Microchip Technology MCP23S17T-E/SS

Overview

MCP23S17T-E/SS from Microchip Technology is a 16-bit SPI-based I/O expander IC used to extend microcontroller GPIO resources in embedded systems. It features dual 8-bit bidirectional ports (PORTA and PORTB), configurable interrupt outputs (INTA/INTB), hardware address pins (A0–A2) for up to eight devices on one bus, and operates from 1.8V to 5.5V across –40°C to +85°C. It is widely deployed in industrial control panels requiring remote digital I/O expansion with deterministic interrupt response.

For engineers reviewing the MCP23S17T-E/SS datasheet, MCP23S17T-E/SS pinout, MCP23S17T-E/SS application, or MCP23S17T-E/SS equivalent, key selection considerations include its 10 MHz SPI interface speed, 1 µA standby current, interrupt-on-change capability per port, internal weak pull-up resistors (75 µA typical at 5V), and SSOP-28 package compatibility with space-constrained PCB layouts.

Technical Context

The MCP23S17T-E/SS implements a register-mapped SPI peripheral with 22 configurable registers-including IODIR, GPIO, OLAT, IPOL, GPINTEN, INTCON, and IOCON-supporting both byte-mode and sequential-mode access. Its interrupt logic allows independent or OR'ed activation of INTA and INTB based on input change or DEFVAL comparison, with glitch filtering (150 ns) and interrupt capture (INTCAP) for state preservation.

It uses Schmitt-trigger inputs on CS, SCK, SI, and RESET for noise immunity, TTL-level inputs on A0–A2, and supports SPI Mode 0,0 and Mode 1,1. The device includes an external hardware reset (active-low), power-on reset circuitry, and internal weak pull-ups (40–115 µA at 5V) configurable per pin. All I/Os are rated for ±25 mA output drive and tolerate 5.5V on VDD.

Key Specifications

Pinout & Package

Package: 28-pin SSOP (Shrink Small Outline Package), 5.30 mm body width, surface-mount, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP23017T-E/SS, the MCP23S17T-E/SS offers higher serial throughput and deterministic timing but requires SPI resource allocation; versus TCA9554APWR, it delivers full 16-bit expandability, dual interrupts, and robust industrial-grade features at modest cost premium.

Availability

MCP23S17T-E/SS is available at Aetrix Electronics and suitable for industrial HMI panels, smart energy meters, automotive body control modules, and IoT sensor hubs requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MCP23S17T-E/SS 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, serving industrial, automotive, and consumer markets with vertically integrated silicon and development tools.

The MCP23X17 product line was designed to deliver scalable, low-power, interrupt-capable parallel I/O expansion for resource-constrained microcontrollers - emphasizing register compatibility, voltage flexibility, and robust ESD/EMI performance.

FAQ

What is the maximum SPI clock frequency supported by the MCP23S17T-E/SS?

The MCP23S17T-E/SS supports up to 10 MHz SPI clock frequency when operating at VDD ≥ 2.7V. At 1.8V supply, the maximum clock rate is 5 MHz. These limits are specified in Table 1-4 of the DS20001952D datasheet and reflect guaranteed timing margins across temperature and voltage ranges. The MCP23S17T-E/SS must be configured for SPI Mode 0,0 or Mode 1,1 per its control byte format.

Does the MCP23S17T-E/SS require external pull-up resistors on its SPI lines?

No, the MCP23S17T-E/SS does not require external pull-up resistors on SI, SO, or SCK - these pins are driven actively by the host and device. However, the CS pin must be pulled high externally when inactive to prevent spurious selection. A0–A2 address pins also require external bias (VDD or VSS) to set device address; floating states are undefined and prohibited.

How does the interrupt logic work on the MCP23S17T-E/SS?

The MCP23S17T-E/SS supports two interrupt sources per port: change from the last-read GPIO value (default) or change from a user-defined DEFVAL register. INTA and INTB can operate independently or be logically OR'ed via IOCON.MIRROR. Interrupts are latched until the corresponding INTF register is read, and the INTCAP register captures port state at interrupt time - ensuring no event loss during host servicing.

Can the MCP23S17T-E/SS drive LEDs directly?

Yes, the MCP23S17T-E/SS can drive LEDs directly: each I/O pin supports ±25 mA output current at VDD = 4.5V, sufficient for standard 2–20 mA indicator LEDs. For common-anode configurations, configure the pin as output with low-level drive; for common-cathode, use high-level drive with series resistor. Total package current must remain within 125 mA into VDD and 150 mA out of VSS limits.

Is the MCP23S17T-E/SS AEC-Q100 qualified?

Yes, the MCP23S17T-E/SS is AEC-Q100 qualified for Grade 3 (–40°C to +85°C) operation. This qualification covers stress testing for temperature cycling, humidity, ESD, and latch-up - confirming suitability for automotive body electronics applications. The qualification applies specifically to the -E/SS variant and is documented in Microchip's official AEC-Q100 certificate for the MCP23X17 family.