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Microchip Technology MIC74BQS
- Part No.:
- MIC74BQS
- Manufacturer:
- Microchip Technology
- Category:
- I/O Expanders
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
MIC74BQS.pdf
- Description:
- IC XPNDR 100KHZ I2C SMBUS 16QSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,389
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Product details
Overview
MIC74BQS 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 for direct LED driving - deployed in PC system management and microcontroller I/O expansion.
For engineers reviewing the MIC74BQS datasheet, MIC74BQS pinout, MIC74BQS application, or MIC74BQS 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 precise register-level configuration details for I/O direction, output type, and interrupt masking - all directly extracted from Microchip DS20005969A.
Technical Context
The MIC74BQS implements a dedicated SMBus-compliant 2-wire interface with clock stretching support and ARA (Alert Response Address) protocol handling, enabling multi-device bus sharing (up to 8 units via A0–A2 address inputs). Its internal state machine manages fan startup sequencing (/FS2–/FS0 and /SHDN timing with tSTART/2 delays) without host intervention.
It features seven user-accessible registers - DEV_CFG (global IE/FAN control), DIR (per-bit input/output selection), OUT_CFG (push-pull vs. open-drain), STATUS (input-change flags), INT_MASK (per-bit interrupt enable), DATA (I/O read/write), and FAN_SPEED (3-bit fan mode control) - all accessible via standard SMBus Write_Byte/Read_Byte transactions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Interface | SMBus™/I²C™-compatible 2-wire serial with /ALERT interrupt output and ARA support |
| Supply Voltage | 2.7V to 3.6V - compatible with 3.3V logic systems; supports stable operation across industrial temperature range (–40°C to +85°C) |
| I/O Capability | 8 bidirectional pins (P0–P7); each configurable as input or output; outputs drive 10 mA (VOL ≤ 0.4V at IOL = 3 mA) for direct LED interfacing |
| Fan Control | Hardware-accelerated fan speed control using /FS2–/FS0 and /SHDN outputs; tSTART = 1 sec startup pulse ensures reliable low-speed fan initiation |
| Quiescent Current | 2 µA typical (IDD) - enables ultra-low-power system monitoring in standby or battery-backed applications |
| Input Tolerance | 5V-tolerant I/O - allows safe interfacing with mixed-voltage systems without level-shifting circuitry |
| Interrupt Latency | t/INT ≤ 4 µs - guarantees rapid host notification of input state changes without polling overhead |
Pinout & Package
Package: 16-pin QSOP (QS), ultra-small footprint, 1.0 mm max height - optimized for space-constrained portable and desktop PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1–3 (A0, A1, A2) | Address Input | Set 3 LSBs of 7-bit SMBus client address (20h–27h); sampled once at power-on; determines bus position among up to 8 devices |
| 4–7 (P0–P3) | General-Purpose I/O | Programmable input/output; direction and output type (push-pull/open-drain) controlled by DIR/OUT_CFG registers; support interrupt-on-change |
| 8 (GND) | Ground Reference | Common return path for all internal circuitry and I/O signals |
| 9–12 (P4–P7) | Configurable I/O or Fan Control | In I/O mode: general-purpose pins; in fan mode (FAN=1): P4=/SHDN, P5=/FS0, P6=/FS1, P7=/FS2 - outputs driven exclusively by FAN_SPEED register |
| 13 (/ALERT) | Interrupt Output | Active-low, open-drain signal asserting on enabled input state changes; cleared after ARA response or STATUS register read |
| 14 (CLK) | Serial Clock Input | Host-provided SMBus clock; supports clock stretching; tLOW ≥ 4.7 µs, tHIGH ≥ 4 µs, tTIMEOUT = 25–35 ms |
| 15 (DATA) | Serial Data I/O | Open-drain bidirectional data line requiring external pull-up; supports standard SMBus Read_Byte/Write_Byte protocols |
| 16 (VDD) | Power Supply | 2.7V–3.6V supply input; internal regulation supports low-noise I/O operation and fan control logic |
Key Features
| Feature | Design Value |
|---|---|
| Eight independent programmable I/O bits | Each P0–P7 individually configured as input or output via DIR register; no shared port constraints |
| Hardware fan speed control logic | Internal state machine sequences /FS2–/FS0 and /SHDN with precise tSTART/2 timing - eliminates bit-banging firmware overhead |
| Interrupt-on-change with /ALERT output | Dedicated open-drain /ALERT pin asserts within ≤4 µs of input transition; masks individual pins via INT_MASK register |
| 5V-tolerant I/O with 2 µA quiescent current | Enables direct connection to 5V sensors/switches while maintaining <2 µA sleep current - critical for battery-powered monitoring |
| Up to 8 devices per SMBus segment | A0–A2 address pins allow unique 7-bit addresses (20h–27h); supports scalable I/O expansion without additional bus controllers |
Applications
| PC System Management | Microcontroller I/O Expansion |
|---|---|
Use Scenario: Monitoring thermal sensors, chassis intrusion switches, and power-good signals in desktop/laptop motherboards. IC Role / Device Role / Timing Role: Acts as SMBus slave providing 8-bit parallel status reporting and interrupt-driven alerting to the EC (Embedded Controller). Use Value: Reduces EC GPIO usage; eliminates polling cycles via /ALERT; supports hot-plug detection with sub-4 µs latency. |
Use Scenario: Adding digital inputs/outputs to resource-constrained MCU designs (e.g., PIC, ARM Cortex-M0+). IC Role / Device Role / Timing Role: Serial-to-parallel bridge extending MCU's native I/O count using only two pins (CLK/DATA) plus /ALERT. Use Value: Saves MCU GPIOs and firmware resources; enables 10 mA LED drive per pin without external drivers. |
| Fan Speed Control | Distributed Sensing & Control |
Use Scenario: Regulating cooling fans in network equipment or industrial controllers based on temperature feedback. IC Role / Device Role / Timing Role: Dedicated fan controller generating /FS0–/FS2 and /SHDN waveforms per FAN_SPEED register value. Use Value: Guarantees reliable fan startup with 1-second high-speed pulse (tSTART); avoids firmware timing-critical bit-banging. |
Use Scenario: Reading multiple remote switches, encoders, or status indicators across a distributed embedded system. IC Role / Device Role / Timing Role: Remote I/O node on SMBus providing synchronized status reads and interrupt-triggered event reporting. Use Value: Enables deterministic response to mechanical switch closures or sensor transitions without bus contention. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar I/O expansion applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| PCA9555DWR | 16-bit I/O expander; no integrated fan control; higher IDD (≈10 µA); supports 1.65–5.5V supply | Lacks hardware fan sequencing; requires external logic or MCU firmware for fan PWM generation | Select when >8 I/O bits are needed and fan control is handled elsewhere; verify voltage compatibility with 3.3V-only systems. |
| TCA6424ARGJR | 24-bit I/O expander; includes reset pin and glitch filtering; 1 µA standby current; 1.65–3.6V operation | No fan control logic; interrupt output lacks ARA protocol support; requires external pull-ups on all I/O | Prefer for high-channel-count, ultra-low-power sensing nodes where fan control is unnecessary and reset functionality is critical. |
Compared with PCA9555DWR and TCA6424ARGJR, the MIC74BQS uniquely integrates fan speed control logic and delivers lower quiescent current (2 µA) in a compact QSOP-16 package - making it optimal for space- and power-sensitive PC thermal management and embedded fan control applications.
Availability
MIC74BQS is available at Aetrix Electronics and suitable for PC system management, microcontroller I/O expansion, and fan control applications requiring stable component supply, long-term lifecycle assurance, and traceable sourcing for industrial and computing platforms.
Supply support for MIC74BQS 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 is a leading provider of microcontrollers, analog components, and connectivity solutions, serving automotive, industrial, consumer, and computing markets with high-reliability silicon and development tools.
The MIC74BQS belongs to Microchip's system management IC product line, designed specifically for SMBus-based platform monitoring, thermal control, and I/O extension in space-constrained computing and embedded systems.
FAQ
What is the exact package type and footprint of the MIC74BQS?
The MIC74BQS is packaged in a 16-pin QSOP (Quad Small Outline Package) with standard 0.65 mm lead pitch and 1.0 mm maximum package height. Its pinout matches the Microchip DS20005969A datasheet Figure 1, and the package is designated "QS" in Microchip's ordering nomenclature - confirming physical compatibility with QSOP-16 footprints and reflow profiles.
Does the MIC74BQS support true I²C communication or only SMBus?
The MIC74BQS is fully compatible with both SMBus 2.0 and standard I²C protocols. It implements required SMBus features including Alert Response Address (ARA = 0x14), timeout detection (tTIMEOUT = 25–35 ms), and clock stretching, while also supporting standard I²C Start/Stop conditions, ACK/NAK, and 7-bit addressing - ensuring interoperability with generic I²C masters.
How does fan control work on the MIC74BQS, and what happens during startup?
When the FAN bit in the DEV_CFG register is set, P4–P7 become /SHDN, /FS0, /FS1, and /FS2 - driven exclusively by the FAN_SPEED register. Upon writing a non-zero value to FAN_SPEED from zero, the MIC74BQS asserts all /FS outputs high and /SHDN low for tSTART ≈ 1 second to ensure fan spin-up, then transitions to the programmed speed - all managed autonomously by internal logic.
What is the maximum sink current per I/O pin on the MIC74BQS, and under what conditions is it guaranteed?
The MIC74BQS guarantees 10 mA sink current per I/O pin (P0–P7) when configured as open-drain or push-pull output, with VOL ≤ 0.4 V at IOL = 3 mA (VDD = 2.7V) and VOL ≤ 1.0 V at IOL = 10 mA (VDD = 3.3V), per Table 1-1 in DS20005969A - enabling direct LED driving without external drivers.
Can the MIC74BQS operate with a 5V microcontroller I/O interface despite its 3.3V supply?
Yes - all I/O pins (P0–P7, A0–A2, /ALERT, DATA, CLK) are 5V-tolerant per Absolute Maximum Ratings (VIN = GND – 0.3V to +5.5V), allowing safe connection to 5V logic levels while powered from 2.7–3.6V. This eliminates level shifters in mixed-voltage systems, as confirmed in Section 1.0 and Table 1-1 of DS20005969A.
MIC74BQS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Discontinued at Digi-Key
- Programmable:
- Not Verified
- Number of I/O:
- 8
- Interface:
- I2C, SMBus
- Interrupt Output:
- Yes
- Features:
- Fan Speed Controller
- Output Type:
- Open Drain, Push-Pull
- Current - Output Source/Sink:
- 7mA, 10mA
- Clock Frequency:
- 100 kHz
- Voltage - Supply:
- 2.7V ~ 3.6V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QSOP
MIC74BQS FAQ
1.How can I place an order for MIC74BQS through Aetrix?
Please submit a Request for Quotation (RFQ) for MIC74BQS on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for MIC74BQS reliable?
The price and inventory of MIC74BQS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MIC74BQS is usually 5 days.
3.What payment methods are accepted for MIC74BQS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MIC74BQS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MIC74BQS?
MIC74BQS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MIC74BQS order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for MIC74BQS?
For technical support, including MIC74BQS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MIC74BQS requirements.
6.How does Aetrix verify that MIC74BQS is sourced from the original manufacturer or authorized distributors?
All MIC74BQS products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MIC74BQS meets industry standards.
7.What is the process for return or replacement of MIC74BQS?
All MIC74BQS units undergo pre-shipment inspection (PSI). If there is an issue with MIC74BQS, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The MIC74BQS part is unused and in its original packaging.
Return procedure for MIC74BQS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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