Microchip Technology MCP23S09T-E/MG

Overview

MCP23S09T-E/MG from Microchip Technology is an 8-bit SPI-based I/O expander with open-drain outputs, designed for remote parallel port expansion in microcontroller-constrained systems. It operates from 1.8V to 5.5V, supports 10 MHz SPI, delivers 25 mA sink per pin (200 mA total), and features configurable interrupt output and hardware reset - used in industrial HMI panels for GPIO extension of ARM Cortex-M4 controllers.

For engineers reviewing the MCP23S09T-E/MG datasheet, MCP23S09T-E/MG pinout, MCP23S09T-E/MG application, or MCP23S09T-E/MG equivalent, key selection criteria include SPI interface timing compliance, 5.5V-tolerant input capability, interrupt-on-change configuration flexibility, open-drain drive strength, and QFN-16 (3×3 mm) thermal pad layout requirements.

Technical Context

The MCP23S09T-E/MG implements a dedicated SPI slave interface operating in Mode 0,0 and Mode 1,1, with chip select (CS), serial clock (SCK), data in (SI), and data out (SO) pins. Its internal register map includes 11 addressable control and status registers - IODIR, IPOL, GPINTEN, DEFVAL, INTCON, IOCON, GPPU, INTF, INTCAP, GPIO, and OLAT - all accessible via 8-bit opcode + address + data framing.

It uses a hardware reset (RESET) input to initialize all registers to POR defaults and provides an active-high/active-low/open-drain configurable INT output that flags I/O state changes. The device supports two interrupt triggering modes: comparison against previous state or against programmable DEFVAL register values, with INTCAP capturing port state at interrupt time.

Key Specifications

Pinout & Package

Package: 16-lead QFN (3×3×0.9 mm) with exposed thermal pad (EP), RoHS-compliant, moisture sensitivity level 3.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I/O expander applications.

Compared with MCP23S09T-E/MG, MCP23S17-E/SO offers double I/O width and advanced interrupt control at the cost of larger footprint and non-drop-in compatibility, while PCA9555D,118 trades SPI speed and hardware reset for I²C ecosystem integration - neither matches the exact 8-bit SPI + QFN + RESET + INT feature set of MCP23S09T-E/MG.

Availability

MCP23S09T-E/MG is available at Aetrix Electronics and suitable for industrial HMI panels, smart energy meters, factory automation gateways, and medical diagnostic equipment requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant QFN packaging.

Supply support for MCP23S09T-E/MG 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

Microchip Technology Inc. is a leading provider of microcontrollers, analog components, and connectivity solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The MCP23X09 family was developed specifically for cost-sensitive, space-constrained embedded systems needing reliable, low-power GPIO expansion over standard serial buses - emphasizing ease of integration, interrupt efficiency, and wide voltage operation.

FAQ

What is the maximum SPI clock frequency supported by the MCP23S09T-E/MG?

The MCP23S09T-E/MG supports SPI clock frequencies up to 10 MHz under standard operating conditions (VDD ≥ 2.3V). At lower supply voltages (1.8V–2.2V), the maximum guaranteed clock rate is reduced to 5 MHz per Microchip's DS20002121C specification. This ensures robust timing margin for high-throughput GPIO updates in real-time control applications using the MCP23S09T-E/MG.

Does the MCP23S09T-E/MG support hardware reset, and how is it implemented?

Yes, the MCP23S09T-E/MG includes a dedicated active-low hardware RESET pin (Pin 7 in QFN-16). Asserting RESET ≤ 100 ns initiates a full Power-On Reset sequence, restoring all internal registers (IODIR, IPOL, GPPU, etc.) to their POR default states and halting ongoing SPI transactions. This function is critical for system recovery in harsh environments and is fully documented in Section 1.2 of the MCP23S09T-E/MG datasheet.

Can the MCP23S09T-E/MG drive 5V logic inputs while operating from a 3.3V supply?

Yes, the MCP23S09T-E/MG GPIO pins (GP0–GP7) are explicitly rated for 5.5V-tolerant inputs regardless of VDD voltage (1.8V–5.5V). When powered from 3.3V, it safely accepts 5V TTL/CMOS logic levels on input pins without damage or level-shifting circuitry - a key feature confirmed in Table 1-2 and Section 1.5 of the MCP23S09T-E/MG datasheet.

How does the interrupt capture register (INTCAP) improve system reliability in the MCP23S09T-E/MG?

The INTCAP register in the MCP23S09T-E/MG captures the exact GPIO port state at the instant an interrupt occurs, providing a deterministic snapshot independent of subsequent pin transitions. This prevents missed or misattributed events during host read latency, especially in noisy industrial settings - a capability absent in basic I/O expanders and explicitly defined in Register 1-9 of the MCP23S09T-E/MG datasheet.

Is the exposed thermal pad (EP) on the MCP23S09T-E/MG package required to be connected to ground?

The exposed thermal pad (EP) on the MCP23S09T-E/MG QFN package is not electrically required to be connected, but Microchip strongly recommends soldering it to the PCB ground plane. Doing so improves thermal resistance by ~30°C/W and enhances mechanical reliability. Table 1-2 and Figure 1-1 in the MCP23S09T-E/MG datasheet confirm EP may be left floating or tied to VSS - however, production designs should connect it for optimal performance.