NXP Semiconductors PCA9545AD,112

Overview

PCA9545AD,112 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, enabling voltage translation between 1.8 V, 2.5 V, 3.3 V, and 5 V buses, and used in multi-sensor server management systems.

For engineers reviewing the PCA9545AD,112 datasheet, PCA9545AD,112 pinout, PCA9545AD,112 application, or PCA9545AD,112 equivalent, key selection criteria include channel-selectable I²C isolation, per-channel interrupt aggregation, reset-recovery from bus lockup, and SO20 package compatibility with legacy board layouts.

Technical Context

The PCA9545AD,112 implements four independent pass-gate switches controlled via an I²C-accessible 8-bit control register, where bits B0–B3 select any combination of downstream SCx/SDx channels. Its interrupt logic performs a wired-AND of INT0–INT3 onto the open-drain INT output, with status bits B4–B7 readable for source identification.

Reset functionality is implemented as an asynchronous active-low signal that clears the control register and disables all channels, complementing internal power-on reset (POR) at VPOR = 1.6–2.1 V. Voltage translation is achieved by clamping downstream bus high-levels using VDD-limited pass-gate threshold, with Ron = 4–30 Ω depending on supply and load conditions.

Key Specifications

Pinout & Package

PCA9545AD,112 is housed in a plastic small outline package (SO20) with 20 leads, 7.5 mm body width, and standard JEDEC MS-013 footprint (SOT163-1). Thermal resistance is 90 °C/W (junction-to-ambient).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9545A and PCA9544A, the PCA9545AD,112 offers full 4-channel capability with NXP's validated 1.6 V POR and lowest typical Ron (4 Ω), making it optimal for high-reliability, mixed-voltage server and industrial applications requiring maximum flexibility and fault resilience.

Availability

PCA9545AD,112 is available at Aetrix Electronics and suitable for server baseboard management, industrial PLC I/O expansion, and automotive ADAS sensor hub applications requiring stable component supply and long-term industrial temperature support (−40 °C to +85 °C).

Supply support for PCA9545AD,112 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 company specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with leadership in I²C infrastructure and system management ICs.

The PCA9545A product line was designed to solve I²C bus congestion and voltage-domain isolation challenges in dense multi-peripheral systems, targeting server, telecom, and industrial control markets.

FAQ

What is the I²C address configuration method for PCA9545AD,112?

The PCA9545AD,112 uses two hardware address pins (A0 and A1) to configure its 7-bit I²C slave address as 11100A1A0R/W. Both pins must be externally pulled HIGH or LOW - no internal pull-ups exist. This allows up to four PCA9545AD,112 devices on the same I²C bus without address conflict, supporting scalable system architectures.

How does the PCA9545AD,112 handle voltage translation between different I²C buses?

The PCA9545AD,112 achieves voltage translation by using its VDD supply to set the maximum pass-gate output voltage (Vo(sw)). For example, with VDD = 3.3 V, Vo(sw) is clamped to ~1.9 V, allowing safe interfacing of a 5 V upstream bus with 3.3 V or 1.8 V downstream peripherals. External pull-up resistors on each channel set final bus voltage levels.

Can multiple channels of PCA9545AD,112 be enabled simultaneously?

Yes, the PCA9545AD,112 supports simultaneous activation of any combination of its four channels via bits B0–B3 in the control register. However, designers must ensure total capacitive load on the upstream SCL/SDA lines remains within I²C specification limits (≤400 pF) to maintain signal integrity and timing compliance at 400 kHz.

What is the function of the RESET pin on PCA9545AD,112 and how should it be connected?

The RESET pin on PCA9545AD,112 is an active-low asynchronous input that immediately clears the control register and deselects all channels upon assertion. It must be connected to VDD via a pull-up resistor (typically 10 kΩ) and driven LOW for ≥4 ns to trigger reset. This feature enables recovery from downstream bus lockups without requiring controller intervention.

Does PCA9545AD,112 support hot insertion of downstream I²C peripherals?

Yes, the PCA9545AD,112 supports hot insertion: its pass-gate architecture prevents back-driving of upstream lines during plug-in events, and the absence of glitch on power-up ensures stable initialization. Combined with 5 V tolerant I/O pins and robust ESD protection (2000 V HBM), PCA9545AD,112 safely accommodates live peripheral attachment in field-serviceable systems.