NXP Semiconductors PCA9847PWJ

Overview

PCA9847PWJ from NXP Semiconductors is an ultra-low voltage, 8-channel bidirectional I²C-bus multiplexer with active-low reset and software reset capability. It enables channel selection via I²C control register (B3–B0), supports Fm+ (1 MHz) operation, allows voltage translation between 0.8 V, 1.8 V, 2.5 V, and 3.3 V buses, and features dual supply rails (VDD1 = 0.8–3.6 V, VDD2 = 1.65–3.6 V) for flexible system-level interfacing in multi-voltage embedded designs.

For engineers reviewing the PCA9847PWJ datasheet, PCA9847PWJ pinout, PCA9847PWJ application, or PCA9847PWJ equivalent, this device delivers deterministic channel isolation, bus fault recovery via hardware RESET and I²C General Call (00h + 06h), voltage-level translation without external level shifters, and support for up to 16 devices on one I²C-bus using A0/A1 address pins - critical for dense sensor hubs and power management subsystems.

Technical Context

The PCA9847PWJ implements a pass-gate-based 1-of-8 multiplexer architecture controlled by an 8-bit I²C target interface. Its control register (read/write) uses B0–B3 to select exactly one downstream SCx/SDx channel, with all channels deselected at power-up or after RESET assertion. The internal state machine requires a STOP condition to activate the selected channel, preventing false bus transitions.

Voltage translation is achieved through VDD1-dependent input thresholds (VIL = 0.3×VDD1, VIH = 0.7×VDD1) and pass-transistor clamping, where VDD1 sets the maximum high-voltage level passed to downstream buses. VDD2 powers core logic and directly impacts Ron (lower Ron at higher VDD2), while all I/O pins remain 3.6 V tolerant regardless of supply configuration.

Key Specifications

Pinout & Package

TSSOP24 package (SOT355-1), 4.4 mm body width, 24-pin surface-mount. Pin 1 index located at top-left corner; exposed pad not present (HVQFN24 has thermal pad, TSSOP24 does not).

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9847PWJ, TCA9548APWR offers simpler supply routing but forfeits ultra-low-voltage operation and hardware fault recovery, while PCA9548APW lacks both Fm+ speed and voltage translation flexibility - making PCA9847PWJ uniquely suited for next-generation low-power, multi-rail I²C architectures.

Availability

PCA9847PWJ is available at Aetrix Electronics and suitable for server baseboard management, industrial PLC I/O modules, automotive body control units, and portable medical sensor hubs requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for PCA9847PWJ 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 management, and embedded processing technologies.

The PCA9847 belongs to NXP's precision I²C infrastructure portfolio, designed specifically to solve voltage-domain interoperability and bus congestion challenges in resource-constrained, multi-supply embedded systems.

FAQ

What is the minimum VDD1 voltage required for PCA9847PWJ to operate with a 0.8 V microcontroller?

The PCA9847PWJ supports VDD1 down to 0.8 V, which directly sets its input logic thresholds (VIL = 0.24 V, VIH = 0.56 V). At this level, it reliably interfaces with 0.8 V-core microcontrollers while maintaining noise margin. Operation below 0.8 V is not characterized or guaranteed per the datasheet, and VDD2 must remain ≥1.65 V for functional core logic. PCA9847PWJ remains fully operational under these conditions.

How does the PCA9847PWJ handle simultaneous selection of multiple downstream channels?

The PCA9847PWJ does not support simultaneous channel selection. Its control register (B3–B0) enables only one SCx/SDx pair at a time; writing any value with B3 = 0 deselects all channels. Attempting to assert multiple channel bits results in undefined behavior - the device defaults to no channel enabled. This design ensures strict bus isolation and prevents signal contention. PCA9847PWJ enforces single-channel activation by hardware.

Can the PCA9847PWJ be used without connecting the RESET pin?

Yes, the RESET pin may be left unconnected or tied to VDD1 if hardware-initiated bus recovery is not required. The PCA9847PWJ includes an internal Power-On Reset (POR) that initializes all registers and deselects channels at power-up. However, omitting external RESET removes the ability to recover from downstream bus lockups (e.g., stuck LOW condition), so it is recommended for robust systems. PCA9847PWJ remains functional without external RESET but loses fault-recovery capability.

What is the purpose of having separate VDD1 and VDD2 supplies on the PCA9847PWJ?

VDD1 sets the input switching thresholds (VIL/VIH) for SCL/SDA and clamps the maximum voltage passed to downstream buses, enabling precise voltage translation. VDD2 powers the internal logic and switch drivers, directly influencing Ron and speed performance. Separating them allows optimization: e.g., VDD1 = 0.8 V for 0.8 V MCU compatibility, VDD2 = 3.3 V for lowest Ron and full 1 MHz operation. PCA9847PWJ leverages this dual-rail architecture for true mixed-voltage interoperability.

Does the PCA9847PWJ support hot-plug insertion of downstream I²C peripherals?

Yes - the PCA9847PWJ powers up with all channels deselected, preventing bus contention during hot insertion. Its 3.6 V-tolerant I/O pins withstand voltage transients, and the absence of internal pull-ups avoids unintended biasing. When a peripheral is inserted, the host MCU can safely configure the channel via I²C without risk of short-circuit or address collision. This behavior is guaranteed by design and explicitly documented for PCA9847PWJ.