PCF8574TS/3,118

A concise intro to PCF8574TS/3,118
- What it is: The PCF8574TS is an 8‑bit I/O expander for the I2C bus (from NXP/Philips). It adds eight quasi‑bidirectional I/O pins to a microcontroller.
- How it works: Communicate over I2C to read the input pins or to set the output latch. Writing a 0 drives the pin low; writing a 1 lets the pin be pulled high by an internal weak pull-up (useful for inputs or open‑drain style outputs).
- Addressing: Up to 8 devices on the same bus via A0–A2 address pins.
- Electricals: Operates on 2.5–6 V (common for microcontroller systems); low power when idle.
- Packaging: TS suffix typically indicates a specific package/lead form (e.g., surface-mount, tape-and-reel variants). The “/3,118” is usually a date/lot code and not functionally relevant.
- Applications: Expanding MCU I/O for LEDs, switches/keypads, sensors, or simple peripheral control without adding more MCU pins.
For precise electrical characteristics and package options, refer to the PCF8574/PCF8574TS datasheet.

Equivalent devices (8‑bit I2C I/O expanders):
- Microchip MCP23008
- TI TCA9534 / TCA9534A
- ON Semiconductor CAT8574 / CAT8574A
- NXP PCA8574 / PCA8574A
- NXP PCF8574 / PCF8574A (same family)

Key features of PCF8574TS/3,118 (I2C 8-bit I/O expander):
- 8-bit I/O expander for I2C-bus (P0–P7).
- Quasi-bidirectional, latched I/O pins; no separate direction register.
- Write 0 to drive a pin low; write 1 to release to input with a weak pull-up.
- I2C interface with 7-bit addressing; A0–A2 for device addressing (up to 8 devices on a bus).
- Wide operating supply: typically 2.5–6 V (compatible with 3.3V/5V systems).
- Simple read/write protocol: one 8-bit data write updates outputs; reads return pin states.
- Low power consumption suitable for battery-powered apps.
- Available in common packaging variants for both PCB and surface-mount use.
- Applications: I/O expansion for microcontrollers, keypad/LED control, simple I2C-to-IO interface.

The PCF8574 (PCF8574TS/3,118) is a 16-pin device. It is an I²C-bus controlled 8-bit quasi‑bidirectional I/O expander. Key pins/functions:
- P0–P7: eight quasi‑bidirectional I/O ports
- SDA, SCL: I²C data and clock lines
- A0, A1, A2: hardware address inputs (set the 7‑bit slave address)
- VCC (VDD) and GND (VSS): power supply pins
(The remaining pin(s) are NC or package-specific).

Manufacturer: NXP Semiconductors N.V. (formerly Philips Semiconductors).
What kind of company: Dutch multinational semiconductor company that designs and manufactures a broad range of integrated circuits and electronic components for automotive, industrial, consumer, and communications markets.

PCF8574TS/3,118 are I2C 8-bit I/O expanders (quasi-bidirectional). Common applications:
- Expand MCU/SBC I/O when pins are scarce
- Drive LED indicators and simple LED segments
- Read switches, buttons, and basic digital sensors
- Interface with LCD/backlight drivers and display panels
- Keyboard scanning and remote I/O in consumer electronics, appliances, and industrial controllers
- Prototyping and hobby projects (Arduino, Raspberry Pi) needing extra I/O on the I2C bus

PCF8574TS is a 16‑pin surface‑mount package, i.e., SOP‑16 (SSOP/SOP‑16 family).