NXP Semiconductors PCA9545ABS,118

Overview

PCA9545ABS,118 from NXP Semiconductors is a 4-channel bidirectional I²C-bus switch with integrated interrupt logic and active-low reset, supporting voltage translation between 1.8 V, 2.5 V, 3.3 V, and 5 V buses. It features 20-pin HVQFN packaging, 0 Hz–400 kHz clock compatibility, and operates across –40 °C to +85 °C for use in multi-sensor server management systems.

For engineers reviewing the PCA9545ABS,118 datasheet, PCA9545ABS,118 pinout, PCA9545ABS,118 application, or PCA9545ABS,118 equivalent, this device enables selective routing of I²C traffic across isolated downstream buses while monitoring interrupt sources and recovering from bus lockups-critical for fault-tolerant embedded control and modular sensor subsystems.

Technical Context

The PCA9545ABS,118 implements four independent pass-gate switches controlled via an I²C-accessible 8-bit register, where bits B0–B3 select active channels (0–3) and bits B4–B7 reflect interrupt status from INT0–INT3. Its interrupt output (INT) functions as a wired-AND of all four inputs, enabling centralized fault detection without channel arbitration.

Reset recovery is hardware-triggered: asserting RESET low for ≥4 ns resets the internal state machine and deselects all channels, while power-on reset initializes the control register to 0x00. Voltage translation is achieved by clamping downstream bus high-level voltages using VDD as the gate threshold reference, with Vo(sw) ranging from 1.1 V (VDD = 2.3 V) to 4.5 V (VDD = 5.5 V).

Key Specifications

Pinout & Package

HVQFN20 package: 5 mm × 5 mm × 0.85 mm body, thermally enhanced exposed pad, 20-terminal no-lead construction (SOT662-1). Requires soldering of exposed pad to PCB thermal pad with vias for optimal thermal performance and electrical stability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9545APWR and PCA9544ADS,118, the PCA9545ABS,118 delivers superior thermal efficiency via HVQFN packaging and integrated interrupt monitoring - critical for dense, fanless, or high-reliability deployments where bus fault visibility and thermal margin are design constraints.

Availability

PCA9545ABS,118 is available at Aetrix Electronics and suitable for server baseboard management, industrial sensor hubs, modular test equipment, and automotive diagnostic interfaces requiring stable component supply across extended temperature ranges.

Supply support for PCA9545ABS,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, power, and sensing technologies.

The PCA9545A family was designed to solve I²C bus congestion and voltage incompatibility in complex embedded systems - delivering scalable, interrupt-aware bus segmentation without sacrificing timing fidelity or reliability.

FAQ

What is the primary function of the PCA9545ABS,118 in an I²C system?

The PCA9545ABS,118 functions as a programmable 4-channel I²C bus switch that selectively routes upstream SCL/SDA signals to one or more downstream bus segments. It enables isolation, voltage translation, interrupt aggregation, and hardware reset recovery - making it essential for managing complex, multi-peripheral I²C topologies where address conflicts, noise, or voltage mismatches would otherwise prevent reliable communication. The PCA9545ABS,118 achieves this with zero software overhead for channel switching and deterministic interrupt reporting.

How does the PCA9545ABS,118 handle voltage level translation between different I²C buses?

The PCA9545ABS,118 uses VDD-supplied pass-gate transistors to clamp the maximum high-level voltage passed between upstream and downstream buses. For example, with VDD = 3.3 V, Vo(sw) is limited to ~1.9 V (typ), allowing safe interfacing of a 5 V master with 3.3 V or 2.5 V slaves. External pull-up resistors on each downstream bus set the final logic-high voltage, while the PCA9545ABS,118 ensures no overshoot exceeds VDD. This eliminates need for discrete level shifters while preserving I²C timing compliance.

Can multiple PCA9545ABS,118 devices share the same I²C bus? How is addressing managed?

Yes, up to four PCA9545ABS,118 devices can coexist on a single I²C bus using hardware-configurable addresses. Pins A0 and A1 determine the two LSBs of the 7-bit slave address (base 0x70), yielding addresses 0x70–0x73. These pins must be externally pulled HIGH or LOW - no internal pull-ups exist. Each device responds only to its assigned address, enabling independent control of multiple switch banks from one master controller. The PCA9545ABS,118 does not support software-addressable aliases or broadcast writes.

What happens to the I²C bus state when the RESET pin of the PCA9545ABS,118 is asserted?

Asserting RESET low (for ≥4 ns) forces the PCA9545ABS,118 to clear its internal control register to 0x00, deselecting all four channels and disabling all downstream paths. It also resets the I²C state machine, releasing SCL and SDA lines to high-impedance. This recovers the upstream bus if any downstream segment is holding SCL or SDA low due to a fault. Upon RESET release, the device remains idle until the next valid I²C command - no automatic re-enabling occurs. The PCA9545ABS,118 requires no power cycle or register reinitialization after RESET.

Is the exposed thermal pad on the HVQFN20 package of the PCA9545ABS,118 electrically connected?

Yes, the exposed center pad of the PCA9545ABS,118's HVQFN20 package is internally connected to VSS (ground) and must be soldered to a corresponding PCB thermal pad tied to the system ground plane. This connection is mandatory for proper device operation - not optional. Thermal vias beneath the pad improve heat dissipation (Rθ(j-a) = 32 °C/W) and reduce junction temperature rise during sustained operation. Leaving the pad unconnected risks functional instability, increased leakage, and premature failure. The PCA9545ABS,118 datasheet explicitly states VSS pin and exposed pad must both connect to supply ground.