Texas Instruments PCA8550DR

Overview

PCA8550DR from Texas Instruments is a nonvolatile 5-bit register IC with I²C interface, designed for jumperless configuration of PC motherboards. It integrates a 4-bit 1-of-2 multiplexer and latched non-muxed output, operates from 3 V to 3.6 V, supports fast-mode (400 kbit/s) I²C, and provides 2.5-V MUX OUT and 3.3-V NON-MUXED OUT signals.

For engineers reviewing the PCA8550DR datasheet, PCA8550DR pinout, PCA8550DR application, or PCA8550DR equivalent, this device serves as a configurable I²C-addressable logic control element for BIOS/UEFI configuration storage, motherboard strapping, and hardware option selection in embedded computing platforms.

Technical Context

The PCA8550DR implements a slave-only I²C interface with fixed 7-bit address 1001110 (0x4E), Schmitt-trigger SCL/SDA inputs tolerant to 5.5 V, and integrated pullup resistors. Its internal architecture includes a 5-bit nonvolatile EPROM register (1000 write cycles, 10-year retention) and a transparent latch for the NON-MUXED OUT signal.

Functionally, it combines parallel input routing (MUX IN A–D) with I²C-controlled register read/write, where OVERRIDE forces all outputs low and WP enables/disables register writes. The MUX SELECT input determines whether outputs reflect register contents (low) or parallel inputs (high).

Key Specifications

Pinout & Package

PCA8550DR is supplied in a 16-pin SOIC (D) package per JEDEC MS-012, with 1.27-mm pitch and 10.3-mm body width. Thermal resistance θ_JA = 113°C/W enables operation in standard PCB layouts without forced cooling.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar nonvolatile I²C configuration register applications.

Compared with PCA9554APW and AT24C02C-SSHM-T, the PCA8550DR uniquely integrates nonvolatile storage, multiplexing, and latched output in a single 16-pin package-reducing component count and eliminating external glue logic required by alternatives.

Availability

PCA8550DR is available at Aetrix Electronics and suitable for PC motherboard design, embedded system configuration, and industrial control hardware requiring stable component supply and long-term obsolescence management.

Supply support for PCA8550DR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company founded in 1930, specializing in analog, embedded processing, and connectivity technologies for industrial, automotive, and communications markets.

The PCA8550DR belongs to TI's legacy interface and logic portfolio, designed specifically for hardware configuration management in x86-compatible and embedded computing platforms requiring reliable, low-pin-count nonvolatile strapping.

FAQ

What is the I²C slave address of the PCA8550DR?

The PCA8550DR has a fixed 7-bit I²C slave address of 1001110 (0x4E), with no address pins for modification. This address is used during both read and write operations to access the nonvolatile register. The PCA8550DR does not respond to the general call address, ensuring predictable bus behavior in multi-device systems. All communication follows standard I²C protocol timing requirements defined in the datasheet.

Does the PCA8550DR support 5-V I²C buses?

Yes, the PCA8550DR supports 5-V I²C buses because its SCL and SDA inputs are 5.5-V tolerant and include integrated pullup resistors. This allows direct connection to 5-V microcontrollers without external level shifters. However, VCC must remain within 3.0 V–3.6 V, so the device itself operates from a 3.3-V supply while interfacing safely with higher-voltage buses.

How does the OVERRIDE pin function on the PCA8550DR?

The OVERRIDE pin on the PCA8550DR is an active-high control that forces all four MUX OUT outputs and the NON-MUXED OUT output to logic low, overriding both register contents and parallel inputs. This provides a hardware reset mechanism independent of I²C activity or register state. When OVERRIDE is deasserted (low), normal multiplexer operation resumes based on MUX SELECT and register or input values.

What is the purpose of the latched NON-MUXED OUT in the PCA8550DR?

The latched NON-MUXED OUT in the PCA8550DR captures and holds its value at the moment MUX SELECT transitions from low to high, preventing transient changes during register writes or multiplexer switching. This ensures stable hardware configuration signals during critical boot sequences. Unlike the MUX OUT signals, which track register or input changes immediately, the latched output guarantees glitch-free assertion of strapping bits used by BIOS or FPGA configuration logic.

Can the PCA8550DR be used in new designs today?

Yes, the PCA8550DR remains viable for new designs where its specific feature set-nonvolatile 5-bit storage, dual-mode multiplexing, and 3.3-V/2.5-V output levels-is required. Texas Instruments continues to list it as active and available through authorized distributors. Designers should verify long-term supply commitments and consider its legacy process node (EPIC submicron CMOS) when evaluating reliability requirements for high-volume or mission-critical applications.