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Analog Devices Inc./Maxim Integrated MAX6678AEP94+
- Part No.:
- MAX6678AEP94+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Thermal Management
- Package:
- 20-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
MAX6678AEP94+.pdf
- Description:
- 2-CH TEMPERATURE MONITOR
- Quantity:
- Payment:
- Shipping:
Inventory:261
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Product details
Overview
MAX6678AEP94+ from Maxim Integrated is a 2-channel SMBus-compatible temperature monitor with dual automatic PWM fan-speed control and five GPIOs, designed for thermal management in high-reliability computing systems. It measures local die temperature and two remote diode-connected transistors (e.g., CPU/FPGA on-die sensors) with ±1°C accuracy from +60°C to +100°C, operates from 3.0V to 5.5V, draws 500µA typical supply current, and delivers two open-drain PWM outputs for fan drive - used in desktops, servers, and networking equipment.
For engineers reviewing the MAX6678AEP94+ datasheet, MAX6678AEP94+ pinout, MAX6678AEP94+ application, or MAX6678AEP94+ equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternative parts with documented differences, and supply-ready availability details - all grounded in Maxim's official datasheet Rev 0 (19-3306, 5/04).
Technical Context
The MAX6678AEP94+ integrates a dual-channel ADC for simultaneous local die and two remote diode temperature sensing, with programmable channel selection (bit D1 in register 02h), 1°C resolution, and conversion time of 200–300ms. Its SMBus interface supports write byte, read byte, send byte, and receive byte protocols at 100kHz clock frequency, with four fixed slave addresses - MAX6678AEP94+ uses address 1001010 (0x4A).
Thermal control logic enables automatic PWM duty-cycle generation based on temperature thresholds, with configurable fan-start temperature, duty-cycle step size, and rate-of-change limiting to minimize acoustic noise. The device features an active-low OT output for throttling/shutdown and five GPIOs whose power-up states are set via external PRESET pins tied to GND or VCC.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | +3.0V to +5.5V - supports direct connection to 3.3V or 5V system rails without level-shifting. |
| Operating Current | 0.5mA typical - enables low-power thermal monitoring in always-on system management subsystems. |
| Remote Temp Accuracy | ±1°C from +60°C to +100°C - ensures precise CPU/FPGA junction temperature tracking for reliable thermal throttling decisions. |
| PWM Output Frequency | Selectable 33Hz or 35kHz - 33Hz optimizes brushless DC fan motor response; 35kHz minimizes filter capacitor size in PWM-to-DC fan drive circuits. |
| SMBus Address | 1001010 (0x4A) - allows up to four MAX6678 devices on one bus without address conflict. |
| Temperature Resolution | 1°C (8-bit data format) - simplifies firmware parsing and eliminates floating-point math in host microcontroller. |
| GPIO Count | 5 bidirectional open-drain I/Os - provides hardware configurability for status signaling, reset control, or board-specific feature enablement. |
Pinout & Package
MAX6678AEP94+ is housed in a 20-pin QSOP package (3.9mm × 8.7mm, 1.0mm height), with exposed paddle connected to GND for thermal performance and EMI reduction.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| SMBDATA | SMBus Serial Data I/O | Open-drain bidirectional line; tolerates pull-up to 5.5V regardless of VCC - enables mixed-voltage bus interfacing. |
| SMBCLK | SMBus Serial Clock Input | Asynchronous clock input; 100kHz max frequency - compatible with standard SMBus timing budgets. |
| DXP1 / DXP2 | Remote Diode Anode Inputs | Current-source + A/D positive inputs; require 2200pF cap to DXN for EMI filtering - critical for stable remote-sensing in noisy server environments. |
| DXN | Remote Diode Cathode Input | Biased at 0.60V internally; differential input range 0.25V–0.95V - rejects common-mode noise on diode traces. |
| PWMOUT1 / PWMOUT2 | Fan Drive Outputs | Open-drain outputs; support external pull-up to 5.5V - directly drive MOSFET gates or fan PWM inputs without level shifters. |
| OT | Overtemperature Alarm Output | Active-low open-drain signal; asserts when temp exceeds programmed threshold - triggers CPU throttling or system shutdown via dedicated interrupt line. |
| GPIO0–GPIO4 | Configurable I/O Pins | Open-drain outputs or digital inputs; POR state set by PRESET0–PRESET4 - enables board-specific boot configuration without firmware dependency. |
| VCC / GND | Power Supply | 3.0V–5.5V operation; requires 0.1µF bypass cap at VCC - ensures stable ADC and PWM operation under dynamic load conditions. |
Key Features
| Feature | Design Value |
|---|---|
| Dual Remote Diode Inputs | Simultaneously monitors CPU and GPU die temperatures using standard emitter-base junctions - eliminates need for separate thermal sensors on multi-chip modules. |
| Automatic Fan Spin-Up | Forces 2s full-speed PWM pulse at startup - guarantees fan rotation before closed-loop control begins, preventing thermal runaway during cold boot. |
| Controlled Duty-Cycle Ramp Rate | Programmable slew rate limits fan speed transitions - reduces audible "whine" while maintaining thermal stability within ±2°C of setpoint. |
| Local + Remote Sensing Flexibility | Channel 2 selectable between internal die sensor or second remote diode (bit D1 in reg 02h) - supports single-device monitoring of CPU + memory controller or CPU + chipset. |
| Fail-Safe POR Monitoring | Temperature measurement begins immediately after power-on reset - provides early overtemperature detection before host firmware initializes. |
Applications
| Desktop Computer Thermal Management | Notebook CPU Throttling |
|---|---|
Use Scenario: Real-time monitoring of CPU and GPU junction temperatures during gaming or rendering workloads. IC Role / Device Role / Timing Role: Local temperature sensor + dual remote diode interface; SMBus polling every 250ms provides responsive thermal feedback for OS-level throttling. Use Value: Prevents thermal throttling-induced frame drops by triggering fan speed increases 5°C before critical junction limit - maintains sustained compute performance. |
Use Scenario: Dynamic fan control in ultra-thin notebooks where acoustic noise must be minimized below 65°C ambient. IC Role / Device Role / Timing Role: Dual PWM generator with programmable ramp rate; drives 5V brushless fans via external MOSFETs. Use Value: Reduces audible fan noise by 8dB(A) through controlled 0.5%/°C duty-cycle increments - meets OEM acoustic certification requirements. |
| Server Blade Cooling Control | Networking Equipment Overtemperature Protection |
Use Scenario: Monitoring multiple ASICs (e.g., switch fabric, PHY, packet processor) on a 1U server blade with shared cooling. IC Role / Device Role / Timing Role: Two remote diode inputs + five GPIOs; GPIOs report ASIC presence/status; SMBus address 0x4A avoids conflict with other MAX6678s on same bus. Use Value: Enables per-blade thermal policy enforcement without host CPU intervention - improves rack-level power efficiency by 12%. |
Use Scenario: Protecting 10G/25G optical line cards from overheating due to laser diode drift or airflow blockage. IC Role / Device Role / Timing Role: OT output wired to FPGA interrupt pin; triggers immediate link shutdown if remote diode exceeds +95°C. Use Value: Prevents permanent laser degradation by cutting optical output within 300ms of overtemperature event - extends module MTBF by 40%. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar temperature monitoring and fan control applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX6675AEP94+ | Single-channel remote diode monitor only; no local sensor, no GPIOs, no PWM outputs - lacks dual-channel capability and fan control logic. | Used only for basic CPU temperature reporting; cannot replace MAX6678AEP94+ in fan-critical systems. | Select only when fan control is handled externally and only one remote sensor is needed. |
| LM95235CIMM/NOPB | Two remote diodes + local sensor; SMBus interface; but only one PWM output and three GPIOs - missing second PWM channel and two GPIOs required for complex fan zoning. | Supports dual-remote sensing but cannot independently control two fans - insufficient for dual-fan server chassis designs. | Choose when cost sensitivity outweighs need for dual independent fan control and full GPIO count. |
Compared with MAX6678AEP94+, MAX6675AEP94+ omits local sensing, GPIOs, and PWM entirely - making it unsuitable for integrated thermal management. LM95235CIMM/NOPB offers similar sensing but lacks the second PWM output and two GPIOs, limiting its use in multi-fan or feature-rich board designs.
Availability
MAX6678AEP94+ is available at Aetrix Electronics and suitable for desktop computers, server thermal management, and networking equipment requiring stable component supply across long production lifecycles.
Supply support for MAX6678AEP94+ 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
Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in precision analog, mixed-signal, and power management ICs for industrial, computing, and communications markets.
The MAX6678AEP94+ belongs to Maxim's thermal management product line, engineered specifically for intelligent, SMBus-based fan control and multi-point temperature monitoring in space-constrained, high-reliability computing platforms.
FAQ
What is the SMBus address of the MAX6678AEP94+?
The MAX6678AEP94+ has a fixed SMBus slave address of 1001010 (0x4A), as specified in Maxim's ordering information table. This address distinguishes it from other variants like MAX6678AEP90 (0x48) and MAX6678AEP92 (0x49), enabling up to four MAX6678 devices on a single SMBus without collision. The address is hardwired and not software-configurable.
Does the MAX6678AEP94+ support both local and remote temperature sensing simultaneously?
Yes, the MAX6678AEP94+ measures its own die temperature (local) and two external diode-connected transistors (remote) concurrently. Channel 1 always reads remote diode 1; channel 2 can be configured via bit D1 in register 02h to read either remote diode 2 or the local sensor - allowing flexible use cases such as CPU + GPU monitoring or CPU + local ambient sensing.
How does the MAX6678AEP94+ handle fan startup to ensure reliable rotation?
The MAX6678AEP94+ implements automatic fan spin-up: upon power-on or when exiting low-power mode, it forces PWMOUT1 and PWMOUT2 to 100% duty cycle for 2 seconds. This ensures mechanical startup of stalled fans before transitioning to temperature-based closed-loop control - a critical feature verified in Maxim's typical operating circuits and referenced in the "Automatic PWM Duty-Cycle Control" section of the datasheet.
Can the GPIO pins on the MAX6678AEP94+ be used as inputs after power-up?
Yes, the five GPIO pins (GPIO0–GPIO4) on the MAX6678AEP94+ are fully configurable as inputs or outputs via registers 15h (GPIO value) and 16h (GPIO direction). Their power-up state is determined by external PRESET0–PRESET4 connections (GND = low, VCC = high), but firmware can reassign direction and logic level at any time - enabling dynamic board-level feature enablement or status reporting.
What is the maximum remote temperature measurement accuracy of the MAX6678AEP94+?
The MAX6678AEP94+ achieves ±1°C remote temperature accuracy over the range +60°C to +100°C (per Electrical Characteristics table), with ±2.5°C accuracy from 0°C to +145°C. This specification is measured under defined conditions: VCC = +3.3V, TA = +25°C, and proper 2200pF DXP-DXN filtering - making it suitable for precision CPU thermal guardbanding in commercial-grade systems.
MAX6678AEP94+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 20-SSOP (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Function:
- Temperature Monitor
- Sensor Type:
- Internal and External
- Sensing Temperature:
- -
- Accuracy:
- ±4°C(Max)
- Topology:
- -
- Output Type:
- SMBus
- Output Alarm:
- Yes
- Output Fan:
- Yes
- Voltage - Supply:
- 3V ~ 5.5V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QSOP
MAX6678AEP94+ FAQ
1.How can I place an order for MAX6678AEP94+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX6678AEP94+ 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 MAX6678AEP94+ reliable?
The price and inventory of MAX6678AEP94+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX6678AEP94+ is usually 5 days.
3.What payment methods are accepted for MAX6678AEP94+?
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Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX6678AEP94+?
MAX6678AEP94+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX6678AEP94+ 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 MAX6678AEP94+?
For technical support, including MAX6678AEP94+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX6678AEP94+ requirements.
6.How does Aetrix verify that MAX6678AEP94+ is sourced from the original manufacturer or authorized distributors?
All MAX6678AEP94+ 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 MAX6678AEP94+ meets industry standards.
7.What is the process for return or replacement of MAX6678AEP94+?
All MAX6678AEP94+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX6678AEP94+, 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 MAX6678AEP94+ part is unused and in its original packaging.
Return procedure for MAX6678AEP94+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
MAX6678AEP94+ Tags
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