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Analog Devices Inc./Maxim Integrated MAX6644LBAAEE+T
- Part No.:
- MAX6644LBAAEE+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Thermal Management
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
MAX6644LBAAEE+T.pdf
- Description:
- IC CNTRLR FAN SPEED 16-QSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,570
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Product details
Overview
MAX6644LBAAEE+T from Analog Devices is a dual-channel remote-diode temperature monitor and automatic PWM fan-speed controller that measures two external transistor-based temperatures and adjusts fan speed via 32Hz PWM output with 1.6% duty-cycle steps. It operates from 3.0V to 5.5V, consumes 500µA typical supply current, and features pin-selectable high/low trip thresholds (in 5°C increments) for precise thermal management in multi-fan systems.
For engineers reviewing the MAX6644LBAAEE+T datasheet, MAX6644LBAAEE+T pinout, MAX6644LBAAEE+T application, or MAX6644LBAAEE+T equivalent, key selection considerations include its 16-pin QSOP package, dual FAN_IN inputs supporting tachometer/current-sense/locked-rotor failure detection, OT alarm output, and compatibility with discrete 2N3904/2N3906-style remote sensors with ideality factor ~1.01.
Technical Context
The MAX6644LBAAEE+T implements a dedicated analog front-end for two remote diode-connected transistors, using switched-current sensing and integrating ADCs with 2°C measurement accuracy over –40°C to +125°C. Its PWM engine generates a fixed 32Hz waveform with 64-step (1.5% per step) duty-cycle control, updated every 4 seconds based on the larger of two measured temperatures.
It supports three fan-fail detection modes per channel-tachometer pulse counting, current-sense resistor AC-coupled waveform analysis, or locked-rotor logic monitoring-configured via the TACHSET pin. The device asserts FANFAIL (open-drain, active-low) only when PWM duty cycle reaches 100%, ensuring fault detection during spin-up or sustained high-temperature operation.
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 regulation. |
| PWM Output Frequency | 32Hz ±1Hz - Fixed frequency optimized for acoustic performance and MOSFET gate drive efficiency. |
| Temperature Accuracy | ±2°C (20°C–100°C), ±3°C (0°C–125°C) - Enables reliable thermal throttling within server and storage thermal envelopes. |
| Duty-Cycle Resolution | 1.5% per step (64 steps total) - Minimizes audible fan-speed transitions while enabling fine-grained cooling response. |
| Fan-Fail Detection Window | 2-second pulse count at 100% duty cycle - Detects <480 RPM (2-pulse/rev) or sustained locked-rotor condition. |
| Remote Diode Current | 100µA typical sourcing - Matches standard small-signal transistor bias requirements (e.g., 2N3904). |
| Operating Current | 500µA typical (no load) - Enables low-power thermal monitoring in always-on subsystems. |
Pinout & Package
MAX6644LBAAEE+T is housed in a 16-pin QSOP (E16-1) package with 0.154" body width and 0.025" lead pitch, suitable for automated SMT assembly and high-density PCB layouts.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1, 15 | TH1, TH2 | High-temperature threshold select inputs - Set THIGH in 5°C steps (20°C–60°C) via VDD/GND/floating combinations. |
| 2, 3 | TL2, TL1 | Low-temperature threshold select inputs - Set TLOW in 5°C steps (15°C–55°C) to define fan-speed dead band. |
| 4 | FANFAIL | Active-low open-drain alarm - Signals fan failure only during 100% PWM duty cycle (spin-up or thermal overload). |
| 5 | TACHSET | Fan-fail mode selector - Configures FAN_IN1/FAN_IN2 for tachometer, current-sense, or locked-rotor detection. |
| 7 | GND | Analog/digital ground reference - Requires low-impedance connection to system ground plane. |
| 9 | OT | Active-low open-drain overtemperature output - Asserts when measured temperature exceeds factory/pin-set TOVERT (60°C–100°C). |
| 10, 11 | FAN_IN2, FAN_IN1 | Fan status input channels - Accept tach pulses, AC-coupled current-sense waveforms, or logic-level locked-rotor signals. |
| 12 | PWM_OUT | Open-drain PWM output - Drives N-channel MOSFET gate or NPN base; requires external pull-up to ≤5.5V. |
| 13, 14 | OT2, OT1 | Overtemperature threshold select inputs - Set TOVERT in 5°C steps (60°C–100°C) independent of fan-control thresholds. |
| 16 | VDD | Power supply input - Bypass with 0.1µF ceramic capacitor close to pin for noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Dual remote-diode sensing | Measures two external transistor junctions simultaneously - Enables zone-based thermal control across CPU and VRM or multiple ASICs. |
| Configurable fan-fail detection | Three detection modes per channel (tachometer/current-sense/locked-rotor) - Adapts to 2-wire, 3-wire, or 4-wire fan types without external circuitry. |
| Spin-up time & startup delay | 8s spin-up + 0.5s startup delay - Ensures reliable fan start under cold conditions while limiting inrush current at power-on. |
| Controlled duty-cycle ramp rate | Max 0.4% per second (1.5% per 4s) - Prevents abrupt fan acceleration/deceleration that causes acoustic noise or mechanical stress. |
| Remote sensor compatibility | Optimized for n ≈ 1.01 diodes (e.g., 2N3904, 2N3906, CPU on-die diodes) - Delivers ±2°C accuracy without calibration across industrial temperature range. |
Applications
| Server Rack Thermal Management | Enterprise Storage Enclosure Cooling |
|---|---|
|
Use Scenario: Dual-fan cooling in 1U/2U rack servers with CPU and memory DIMM temperature zones. IC Role / Device Role / Timing Role: Monitors remote diodes on CPU and VRM, dynamically adjusts two fans via independent PWM outputs to maintain sub-85°C junction temperatures. Use Value: Eliminates need for microcontroller-based thermal loops; reduces firmware complexity and BOM cost while meeting ASHRAE A4 environmental limits. |
Use Scenario: Fan-speed control in JBOD or NAS enclosures with up to 24 hot-swap drives generating localized heat. IC Role / Device Role / Timing Role: Uses FAN_IN1/FAN_IN2 to monitor tachometer outputs from redundant fans, triggering FANFAIL if either drops below 480 RPM during 100% duty cycle. Use Value: Provides hardware-level fan redundancy assurance without host CPU intervention, improving system uptime and predictive maintenance capability. |
| Network Switch Chassis Cooling | Workstation GPU/ASIC Thermal Control |
|
Use Scenario: Multi-board chassis with line cards, fabric modules, and power supplies requiring independent thermal zones. IC Role / Device Role / Timing Role: Configured with THIGH = 60°C/TLOW = 45°C to maintain 15°C hysteresis; OT set to 90°C for emergency shutdown coordination. Use Value: Enables silent operation at ambient temperatures while delivering rapid response to sudden load-induced thermal spikes in packet processing pipelines. |
Use Scenario: High-performance workstation with discrete GPU and FPGA accelerator sharing a common heatsink and dual-fan assembly. IC Role / Device Role / Timing Role: Measures GPU die and FPGA remote diode temperatures; uses larger temperature value to drive both fans synchronously via single PWM_OUT. Use Value: Prevents GPU thermal throttling during compute-intensive workloads by proactively increasing airflow before junction temperature exceeds 95°C. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-channel PWM fan-speed control applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX6643LBBAEE+T | Includes FULLSPD input and internal die temperature sensor; lacks DXP2 pin - monitors one remote diode + local die temp. | Best suited for single-fan systems where local IC temperature is primary thermal metric (e.g., microcontroller thermal guardbanding). | Select MAX6643LBBAEE+T when full-speed override or on-die thermal feedback is required; not drop-in compatible due to different pinout and feature set. |
| LM87CIMTX/NOPB | Integrated SMBus interface, 9-channel voltage monitoring, and hardware watchdog - adds system management beyond fan control. | Used in complex embedded platforms requiring coordinated thermal/voltage/fault management (e.g., telecom line cards with PMBus compliance). | Choose LM87CIMTX/NOPB when SMBus communication, multi-rail monitoring, or watchdog timer functionality is mandatory; requires firmware integration. |
Compared with MAX6644LBAAEE+T, the MAX6643LBBAEE+T provides local die sensing and forced-full-speed capability but sacrifices dual remote sensing, while the LM87CIMTX/NOPB adds digital system management at the cost of higher design complexity and no pin compatibility.
Availability
MAX6644LBAAEE+T is available at Aetrix Electronics and suitable for networking equipment, enterprise storage systems, and server motherboard designs requiring stable component supply, long-term lifecycle support, and guaranteed traceability for industrial deployments.
Supply support for MAX6644LBAAEE+T 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
Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets since 1965.
The MAX6644LBAAEE+T belongs to Analog Devices' precision thermal management product line, designed specifically for autonomous, low-firmware-footprint fan control in high-reliability computing infrastructure.
FAQ
What is the maximum remote diode series resistance supported by the MAX6644LBAAEE+T without exceeding ±3°C error?
The MAX6644LBAAEE+T tolerates up to 3Ω of remote diode series resistance before introducing >1.36°C offset at +60°C, based on its 90µA current step and 198.6µV/°C sensitivity. For applications with longer sensor traces or PCB routing resistance, use twisted-pair cabling and minimize loop area to keep total resistance below 2Ω to maintain ±2°C accuracy across the full operating range.
Can the MAX6644LBAAEE+T control fans powered from 12V while operating from a 3.3V supply?
Yes, the MAX6644LBAAEE+T supports this configuration: its PWM_OUT pin is open-drain and rated for up to 5.5V pull-up, allowing connection to a 12V rail via an external pull-up resistor. The 3.3V VDD powers internal logic and sensing circuits, while the 12V pull-up enables direct drive of N-channel MOSFET gates controlling 12V fan supplies - confirmed in Figure 3 of the datasheet.
How does the MAX6644LBAAEE+T handle mismatched ideality factors between the remote sensor and its 1.01 nominal calibration?
The MAX6644LBAAEE+T's temperature reading scales predictably with ideality factor deviation: measured temperature TM = TACTUAL × (nNOMINAL / n1), where nNOMINAL = 1.01. For example, with a CPU diode having n1 = 1.008, the error is –0.66°C at +60°C. This correction is deterministic and can be applied in system firmware if absolute accuracy is critical.
Is the MAX6644LBAAEE+T compatible with 2-wire fans lacking tachometer outputs?
Yes, the MAX6644LBAAEE+T supports 2-wire fan failure detection via current-sense resistor monitoring: configure TACHSET to GND to enable AC-coupled waveform analysis on FAN_IN1/FAN_IN2. A 2Ω sense resistor (as shown in Figure 3) develops sufficient voltage swing (>±200mV) for reliable locked-rotor or stall detection without requiring tach feedback.
What is the purpose of the 2200pF capacitor specified between DXP and GND in the MAX6644LBAAEE+T layout guidelines?
The 2200pF capacitor filters high-frequency EMI at the DXP pin, preventing noise from corrupting the remote diode voltage measurement. It compensates for the switched-current source's rise time and ensures stable ADC integration - values above 3300pF introduce timing errors, while lower values reduce noise rejection in electrically noisy environments like server motherboards.
MAX6644LBAAEE+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Fan Control, Temp Monitor
- Sensor Type:
- Internal and External
- Sensing Temperature:
- -40°C ~ 125°C, External Sensor
- Accuracy:
- ±3.5°C Local(Max), ±3°C Remote(Max)
- Topology:
- ADC, PWM Generator, Tach Counter
- Output Type:
- PWM
- 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:
- 16-QSOP
MAX6644LBAAEE+T FAQ
1.How can I place an order for MAX6644LBAAEE+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX6644LBAAEE+T 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 MAX6644LBAAEE+T reliable?
The price and inventory of MAX6644LBAAEE+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX6644LBAAEE+T is usually 5 days.
3.What payment methods are accepted for MAX6644LBAAEE+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX6644LBAAEE+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX6644LBAAEE+T?
MAX6644LBAAEE+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX6644LBAAEE+T 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 MAX6644LBAAEE+T?
For technical support, including MAX6644LBAAEE+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX6644LBAAEE+T requirements.
6.How does Aetrix verify that MAX6644LBAAEE+T is sourced from the original manufacturer or authorized distributors?
All MAX6644LBAAEE+T 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 MAX6644LBAAEE+T meets industry standards.
7.What is the process for return or replacement of MAX6644LBAAEE+T?
All MAX6644LBAAEE+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX6644LBAAEE+T, 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 MAX6644LBAAEE+T part is unused and in its original packaging.
Return procedure for MAX6644LBAAEE+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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