint) — differing in ADC, Package, USB, Operating Temperature, SRAM.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATSAMD21J16B-MU
✅ Drop-In✓ In Stock
$2.18 / Unit
View Datasheet →ATSAMD21J17D-MU
✅ Drop-In✓ In Stock
$2.21 / Unit
View Datasheet →ATSAMD21J18A-MU
✅ Drop-In📋 Reference alternative (not in catalog)
ATSAMD21J15B-MUT
✅ Drop-In✓ In Stock
$1.92 / Unit
View Datasheet →ATSAMD21J15B-MFT
✅ Drop-In✓ In Stock
$2.39 / Unit
View Datasheet →ATSAMD21J15B-MU Maximum Ratings & Electrical Characteristics
| Core | ARM Cortex-M0+ |
| Core Architecture | ARMv6-M, 32-bit |
| Maximum Clock Frequency | 48 MHz |
| CoreMark/MHz | 2.46 |
| Flash Program Memory | 32 KB |
| SRAM | 4 KB |
| Supply Voltage | 1.62 V to 3.63 V |
| Operating Temperature | -40 C to +85 C (industrial) |
| Package | 64-pin QFN (9x9 mm) with exposed pad |
| ADC | 12-bit, up to 350 ksps, up to 14 channels |
| DAC | 10-bit, 350 ksps, 1 channel |
| SERCOM Modules | Up to 6 (configurable as I2C/SPI/UART) |
| USB | USB 2.0 Full-Speed Device/Host with on-chip transceiver |
| Timers/Counters | Three 24-bit TC, one 16-bit TCC |
| I2S | 2 interfaces |
| External Interrupts | 16 channels plus 1 NMI |
| Debug Interface | Two-pin Serial Wire Debug (SWD) |
| RoHS Status | Compliant |
ATSAMD21J15B-MU Pin Configuration
| Pin 1 | PA00 — GPIO / XIN32 (32.768 kHz crystal input) |
| Pin 2 | PA01 — GPIO / XOUT32 (32.768 kHz crystal output) |
| Pin 3 | PA02 — GPIO / ADC AIN0 / DAC VOUT |
| Pin 4 | PA03 — GPIO / ADC AIN1 / VREFA |
| Pin 5 | GND — Ground |
| Pin 6 | VDD — I/O supply voltage |
| Pin 7 | PA04 — GPIO / ADC AIN2 / TC0 WO0 |
| Pin 8 | PA05 — GPIO / ADC AIN3 / TC0 WO1 |
| Pin 9 | PA06 — GPIO / ADC AIN4 / TC1 WO0 |
| Pin 10 | PA07 — GPIO / ADC AIN5 / TC1 WO1 |
| Pin 11 | PA08 — GPIO / ADC AIN6 / TC2 WO0 |
| Pin 12 | PA09 — GPIO / ADC AIN7 / TC2 WO1 |
| Pin 13 | PA10 — GPIO / ADC AIN8 / TCC0 WO0 |
| Pin 14 | PA11 — GPIO / ADC AIN9 / TCC0 WO1 |
| Pin 15 | GND — Ground |
| Pin 16 | VDD — I/O supply voltage |
| Pin 17 | PA12 — GPIO / SERCOM2 PAD0 / I2S FS0 |
| Pin 18 | PA13 — GPIO / SERCOM2 PAD1 / I2S MCK0 |
| Pin 19 | PA14 — GPIO / SERCOM2 PAD2 / I2S SCK0 |
| Pin 20 | PA15 — GPIO / SERCOM2 PAD3 / I2S SD0 |
| Pin 21 | PA16 — GPIO / SERCOM1 PAD0 / I2S SD1 |
| Pin 22 | PA17 — GPIO / SERCOM1 PAD1 / I2S SCK1 |
| Pin 23 | PA18 — GPIO / SERCOM1 PAD2 |
| Pin 24 | PA19 — GPIO / SERCOM1 PAD3 |
| Pin 25 | PA20 — GPIO / SERCOM5 PAD2 / TCC1 WO2 |
| Pin 26 | PA21 — GPIO / SERCOM5 PAD3 / TCC1 WO3 |
| Pin 27 | PA22 — GPIO / SERCOM3 PAD0 / TCC0 WO2 |
| Pin 28 | PA23 — GPIO / SERCOM3 PAD1 / TCC0 WO3 |
| Pin 29 | PA24 — GPIO / USB DM |
| Pin 30 | PA25 — GPIO / USB DP |
| Pin 31 | GND — Ground (USB shield reference) |
| Pin 32 | VBUS — USB VBUS detect input |
| Pin 33 | PA27 — GPIO |
| Pin 34 | GND — Ground |
| Pin 35 | VDD — I/O supply voltage |
| Pin 36 | RESETN — Reset (active low) |
| Pin 37 | PA30 — GPIO / SWD clock input |
| Pin 38 | PA31 — GPIO / SWD data I/O |
| Pin 39 | PB00 — GPIO |
| Pin 40 | PB01 — GPIO |
| Pin 41 | PB02 — GPIO / SERCOM5 PAD0 / TCC1 WO0 |
| Pin 42 | PB03 — GPIO / SERCOM5 PAD1 / TCC1 WO1 |
| Pin 43 | PB04 — GPIO / SERCOM3 PAD2 |
| Pin 44 | PB05 — GPIO / SERCOM3 PAD3 |
| Pin 45 | PB06 — GPIO / SERCOM0 PAD0 |
| Pin 46 | PB07 — GPIO / SERCOM0 PAD1 |
| Pin 47 | PB08 — GPIO / SERCOM4 PAD0 / TC3 WO0 |
| Pin 48 | PB09 — GPIO / SERCOM4 PAD1 / TC3 WO1 |
| Pin 49 | PB10 — GPIO / SERCOM4 PAD2 / TCC0 WO4 |
| Pin 50 | PB11 — GPIO / SERCOM4 PAD3 / TCC0 WO5 |
| Pin 51 | PB12 — GPIO / SERCOM4 PAD0 alt / TC4 WO0 |
| Pin 52 | PB13 — GPIO / SERCOM4 PAD1 alt / TC4 WO1 |
| Pin 53 | PB14 — GPIO / SERCOM4 PAD2 alt / TC5 WO0 |
| Pin 54 | PB15 — GPIO / SERCOM4 PAD3 alt / TC5 WO1 |
| Pin 55 | PB16 — GPIO / SERCOM5 PAD2 alt / TCC1 WO2 alt |
| Pin 56 | PB17 — GPIO / SERCOM5 PAD3 alt / TCC1 WO3 alt |
| Pin 57 | PB18 — GPIO / SERCOM5 PAD0 alt |
| Pin 58 | PB19 — GPIO / SERCOM5 PAD1 alt |
| Pin 59 | PB20 — GPIO / SERCOM3 PAD2 alt |
| Pin 60 | PB21 — GPIO / SERCOM3 PAD3 alt |
| Pin 61 | GND — Ground (core) |
| Pin 62 | VDDCORE — Internal core voltage (decoupling only) |
| Pin 63 | VSW — Voltage switch output |
| Pin 64 | VDDIN — Voltage regulator input |
Typical Applications
ATSAMD21J15B-MU is suitable for 6 applications: IoT Wireless Sensor Node, USB HID / CDC Device, Battery-Powered Wearable, Industrial HMI Control Panel, Smart Home Sensor Hub, Low-Cost Audio Playback Device.
IoT Wireless Sensor Node
The ATSAMD21J15B-MU fits IoT sensor hubs because its Cortex-M0+ core delivers 2.46 CoreMark/MHz while drawing only a few hundred microamps in active sleep mode. With 6 SERCOM channels, an SPI-connected radio (LoRa, Sub-GHz, or BLE module) can coexist with I2C sensors and a UART debug port. The 32 KB Flash is sufficient for over-the-air bootloader + application firmware. Power dissipation at 48 MHz / 3.3 V is roughly 7 mA active, enabling multi-year coin-cell operation when duty-cycled. The 12-bit ADC supports up to 14 channels for temperature, humidity, and motion sensing without an external mux.
Recommended
USB HID / CDC Device
The ATSAMD21J15B-MU's on-chip full-speed USB 2.0 transceiver eliminates the external PHY typical of competing parts, reducing BOM cost and PCB area. The 48 MHz Cortex-M0+ core handles USB polling plus HID report generation, while 4 KB SRAM buffers HID reports without data loss. The device can be enumerated as HID Keyboard, HID Mouse, CDC Serial, or Vendor class. The 32 KB Flash is sufficient for the USB stack plus application logic in TinyUSB or ASF. The exposed pad on the QFN-64 keeps junction temperature manageable under continuous USB traffic.
Recommended
Battery-Powered Wearable
The ATSAMD21J15B-MU is well-suited to wearables where Cortex-M0+ efficiency and SAM D21's sleep modes matter most. Sleep currents below 5 uA (deepest sleep with RTC running) extend battery life to weeks on a small Li-Po cell. The 12-bit ADC digitizes bioelectric signals (heart rate, galvanic skin response), and the 10-bit DAC drives a small audio cue or haptic waveform. The 64-pin QFN-64 (9x9 mm) is small enough for wristband PCBs. The integrated USB allows firmware updates and charging-logic communication without an extra chip.
Recommended
Industrial HMI Control Panel
Industrial HMI panels benefit from the ATSAMD21J15B-MU's 14 ADC channels for reading analog sensors (pressure, flow, level), 6 SERCOM channels for multiple RS-485 / UART field-bus connections, and a deterministic 48 MHz Cortex-M0+ for scan loops. The -40 C to +85 C industrial temperature rating and brown-out detector suit factory-floor environments. The 32 KB Flash supports Modbus RTU stack plus a small LVGL or custom UI loop, while 4 KB SRAM holds framebuffer rows for a small graphic LCD.
Recommended
Smart Home Sensor Hub
Smart-home sensor hubs combine Wi-Fi/BLE via an attached module, multiple wired sensors, and a control output (relay or triac). The ATSAMD21J15B-MU's 6 SERCOM channels can drive an SPI Wi-Fi module (e.g., ATWINC1500), a UART BLE module, and several I2C sensors (light, temperature, motion). The hardware Event System allows GPIO-triggered wake-ups without CPU intervention, reducing system latency. The 64-pin QFN exposes enough GPIO for relay drivers and rotary-encoder inputs typical of wall-mounted thermostats and security panels.
Recommended
Low-Cost Audio Playback Device
I2S playback from a small Flash-based audio file is feasible on the ATSAMD21J15B-MU: the two I2S interfaces connect to an external DAC (e.g., PCM5102A) without glue logic. The 32 KB Flash can hold the application code while a serial Flash holds compressed audio samples. The 10-bit internal DAC is sufficient for low-fidelity tones or click-track generation. The 48 MHz Cortex-M0+ can decode ADPCM or basic WAV streams in real time at 16 kHz sample rate without glitching.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21J15B-MU — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21J16B-MU | ATSAMD21J17D-MU | ATSAMD21J18A-MU | ATSAMD21J15B-MUT | ATSAMD21J15B-MFT |
|---|---|---|---|---|---|---|
| Package | 64-QFN (9x9 mm) | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same | 64-QFN (9x9 mm) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Core | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ | ARM Cortex-M0+ |
| Maximum Clock Frequency | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz |
| Flash | 32 KB | 64 KB | 128 KB | 256 KB | 32 KB | 32 KB |
| SRAM | 4 KB | 8 KB | 16 KB | 32 KB | 4 KB | 4 KB |
| USB 2.0 Transceiver | Yes (on-chip) | Yes | Yes | Yes | Yes | Yes |
| SERCOM Modules | 6 | 6 | 6 | 6 | 6 | 6 |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C (AEC-Q100 qualified) |
Key Differentiators
- On-chip full-speed USB 2.0 transceiver (vs ATSAMD20J15A-MU)
- 6 SERCOM modules vs fixed peripheral pins (vs STM32L0x2 Cortex-M0+ parts)
- Event System for zero-CPU peripheral signaling (vs Generic Cortex-M0+ MCUs)
Design Notes
Estimated: at 48 MHz / 3.3 V the Cortex-M0+ core consumes about 7 mA active. Decoupling per the SAM D21/DA1 family datasheet: place a 100 nF X7R ceramic close to each VDD pin, plus a 4.7 uF bulk capacitor on the VDDIN pin. The internal voltage regulator (LDO) requires an external 1 uF on VDDCORE. Use the brown-out detector (BOD) with threshold 33 (3.3 V) to safely reset the MCU on supply dips.
The QFN-64 exposed thermal pad (EP) MUST be soldered to a copper pad of at least the same area as the EP itself, with thermal vias (typically 0.3 mm drill, 0.6 mm pitch, 9 vias) to an inner ground plane. The QFN-64 has 0.5 mm pitch pads - use NSMD (non-solder mask defined) pads with 0.27 mm width for reliable stencil printing. Keep high-speed signals (USB DP/DM) matched within 150 mils and route over a continuous ground reference.
Do not leave any GPIO floating - unused inputs must be configured as outputs or pulled to VDD/GND via internal pull-up/down to avoid shoot-through current. The 32.768 kHz crystal must have NPO dielectric load capacitors matched to its specified load (typically 7 pF or 12.5 pF). Do not exceed VDD = 3.63 V (the absolute maximum is 3.8 V). When using the FDPLL96M, configure the reference to be 32.768 kHz; do not feed it the 48 MHz DFLL output as the PLL reference.
Compliance Information
RoHS and REACH compliant per Microchip product page. Industrial grade -40C to +85C. For automotive AEC-Q100 qualification, choose ATSAMD21J15B-MFT in the same QFN-64 footprint.
