NXP Semiconductors PCA9545BPW,118

Overview

PCA9545BPW,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, 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 PCA9545BPW,118 datasheet, PCA9545BPW,118 pinout, PCA9545BPW,118 application, or PCA9545BPW,118 equivalent, key selection criteria include channel-selectable I²C isolation, interrupt aggregation (INT0–INT3 → INT), low Ron (≤11 Ω at 3.6 V), 5 V-tolerant I/O, and TSSOP20 package compatibility with space-constrained embedded control designs.

Technical Context

The PCA9545BPW,118 implements four independent bidirectional pass-gate switches controlled via an I²C-addressable 8-bit register, where bits B0–B3 select active downstream channels (SCx/SDx) while bits B4–B7 reflect real-time interrupt status from each channel. Its interrupt logic performs wired-AND of INT0–INT3 onto open-drain INT output.

It features dual-level fault recovery: active-low RESET resets the internal state machine and deselects all channels, while power-on reset (VPOR = 1.6–2.1 V) ensures default deselected state. Voltage translation is achieved by clamping Vo(sw) via VDD-e.g., setting VDD = 3.3 V limits max switched output to ~1.9 V, enabling safe interfacing of 3.3 V controllers with 2.7 V peripherals.

Key Specifications

Pinout & Package

TSSOP20 package (SOT360-1), 4.4 mm body width, 0.65 mm pitch, thermally enhanced for industrial ambient (−40 °C to +85 °C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9545APWR and PCA9544APW,118, the PCA9545BPW,118 delivers superior signal integrity via lower Ron, hardware-accelerated fault detection through interrupt logic, and full drop-in compatibility with existing NXP-based I²C multiplexer layouts using TSSOP20 footprint.

Availability

PCA9545BPW,118 is available at Aetrix Electronics and suitable for server management systems, industrial PLC backplanes, automotive body control modules, and medical diagnostic equipment requiring stable component supply across extended temperature and long product lifecycles.

Supply support for PCA9545BPW,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 family-including PCA9545BPW,118-is designed specifically for high-reliability I²C bus expansion in resource-constrained embedded systems requiring voltage translation, fault isolation, and interrupt-driven peripheral management.

FAQ

What is the maximum I²C clock frequency supported by the PCA9545BPW,118?

The PCA9545BPW,118 supports I²C clock frequencies up to 400 kHz, compliant with Fast-mode I²C specifications. This is confirmed in Section 12 of the datasheet under dynamic characteristics (fSCL Max = 400 kHz). The device maintains signal integrity within timing budgets even at this rate due to low propagation delay (tPD ≤ 0.3 ns) and controlled rise/fall times.

Does the PCA9545BPW,118 require external pull-up resistors on its I²C lines?

Yes, the PCA9545BPW,118 requires external pull-up resistors on all SCL, SDA, and SCx/SDx lines, as well as on INT0–INT3 if used as interrupt inputs. The device has no internal pull-ups. Resistor values depend on bus capacitance and speed-e.g., 2.2 kΩ for 100 kHz, 1 kΩ for 400 kHz with ≤200 pF total load-as specified in Figure 14 and Section 8 of the datasheet.

How does the PCA9545BPW,118 handle voltage translation between different I²C bus domains?

The PCA9545BPW,118 uses VDD-supplied gate control to clamp the maximum switched output voltage (Vo(sw)). For example, with VDD = 3.3 V, Vo(sw) ≤ 1.9 V (typ), enabling safe communication from a 3.3 V controller to 2.7 V peripherals. This is achieved passively via MOSFET threshold tuning-not external level shifters-per Section 6.5 and Figure 7 of the datasheet.

Can multiple PCA9545BPW,118 devices share the same I²C bus?

Yes, up to four PCA9545BPW,118 devices can coexist on one I²C bus using hardware address pins A0 and A1. These pins set the two LSBs of the 7-bit slave address (11100xxR/W), yielding addresses 0xE0–0xE6 (even for write, odd for read). No address conflict occurs if A0/A1 are hardwired uniquely per device, as detailed in Section 6.1 and Figure 5.

What happens to downstream I²C buses when the PCA9545BPW,118 is reset?

Upon assertion of the active-low RESET pin (or power-on reset), the PCA9545BPW,118 immediately deselects all four downstream channels (SC0/SD0–SC3/SD3), places them in high-impedance state, and clears the control register to 0x00. This isolates all downstream buses from the upstream SCL/SDA, preventing bus contention and allowing recovery from stuck-low conditions-per Section 6.3 and Table 4.