NXP Semiconductors PCA9545CPW,118

Overview

PCA9545CPW,118 from NXP Semiconductors is a quad-channel bidirectional I²C-bus switch with integrated interrupt logic and active-low reset. It enables selective routing of SCL/SDA signals across four downstream buses, supports voltage translation between 1.8 V, 2.5 V, 3.3 V, and 5 V domains, features 4 independent INT inputs and a single ANDed INT output, and operates from 2.3 V to 5.5 V supply - used in multi-sensor server management subsystems requiring isolated I²C domain control.

For engineers reviewing the PCA9545CPW,118 datasheet, PCA9545CPW,118 pinout, PCA9545CPW,118 application, or PCA9545CPW,118 equivalent, key selection criteria include slave address compatibility (10110xx), TSSOP20 package thermal performance (R_th(j-a) = 146 °C/W), channel-selectable pass-gate R_on (5–30 Ω), 400 kHz Fast-mode support, and interrupt-driven fault detection without bus contention.

Technical Context

The PCA9545CPW,118 implements a register-controlled 1-of-4 analog switch matrix with dedicated interrupt aggregation logic: each SCx/SDx channel has an associated active-low INTx input, and the open-drain INT output reflects the logical AND of all four. Its pass-gate architecture uses VDD as a clamping reference to enable bidirectional level translation without external components.

Control is fully I²C-based: a single write to the 8-bit control register (bits B0–B3 for channel enable, bits INT3–INT0 read-only) selects one or multiple channels; selection takes effect after STOP condition to prevent glitches. The device includes power-on reset and active-low hardware RESET that clears the control register and deselects all channels.

Key Specifications

Pinout & Package

TSSOP20 package (SOT360-1): 20-pin plastic thin shrink small outline, 4.4 mm body width, 0.65 mm pitch, exposed pad not present - suitable for high-density PCB layouts with moderate thermal dissipation needs (R_th(j-a) = 146 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9545APW,118 and PCA9545BPW,118, the PCA9545CPW,118 offers identical switching performance and thermal characteristics but occupies the 10110xx I²C address space - enabling deterministic allocation in multi-switch topologies without software remapping or hardware jumpers.

Availability

PCA9545CPW,118 is available at Aetrix Electronics and suitable for server management, industrial sensor hubs, telecom line cards, and automotive ADAS domain controllers requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for PCA9545CPW,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 specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with deep expertise in I²C, SMBus, and system management interfaces.

The PCA9545 series belongs to NXP's system-level bus management portfolio, designed specifically to simplify I²C domain isolation, voltage translation, and interrupt consolidation in resource-constrained embedded systems.

FAQ

What is the I²C slave address of PCA9545CPW,118?

The PCA9545CPW,118 has a fixed 7-bit slave address prefix of 10110xx, where the two least-significant bits (xx) are determined by the logic levels on A0 and A1 pins. This distinguishes it from PCA9545APW,118 (11100xx) and PCA9545BPW,118 (11010xx), allowing up to 12 devices on a single I²C bus. The PCA9545CPW,118 address ensures deterministic allocation in multi-switch configurations without software address remapping.

Does PCA9545CPW,118 support voltage translation between 1.8 V and 5 V I²C buses?

Yes, the PCA9545CPW,118 supports bidirectional voltage translation between 1.8 V, 2.5 V, 3.3 V, and 5 V I²C domains using its VDD pin as a clamping reference. When VDD is set to 3.3 V, Vo(sw) is limited to ≤2.7 V, enabling safe interfacing of 5 V upstream devices with 3.3 V or lower downstream peripherals - no external level shifters are needed. The PCA9545CPW,118 achieves this via pass-gate transistor design, not active logic translation.

How does the interrupt logic work on PCA9545CPW,118?

The PCA9545CPW,118 provides four active-low interrupt inputs (INT0–INT3), one per downstream channel, and a single open-drain interrupt output (INT) that acts as an AND of all four. When any downstream device asserts its INTx line, the corresponding bit in the control register (INT0–INT3) is set, and INT is pulled low. Reading the control register reveals which channel triggered the event, allowing the host to selectively enable that channel and service the interrupt. The PCA9545CPW,118 does not require the channel to be active for interrupt detection.

What is the purpose of the RESET pin on PCA9545CPW,118?

The RESET pin on PCA9545CPW,118 is an active-low asynchronous input that forces the device into a known state: it clears the control register (deselecting all channels), resets the I²C-bus state machine, and releases any stuck bus condition. It requires a minimum pulse width of 4 ns and must be pulled up externally. This hardware reset complements the internal power-on reset and enables reliable recovery from downstream bus faults - a critical feature in mission-critical systems where software-initiated recovery may be unavailable. The PCA9545CPW,118 guarantees deterministic behavior after RESET assertion.

Is PCA9545CPW,118 pin-compatible with other PCA9545 variants?

Yes, the PCA9545CPW,118 is fully pin-compatible with PCA9545APW,118 and PCA9545BPW,118 in the TSSOP20 package - same pinout, same electrical characteristics, same thermal profile. The only difference is the hardwired slave address prefix (10110xx for PCA9545CPW,118 versus 11100xx and 11010xx). This allows direct substitution in existing designs when address space reallocation is needed, without PCB layout changes or firmware modifications beyond I²C address updates. The PCA9545CPW,118 maintains full functional equivalence across all three variants.