Specs side by side
2 parts compared · 14 differing specs across 14 total parameters.
| Parameter | ||
|---|---|---|
| Supply voltage | - | Same I2C practice: bus pull-ups present on most modules, verify on all. |
| Memory & Peripherals | - | The bench discipline for this whole family: run a bus scan (i2cdetect or an equivalent) and read the responding address before writing any firmware constant - 0x20-range means the plain die, 0x38-range the A. |
| Case | DIP-16 / SOIC-16 (SSOP-20 variant) | Module boards |
| Compatibility Level | - | Functional Equivalent |
| Component Category | I/O Expanders (I2C) | - |
| Core & Architecture | - | The breakout boards sold as "PCF8574": frequently carrying the A-suffix die, with the address set by jumpers or traces whose defaults vary by batch - the same part and the same law, under a label that may not match the die. |
| Firmware Notes | - | Two lines save an evening: scan, then code the address you SAW. The module label, the marketplace listing and the schematic legend are all secondary evidence. |
| Hardware Notes | - | Module pin order varies between vendors - check the header labels against the module drawing. |
| Lead Time Advantage | - | Shenzhen Spot Stock (24-48h Dispatch) |
| Market Reality | The PCF8574 is the 8-bit I2C port expander of button matrices, relay cards, LCD backpacks and a thousand hobby and industrial boards: eight quasi-bidirectional pins, an interrupt output, and three address pins - with one family quirk that fills every forum: the A suffix is the SAME chip at a DIFFERENT I2C address. The plain part answers at 0x20-0x27, the A part at 0x38-0x3F, pin for pin and function for function per both NXP and TI - and the cheap module trade ships whichever die was cheaper that month, label notwithstanding. The other half of this page is behavioral: a quasi-bidirectional port is not a normal GPIO, and its write-1-to-read law explains most "the input does not work" posts in existence. | - |
| Reference Part | - | PCF8574 |
| Role In Circuit | Original Reference Part | - |
| Sourcing Advantage | - | Photographed lots with the responding address noted per batch where we can. |
| Sourcing Status | Active Shenzhen Spot Sourcing (24–48h) | - |
Parts
- PCF8574 · nxp
- PCF8574 modules (market grade) · nxp