PCA9536

@@ -0,0 +1,52 @@+# PCA9536++**Texas Instruments** · I2C I/O expander · SOIC-8++Adds four general-purpose I/O pins to a host over I2C/SMBus. Each of the four pins (P0-P3) is independently set as input or output through a configuration register, and the host reads or drives them over a two-wire bus at a fixed address, so a microcontroller short on pins gains four more without extra wiring. Power-on default is all inputs. A small, cheap way to break out a handful of switches, LEDs, or enable lines.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | P0 | bidirectional | P-port bit 0. Push-pull bidirectional I/O; configurable as input or output via the Configuration register. Powers up as an input with a weak pull-up to VCC. High-current drive (up to ~25 mA sink) sufficient for direct LED drive. |+| 2 | P1 | bidirectional | P-port bit 1. Push-pull bidirectional I/O; configurable as input or output via the Configuration register. Powers up as an input with a weak pull-up to VCC. |+| 3 | P2 | bidirectional | P-port bit 2. Push-pull bidirectional I/O; configurable as input or output via the Configuration register. Powers up as an input with a weak pull-up to VCC. |+| 4 | GND | power_in | Device ground return. Connect to the system ground plane. |+| 5 | P3 | bidirectional | P-port bit 3. Push-pull bidirectional I/O; configurable as input or output via the Configuration register. Powers up as an input with a weak pull-up to VCC. |+| 6 | SCL | input | I2C serial clock input. Open-drain bus line; connect to VCC through an external pull-up resistor. Supports standard mode (100 kHz) and fast mode (400 kHz). |+| 7 | SDA | bidirectional | I2C serial data line. Open-drain bidirectional bus; connect to VCC through an external pull-up resistor. |+| 8 | VCC | power_in | Supply voltage input, 2.3 V to 5.5 V. Bypass locally with a ceramic decoupling capacitor to GND. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | 4-bit I2C / SMBus I/O expander |+| Interface | I2C / SMBus (fixed address) |+| I/O | 4 pins (P0-P3), each input or output |+| Supply | 2.3-5.5 V |+| Bus speed | Up to 400 kHz |+| Default | All I/O as inputs at power-on |+| Package | SOIC-8 |++## Ordering variants++- `PCA9536D (SOIC-8, tube)`+- `PCA9536DR (SOIC-8, tape & reel)`+- `PCA9536DGKR (VSSOP-8)`++## CAD (KiCad official)++- Symbol: `Interface_Expansion:PCA9536D (KiCad official)`+- Footprint: `Package_SO:SOIC-8_3.9x4.9mm_P1.27mm`+- 3D model: SOIC-8 (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Texas Instruments datasheet](https://www.ti.com/lit/ds/symlink/pca9536.pdf) (35 pp, sha256 `bc9e7a06865817ab`, retrieved 2026-08-17, tier: manufacturer)+- **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/pca9536-datasheet.pdf)

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