Key Selection Information
| Selection Parameter | Confirmed Information |
|---|---|
| Keypad | Matrix scanning for up to 80 buttons |
| GPIO | 18 pins shared between keypad and general GPIO |
| Bus | I²C Fast-Mode Plus up to 1 MHz |
| Event Buffer | 10-byte FIFO for key presses/releases |
| Debounce | Integrated 50 µs debounce stated feature |
| Supply | 1.65 V to 3.6 V |
| Control | Open-drain interrupt; integrated ESD on GPIOs |
| Exact Package / Packing | WQFN (RTW), 24 pins; 3000-piece large tape and reel |
Product Overview
TCA8418RTWR is not merely a large GPIO expander; its primary function is autonomous matrix-keypad scanning. Eighteen pins can form row/column matrices supporting up to 80 keys while hardware debouncing and an event FIFO reduce MCU polling and interrupt load.
The 10-byte FIFO records key press/release events so firmware can service the keypad in bursts. This is especially useful on HMIs where the host sleeps or is busy, but software must drain the FIFO quickly enough during rapid multi-key activity.
Unused keypad pins can serve as GPIO, giving the designer a tradeoff between matrix size and general-purpose expansion. The 1.65–3.6 V supply makes it better suited to modern low-voltage processors than 5 V-oriented legacy keypad logic.
For related devices, see HKEQGOO’s I/O Expanders category.
Technical Specifications
| Parameter | Verified Information |
|---|---|
| Manufacturer | Texas Instruments |
| Exact MPN | TCA8418RTWR |
| Keypad | Matrix scanning for up to 80 buttons |
| GPIO | 18 pins shared between keypad and general GPIO |
| Bus | I²C Fast-Mode Plus up to 1 MHz |
| Event Buffer | 10-byte FIFO for key presses/releases |
| Debounce | Integrated 50 µs debounce stated feature |
| Supply | 1.65 V to 3.6 V |
| Control | Open-drain interrupt; integrated ESD on GPIOs |
| Exact Package / Packing | WQFN (RTW), 24 pins; 3000-piece large tape and reel |
| Manufacturer Status | Active / Production |
| Part Marking | PZ418 |
Functional Highlights
Hardware scanning offloads repetitive matrix timing from firmware
The host receives events rather than manually driving rows and reading columns. That reduces wakeups and makes key timing more deterministic.
FIFO depth defines the burst-event margin
Ten events are buffered. Key-repeat, multi-key use and host interrupt latency should be tested so events are not lost under the real user-input pattern.
Design Considerations
- Allocate row/column pins from the required maximum simultaneous keypad size before counting remaining GPIOs.
- Set firmware to drain the event FIFO on INT and handle overflow/status conditions.
- Use board-level ESD protection appropriate to the actual keypad exposure even though the IC includes ESD-rated GPIO structures.
Product Status and Exact Order Code
Manufacturer status: Active / Production
Texas Instruments lists TCA8418RTWR as Active / Production; WQFN (RTW), 24 pins; 3000-piece large tape and reel; Level-2-260C-1 YEAR; −40°C to +85°C; marking PZ418.
Related Engineering Resources
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