Diodes Incorporated PI4MSD5V9545ALEX

Overview

PI4MSD5V9545ALEX from Diodes Incorporated is a quad 1-of-4 bidirectional I²C bus switch with integrated interrupt logic and active-low reset, designed for voltage-level translation between mixed-voltage I²C subsystems (1.2 V, 1.8 V, 2.5 V, 3.3 V, and 5 V). It features four independently selectable downstream I²C channels (SC0/SD0 to SC3/SD3), 5 V-tolerant I/O pins, 0 Hz–400 kHz clock support, and low Ron (4 Ω typical at 5 V) for minimal signal degradation in server management, embedded computing, and multi-sensor systems.

For engineers reviewing the PI4MSD5V9545ALEX datasheet, PI4MSD5V9545ALEX pinout, PI4MSD5V9545ALEX application, or PI4MSD5V9545ALEX equivalent, key selection criteria include its I²C channel arbitration capability, interrupt aggregation (INT0–INT3 → open-drain INT), hardware address configuration (A0/A1), power-up default (all channels deselected), and voltage translation control via VCC-dependent pass-gate clamping - critical for interoperability across heterogeneous voltage domains.

Technical Context

The PI4MSD5V9545ALEX implements a bidirectional translating multiplexer architecture where upstream SCL/SDA signals fan out to four downstream SCx/SDx pairs, each isolated by low-Ron pass gates controlled via an I²C-accessible 8-bit control register. Channel selection is nonvolatile only across I²C transactions - no internal memory retains state after power loss.

Its interrupt logic performs real-time OR-ing of four active-low inputs (INT0–INT3) into a single open-drain output (INT), while the active-low RESET pin forces full register initialization and channel deselection independent of I²C activity. The device uses VCC as a voltage clamp reference to limit pass-through high-level voltage (Vpass), enabling safe level-shifting without external translators.

Key Specifications

Pinout & Package

PI4MSD5V9545ALEX is housed in a 20-pin TSSOP (Thin Shrink Small Outline Package), 173 mil wide, with exposed pad not electrically connected. The package supports standard reflow profiles and provides thermal performance suitable for dense PCB layouts in industrial and telecom equipment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9545APWR and PCA9545ADW, PI4MSD5V9545ALEX delivers integrated interrupt handling, hardware reset, and full 1.65–5.5 V operation - reducing BOM count, simplifying layout, and enabling robust fault recovery in mission-critical mixed-voltage systems.

Availability

PI4MSD5V9545ALEX is available at Aetrix Electronics and suitable for server baseboard management, industrial PLC I/O expansion, automotive infotainment gateways, and medical diagnostic equipment requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for PI4MSD5V9545ALEX 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability power management, signal integrity, and interface solutions for industrial, computing, and automotive markets.

The PI4MSD5V9545ALEX belongs to Diodes' Pericom® interface product line, engineered specifically for robust I²C bus expansion, voltage translation, and system-level fault management in space-constrained, multi-rail embedded platforms.

FAQ

What is the function of the VCC pin beyond powering the device?

VCC serves as the voltage clamp reference for the internal pass-gate transistors. Its value directly determines the maximum pass-through voltage (Vpass) seen on downstream I²C lines - e.g., setting VCC = 3.3 V limits Vpass to ≤2.8 V, enabling safe 5 V-to-3.3 V translation without external components. This dual role eliminates need for separate level-shifter ICs.

How does the interrupt aggregation logic behave when multiple INTn inputs assert simultaneously?

The INT output is an active-low AND of INT0–INT3, so it goes LOW whenever ≥1 input is LOW. The control register (bits 4–7) captures the instantaneous state of all four INTn lines on read - allowing the host to identify exactly which channels have pending interrupts. No priority encoding or masking is performed internally.

Can unused interrupt inputs (INT0–INT3) be left floating?

No. Unused INTn pins must be tied to VCC via a pull-up resistor (typically 10 kΩ) to prevent false triggering due to noise or leakage. The datasheet explicitly states floating interrupt inputs are undefined and may cause spurious INT assertion. This requirement applies regardless of whether interrupt functionality is used in the design.

What happens to downstream bus capacitance when a channel is deselected?

When a channel is deselected, the corresponding SCx/SDx pins are electrically isolated from the upstream SCL/SDA lines via high-impedance pass gates. This removes their load capacitance (≤15 pF per pin) from the main bus, preserving signal rise/fall times and ensuring timing compliance - especially critical in Fast Mode (400 kHz) or multi-drop configurations.