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Pinout
Key specifications
Ordering variants
CAD (KiCad official)
Provenance

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AB1805-T3

Abracon LLC · Real-time Clocks (RTC) · QFN-16(3x3)

AB1805-T3 from Abracon LLC, in a QFN-16(3x3). Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	nRST	output	Active-low external reset output (open-drain). Requires an external pull-up when used; polarity is set by the RSP register bit (defaults to active-low on POR). Can be left floating if unused.
2	WDI	input	Watchdog Timer reset input. Can also generate the External 2 interrupt (polarity via EX2P, enabled by EX2E); state readable in the WDIN bit. No internal pull; must be tied to VCC or VSS if unused to avoid extra current.
3	nEXTR	input	Active-low external reset input. When low with RS1E set, drives nRST to its asserted state. No internal pull; must be tied to VCC or VSS if unused.
4	PSW/nIRQ2	output	Secondary interrupt / power-switch output (open-drain). Selectable via OUT2S: OUTB value, SQW, /IRQ, /AIRQ, TIRQ, or a ~1 Ω power-switch to VSS (~50 mA continuous, 150 mA 1 s pulse) when PWR2 is set. May be left floating if unused.
5	VBAT	power_in	Battery-backup power input (1.5-3.6 V). Also feeds the internal analog comparator input. Tie directly to VSS if no backup battery is used.
6	SDA	bidirectional	I2C serial data line (up to 400 kHz). Open-drain; requires an external pull-up resistor to VCC.
7	SCL	input	I2C serial clock input (up to 400 kHz). Requires an external pull-up resistor to VCC.
8	CLKOUT/nIRQ3	output	Push-pull square-wave / clock / interrupt 3 output. Selectable to drive the OUT bit value or the SQW output when SQWE is set.
9	VSS	power_in	Ground return. Must be connected together with the thermal pad (pin 17).
10	EXTI	input	External interrupt input. Generates the External 1 interrupt (polarity via EX1P, enabled by EX1E); state readable in the EXIN bit. No internal pull; must be tied to VCC or VSS if unused to avoid extra current.
11	FOUT/nIRQ	output	Primary interrupt / function output (open-drain, requires external pull-up). Selectable via OUT1S: OUT bit, inverted combined IRQ, SQW output when SQWE is set, or inverted alarm interrupt AIRQ. Held low on power-up until the AB1805 exits reset and is accessible via the serial interface.
12	nTIRQ	output	Active-low timer interrupt output (open-drain, only present on the I2C variant). Requires an external pull-up when used; may be left floating if unused.
13	VCC	power_in	Primary system supply input (1.5-3.6 V; absolute max 3.8 V). Must be connected if a single supply is used.
14	AF	passive	Autocalibration filter pin. Requires an external 47 pF ceramic capacitor from this pin to VSS for accurate Autocalibration-mode timing.
15	XO	output	32.768 kHz crystal oscillator output. Integrated load capacitor and feedback resistor; connect directly to the crystal (no external caps required).
16	XI	input	32.768 kHz crystal oscillator input. Integrated load capacitor and feedback resistor; connect directly to the crystal (no external caps required).
17	VSS	power_in	Exposed thermal / ground pad on the bottom of the QFN-16 package. Must be connected to VSS.

Key specifications

Parameter	Value
Manufacturer	Abracon LLC
Package	QFN-16(3x3)
Category	RTC
Pins	17

Ordering variants

AB1805-T3

CAD (KiCad official)

Symbol: AB1805-T3
Footprint: Package_DFN_QFN:QFN-16-1EP_3x3mm_P0.5mm_EP1.7x1.7mm
3D model: QFN-16(3x3) (KiCad packages3D, STEP)

Provenance

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

Datasheet: Abracon LLC datasheet (None pp, sha256 8f5073f018cbaa67, retrieved 2026-08-17, tier: lcsc)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF

Symbol & Footprint

Schematic Symbol

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PCB Footprint