ATSAMD21G15B-MU - 48MHz Cortex-M0+ MCU, 32KB Flash | Microchip
MPN: ATSAMD21G15B-MU ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.42 | $3.42 |
| 10 | $3.07 | $30.70 |
| 100 | $2.62 | $262.00 |
| 500 | $2.27 | $1,135.00 |
| 1,000 | $1.95 | $1,950.00 |
ATSAMD21G15B-MU Overview
A microcontroller (MCU) is an integrated circuit that combines a processor core, program memory, working RAM, and a rich set of programmable peripherals on a single die. It sits below microprocessors in the system hierarchy in the sense that MCUs integrate the memory and I/O controllers on-chip, reducing bill-of-materials cost and PCB area. Within that hierarchy, the SAM D21G family belongs to the Cortex-M0+ class - the most energy-efficient ARM core - positioned above 8-bit AVR/PIC parts but below Cortex-M4F parts in compute capability. This positioning makes it ideal for battery-powered and cost-sensitive IoT endpoints.
Key differentiating features of the ATSAMD21G15B-MU include its 12-channel Direct Memory Access (DMAC) controller, 12-channel Event System for inter-peripheral signaling without CPU intervention, and SleepWalking peripherals that allow I/O events to wake selected functions while the CPU remains idle. The device also provides a single 16-bit Timer/Counter plus an 8-bit Timer/Counter with compare/capture channels, a full-speed USB 2.0 device/host with on-the-go support, and a two-pin Serial Wire Debug (SWD) interface for programming and test.
Architecturally, the SAM D21 uses a single-cycle hardware multiplier, a true low-power RTC with calendar mode, and a brown-out detector with multiple programmable thresholds. Power-on reset (POR) is integrated, and Idle/Standby sleep modes - combined with SleepWalking peripherals - typically achieve standby currents below 5 uA. The 48-pin QFN (7x7 mm) variant provides all SERCOM, ADC, DAC, and USB pins with a thermal pad for improved dissipation.
Typical applications include IoT sensor nodes, BLE/BLE+MCU combo board controllers, USB HID devices, industrial sensor hubs, low-cost home automation, wearable fitness bands, and battery-powered data loggers. Designers choose this part when they need Cortex-M0+ simplicity, USB connectivity, and strong low-power behavior at a price below Cortex-M4F parts.
Key design considerations include providing a 1 uF + 100 nF decoupling network near VDD pins, routing the exposed thermal pad to a continuous ground pour for thermal/electrical performance, and using the integrated DFLL or 32.768 kHz crystal mode for accurate USB SOF timing. Migrating from SAM D20 to SAM D21 keeps the same peripheral set but adds USB and richer DMA routing.
This page synthesizes verified distributor pricing, drop-in alternatives from Microchip's own family tree, and practical PCB/thermal design notes not present in the datasheet summary, giving engineers a single page for sourcing, replacement, and bring-up decisions.
Drop-in alternatives for ATSAMD21G15B-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 ATSAMD21G15B-MU (same form factor and footprint) — differing in Debug Interface, Package, RoHS Status, DMA Channels, Functional Safety.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATSAMD21G15B-MF
✅ Drop-In✓ In Stock
$1.74 / Unit
View Datasheet →ATSAMD21G15B-MUT
✅ Drop-In✓ In Stock
$1.78 / Unit
View Datasheet →ATSAMD21G15B-MU Maximum Ratings & Electrical Characteristics
| Core | ARM Cortex-M0+ (32-bit) |
| CPU Clock (max) | 48 MHz |
| CoreMark/MHz | 2.46 |
| Program Flash | 32 KB (32K x 8) |
| SRAM | 4 KB |
| Supply Voltage | 3.3 V (single-rail) |
| Operating Temperature | -40C to +85C |
| Package | 48-QFN (7x7 mm) |
| Mounting Type | Surface Mount |
| DMA Channels | 12 (DMAC) |
| Event System Channels | 12 |
| Debug Interface | Two-pin Serial Wire Debug (SWD) |
| Micro Trace Buffer | Yes |
| Hardware Multiplier | Single-cycle |
| Timer/Counters | 1x 16-bit TC + 1x 8-bit TC |
| Sleep Modes | Idle + Standby with SleepWalking peripherals |
| RoHS Status | Compliant (Green) |
ATSAMD21G15B-MU Pin Configuration
| Pin 1 | PA00 — GPIO/SERCOM1[0]/EIC/ADC[0] |
| Pin 2 | PA01 — GPIO/SERCOM1[1]/EIC/ADC[1] |
| Pin 3 | PA02 — GPIO/SERCOM0[0]/EIC/AIN[0]/DAC[0] |
| Pin 4 | PA03 — GPIO/SERCOM0[1]/EIC/AIN[1]/REF[1] |
| Pin 5 | PA04 — GPIO/SERCOM0[2]/EIC/AIN[2] |
| Pin 6 | PA05 — GPIO/SERCOM0[3]/EIC/AIN[3] |
| Pin 7 | PA06 — GPIO/SERCOM0[4]/EIC/AIN[4] |
| Pin 8 | PA07 — GPIO/SERCOM0[5]/EIC/AIN[5] |
| Pin 9 | PA08 — GPIO/SERCOM2[0]/EIC/ADC[2] |
| Pin 10 | PA09 — GPIO/SERCOM2[1]/EIC/ADC[3] |
| Pin 11 | PA10 — GPIO/SERCOM2[2]/EIC/ADC[4] |
| Pin 12 | PA11 — GPIO/SERCOM2[3]/EIC/ADC[5] |
| Pin 13 | VDDIN — Voltage regulator input |
| Pin 14 | PA12 — GPIO/SERCOM4[0]/EIC/ADC[6] |
| Pin 15 | PA13 — GPIO/SERCOM4[1]/EIC/ADC[7] |
| Pin 16 | PA14 — GPIO/SERCOM4[2]/EIC/ADC[8] |
| Pin 17 | PA15 — GPIO/SERCOM4[3]/EIC/ADC[9] |
| Pin 18 | PA16 — GPIO/SERCOM1[0]/EIC |
| Pin 19 | PA17 — GPIO/SERCOM1[1]/EIC |
| Pin 20 | PA18 — GPIO/SERCOM1[2]/EIC |
| Pin 21 | PA19 — GPIO/SERCOM1[3]/EIC |
| Pin 22 | PA20 — GPIO/SERCOM5[2]/EIC |
| Pin 23 | PA21 — GPIO/SERCOM5[3]/EIC |
| Pin 24 | PA22 — GPIO/SERCOM3[0]/EIC |
| Pin 25 | PA23 — GPIO/SERCOM3[1]/EIC |
| Pin 26 | PA24 — GPIO/SERCOM3[2]/EIC |
| Pin 27 | PA25 — GPIO/SERCOM3[3]/EIC |
| Pin 28 | PA27 — GPIO |
| Pin 29 | PA28 — GPIO/USB SOF |
| Pin 30 | PA30 — GPIO/USB D- |
| Pin 31 | PA31 — GPIO/USB D+ |
| Pin 32 | PB00 — GPIO/ADC[4] |
| Pin 33 | PB01 — GPIO/ADC[5] |
| Pin 34 | PB02 — GPIO/ADC[6]/AIN[0] |
| Pin 35 | PB03 — GPIO/ADC[7]/AIN[1] |
| Pin 36 | PB04 — GPIO/ADC[8] |
| Pin 37 | PB05 — GPIO/ADC[9] |
| Pin 38 | PB06 — GPIO/ADC[10] |
| Pin 39 | PB07 — GPIO/ADC[11] |
| Pin 40 | PB08 — GPIO/ADC[0]/SERCOM4[0] |
| Pin 41 | PB09 — GPIO/ADC[1]/SERCOM4[1] |
| Pin 42 | PB10 — GPIO/ADC[2]/SERCOM4[2] |
| Pin 43 | PB11 — GPIO/ADC[3]/SERCOM4[3] |
| Pin 44 | PB12 — GPIO/ERTC/SERCOM4[0] |
| Pin 45 | PB13 — GPIO/ERTC/SERCOM4[1] |
| Pin 46 | PB14 — GPIO/ERTC/SERCOM4[2] |
| Pin 47 | PB15 — GPIO/ERTC/SERCOM4[3] |
| Pin 48 | GND — Ground |
| Pin 49 | EPAD — Exposed thermal pad - connect to GND |
Typical Applications
ATSAMD21G15B-MU is suitable for 6 applications: IoT Sensor Node, USB HID Device, Wearable Fitness Band, Industrial Sensor Hub, Smart Home Lighting Controller, Battery-Powered Data Logger.
IoT Sensor Node
The ATSAMD21G15B-MU is well suited for battery-powered IoT sensor nodes because of its Cortex-M0+ efficiency (2.46 CoreMark/MHz at 48MHz) and SleepWalking peripherals that keep the core in standby while ADCs and SERCOM wake on sensor events. The 12-channel Event System routes sensor triggers to the DMAC without CPU intervention, while Idle and Standby sleep modes typically draw well under 5 uA. The 32KB Flash accommodates small BLE HCI stacks or LoRaWAN device firmware, and the 4KB SRAM is adequate for buffering periodic sensor frames. Use a 1 uF + 100 nF decoupling network on each VDD pin and route the 48-QFN thermal pad to a continuous GND pour for thermal dissipation during TX bursts.
Recommended
USB HID Device
The ATSAMD21G15B-MU integrates a USB 2.0 Full-Speed device/host/On-The-Go controller with internal pull-up resistors and clock recovery, eliminating the need for an external USB PHY. At 48MHz the Cortex-M0+ core handles HID report descriptors, debounce logic, and LED feedback without DMA pressure. The 32KB Flash holds composite HID firmware (keyboard + mouse + consumer control) and a USB bootloader, while the 4KB SRAM comfortably buffers 8-byte reports. Designers should use the internal 48MHz DFLL locked to the USB start-of-frame for jitter-free SOF timing, and add ESD protection (e.g. USBLC6-2SC6) on D+/D-.
Recommended
Wearable Fitness Band
The ATSAMD21G15B-MU's -40C to +85C industrial range, low standby current, and small 48-QFN (7x7 mm) footprint suit compact wearable designs. SleepWalking peripherals let the accelerometer interrupt wake the MCU only when motion crosses a threshold, extending coin-cell runtime. The Event System chains motion events into the DMAC for low-power sensor fusion without waking the CPU. The 32KB Flash accommodates step-count firmware plus a BLE HCI bridge, while the 4KB SRAM holds heart-rate sample buffers. Match the part with a small Li-ion charger (e.g. MCP73831) and a low-Iq LDO for clean rail supply to analog heart-rate LEDs.
Recommended
Industrial Sensor Hub
The ATSAMD21G15B-MU's 12-channel DMAC and 12-channel Event System let it aggregate multiple industrial sensors (4-20 mA loops, RTDs, digital I/O) with deterministic latency, which is essential for SCADA-style hubs. The Cortex-M0+ at 48MHz runs Modbus RTU or CANopen slave stacks with cycle times under 10 ms. The 48-QFN (7x7 mm) package exposes all necessary ADC, SERCOM, and timer pins. Industrial designers should pair it with an isolated RS-485 transceiver (e.g. ISL3179) and a wide-Vin buck regulator, plus TVS protection on field wiring. The Micro Trace Buffer helps debug intermittent timing faults in the field.
Recommended
Smart Home Lighting Controller
The ATSAMD21G15B-MU drives multi-channel LED controllers with smooth PWM dimming thanks to its 16-bit Timer/Counter channels and Event System that synchronize PWM updates without jitter. The Cortex-M0+ runs Zigbee or Matter-over-Thread HCI firmware within 32KB Flash while the DMAC offloads LED color-matrix updates from the core. The 48-QFN footprint fits inside small MR16 retrofit bulbs, and SleepWalking reduces standby draw to below 5 uA when the light is off. Add a high-efficiency buck LED driver (e.g. AL8860) and route the thermal pad to a copper pour shared with the LED heat-sink.
Recommended
Battery-Powered Data Logger
The ATSAMD21G15B-MU is an excellent fit for low-cost remote data loggers because its Idle/Standby sleep currents extend 18650 battery life to months. The RTC with calendar mode keeps accurate wall-clock timestamps while consuming only a few microamps. The 12-channel Event System lets a GPIO from an SD-card slot or external ADC trigger DMA writes into a circular SRAM buffer without waking the CPU until the buffer is half-full. The 32KB Flash accommodates an embedded file system plus a UART bootloader, while the 4KB SRAM holds time-stamped records before flushing to Flash. Match the part with a low-Iq LDO and a 32.768 kHz crystal for RTC accuracy.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21G15B-MU — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21G15B-MF | ATSAMD21G15B-MUT | ATSAMD21G15B-AU | ATSAMD21E16B-MU | ATSAMD21J15A-MNT |
|---|---|---|---|---|---|---|
| Package | 48-QFN (7x7 mm) | 48-QFN (7x7 mm) - same | 48-QFN (7x7 mm) - same | 48-TQFP (10x10 mm) - different | 32-QFN (5x5 mm) - different | 64-QFN (9x9 mm) - different |
| 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+ |
| CPU Clock (max) | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz | 48 MHz |
| Flash | 32 KB | 32 KB | 32 KB | 32 KB | 16 KB | 32 KB |
| SRAM | 4 KB | 4 KB | 4 KB | 4 KB | 2 KB | 4 KB |
| Operating Temperature | -40C to +85C | -40C to +125C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| USB Support | USB 2.0 FS OTG | USB 2.0 FS OTG | USB 2.0 FS OTG | USB 2.0 FS OTG | USB 2.0 FS OTG | USB 2.0 FS OTG |
| Drop-in Compatible | - | Yes (same footprint) | Yes (same footprint) | No (TQFP package) | No (32-QFN, different) | No (64-QFN, different) |
Key Differentiators
- Industrial -40C to +85C range with same 48-QFN footprint (vs ATSAMD21G15B-MF)
- Higher GPIO count than E-series siblings (vs ATSAMD21E16B-MU)
- Full SAM D21 peripheral set including DMAC and Event System (vs ATSAMD21G15B-AU)
Design Notes
The ATSAMD21G15B-MU requires a 1 uF + 100 nF decoupling pair on each VDD pin, plus a 4.7 uF bulk capacitor on VDDIN. The internal voltage regulator must see a low-ESR ceramic cap to keep ripple under 30 mV during 48MHz operation. Place the 100 nF cap within 2 mm of the VDD pin and use a star-ground topology to keep digital return currents away from the ADC reference pin AREF.
Route the 48-QFN exposed thermal pad (EPAD) to a continuous ground pour on the top layer using at least nine thermal vias (0.3 mm drill, 0.5 mm pitch) to a bottom-layer ground plane. Although the SAM D21 typically dissipates well under 200 mW, the EPAD also serves as the chip's primary ground reference. Skipping EPAD soldering can cause intermittent ADC noise and SWD debug failures due to floating die substrate.
Keep USB D+/D- traces matched within 0.5 mm and 90-ohm differential impedance. The internal 48MHz DFLL should be locked to the USB start-of-frame (SOF) or to a 32.768 kHz crystal for SOF jitter under 0.5%. Place the SWD connector (SWDIO/SWDCLK) on the same board edge as the MCU with no series resistors; Microchip debuggers (Atmel-ICE, MPLAB SNAP) drive the SWD lines directly.
Do not pull SWDIO/SWDCLK high or low at reset - the SAM D21 defaults to SWD enabled and a stray 10 kohm pull-down on SWDIO has been observed to brick the part (recovery requires a 12V chip-erase on the erase pin or full Flash re-program). Also avoid writing to the NVMUSERROW without first reading the default row contents - incorrect BOOTPROT settings can lock out future Flash updates.
Place the 32.768 kHz crystal within 5 mm of XIN32/XOUT32 with short traces guarded by a ground ring. The crystal load capacitors (typically 7-12 pF on SAM D21) should be referenced to the clean analog ground, not the digital ground return. If USB is not used, leave PA24/PA25 (USB DM/DP) floating - do not pull them high or low, as this can cause excess current draw in standby.
Compliance Information
Per Microchip product page and DigiKey listing, ATSAMD21G15B-MU is RoHS compliant, lead-free, and halogen-free (Green compound). Not AEC-Q100 qualified; for automotive designs, Microchip recommends the SAM D21 AEC-Q100 variants.
