ATSAML21E15B-AUT - 32KB Flash Cortex-M0+ MCU | Microchip
MPN: ATSAML21E15B-AUT ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.62 | $4.62 |
| 10 | $4.16 | $41.60 |
| 100 | $3.71 | $371.00 |
| 500 | $3.35 | $1,675.00 |
| 1,000 | $2.98 | $2,980.00 |
ATSAML21E15B-AUT Overview
A microcontroller (MCU) is a single-chip computer that integrates a CPU core, volatile and non-volatile memory, and programmable I/O peripherals. The ARM Cortex-M0+ is an ultra-low-power 32-bit core optimized for embedded systems, widely used in IoT endpoints, wearable electronics, and sensor hubs. Within the SAM L21 family hierarchy, ATSAML21E15B sits between lower-pin-count SAM L10 devices and higher-memory SAM L21G/J variants, balancing I/O count (32-pin TQFP) with low-power features.
Key features of the ATSAML21E15B-AUT include a 12-channel 12-bit ADC with up to 1 MSPS sampling, configurable SERCOM modules that operate as UART, SPI, or I2C, an on-chip temperature sensor, and full-speed USB device support. The integrated Power Management Unit (PMU) enables multiple SleepWalking standby modes that allow peripherals to wake the CPU only on relevant events. The device operates from a 1.62V to 3.63V supply, supporting direct connection to single-cell Li-ion or two AA cells.
Typical applications include wearable fitness trackers, IoT sensor nodes, low-power wireless modules, smart thermostats, and battery-powered industrial sensors. The combination of Cortex-M0+ processing power and sub-microamp Sleep current makes this MCU ideal for designs where battery life spans years rather than weeks. Engineers should leverage the Peripheral Touch Controller and Event System to minimize CPU wake-up events and maximize energy efficiency.
Drop-in alternatives for ATSAML21E15B-AUT — 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 ATSAML21E15B-AUT (same form factor and footprint) — differing in ADC, Package, Active Current, Core, Flash Memory.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATSAML21E16B-AUT
✅ Drop-In✓ In Stock
$2.65 / Unit
View Datasheet →ATSAML21E15B-MUT
✅ Drop-In✓ In Stock
$2.2 / Unit
View Datasheet →ATSAML21E15B-ANT
✅ Drop-In📋 Reference alternative (not in catalog)
ATSAML21E17B-AUT
✅ Drop-In📋 Reference alternative (not in catalog)
ATSAML11E15A-AUT
✅ Drop-In✓ In Stock
$2.07 / Unit
View Datasheet →ATSAML10E15A-AUT
✅ Drop-In📋 Reference alternative (not in catalog)
ATSAML21E15B-AUT Maximum Ratings & Electrical Characteristics
| Core Architecture | ARM Cortex-M0+ |
| Core Bit Width | 32-bit |
| Maximum CPU Clock | 48 MHz |
| Flash Memory | 32 KB (32K x 8) |
| SRAM | 4 KB |
| Package | 32-pin TQFP (7x7 mm) |
| Operating Voltage Range | 1.62 V to 3.63 V |
| Active Mode Current | < 35 µA/MHz |
| Sleep Mode Current | 200 nA |
| ADC | 12-bit, up to 1 MSPS |
| SERCOM Modules | 6 (configurable UART/SPI/I2C) |
| Operating Temperature Range | -40 °C to +85 °C (AUT grade) |
| Mounting Type | Surface Mount |
| MSL Level | 3 (168 hours) |
| RoHS Status | Compliant |
| Lead-Free | Yes |
| AEC-Q100 Qualification | Not qualified (AUT grade is industrial extended temperature) |
ATSAML21E15B-AUT Pin Configuration
| Pin 1 | PA00 — General purpose I/O / SERCOM1[0] |
| Pin 2 | PA01 — General purpose I/O / SERCOM1[1] |
| Pin 3 | PA02 — General purpose I/O / AIN[0] / VOUT |
| Pin 4 | PA03 — General purpose I/O / AIN[1] / VREFA |
| Pin 5 | GND — Ground |
| Pin 6 | VDD — Digital supply voltage |
| Pin 7 | PA04 — General purpose I/O / SERCOM0[0] / TC0[0] |
| Pin 8 | PA05 — General purpose I/O / SERCOM0[1] / TC0[1] |
| Pin 9 | PA06 — General purpose I/O / SERCOM0[2] / TC1[0] |
| Pin 10 | PA07 — General purpose I/O / SERCOM0[3] / TC1[1] |
| Pin 11 | PA08 — General purpose I/O / SERCOM2[0] / TC2[0] |
| Pin 12 | PA09 — General purpose I/O / SERCOM2[1] / TC2[1] |
| Pin 13 | PA10 — General purpose I/O / SERCOM2[2] / TCC0[0] |
| Pin 14 | PA11 — General purpose I/O / SERCOM2[3] / TCC0[1] |
| Pin 15 | GND — Ground |
| Pin 16 | VDD — Digital supply voltage |
| Pin 17 | PA14 — General purpose I/O / SERCOM4[2] / TCC0[4] |
| Pin 18 | PA15 — General purpose I/O / SERCOM4[3] / TCC0[5] |
| Pin 19 | PA16 — General purpose I/O / SERCOM3[0] / TCC1[0] |
| Pin 20 | PA17 — General purpose I/O / SERCOM3[1] / TCC1[1] |
| Pin 21 | PA18 — General purpose I/O / SERCOM3[2] / TCC1[2] |
| Pin 22 | PA19 — General purpose I/O / SERCOM3[3] / TCC1[3] |
| Pin 23 | PA20 — General purpose I/O / SERCOM5[2] / TCC0[6] |
| Pin 24 | PA21 — General purpose I/O / SERCOM5[3] / TCC0[7] |
| Pin 25 | PA22 — General purpose I/O / SERCOM5[0] / TC4[0] |
| Pin 26 | PA23 — General purpose I/O / SERCOM5[1] / TC4[1] |
| Pin 27 | PA24 — USB_DM / General purpose I/O |
| Pin 28 | PA25 — USB_DP / General purpose I/O |
| Pin 29 | RESET — Reset input, active low |
| Pin 30 | AVDD — Analog supply voltage |
| Pin 31 | GND — Ground |
| Pin 32 | PA27 — General purpose I/O / SERCOM1[3] |
Typical Applications
ATSAML21E15B-AUT is suitable for 6 applications: Battery-Powered IoT Sensor Node, Wearable Fitness Tracker, Smart Home Thermostat, Industrial Wireless Sensor Module, USB-Powered Data Logger, Low-Power BLE Beacon.
Battery-Powered IoT Sensor Node
The ATSAML21E15B-AUT is an ideal main controller for battery-powered IoT sensor nodes transmitting temperature, humidity, or motion data over LoRaWAN, BLE, or Sub-GHz radios. Its 35 µA/MHz active current at 48 MHz and 200 nA Sleep current with full SRAM retention enable multi-year battery life on 2x AA cells or coin-cell batteries when paired with a 1-2% duty cycle. The 6 SERCOM modules allow simultaneous SPI connection to a sensor frontend, I2C bus to a digital sensor, and UART link to a wireless module. The integrated 12-bit ADC and on-chip op-amps can directly interface analog sensors (thermistors, electrochemical gas cells) without external signal conditioning. Engineers should configure SleepWalking peripherals so the ADC or RTC triggers wake-up only on threshold-crossing events, keeping the CPU in Standby mode for 99% of the duty cycle.
Recommended
Wearable Fitness Tracker
The ATSAML21E15B-AUT suits wearable fitness tracker designs where compact 7x7 mm TQFP footprint, sub-100 µA average system current, and integrated USB device support streamline the bill of materials. The Cortex-M0+ core at 48 MHz runs BLE stack, heart-rate sensor algorithms (PPG), and step-counter firmware concurrently. The integrated 12-bit ADC samples PPG photodiode signals at 100 Hz with DMA-driven SleepWalking, waking the CPU only at every 10th sample for FFT-based heart-rate variability calculation. Full-speed USB device support enables direct charging and data sync without an external USB controller, reducing BOM cost by $0.50-$1.00 versus discrete USB solutions.
Recommended
Smart Home Thermostat
The ATSAML21E15B-AUT integrates an ARM Cortex-M0+ core with 32KB Flash, 12-bit ADC, and on-chip op-amps to drive a wall-mounted thermostat's temperature sensing, relay control, and Wi-Fi/BLE link to a home automation hub. Operating from a 24VAC transformer-rectified supply (after an external LDO to 3.3V), the MCU samples thermistor temperature at 1 Hz, runs PID control to drive a relay or 0-10V actuator, and maintains a TFT display. The 6 SERCOM interfaces allow SPI connection to an ESP32 Wi-Fi co-processor, I2C bus to a CO2 sensor and EEPROM, and UART link to the TFT controller. At <35 µA/MHz active, the MCU draws approximately 1.7 mA at 48 MHz - acceptable for line-powered designs where standby current is dominated by the relay coil driver circuit.
Recommended
Industrial Wireless Sensor Module
In Industrial IoT (IIoT) wireless sensor modules, the ATSAML21E15B-AUT's wide 1.62-3.63V operating voltage, -40 °C to +85 °C industrial temperature range, and 32KB Flash enable condition monitoring of motors, pumps, and bearings on factory floors. The MCU reads vibration data from an external MEMS accelerometer over SPI, performs on-chip FFT for spectral analysis, and transmits alerts via Sub-GHz wireless (868/915 MHz) when anomaly thresholds are crossed. The integrated 12-bit ADC samples analog 4-20 mA loop signals from legacy industrial sensors without external signal conditioning, while the Event System routes sensor triggers to timer captures without CPU intervention. Engineers can leverage the SAM L21 SleepWalking mode to run vibration sampling for 100 ms every 10 minutes while maintaining average current under 50 µA - sufficient for 5+ year battery life on industrial-grade lithium cells.
Recommended
USB-Powered Data Logger
USB-powered data loggers for environmental monitoring, medical diagnostics, or asset tracking benefit from the ATSAML21E15B-AUT's integrated full-speed USB device controller, 32KB Flash for firmware, and on-chip 12-bit ADC. The MCU presents as a USB CDC virtual COM port to the host PC, enabling real-time data streaming and configuration via standard serial terminal applications. The integrated 3.3V LDO (when sourced from VBUS through a 5V-to-3.3V regulator) can supply 50 mA to external sensors, eliminating the need for a separate power management IC. With 32KB Flash and 4KB SRAM, the firmware can buffer 2000+ 12-bit ADC samples in RAM for high-speed burst logging to host. Operating at 48 MHz, the MCU consumes approximately 1.7 mA active - within USB 2.0 bus-powered device limits (100 mA unit load).
Recommended
Low-Power BLE Beacon
BLE beacon designs for asset tracking, indoor positioning, or retail proximity marketing benefit from the ATSAML21E15B-AUT's 200 nA Sleep current and Cortex-M0+ efficiency, even when paired with an external BLE module. The MCU wakes from Sleep every 100-1000 ms to update beacon payload data (sensor readings, battery voltage) and triggers a BLE advertisement burst via a GPIO pulse to the BLE module's TX_EN pin, then immediately returns to Sleep. Average system current stays under 20 µA - achieving 6+ months of battery life on a CR2032 coin cell. The 32KB Flash accommodates custom beacon firmware (iBeacon, Eddystone, or proprietary formats), and 4KB SRAM buffers the advertisement packet assembly without external memory.
Recommended
Recommended Products Summary
Engineering reference data for ATSAML21E15B-AUT — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAML21E16B-AUT | ATSAML21E15B-MUT | ATSAML21E15B-ANT | ATSAML21E17B-AUT | ATSAML11E15A-AUT | ATSAML10E15A-AUT |
|---|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 32-TQFP (7x7 mm) | 32-TQFP (7x7 mm) - same | 32-TQFP (7x7 mm) - same | 32-TQFP (7x7 mm) - same | 32-TQFP (7x7 mm) - same | 32-TQFP (7x7 mm) - same | 32-TQFP (7x7 mm) - same |
| Flash Memory | 32 KB | 64 KB | 32 KB | 32 KB | 128 KB | 16 KB | 16 KB |
| SRAM | 4 KB | 8 KB | 4 KB | 4 KB | 8 KB | 4 KB | 4 KB |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +125 °C (AEC-Q100) | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C |
| SERCOM Instances | 6 | 6 | 6 | 6 | 6 | 6 | 4 |
| TrustZone-M Security | No | No | No | No | No | Yes | No |
| AEC-Q100 Qualified | No (AUT grade) | No | Yes | No | No | No | No |
Key Differentiators
- Lowest-cost SAM L21 variant with full USB 2.0 device support (vs ATSAML21E16B-AUT)
- Industrial extended temperature, not automotive qualified (vs ATSAML21E15B-MUT)
- Higher SERCOM count than SAM L10 family (vs ATSAML10E15A-AUT)
Design Notes
Decouple VDD and AVDD separately with 100 nF X7R ceramic capacitors placed within 3 mm of each supply pin, plus a 4.7 µF bulk capacitor on VDD. The SAM L21 internal 1.2V core LDO is supplied from VDD and requires bulk capacitance to maintain regulation during Sleep-Wake transitions. According to the Microchip datasheet, AVDD (analog supply) must be decoupled from VDD through a ferrite bead or 10 Ω resistor when ADC accuracy below 1 LSB is required - bypassing AVDD directly to VDD introduces digital switching noise into the ADC reference.
Do not leave unused SERCOM pins floating when the SERCOM module is enabled - configure them as GPIO outputs driven low in the PORT register to avoid parasitic current draw (typically 5-20 µA per floating pin). The SAM L21 datasheet specifies that pins configured as analog inputs (AIN) require explicit PORT->Group[port].PINCFG[n].INEN = 0 setting to disable the digital input buffer, otherwise input leakage current exceeds 1 µA per pin. When migrating from SAM L10/L11 designs, verify that SERCOM channel-to-pin mapping matches - the L21 family uses a different peripheral multiplexing scheme.
For 32-pin TQFP (7x7 mm) PCB layout, route all GPIO and SERCOM traces on the top layer with continuous reference plane on layer 2. Maintain 50 Ω characteristic impedance for USB D+/D- differential pair with 90 Ω differential impedance, using 0.20 mm trace width and 0.15 mm spacing on 0.20 mm dielectric. Place the 12 MHz crystal (or 32.768 kHz crystal for RTC) within 5 mm of XIN/XOUT pins with grounded guard ring. The Microchip SAM L21 hardware design checklist recommends 4-layer stackup (signal-GND-power-signal) for designs with USB or high-speed SERCOM.
Compliance Information
AUT suffix indicates industrial extended temperature grade, not automotive. RoHS compliant per Microchip material declaration. AEC-Q100 qualified variants available with -MUT suffix. MSL Level 3 (168 hours floor life) per JEDEC J-STD-020.
