ATSAMD21G16B-MU from Microchip Tech, in a QFN-48-EP(7x7). Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	PA00	bidirectional	General-purpose I/O on VDDANA with EXTINT[0], SERCOM1/PAD[0] and TCC2/WO[0] functions, and XIN32 for the 32kHz crystal oscillator.
2	PA01	bidirectional	General-purpose I/O on VDDANA with EXTINT[1], SERCOM1/PAD[1] and TCC2/WO[1] functions, and XOUT32 for the 32kHz crystal oscillator.
3	PA02	bidirectional	General-purpose I/O on VDDANA with EXTINT[2], ADC AIN[0], PTC Y[0] and DAC VOUT functions.
4	PA03	bidirectional	General-purpose I/O on VDDANA with EXTINT[3], ADC/DAC VREFA, ADC AIN[1] and PTC Y[1] functions.
5	GNDANA	power_in	Analog ground; supplies the VDDANA I/O cluster.
6	VDDANA	power_in	Analog supply for the analog I/O pins (PA00-PA07, PB00-PB05, PB08-PB09).
7	PB08	bidirectional	General-purpose I/O on VDDANA with EXTINT[8], ADC AIN[2], PTC Y[14], SERCOM4/PAD[0] and TC4/WO[0] functions.
8	PB09	bidirectional	General-purpose I/O on VDDANA with EXTINT[9], ADC AIN[3], PTC Y[15], SERCOM4/PAD[1] and TC4/WO[1] functions.
9	PA04	bidirectional	General-purpose I/O on VDDANA with EXTINT[4], ADC VREFB, ADC AIN[4], AC AIN[0], PTC Y[2], SERCOM0/PAD[0] and TCC0/WO[0] functions.
10	PA05	bidirectional	General-purpose I/O on VDDANA with EXTINT[5], ADC AIN[5], AC AIN[1], PTC Y[3], SERCOM0/PAD[1] and TCC0/WO[1] functions.
11	PA06	bidirectional	General-purpose I/O on VDDANA with EXTINT[6], ADC AIN[6], AC AIN[2], PTC Y[4], SERCOM0/PAD[2] and TCC1/WO[0] functions.
12	PA07	bidirectional	General-purpose I/O on VDDANA with EXTINT[7], ADC AIN[7], AC AIN[3], PTC Y[5], SERCOM0/PAD[3], TCC1/WO[1] and I2S SD[0] functions.
13	PA08	bidirectional	General-purpose I/O on VDDIO with NMI, ADC AIN[16], PTC X[0], SERCOM0/2 PAD[0] and TCC0/WO[0] functions; supports I2C mode.
14	PA09	bidirectional	General-purpose I/O on VDDIO with EXTINT[9], ADC AIN[17], PTC X[1], SERCOM0/2 PAD[1] and TCC0/WO[1] functions; supports I2C mode.
15	PA10	bidirectional	General-purpose I/O on VDDIO with EXTINT[10], ADC AIN[18], PTC X[2], SERCOM0/2 PAD[2], TCC1/WO[0] and GCLK_IO[4] functions.
16	PA11	bidirectional	General-purpose I/O on VDDIO with EXTINT[11], ADC AIN[19], PTC X[3], SERCOM0/2 PAD[3], TCC1/WO[1] and GCLK_IO[5] functions.
17	VDDIO	power_in	Digital I/O supply for the I/O pins of this cluster (PA08-PA15, PB10-PB11).
18	GND	power_in	Ground for the digital I/O supply.
19	PB10	bidirectional	General-purpose I/O on VDDIO with EXTINT[10], SERCOM4/PAD[2], TC5/WO[0], TCC0/WO[4], I2S MCK[1] and GCLK_IO[4] functions.
20	PB11	bidirectional	General-purpose I/O on VDDIO with EXTINT[11], SERCOM4/PAD[3], TC5/WO[1], TCC0/WO[5], I2S SCK[1] and GCLK_IO[5] functions.
21	PA12	bidirectional	General-purpose I/O on VDDIO with EXTINT[12], SERCOM2/PAD[0], SERCOM4/PAD[0], TCC2/WO[0], TCC0/WO[6] and AC CMP[0] functions; supports I2C mode.
22	PA13	bidirectional	General-purpose I/O on VDDIO with EXTINT[13], SERCOM2/PAD[1], SERCOM4/PAD[1], TCC2/WO[1], TCC0/WO[7] and AC CMP[1] functions; supports I2C mode.
23	PA14	bidirectional	General-purpose I/O on VDDIO with EXTINT[14], SERCOM2/PAD[2], TC3/WO[0] and GCLK_IO[0] functions, and XIN for the crystal oscillator.
24	PA15	bidirectional	General-purpose I/O on VDDIO with EXTINT[15], SERCOM2/PAD[3], TC3/WO[1] and GCLK_IO[1] functions, and XOUT for the crystal oscillator.
25	PA16	bidirectional	General-purpose I/O on VDDIO with EXTINT[0], PTC X[4], SERCOM1/3 PAD[0], TCC2/WO[0], TCC0/WO[6] and GCLK_IO[2] functions; supports I2C mode.
26	PA17	bidirectional	General-purpose I/O on VDDIO with EXTINT[1], PTC X[5], SERCOM1/3 PAD[1], TCC2/WO[1], TCC0/WO[7] and GCLK_IO[3] functions; supports I2C mode.
27	PA18	bidirectional	General-purpose I/O on VDDIO with EXTINT[2], PTC X[6], SERCOM1/3 PAD[2], TC3/WO[0], TCC0/WO[2] and AC CMP[0] functions.
28	PA19	bidirectional	General-purpose I/O on VDDIO with EXTINT[3], PTC X[7], SERCOM1/3 PAD[3], TC3/WO[1], TCC0/WO[3], I2S SD[0] and AC CMP[1] functions.
29	PA20	bidirectional	General-purpose I/O on VDDIO with EXTINT[4], PTC X[8], SERCOM5/3 PAD[2], TC7/WO[0], TCC0/WO[6], I2S SCK[0] and GCLK_IO[4] functions.
30	PA21	bidirectional	General-purpose I/O on VDDIO with EXTINT[5], PTC X[9], SERCOM5/3 PAD[3], TC7/WO[1], TCC0/WO[7], I2S FS[0] and GCLK_IO[5] functions.
31	PA22	bidirectional	General-purpose I/O on VDDIO with EXTINT[6], PTC X[10], SERCOM3/5 PAD[0], TC4/WO[0], TCC0/WO[4] and GCLK_IO[6] functions; supports I2C mode.
32	PA23	bidirectional	General-purpose I/O on VDDIO with EXTINT[7], PTC X[11], SERCOM3/5 PAD[1], TC4/WO[1], TCC0/WO[5], USB SOF 1kHz and GCLK_IO[7] functions; supports I2C mode.
33	PA24	bidirectional	General-purpose I/O on VDDIO with EXTINT[12], SERCOM3/5 PAD[2], TC5/WO[0], TCC1/WO[2] and USB DM functions; a pull-up is recommended if unconnected.
34	PA25	bidirectional	General-purpose I/O on VDDIO with EXTINT[13], SERCOM3/5 PAD[3], TC5/WO[1], TCC1/WO[3] and USB DP functions; a pull-up is recommended if unconnected.
35	GND	power_in	Ground for the digital I/O supply.
36	VDDIO	power_in	Digital I/O supply for the I/O pins of this cluster (PA16-PA25, PB22-PB23, PA27-PA28).
37	PB22	bidirectional	General-purpose I/O on VDDIO with EXTINT[6], SERCOM5/PAD[2], TC7/WO[0], TCC3/WO[0] and GCLK_IO[0] functions.
38	PB23	bidirectional	General-purpose I/O on VDDIO with EXTINT[7], SERCOM5/PAD[3], TC7/WO[1], TCC3/WO[1] and GCLK_IO[1] functions.
39	PA27	bidirectional	General-purpose I/O on VDDIO with EXTINT[15], TCC3/WO[6] and GCLK_IO[0] functions.
40	RESET	input	External reset input, active low.
41	PA28	bidirectional	General-purpose I/O on VDDIO with EXTINT[8], TCC3/WO[7] and GCLK_IO[0] functions.
42	GND	power_in	Ground for the VDDIN supply.
43	VDDCORE	power_out	Regulated output supply for the core.
44	VDDIN	power_in	Input supply for the device and internal voltage regulator.
45	PA30	bidirectional	General-purpose I/O on VDDIO with EXTINT[10], SERCOM1/PAD[2], TCC1/WO[0], TCC3/WO[4], GCLK_IO[0] and SWCLK (serial wire debug clock) functions.
46	PA31	bidirectional	General-purpose I/O on VDDIO with EXTINT[11], SERCOM1/PAD[3], TCC1/WO[1] and TCC3/WO[5] functions; SWDIO is active only when a debugger is present.
47	PB02	bidirectional	General-purpose I/O on VDDANA with EXTINT[2], ADC AIN[10], PTC Y[8], SERCOM5/PAD[0], TC6/WO[0] and TCC3/WO[2] functions.
48	PB03	bidirectional	General-purpose I/O on VDDANA with EXTINT[3], ADC AIN[11], PTC Y[9], SERCOM5/PAD[1], TC6/WO[1] and TCC3/WO[3] functions.
49	EP	passive	Exposed pad (from the footprint; not named in the datasheet pin table).

Key specifications

Parameter	Value
Manufacturer	Microchip Tech
Package	QFN-48-EP(7x7)
Category	Embedded Processors & Controllers
Pins	49

Electrical characteristics

Limits as printed in the datasheet (page.json metadata.characteristics carries them as data).

Parameter	Symbol	Min	Typ	Max	Unit	Conditions	Page
Operating voltage (SAM D21)	VDD	1.62		3.63	V	SAM D21: 1.62V, 3.63V	2
VDDIO supply voltage	VDDIO	1.62		3.63	V	Powers I/O lines, OSC8M and XOSC	35
VDDIN supply voltage	VDDIN	1.62		3.63	V	Powers I/O lines and the internal regulator	35
VDDANA supply voltage	VDDANA	1.62		3.63	V	Powers I/O lines and the ADC, AC, DAC, PTC, OSCULP32K, OSC32K, XOSC32K	35
Operating temperature (U grade)		-40		85	°C	U = -40 - 85°C Matte Sn Plating	16
CPU clock frequency	Fmax			48	MHz	Arm Cortex-M0+ CPU running at up to 48 MHz	1
VDDCORE regulated output voltage	VDDCORE		1.2		V	Internal regulated voltage output	35

Materials and finish

As the datasheet states them (page.json metadata.appearance; the 3D model's colours follow it).

Part	Material	Colour / plating	Datasheet says	Page
contacts		tin	including indium tin oxide (ITO) sensor grids. The PTC requires one pin per X-line and one pin per Y-line. In the self-capacitance mode, the PTC requires only one pin (Y-line) for each touch sensor.	859

CAD (KiCad official)

Symbol: ATSAMD21G16B-MU
Footprint: Package_DFN_QFN:QFN-48-1EP_7x7mm_P0.5mm_EP5.15x5.15mm
3D model: QFN-48-EP(7x7) (KiCad packages3D, STEP)
3D model files: atsamd21g16b-mu-etched.step / atsamd21g16b-mu-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); atsamd21g16b-mu.step / atsamd21g16b-mu.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Microchip Tech datasheet (1148 pp, sha256 18ca1ccab5aa330f, retrieved 2026-10-30, tier: manufacturer)
Extractor: parts-factory 2.0.0 / extract_pins 0.3, primary claude-sonnet-5-5 (text), consensus claude-sonnet-5-5 (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF

ATSAMD21G16B-MU

Verified ATSAMD21G16B-MU

Verification log 1 record

3D Model

Symbol & Footprint

Schematic Symbol

PCB Footprint

Datasheet

README