PCF8591

@@ -0,0 +1,61 @@+# PCF8591++**NXP** · ADC + DAC · SOIC-16++Combines a four-channel 8-bit analog-to-digital converter and one 8-bit digital-to-analog output on a single I2C device, so a host reads four analog inputs and drives one analog output over two wires. The ADC inputs work single-ended or as differential pairs, an external VREF sets the span, and three address pins put up to eight devices on one bus. It runs from 2.5 to 6 V. The classic all-in-one analog I/O expander for hobby and instrument boards.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | AIN0 | input | Analog input channel 0 to the A/D converter. Selectable as single-ended or differential input via the control byte. |+| 2 | AIN1 | input | Analog input channel 1 to the A/D converter. Selectable as single-ended or differential input via the control byte. |+| 3 | AIN2 | input | Analog input channel 2 to the A/D converter. Selectable as single-ended or differential input via the control byte. |+| 4 | AIN3 | input | Analog input channel 3 to the A/D converter. Selectable as single-ended or differential input via the control byte. |+| 5 | A0 | input | Hardware slave address bit 0. Tied to VSS or VDD to program the I2C slave address (LSB of hardware address). |+| 6 | A1 | input | Hardware slave address bit 1. Tied to VSS or VDD to program the I2C slave address. |+| 7 | A2 | input | Hardware slave address bit 2. Tied to VSS or VDD to program the I2C slave address (MSB of hardware address). |+| 8 | VSS | power_in | Ground supply / digital ground reference (0 V). |+| 9 | SDA | bidirectional | I2C-bus serial data input/output line. Open-drain; requires an external pull-up resistor to VDD. |+| 10 | SCL | input | I2C-bus serial clock input from the master. Requires an external pull-up resistor to VDD. |+| 11 | OSC | bidirectional | Oscillator input/output. When the internal oscillator is used (EXT tied to VSS), OSC provides the oscillator frequency output; when EXT is tied to VDD, OSC becomes the external clock input. |+| 12 | EXT | input | External/internal oscillator select. Tie to VSS to enable the internal oscillator; tie to VDD to disable the internal oscillator and use an external clock applied at OSC. |+| 13 | AGND | power_in | Analog ground supply for the ADC/DAC resistor divider chain. Must be connected to the system analog ground; may sit at a DC offset with respect to VSS. |+| 14 | VREF | input | Voltage reference input for the on-chip ADC/DAC resistor divider chain. Sets the analog full-scale span between AGND and VREF; must be kept stable during conversion. |+| 15 | AOUT | output | Analog output from the on-chip 8-bit D/A converter. Buffered by an auto-zeroed unity-gain amplifier; high-impedance when the analog-output-enable flag in the control register is 0. |+| 16 | VDD | power_in | Positive supply voltage, 2.5 V to 6.0 V. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | 8-bit ADC (4-ch) + 8-bit DAC |+| Interface | I2C |+| ADC inputs | 4 single-ended or 2 differential |+| DAC | 1 analog output (AOUT) |+| Reference | External (VREF) |+| Addresses | 8 (A0-A2) |+| Supply | 2.5-6 V |+| Package | SOIC-16 |++## Ordering variants++- `PCF8591T (SOIC-16)`+- `PCF8591P (DIP-16)`+- `PCF8591TS (SSOP-20)`++## CAD (KiCad official)++- Symbol: `Interface_Expansion:PCF8591 (KiCad official)`+- Footprint: `Package_SO:SOIC-16_3.9x9.9mm_P1.27mm`+- 3D model: SOIC-16 (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [NXP datasheet](https://www.nxp.com/docs/en/data-sheet/PCF8591.pdf) (31 pp, sha256 `b89feb48ffdbebfe`, 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/pcf8591-datasheet.pdf)

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