NXP Semiconductors PCA9545AD,118

Overview

PCA9545AD,118 from NXP Semiconductors is a 4-channel bidirectional I²C-bus switch with integrated interrupt logic and active-low reset, operating from 2.3 V to 5.5 V supply, supporting up to 400 kHz clock frequency, and enabling voltage translation between 1.8 V, 2.5 V, 3.3 V, and 5 V buses in server management and multi-sensor systems.

For engineers reviewing the PCA9545AD,118 datasheet, PCA9545AD,118 pinout, PCA9545AD,118 application, or PCA9545AD,118 equivalent, this device delivers channel-selectable bus isolation, hardware-addressable configuration (A0/A1), low-R_ON pass gates (≤11 Ω at 3.6 V), and robust fault recovery via RESET and power-on reset - critical for high-reliability embedded control and modular I²C expansion.

Technical Context

The PCA9545AD,118 implements a register-controlled 1-of-4 (or multi-channel) switching architecture where SCL/SDA upstream signals fan out to four downstream SCx/SDx pairs; channel selection is performed via an 8-bit I²C-accessible control register with writeable channel bits (B0–B3) and read-only interrupt status bits (INT0–INT3).

Its interrupt logic aggregates four active-low inputs (INT0–INT3) into a single open-drain active-low output (INT) using AND logic, while the active-low RESET input forces deselection of all channels and resets the internal state machine - both functions are independent of I²C communication and operate across the full 2.3–5.5 V supply range.

Key Specifications

Pinout & Package

PCA9545AD,118 uses the SO20 (SOT163-1) package: plastic small outline, 20-pin, 7.5 mm body width, 1.27 mm pitch, with thermal resistance R_th(j-a) = 90 °C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9545A and PCA9544A, PCA9545AD,118 provides superior fault resilience via sub-5 ns RESET response and unique interrupt consolidation - making it optimal for systems requiring autonomous bus recovery and reduced host interrupt overhead.

Availability

PCA9545AD,118 is available at Aetrix Electronics and suitable for server management, industrial sensor hubs, automotive body control modules, and automated test equipment requiring stable component supply and long-term industrial lifecycle support.

Supply support for PCA9545AD,118 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

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications, with deep expertise in interface and power management ICs.

The PCA9545A product line was designed specifically for scalable, fault-tolerant I²C bus expansion in resource-constrained embedded systems - emphasizing robustness, voltage flexibility, and minimal host software overhead.

FAQ

What is the maximum I²C clock frequency supported by PCA9545AD,118?

The PCA9545AD,118 supports I²C clock frequencies up to 400 kHz, compliant with Fast-mode I²C specifications. This allows high-speed communication with peripherals such as EEPROMs, ADCs, and real-time clocks while maintaining signal integrity through its low-R_ON pass gates and controlled rise/fall times. The device operates reliably across the full 2.3–5.5 V supply range at this rate.

How does the RESET pin function in PCA9545AD,118?

The RESET pin in PCA9545AD,118 is an active-low input that forces immediate deselection of all four channels and resets the internal I²C state machine - recovering from stuck-bus conditions without host intervention. It requires a minimum 4 ns LOW pulse and must be pulled HIGH via an external resistor. This behavior is identical during power-on reset, ensuring deterministic startup.

Can PCA9545AD,118 translate between 1.8 V and 5 V I²C buses?

Yes, PCA9545AD,118 enables bidirectional voltage translation between 1.8 V and 5 V I²C buses using its VDD-referenced pass-gate architecture. Setting VDD = 2.5 V limits Vo(sw) to ≤1.5 V, safely interfacing 1.8 V peripherals with 5 V controllers. External pull-up resistors on each channel set the local bus voltage, and all I/O pins are 5 V tolerant.

What is the purpose of the INT output in PCA9545AD,118?

The INT output in PCA9545AD,118 is an active-low open-drain signal that acts as an AND of the four INT0–INT3 inputs, providing centralized interrupt notification to the host controller. When any downstream peripheral asserts its interrupt, INT goes LOW - allowing the host to read the control register and identify the active channel, reducing polling overhead and enabling event-driven system responses.

Does PCA9545AD,118 require external pull-up resistors on its I²C lines?

Yes, PCA9545AD,118 requires external pull-up resistors on all SCL/SDA and SCx/SDx lines - no internal pull-ups are present. Resistor values depend on bus capacitance and speed: typical values are 2.2 kΩ for 100 kHz and 1 kΩ for 400 kHz. Pull-ups must be placed on each downstream channel separately to establish correct voltage levels for mixed-voltage operation.