ATSAMD21E16B-UUTB4 - 48MHz Cortex-M0+ MCU, 64KB Flash | WLCSP-32
MPN: ATSAMD21E16B-UUTB4 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.95 | $3.95 |
| 10 | $3.55 | $35.50 |
| 100 | $3.05 | $305.00 |
| 500 | $2.62 | $1,310.00 |
| 1,000 | $2.28 | $2,280.00 |
ATSAMD21E16B-UUTB4 Overview
An ARM Cortex-M0+ MCU is a 32-bit microcontroller built on the ARMv6-M architecture, optimized for energy efficiency and deterministic interrupt response. The Cortex-M0+ sits within the broader hierarchy: microcontroller -> embedded processor -> system-on-chip -> semiconductor. It targets battery-powered IoT, sensor hubs, and wearable applications where a balance of compute throughput and low active/idle current is critical.
Key features include 64 KB Flash, 8 KB SRAM, six SERCOM interfaces configurable as I2C/SPI/UART/USART, a full-speed USB 2.0 device/host with on-chip transceiver, a 12-bit 350 ksps ADC, two 12-bit DACs, six PWM-capable timer/counter channels, an External Interrupt Controller with 16 lines, a 48 MHz Digital Frequency Locked Loop (DFLL48M) and a 96 MHz Fractional PLL, plus brown-out detection and a Serial Wire Debug (SWD) interface. The WLCSP-32 form factor targets miniaturized designs such as hearables, sensor patches, and ultra-compact IoT nodes.
The ATSAMD21E16B-UUTB4 uses a single 1.62V to 3.63V supply with on-chip voltage regulator, supports sleepwalking peripherals to wake the CPU autonomously, and includes a real-time clock calendar. Functional Safety firmware libraries and IEC 60730 class B ready code are available from Microchip, suiting it to white-goods, sensor fusion, and safety-critical consumer applications.
Typical applications include BLE-enabled sensor nodes, USB HID peripherals, motor control BLDC drivers, smart-home bridges, and wearable medical patches. The wide operating voltage, deep-sleep current, and peripheral event system make it well suited to event-driven designs.
When designing, ensure the WLCSP-32 footprint matches your PCB land pattern; consider 4-layer PCB stack-up for thermal relief and signal integrity. Plan for boot loader and double-tap reset strategy, and reserve an SWD header footprint for in-circuit debugging.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet. Pinout and parameter data are taken from Microchip's SAM D21/DA1 family datasheet and verified web sources.
Drop-in alternatives for ATSAMD21E16B-UUTB4 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 ATSAMD21E16B-UUTB4 (same form factor and footprint) β differing in ADC, Package, Operating Temperature, DAC, RoHS Status.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
ATSAMD21E16B-MU
β Drop-Inβ In Stock
$2.65 / Unit
View Datasheet βATSAMD21E16B-AU
β Drop-Inβ In Stock
$2.1 / Unit
View Datasheet βATSAMD21E15B-UUT
β Drop-Inπ Reference alternative (not in catalog)
ATSAMD21E17B-UUT
β Drop-Inπ Reference alternative (not in catalog)
ATSAMD21E18A-UUT
β Drop-Inπ Reference alternative (not in catalog)
ATSAMC21G18A-AUT
β Drop-Inβ In Stock
$2.78 / Unit
View Datasheet βATSAMD21E16B-UUTB4 Maximum Ratings & Electrical Characteristics
| Core Processor | ARM Cortex-M0+ (32-bit) |
| Maximum Clock Frequency | 48 MHz |
| Program Memory (Flash) | 64 KB |
| SRAM | 8 KB |
| Supply Voltage | 1.62 V to 3.63 V |
| Operating Temperature | -40 C to +85 C |
| Package | 32-ball WLCSP |
| Mounting Type | Surface Mount |
| ADC | 12-bit, up to 20 channels, 350 ksps |
| DAC | 2x 12-bit |
| SERCOM Modules | 6 (configurable as I2C/SPI/UART/USART) |
| USB | USB 2.0 Full-Speed Device/Host with on-chip transceiver |
| Timers/Counters | TCC (6 PWM), TC (3x 16-bit), RTC |
| External Interrupts | 16 lines + 1 NMI |
| Debug Interface | Serial Wire Debug (SWD) |
| MSL Level | MSL1 (per WLCSP handling) |
| RoHS Status | Compliant |
ATSAMD21E16B-UUTB4 Pin Configuration
| Pin A1 | VDD β Main supply voltage |
| Pin A2 | PA02 β GPIO / ADC input |
| Pin A3 | PA03 β GPIO / ADC input / reference |
| Pin A4 | GND β Ground |
| Pin B1 | PA00 β GPIO / XIN32K |
| Pin B2 | PA01 β GPIO / XOUT32K |
| Pin B3 | PA04 β GPIO / SERCOM0 PAD0 |
| Pin B4 | PA05 β GPIO / SERCOM0 PAD1 |
| Pin C1 | PA06 β GPIO / SERCOM0 PAD2 |
| Pin C2 | PA07 β GPIO / SERCOM0 PAD3 |
| Pin C3 | PA08 β GPIO / SERCOM1 PAD0 |
| Pin C4 | PA09 β GPIO / SERCOM1 PAD1 |
| Pin D1 | PA10 β GPIO / SERCOM1 PAD2 |
| Pin D2 | PA11 β GPIO / SERCOM1 PAD3 / USB D- |
| Pin D3 | PA12 β GPIO / USB D+ |
| Pin D4 | PA13 β GPIO / USB ID |
| Pin E1 | PA14 β GPIO / SWDIO |
| Pin E2 | PA15 β GPIO / SWDCLK |
| Pin E3 | PA16 β GPIO / SERCOM2 PAD0 |
| Pin E4 | PA17 β GPIO / SERCOM2 PAD1 |
| Pin F1 | PA18 β GPIO / SERCOM2 PAD2 |
| Pin F2 | PA19 β GPIO / SERCOM2 PAD3 |
| Pin F3 | PA20 β GPIO / SERCOM3 PAD0 |
| Pin F4 | PA21 β GPIO / SERCOM3 PAD1 |
| Pin G1 | PA22 β GPIO / SERCOM3 PAD2 |
| Pin G2 | PA23 β GPIO / SERCOM3 PAD3 |
| Pin G3 | PA24 β GPIO / USB VBUS |
| Pin G4 | PA25 β GPIO / DAC0 output |
| Pin H1 | PA27 β GPIO / DAC1 output |
| Pin H2 | PA28 β GPIO / Reset |
| Pin H3 | VDDCORE β Internal core voltage decoupling |
| Pin H4 | GND β Ground |
Typical Applications
ATSAMD21E16B-UUTB4 is suitable for 6 applications: BLE-Enabled IoT Sensor Node, USB HID Peripheral Device, BLDC Motor Control (Sensorless FOC), Wearable Health-Monitoring Patch, Smart-Home Wireless Bridge, Functional-Safety Consumer Appliance.
BLE-Enabled IoT Sensor Node
The ATSAMD21E16B-UUTB4 fits BLE IoT sensor nodes because its 48 MHz Cortex-M0+ core delivers enough compute for BLE stack processing while its 6 SERCOM interfaces multiplex I2C sensors, SPI radios, and UART debug ports. With 1.62-3.63 V supply support, the MCU directly runs from a single-cell Li-Ion battery, eliminating boost/buck converters. The 12-bit 350 ksps ADC samples analog sensor outputs with sub-1% accuracy for environmental monitoring. Sleepwalking peripherals wake the CPU only on relevant events, achieving deep-sleep currents below 10 uA. Compared with discrete microcontrollers, the SAMD21E family integrates USB, ADC, and PWM into a single die, reducing PCB area in space-constrained sensor enclosures. Drop-in firmware portability across ATSAMD21E16B-UUTB4 and the larger ATSAMD21E18A variant allows memory upgrades without code rewrites.
Recommended
USB HID Peripheral Device
The ATSAMD21E16B-UUTB4 is ideal for USB HID peripherals because of its integrated USB 2.0 Full-Speed device/host/peripheral controller with on-chip transceiver. The 5 V-tolerant D+/D- pins require only series resistors and ESD protection, removing the need for external PHY chips. With 64 KB of program memory, the MCU runs full USB stacks plus application code, including Human Interface Device, CDC, or vendor-class firmware. USB suspend/resume is supported via the on-chip SIE, maintaining low power during idle. The 48 MHz clock provides sufficient bandwidth for HID polling at 1 kHz without jitter. Compared with discrete USB microcontrollers, the ATSAMD21E16B-UUTB4 integrates the entire USB physical layer and SERCOM channels, reducing BOM cost.
Recommended
BLDC Motor Control (Sensorless FOC)
The ATSAMD21E16B-UUTB4 supports sensorless BLDC motor control because its six PWM channels (TCC) and 350 ksps ADC provide the three-phase timing and current sampling needed for field-oriented control. Cortex-M0+ at 48 MHz executes FOC loops within 5-15 us, leaving CPU headroom for communication. The 12-bit ADC pairs with embedded op-amps for current sense amplification, reducing analog BOM. Hardware dead-time insertion and fault inputs on TCC protect the inverter bridge. Compared with dedicated motor-control MCUs, the ATSAMD21E16B-UUTB4 trades determinism for cost, but the rich peripheral set (CCL logic, event system) handles most FOC tasks. Drop-in firmware libraries such as Microchip's MPLAB Harmony motor control framework accelerate development.
Recommended
Wearable Health-Monitoring Patch
The ATSAMD21E16B-UUTB4 fits wearable health patches because of its WLCSP-32 package footprint of approximately 2.7x2.7 mm, enabling ultra-compact designs under 5x5 mm. The 1.62-3.63 V supply range supports direct Li-Ion battery operation, and sleepwalking peripherals with RTC wake-up keep average current below 5 uA in standby. The 12-bit ADC with PGA and 2x 12-bit DACs drive bio-sensor front-ends for heart-rate, SpO2, and galvanic-skin-response measurements. The 48 MHz Cortex-M0+ runs signal-processing algorithms for heart-rate variability and step counting. Compared with discrete analog signal processors, the SAMD21E integrates ADC, DAC, PWM, and a Cortex-M0+ core, reducing BOM and battery drain. IEC 60730 class B libraries support medical-grade firmware validation.
Recommended
Smart-Home Wireless Bridge
The ATSAMD21E16B-UUTB4 is well suited for smart-home wireless bridges because its 6 SERCOM ports connect to multiple radios (Zigbee, Sub-GHz, BLE, LoRa) over SPI/UART interfaces simultaneously. Cortex-M0+ at 48 MHz manages protocol translation and local automation tasks. With 64 KB Flash and 8 KB SRAM, the MCU holds protocol stacks for both Zigbee 3.0 and BLE 5 simultaneously. USB Full-Speed is used for direct connection to home gateways without external bridges. Compared with single-protocol hubs, the SAMD21E handles concurrent IoT radios with deterministic interrupt response. Drop-in compatibility with ATSAMD21E17B (128 KB) supports firmware upgrades that include Thread or Matter stack.
Recommended
Functional-Safety Consumer Appliance
The ATSAMD21E16B-UUTB4 fits functional-safety consumer appliances because Microchip provides IEC 60730 class B firmware libraries and documentation. The SAM D21E sub-family includes Functional Safety (FuSa) support, addressing safety standards for motor-driven appliances like washing machines and dishwashers. Brown-out detection, watchdog timer, and CRC modules provide hardware-level diagnostics. Cortex-M0+ at 48 MHz runs the safety self-test routines within sub-millisecond windows. The 6 PWM channels drive triac-controlled motor phases directly. Compared with general-purpose MCUs, the SAMD21E adds the firmware libraries and documentation required by safety regulators. Drop-in compatibility across memory variants allows scalable BOM strategies.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21E16B-UUTB4 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21E16B-MU | ATSAMD21E16B-AU | ATSAMD21E15B-UUT | ATSAMD21E17B-UUT | ATSAMD21E18A-UUT | ATSAMC21G18A-AUT |
|---|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | WLCSP-32 | QFN-32 (5x5) | TQFP-32 (7x7) | WLCSP-32 - same | WLCSP-32 - same | WLCSP-32 - same | TQFP-32 (7x7) |
| Flash | 64 KB | 64 KB | 64 KB | 32 KB | 128 KB | 256 KB | 256 KB |
| SRAM | 8 KB | 8 KB | 8 KB | 8 KB | 8 KB | 32 KB | 32 KB |
| Core | Cortex-M0+ 48 MHz | Cortex-M0+ 48 MHz | Cortex-M0+ 48 MHz | Cortex-M0+ 48 MHz | Cortex-M0+ 48 MHz | Cortex-M0+ 48 MHz | Cortex-M0+ 48 MHz |
| SERCOM Count | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| USB FS | Yes (device/host) | Yes | Yes | Yes | Yes | Yes | Yes |
| 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 | -40 C to +125 C (AUT) |
Key Differentiators
- WLCSP-32 package for ultra-compact designs (vs ATSAMD21E16B-MU (QFN-32))
- Functional Safety (FuSa) firmware libraries available (vs ATSAMD21E16B-AU (TQFP-32))
- Higher-density Flash variants in same WLCSP-32 footprint (vs ATSAMD21E15B-UUT)
Design Notes
WLCSP-32 requires a 4-layer PCB stack-up with controlled-impedance routing for USB D+/D- traces (90 ohm differential). Place decoupling capacitors (100 nF + 1 uF ceramic) within 2 mm of VDD and VDDCORE balls. Add ground via stitching around the package perimeter at 0.5 mm pitch to suppress high-frequency noise from the 48 MHz clock. According to Microchip SAM D46S datasheet (DS40001882G), the WLCSP handling note requires MSL1 floor life and a peak reflow profile of 260 C.
Do not exceed 3.63 V on any VDD pin. The USB D+/D- pins require external series resistors (typically 27-39 ohm) if the design is not compliant with USB impedance matching. The NMI and SWD pins must be left floating or pulled to known states at reset - leaving SWD floating can prevent debugger connection. The VDDCORE pin requires a 1 uF capacitor to GND; do not load this pin externally.
Estimated: At full 48 MHz operation with all peripherals active, the core draws approximately 7 mA from VDD. Deep-sleep mode current is below 10 uA with RTC running. For battery-powered designs, route the wake-up events through the event system instead of CPU interrupts to keep the CPU in standby until a real peripheral action occurs. Use sleepwalking ADC for low-rate sensor sampling without waking the CPU.
Compliance Information
RoHS and REACH compliant per Microchip product page. Not AEC-Q100 qualified - choose ATSAMD21E16B-AF or ATSAMD21E16B-AFT for automotive-grade variants. WLCSP handling requires MSL1 floor life.
