Microchip Technology MIC74YQS

Overview

MIC74YQS from Microchip Technology is an SMBus/I²C-compatible 8-bit serial-to-parallel I/O expander with integrated fan speed control logic, operating from 2.7V to 3.6V, featuring 5V-tolerant I/O pins, 2 µA typical quiescent current, and programmable push-pull or open-drain outputs capable of sourcing/sinking up to 10 mA per pin - deployed in PC system management and microcontroller I/O expansion.

For engineers reviewing the MIC74YQS datasheet, MIC74YQS pinout, MIC74YQS application, or MIC74YQS equivalent, this page delivers verified electrical specs, validated QSOP-16 pin mapping, confirmed fan-control timing behavior (tSTART = 1 sec), real-world interrupt latency (t/INT ≤ 4 µs), and two documented alternative parts for I/O expansion with SMBus interface compatibility.

Technical Context

The MIC74YQS implements a dedicated SMBus 2.0-compliant slave interface with fixed 7-bit client address (0x20–0x27 via A0–A2), supporting Read_Byte/Write_Byte protocols and Alert Response Address (ARA = 0x14) for interrupt arbitration. Its internal register set includes DEV_CFG, DIR, OUT_CFG, STATUS, INT_MASK, DATA, and FAN_SPEED - all accessible over the bus without external configuration hardware.

It integrates dual-mode I/O operation: standard GPIO mode (P0–P7 fully configurable as input/output with interrupt-on-change) and fan control mode (P4–P7 remapped to /SHDN and /FS2–/FS0 with automatic startup pulse tSTART = 1 sec and state-machine-driven sequencing). Fan mode disables interrupt generation on P4–P7 and overrides DIR/OUT_CFG settings for those pins.

Key Specifications

Pinout & Package

Package: 16-pin QSOP (QS), 3.9 mm × 4.9 mm, 1.0 mm height - suitable for space-constrained PCB layouts in desktop and embedded applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MIC74YQS, PCA9555DWR offers double the I/O count but omits fan-specific features, while TCA6408APWR reduces feature depth by removing both interrupt signaling and fan control - making MIC74YQS uniquely suited for thermally managed embedded systems requiring coordinated fan startup and low-latency event reporting.

Availability

MIC74YQS is available at Aetrix Electronics and suitable for PC system management, microcontroller I/O expansion, and embedded fan control applications requiring stable component supply, long-term lifecycle support, and consistent parametric performance across temperature ranges (–40°C to +85°C).

Supply support for MIC74YQS 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 MIC74YQS belongs to Microchip's system management IC product line, designed specifically for SMBus-based I/O expansion and thermal subsystem control in space- and power-constrained computing platforms.

FAQ

What is the SMBus address range supported by the MIC74YQS?

The MIC74YQS supports eight unique SMBus addresses (0x20–0x27) determined by the logic states of A0–A2 pins at power-on. These pins are sampled once during initialization and cannot be reconfigured dynamically. Each address corresponds to a distinct device on the same bus, enabling up to eight MIC74YQS units for 64 total I/O bits.

Does the MIC74YQS require external pull-up resistors on the SMBus lines?

Yes, the MIC74YQS requires external pull-up resistors on both CLK and DATA lines, as its DATA pin is open-drain and CLK is input-only. Typical values are 2.2 kΩ to 10 kΩ depending on bus capacitance and speed requirements. The /ALERT pin also requires a pull-up resistor to function as an active-low interrupt signal.

How does fan mode affect the P4–P7 pins on the MIC74YQS?

When the FAN bit in the DEV_CFG register is set, P4–P7 are remapped to /SHDN and /FS2–/FS0 outputs controlled exclusively by the FAN_SPEED register. Their direction (DIR), output type (OUT_CFG), and interrupt mask (INT_MASK) settings are ignored, and no interrupts can be generated on these pins in fan mode.

What is the maximum sink current per I/O pin on the MIC74YQS?

The MIC74YQS guarantees 7 mA sink current per I/O pin at VOL = 0.4 V with VDD = 2.7 V, and 10 mA at VOL = 1.0 V with VDD = 3.3 V. This allows direct LED driving (10 mA typical) or interfacing with standard logic families without external drivers.

Can the MIC74YQS generate interrupts on all eight I/O pins?

Interrupts are supported on all eight I/O pins (P0–P7) only when the device is in GPIO mode. In fan mode, interrupts are disabled on P4–P7. For P0–P3, interrupts require both the global IE bit (in DEV_CFG) and individual IMn bits (in INT_MASK) to be enabled, and the corresponding pin must be configured as an input via the DIR register.