ab1805-t3

@@ -0,0 +1,56 @@+# 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](docs/ab1805-t3-datasheet.pdf) (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](docs/ab1805-t3-datasheet.pdf)

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