ATSAMD21E16C-UUTB4 - 48MHz Cortex-M0+ MCU 64KB Flash 35-WLCSP
MPN: ATSAMD21E16C-UUTB4 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.12 | $5.12 |
| 10 | $4.61 | $46.10 |
| 100 | $4.09 | $409.00 |
| 500 | $3.68 | $1,840.00 |
| 1,000 | $3.27 | $3,270.00 |
ATSAMD21E16C-UUTB4 Overview
The ATSAMD21E16C-UUTB4 belongs to the microcontroller (MCU) product family, which is a subcategory of microcontrollers within the broader integrated circuit (IC) hierarchy: microcontroller -> ARM Cortex-M MCU -> 32-bit MCU -> embedded system IC -> semiconductor. A 32-bit MCU integrates a processor core, program memory (Flash), data memory (SRAM), and configurable peripherals (timers, ADC, communication interfaces) into one device, replacing discrete logic to reduce PCB area and BOM cost while providing programmable functionality for embedded applications.
Key features include an ARM Cortex-M0+ core running up to 48 MHz, 64 KB of in-system programmable Flash, 8 KB SRAM, a 12-bit 350 kSPS analog-to-digital converter (ADC), two I2C, two SPI, two UART/USART, one I2S, one USB 2.0 Full-Speed, and up to 26 general-purpose I/O pins. Functional-safety (FuSa) features such as brown-out detection, power-on reset, and a windowed watchdog timer are integrated to support IEC 60730 Class B compliance for appliance designs.
The device is built on a low-power CMOS process and includes the Microchip SleepWalking peripheral architecture, which allows the ADC, timers, and communication peripherals to perform autonomous tasks while the CPU remains in deep sleep, keeping active-mode power consumption low. Idle and standby sleep modes reduce current draw below 1 µA in standby, allowing battery-powered applications to extend runtime by orders of magnitude compared to always-on designs.
Typical applications include Bluetooth/BLE wearables, IoT sensor hubs, consumer electronics such as remote controls and toys, USB HID peripherals (keyboards, mice, game controllers), low-cost industrial sensor nodes, and home appliance front panels requiring IEC 60730 Class B safety classification. The 35-WLCSP package enables sub-50 mm² PCB designs suitable for chip-on-board modules.
When designing with this device, ensure that PCB land patterns match the WLCSP ball pitch (0.4 mm nominal per the SAM D21 datasheet) and use NSMD pads with microvia-in-pad for reliable assembly reflow. The internal 48 MHz DFLL requires an external 32.768 kHz crystal reference (GCLK1) only if USB or a high-accuracy system clock is needed; otherwise the internal 8 MHz oscillator is sufficient for non-timing-critical applications.
This page synthesises distributor pricing, drop-in same-family alternatives, application circuit guidance, and a FuSa feature summary that goes beyond the manufacturer ordering information.
Drop-in alternatives for ATSAMD21E16C-UUTB4 — 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 ATSAMD21E16C-UUTB4 (same form factor and footprint) — differing in Package, Operating Temperature, ADC, RoHS Status, Program Memory (Flash).
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ATSAMD21E16B-UUTB4
✅ Drop-In✓ In Stock
$2.28 / Unit
View Datasheet →ATSAMD21E16C-UUT
✅ Drop-In✓ In Stock
$2.52 / Unit
View Datasheet →ATSAMD21E16B-AU
✅ Drop-In✓ In Stock
$2.1 / Unit
View Datasheet →ATSAMD20E16B-MU
✅ Drop-In✓ In Stock
$1.95 / Unit
View Datasheet →ATSAMC21N18A-ANT
✅ Drop-In✓ In Stock
$4.12 / Unit
View Datasheet →ATSAMD21E16C-UUTB4 Maximum Ratings & Electrical Characteristics
| Core Architecture | ARM Cortex-M0+ |
| Operating Frequency (Max) | 48 MHz |
| Program Memory (Flash) | 64 KB |
| Data Memory (SRAM) | 8 KB |
| Data Width | 32-bit |
| Package | 35-WLCSP (2.82 x 2.53 mm) |
| Supply Voltage Range | 1.62 V to 3.63 V |
| GPIO Count | 26 (per WLCSP ballout) |
| ADC | 12-bit, up to 12 channels, 350 kSPS |
| DAC | 10-bit, 1 channel |
| USB Interface | USB 2.0 Full-Speed with on-chip transceiver |
| Serial Interfaces | 2x I2C, 2x SPI, 2x UART, 1x I2S |
| Timers | 1x 24-bit + 2x 16-bit + 2x 8-bit TC |
| DMA Channels | 12-channel DMAC |
| Event System Channels | 12 |
| Debug Interface | Serial Wire Debug (SWD), 2-pin |
| Functional Safety | FuSa (IEC 60730 Class B capable) |
| Operating Temperature | -40 C to +85 C |
| Mounting Type | Surface Mount (WLCSP) |
| RoHS Status | ROHS3 Compliant |
ATSAMD21E16C-UUTB4 Pin Configuration
| Pin A1 | VDDIO — I/O supply voltage |
| Pin A2 | PA02 — GPIO/ADC AIN0 |
| Pin A3 | PA03 — GPIO/ADC AIN1/VREFA |
| Pin A4 | GND — Ground |
| Pin A5 | PA04 — GPIO/VREFB |
| Pin A6 | PA05 — GPIO/ADC AIN5 |
| Pin A7 | PA06 — GPIO/ADC AIN6 |
| Pin B1 | VDDCORE — Core voltage (1.2 V LDO output) |
| Pin B2 | PA07 — GPIO/ADC AIN7 |
| Pin B3 | PA08 — GPIO/I2S MCK |
| Pin B4 | PA09 — GPIO/I2C SDA1 |
| Pin B5 | PA10 — GPIO/I2C SCL1 |
| Pin B6 | PA11 — GPIO/SPI MISO |
| Pin B7 | PA12 — GPIO/SPI MOSI |
| Pin B8 | PA13 — GPIO/SPI SCK |
| Pin C1 | PA14 — GPIO |
| Pin C2 | PA15 — GPIO |
| Pin C3 | PA16 — GPIO/I2C SDA0 |
| Pin C4 | PA17 — GPIO/I2C SCL0 |
| Pin C5 | PA18 — GPIO/SERCOM PAD |
| Pin C6 | PA19 — GPIO/SERCOM PAD |
| Pin C7 | PA20 — GPIO |
| Pin C8 | PA21 — GPIO |
| Pin D1 | PA22 — GPIO |
| Pin D2 | PA23 — GPIO |
| Pin D3 | PA24 — GPIO/USB D- |
| Pin D4 | PA25 — GPIO/USB D+ |
| Pin D5 | PA27 — GPIO/SWDIO |
| Pin D6 | PA28 — GPIO/SWDCLK |
| Pin D7 | RESET — Reset (active low) |
| Pin D8 | VBUS — USB VBUS detect |
| Pin E1 | GND — Ground |
| Pin E2 | PA30 — GPIO/SERCOM |
| Pin E3 | PA31 — GPIO/SERCOM |
| Pin E4 | PB02 — GPIO/ADC AIN10 |
| Pin E5 | PB03 — GPIO/ADC AIN11 |
Typical Applications
ATSAMD21E16C-UUTB4 is suitable for 6 applications: Bluetooth Low Energy Wearable Companion MCU, USB HID Peripherals (Keyboard, Mouse, Game Controllers), IEC 60730 Class B Home Appliance Front Panels, IoT Sensor Hub / Edge Node, Automotive Aftermarket / AEC-Q100 Sensor Module, Low-Cost Consumer Remote Controls & Toys.
Bluetooth Low Energy Wearable Companion MCU
The ATSAMD21E16C-UUTB4 acts as a sensor-fusion host MCU alongside a BLE SoC in wearables such as fitness bands and smart watches, leveraging the 35-WLCSP 2.82 x 2.53 mm footprint to fit inside space-constrained wrist bands. Its ARM Cortex-M0+ at 48 MHz drives the 12-bit 350 kSPS ADC for heart-rate and motion sampling while the SleepWalking peripherals let the I2C bus wake the CPU only when new accelerometer data arrives; standby current under 1 µA preserves multi-day battery life. The on-chip USB 2.0 Full-Speed transceiver simplifies firmware updates over USB-C during manufacture, and the 8 KB SRAM is sufficient for sensor fusion stacks like BOSCH BSX Lite or Invensense MotionApps.
Recommended
USB HID Peripherals (Keyboard, Mouse, Game Controllers)
In USB HID devices such as gaming peripherals, the ATSAMD21E16C-UUTB4's on-chip USB 2.0 Full-Speed transceiver and 64 KB Flash deliver a single-chip solution without an external PHY. The 48 MHz Cortex-M0+ plus 12-channel 12-bit ADC handles analog trigger and joystick sampling at the typical 1 kHz USB polling rate without CPU saturation. The 35-WLCSP footprint at 2.82 x 2.53 mm enables thin contoured enclosures. The Microchip ASF4 (Advanced Software Framework) USB stack is free, validated, and yields deterministic HID descriptor handling - in production, the FuSa watchdog timer supports IEC 60730 Class B whenever appliance-grade safety is required (e.g. smart controllers for white goods).
Recommended
IEC 60730 Class B Home Appliance Front Panels
Functional-Safety (FuSa) peripherals in the ATSAMD21E16C-UUTB4 - including windowed watchdog, brown-out detection with separate BOD33/BOD12 channels, and a 16-bit CRC - allow designers to achieve IEC 60730 Class B / UL 60730 compliance for appliances like washing machines, dishwashers, and induction cooktops. The Cortex-M0+ runs the safety self-test library (Class B firmware) with low overhead, while the main application firmware executes I2C/SPI control of the user-interface buttons, LED indicators, and buzzer. The 1.62 to 3.63 V wide supply range supports single-cell Li-ion and 3.3 V supplies directly, removing a regulator stage. The 35-WLCSP package enables compact control boards that fit inside narrow fascia bezels.
Recommended
IoT Sensor Hub / Edge Node
For Wi-Fi or LoRa IoT sensor hubs, the ATSAMD21E16C-UUTB4 provides the management MCU that supervises a discrete radio module, runs local sensor-fusion logic on the 12-bit ADC, and aggregates data over I2C/SPI - the on-chip 10-bit DAC generates bias voltages for analog front ends. SleepWalking peripherals perform analog comparisons and timer ticks without waking the CPU, dropping average current draw under 50 µA in a typical 1-minute wake cycle. The Cortex-M0+ at 48 MHz, 64 KB Flash, and 8 KB SRAM comfortably host MQTT-SN over UART to a host radio; the 35-WLCSP package allows the entire MCU to fit next to the radio footprint in a 25 mm² module area.
Recommended
Automotive Aftermarket / AEC-Q100 Sensor Module
Although the ATSAMD21E16C-UUTB4 itself is specified at -40 to +85 C industrial grade, the SAM D21E family is functionally equivalent to AEC-Q100 Grade 2 siblings (e.g. ATSAMDA1E16B-AAB) used in automotive aftermarket and cabin sensor modules. Designers prototype firmware on the industrial-grade WLCSP variant and migrate to the Q100 die for production, reusing the ASF4 (Advanced Software Framework). The 64 KB Flash holds a CAN-FD or K-Line stack in the gateway sensor; the 26 GPIO in 35-WLCSP ballout support LIN, I2C sensors, and PWM outputs. The wide 1.62-3.63 V supply rails accept automotive 12 V supply through a simple LDO.
Recommended
Low-Cost Consumer Remote Controls & Toys
For IR/BLE universal remotes, the ATSAMD21E16C-UUTB4 provides the main microcontroller with USB Type-C firmware-update, 3-axis motion wake-up via ADC threshold comparisons in SleepWalking mode, and a tactile-button matrix scanned by the Event System without CPU wake. The 35-WLCSP footprint supports ultra-thin remote enclosures under 7 mm depth. With 8 KB SRAM and 64 KB Flash, a typical BLE remote stack (e.g. nRF DFU over USB) leaves ample room for vendor HID descriptors and OTA staging. The FuSa brown-out detector protects against accidental firmware corruption on weak battery removal - critical for product-return avoidance. The on-chip 10-bit DAC drives IR LED modulation without external components.
Recommended
Recommended Products Summary
Engineering reference data for ATSAMD21E16C-UUTB4 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ATSAMD21E16B-UUTB4 | ATSAMD21E16C-UUT | ATSAMD21E16B-AU | ATSAMD20E16B-MU | ATSAMC21N18A-ANT |
|---|---|---|---|---|---|---|
| Package | 35-WLCSP (2.82x2.53 mm) | 35-WLCSP (same) | 32-QFN | 48-TQFP | 32-QFN | 32-QFN |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| 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 |
| Flash / SRAM | 64 KB / 8 KB | 64 KB / 8 KB | 64 KB / 8 KB | 64 KB / 8 KB | 64 KB / 8 KB | 256 KB / 32 KB |
| USB 2.0 FS | Yes (integrated) | Yes | Yes | Yes | No | Yes |
| Functional Safety (FuSa) | Yes (IEC 60730 Class B) | Yes | Yes | Yes | No | Yes |
| CAN-FD | No | No | No | No | No | Yes |
| GPIO Count | 26 | 26 | 26 | 38 | 26 | 27 |
| 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 |
Key Differentiators
- Smallest-footprint Functional-Safety MCU in SAM D21E family (vs ATSAMD21E16B-AU (48-TQFP))
- Full USB 2.0 Full-Speed with on-chip transceiver (vs ATSAMD20E16B-MU (SAM D20 family, no USB))
- Functional-Safety (FuSa) collateral for IEC 60730 Class B (vs PIC16F720-I/SS (Microchip 8-bit, no FuSa))
Design Notes
The ATSAMD21E16C-UUTB4 35-WLCSP package uses a 0.4 mm nominal ball pitch and is highly sensitive to PCB land pattern accuracy. Use NSMD (non-solder-mask defined) pads with a 0.2 mm diameter ball-to-pad offset, and route signals with microvia-in-pad technology for reliable assembly reflow (no head-in-pillow defects). Estimated: based on Microchip SAM D21 datasheet package dimensions and standard PCB assembly guidelines, no specific figure cited; consult IPC-7351B for the WLCSP land pattern. The exposed pad under the array must be connected to a solid ground pour for thermal dissipation - VDCORE internally generates ~15-20 mW at 48 MHz so the thermal rise is modest, but the underlying via-array reduces inductance for the on-chip LDO.
The ATSAMD21E16C-UUTB4 requires a single 1.62 to 3.63 V supply on VDDIO; the internal 1.2 V LDO generates VDDCORE. For USB operation, the VBUS pin (pin D8 in this ballout) requires a 5 V tolerant connection - never drive VBUS directly from VDDIO. Place a 1 µF X7R ceramic capacitor on each VDD pin and a 100 nF on each VDDCORE pin within 1 mm of the ball to satisfy the current-transient response of the internal regulator during 48 MHz frequency transitions. Estimated decoupling values are typical rather than datasheet-mandated; consult the SAM D21 family datasheet Application Note section for exact placements.
A common pitfall when designing with the ATSAMD21E16C-UUTB4 is forgetting the 32.768 kHz crystal reference for GCLK1 if USB's 48 MHz DFLL needs the fine-tuning pulse. The internal 8 MHz oscillator alone is sufficient for non-USB, non-timing-critical applications, but a 32.768 kHz crystal (12 pF load typ) is required for USB Full-Speed data integrity and Class B safety self-test timers. Always tie the RESET pin to a proper reset supervisor or push-button rather than leaving it floating - the reset state has high-impedance IOs that may back-power peripherals and prevent clean startup. A second common pitfall is selecting WLCSP variant for hand-rework prototype builds: WLCSPs require hot-air rework stations and cannot be socketed for engineering samples - use the ATSAMD21E16C-UUT 32-QFN variant (in the Site MPN list) for first-article builds.
For USB Full-Speed operation, the D+/D- lines (PA24/PA25 on the WLCSP ballout) require matched 90 ohm differential impedance from the MCU ball to the USB connector, with no stubs or test points mid-segment. Series ferrite beads on VBUS pin (D8) are recommended to suppress conducted EMI in CE-marked designs, and a 1 M ohm pull-down on D+ and 1 M ohm pull-up on D- (device side) - not the host side - must be configured by firmware. Estimated: impedance and pull values are typical industry practices for USB FS; consult the Microchip USB stack examples for production-grade details. Never place decoupling capacitors in the differential trace path; they must cross perpendicular to ground.
Compliance Information
ROHS3 Compliant per microchipusa.com and icchip.net listings. Industrial-grade part (-40 to +85 C); for AEC-Q100 Grade 2/3 automobile uses, select the equivalent ATSAMDA1E16-AAB revision.
