Texas Instruments PCA9545ADWR

Overview

PCA9545ADWR from Texas Instruments is a low-voltage, quad-channel I²C and SMBus switch with interrupt logic and active-low reset. It functions as a bidirectional translating multiplexer that routes one upstream SCL/SDA pair to any combination of four downstream SCn/SDn channels. Key confirmed parameters include 2.3 V to 5.5 V operating supply, 0–400 kHz clock support, 5.5 V-tolerant I/O, <11 Ω typical R_ON, and four independent active-low interrupt inputs (INT3–INT0) feeding a single open-drain INT output. It is used in server motherboard I²C bus expansion where multiple temperature sensors share identical slave addresses.

For engineers reviewing the PCA9545ADWR datasheet, PCA9545ADWR pinout, PCA9545ADWR application, or PCA9545ADWR equivalent, this page delivers verified functional role, channel-select timing behavior, voltage-translation capability across 1.8 V/2.5 V/3.3 V/5 V domains, interrupt propagation delay (≤4 μs), and reset recovery timing - all critical for multi-bus arbitration, hot-swap I²C subsystems, and fault-resilient sensor networks.

Technical Context

The PCA9545ADWR implements four independent analog pass-gate switches controlled via an 8-bit I²C-accessible register, where bits B0–B3 select enabled channels and bits B4–B7 reflect real-time interrupt status per channel. Its interrupt logic performs a wired-AND of INT3–INT0 onto the open-drain INT output without requiring channel activation for detection.

Each SCn/SDn channel supports bidirectional level translation by isolating V_CC-referenced pull-up voltages - enabling 1.8-V slaves to communicate with a 5-V master using external resistors. The device includes internal power-on reset (VPOR = 1.6–2.1 V) and an asynchronous active-low RESET input that forces all channels deselected and clears the I²C state machine within 500 ns.

Key Specifications

Pinout & Package

TSSOP-20 package (6.50 mm × 4.40 mm), RoHS-compliant, surface-mountable with standard reflow profile.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I²C bus switching applications.

Compared with TCA9544APWR and PCA9546ADWR, the PCA9545ADWR uniquely delivers per-channel interrupt visibility and hardware reset recovery - making it the only option among the three for fault-resilient, event-driven I²C subsystems requiring zero-software-intervention bus recovery.

Availability

PCA9545ADWR is available at Aetrix Electronics and suitable for server baseboard management, telecom router control planes, and industrial PLC I/O modules requiring stable component supply across extended production lifecycles.

Supply support for PCA9545ADWR 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 specializing in analog and embedded processing solutions, with leadership in interface, power management, and signal chain technologies.

The PCA9545ADWR belongs to TI's I²C switch and multiplexer product line, designed specifically for robust, scalable I²C bus expansion in high-reliability computing and communications infrastructure.

FAQ

What is the primary function of the PCA9545ADWR in an I²C system?

The PCA9545ADWR functions as a quad-channel bidirectional I²C bus switch that enables a single master to selectively route communication to one or more of four isolated downstream I²C buses. It resolves slave address conflicts, supports voltage-level translation between domains (e.g., 1.8 V to 5 V), and provides per-channel interrupt monitoring - all under I²C register control. This makes PCA9545ADWR essential for scalable, fault-tolerant I²C architectures in servers and telecom equipment.

How does the PCA9545ADWR handle bus contention or stuck-bus conditions?

The PCA9545ADWR incorporates both power-on reset (POR) and an asynchronous active-low RESET pin to recover from stuck-bus faults. When RESET is asserted low for ≥6 ns, the internal I²C state machine resets and all channels are deselected within 500 ns - releasing SDA and clearing latched bus states. This ensures PCA9545ADWR can autonomously restore bus integrity without requiring host intervention or power cycle, a key reliability feature absent in simpler switches like PCA9546ADWR.

Can the PCA9545ADWR translate between different I²C voltage domains, and how is it implemented?

Yes, the PCA9545ADWR supports voltage-level translation between 1.8 V, 2.5 V, 3.3 V, and 5 V I²C domains. Its pass-gate architecture uses V_CC to limit maximum passed voltage, while external pull-up resistors on each SCn/SDn pair set the local bus voltage. For example, SDA/SCL upstream may be pulled to 3.3 V, while SD0/SC0 is pulled to 1.8 V and SD3/SC3 to 5 V - enabling interoperability without discrete level shifters. This capability is intrinsic to PCA9545ADWR's analog switch design and verified in TI's electrical characteristics table.

What is the role of the A0 and A1 pins on the PCA9545ADWR?

The A0 and A1 pins on the PCA9545ADWR are hardware-configurable address inputs that set the device's 7-bit I²C slave address. With A0 and A1 tied to GND or V_CC, the base address 0b11100xx yields four unique addresses (0xE0, 0xE2, 0xE4, 0xE6), allowing up to four PCA9545ADWR devices to coexist on the same I²C bus. This eliminates address collisions in complex systems and is fundamental to scalable bus expansion - a feature explicitly defined in the PCA9545ADWR datasheet's "Device Address" section.

How does the interrupt logic of the PCA9545ADWR differ from that of the PCA9546ADWR?

The PCA9545ADWR features four dedicated active-low interrupt inputs (INT0–INT3), one per channel, plus a single open-drain interrupt output (INT) that acts as a wired-AND of all four inputs. In contrast, the PCA9546ADWR has no interrupt inputs or outputs - it is purely a channel-select switch. This means only PCA9545ADWR enables the host to detect and identify which specific downstream channel generated an interrupt without polling, making PCA9545ADWR indispensable for event-driven I²C monitoring in applications like sensor hubs and thermal management subsystems.