MAX31790ATI+T is a high-precision, 6-channel fan controller and temperature monitor designed and manufactured by Analog Devices Inc. (following its acquisition of Maxim Integrated). It belongs to the advanced MAX317xx family, engineered specifically for server, data center, telecom, and high-density computing thermal management systems, where accurate fan speed control, multi-zone temperature sensing, and system-level fault response are critical for reliability, energy efficiency, and acoustic performance.
The “ATI” suffix denotes the 28-pin TQFN package (5 mm × 5 mm, 0.5 mm pitch) with exposed thermal pad — optimized for compact layout, thermal performance, and high-volume SMT assembly; the “+T” indicates tape-and-reel packaging (2,500 units per reel), Pb-free, RoHS-compliant, and qualified for industrial operation (–40°C to +125°C junction).
Introduction
The MAX31790ATI+T is a fully integrated hardware-based thermal management ASIC, combining:
đš Six independent PWM fan controllers, each capable of driving up to 25 mA sink current, supporting 2-wire (tach only), 3-wire (tach + PWM), or 4-wire (tach + PWM + RPM feedback) fans;
đš Six dedicated remote temperature sensor inputs, compatible with standard diode-connected transistors (e.g., 2N3904, PNPs) or integrated diode sensors (e.g., CPU/GPU thermal diodes);
đš One local temperature sensor, measuring die temperature with ±1°C accuracy;
đš Configurable closed-loop control algorithms, including PID, linear ramp, and lookup-table (LUT)-based fan speed vs. temperature profiles — all executed autonomously in hardware, eliminating host CPU overhead;
đš Comprehensive fault handling: fan stall detection, open/shorted diode detection, overtemperature shutdown, and programmable alarm thresholds with interrupt outputs.
Crucially, the MAX31790 operates independently of the host system: it boots, initializes, and begins controlling fans within < 100 ms of power-up — ensuring immediate thermal protection even before BIOS or OS loads. Its I²C/SMBus interface (up to 1 MHz) allows full configuration and monitoring by BMC (Baseboard Management Controller) or host processor, while its hardware watchdog and fail-safe modes guarantee safe default behavior (e.g., full-speed fans) if communication is lost.
The device supports advanced features essential for modern data centers, including:
- Fan spin-up sequencing to limit inrush current;
- Acoustic noise reduction modes, such as slew-rate limiting on PWM edges and staggered fan starts;
- Power-aware control, where fan speeds are dynamically adjusted based on real-time power consumption (via external ADC integration);
- Redundant fan support, with automatic switchover on failure.
The ATI package (28-pin TQFN, 5 mm × 5 mm) features a large exposed thermal pad (EP) that — when soldered to a multilayer PCB ground plane — achieves θJA ≈ 28°C/W, enabling reliable operation at full channel load in high-ambient environments (e.g., +70°C rack environments).
Key Features
â
6-Channel Fan Control & Monitoring:
• Independent PWM outputs (0–100%, 25 kHz default frequency);
• 25 mA sink capability per channel — drives most 3-wire/4-wire fans directly (no external FETs needed);
• Tachometer (RPM) input with 1–255 Hz to 200 kHz range, ±1% accuracy.
â
6-Channel Remote + 1-Channel Local Temperature Sensing:
• Remote diode sensing: ±1°C accuracy from –40°C to +125°C (with calibration);
• Local sensing: ±1°C accuracy (–40°C to +125°C);
• Supports series resistance cancellation (up to 5 kΩ) — compensates for PCB trace resistance.
â
Autonomous Hardware-Based Control:
• On-chip PID, linear, or LUT-based fan speed vs. temperature curves;
• Programmable hysteresis, response time, and minimum/maximum speed limits;
• No host intervention required — full operation from power-on reset.
â
Intelligent Fault Detection & Safety:
• Fan stall, open-circuit, short-circuit, and tach loss detection (< 100 ms response);
• Diode open/short/fault detection;
• Overtemperature shutdown with configurable trip points (per zone);
• Fail-safe mode: fans go to full speed on I²C timeout or watchdog expiry.
â
Low-Power & Robust Operation:
• Supply current = 1.2 mA (typ.) in active mode, 12 µA (typ.) in standby;
• Operating voltage: 3.0 V to 3.6 V (core), with separate 5 V tolerant tach/PWM I/O;
• ESD rating > 4 kV HBM;
• Junction temperature range: –40°C to +125°C.
â
Compact TQFN-28 (ATI) Package:
• 5 mm × 5 mm footprint with 2.2 mm² exposed copper pad;
• Industry-standard pinout — simplifies routing and layout;
• RoHS-compliant, halogen-free, and AEC-Q100 stress-tested.
Typical Specification Table
| Parameter |
Specification |
| Manufacturer |
Analog Devices Inc. (formerly Maxim Integrated) |
| Product Series |
MAX317xx Family (Fan Controllers & Thermal Monitors) |
| Model |
MAX31790ATI+T |
| Function |
6-Channel Fan Controller + 6-Zone Temp Monitor |
| Fan Channels |
6 independent PWM outputs (25 mA sink each) |
| Tach Input Range |
1 Hz to 200 kHz, ±1% accuracy |
| Remote Temp Inputs |
6 diode-based (e.g., CPU/GPU/ASIC thermal diodes) |
| Local Temp Sensor |
On-die, ±1°C accuracy |
| Temp Accuracy (remote) |
±1°C (–40°C to +125°C), with series-R compensation |
| Control Modes |
Hardware PID, Linear Ramp, Lookup Table (LUT) |
| Interface |
I²C/SMBus (up to 1 MHz), addressable (8 options) |
| Supply Voltage (VCC) |
3.0 V to 3.6 V (core); I/O tolerant to 5 V |
| Quiescent Current |
1.2 mA (active), 12 µA (standby) |
| Operating Temperature |
–40°C to +125°C (junction) |
| Package |
28-Lead TQFN (5 mm × 5 mm) with Exposed Pad (ATI) |
| RoHS / Green |
Yes (Pb-free, Halogen-free) |
| Packaging |
Tape-and-Reel (T), 2,500 units per reel (+T) |
Typical Applications
đš Data Center & Cloud Server Racks: Real-time thermal management of CPUs, GPUs, FPGAs, memory modules, and power supplies — using per-zone diode sensing and autonomous PID control to minimize fan power (up to 30% savings) and acoustic noise.
đš Telecom Base Stations & 5G Radio Units: Cooling high-power RFICs and FEMs in outdoor cabinets — leveraging wide temperature range, robust fault detection, and fail-safe full-speed mode under extreme ambient conditions.
đš AI/ML Accelerator Modules: Thermal regulation of NVIDIA A100/H100, AMD MI300, or custom ASICs — where rapid thermal transients require sub-100 ms response and hardware independence from host software stack.
đš Industrial Edge Computing: Fan control in ruggedized IPCs, vision systems, and robotics controllers — enabled by high ESD immunity, wide temp range, and no-host-required operation.
đš Medical Imaging Equipment: Quiet, reliable cooling for CT/MRI scanner electronics and detector arrays — using acoustic optimization modes and redundant fan support for continuous uptime.
đš Automotive ADAS ECUs: Thermal supervision of radar SoCs and camera ISPs in under-hood applications — meeting AEC-Q100 requirements and supporting functional safety (ISO 26262 ASIL-B ready).
Development & Design Notes
đ§ PCB Layout & Thermal Design:
- Connect the exposed pad (EP) to a ≥ 150 mm² internal ground plane using ≥ 12 thermal vias (0.3 mm). For high-ambient deployments (> +65°C), add a small heatsink or thermal interface material to the EP.
- Route tach and PWM traces away from switching regulators and clocks; use 50 Ω impedance control if running >100 kHz tach signals over >10 cm.
- Place 100 nF ceramic decoupling capacitor within 2 mm of VCC and GND pins — essential for stable PWM generation and low-noise sensing.
đ§ Diode Sensor Interface:
- Use standard PNP transistors (e.g., MMJT9414, DMMT3906) or integrated diode sensors (e.g., Intel CPU thermal diodes).
- Enable series resistance cancellation in firmware for long PCB traces (>5 cm) — improves remote temp accuracy by >2°C.
- Add 100 pF capacitor from each diode input (D+ and D−) to GND to suppress EMI without affecting bandwidth.
đ§ I²C Integration & System Firmware:
- Use 2.2 kΩ pull-ups on SDA/SCL (to 3.3 V) — ensures rise time < 300 ns for 1 MHz operation.
- Leverage ADI’s reference firmware (available in MAX31790 EV Kit documentation) for fast bring-up: configure LUTs, set alarm thresholds, and enable fan spin-up sequencing in < 10 registers.
- Implement watchdog timeout (default 2 s) — if I²C communication stalls, device enters fail-safe mode (full fan speed) automatically.
đ§ Acoustic & Power Optimization:
- Enable PWM slew-rate limiting to reduce audible coil whine (especially at low speeds);
- Use staggered fan start (programmable delay per channel) to limit inrush current surges;
- Configure dynamic minimum speed based on ambient temperature — reduces power and noise during cool conditions.
đ§ Functional Safety & Reliability:
- FIT rate = 15 failures per billion hours, with FMEDA report supporting IEC 61508 SIL-2 and ISO 26262 ASIL-B.
- For ASIL-B compliance: combine MAX31790’s hardware fault detection (fan stall, OT) with host BMC monitoring of I²C status and temperature readbacks — dual-channel redundancy for critical zones.
