Sensing & monitoring, control algorithms, actuation & drivers, power & interfaces, acoustics & reliability, heatsinks & airflow, key specs, application patterns, design hooks, and system co-design.
Sensing & Monitoring
Local/Remote Temperature Sensors
I²C/SMBus/PMBus, multi-channel, ±0.25–1 °C for CPU/GPU/FPGA/VRM/DIMM.
Remote Diode/Transistor Sensing
β-compensation, open-circuit detect; junction temperature estimation.
Digital Temp Switch / Comparator
Fixed/programmable thresholds with hysteresis; hardware failsafe alarms.
NTC/PTC Thermistor Networks
Analog sensing & curve linearization for low-cost probe points.
Multi-Sensor Hubs
Temperature/voltage/current/fan-tach with event logs and alerts.
Control & Algorithms
Bang-Bang / Step Control
Simple & robust with hysteresis and minimum on-time.
PWM Duty Curve / Fan Curve
Temp→duty LUT, slope limiting and soft start.
PID / Feedforward
Fast convergence with overshoot suppression for high inertia systems.
Multi-Zone Thermal Control
Multi-probe → multi-fan matrix optimization across zones.
Thermal Derating / Throttling Hooks
DVFS, power limits and frequency capping under thermal events.
Predictive & Health
Fan aging compensation, stall prediction and dust models.
Actuation & Drivers
3-Wire / 4-Wire Fans
PWM input + tach feedback (4-wire) or voltage control (3-wire).
Multi-Channel Fan Controllers
4–16 PWM/tach, fault aggregation, PMBus/I²C configuration.
BLDC Fan/Blower Drivers
Sine/trapezoid commutation, soft start, OCP/OTP.
DC Voltage / LDO / Buck Control
Linear low-noise vs DCDC efficiency trade-offs.
TEC / Peltier Controllers
PID + current loop with ΔT protections for optics/lasers.
Valves / Pumps (Liquid Cooling)
PWM/voltage control with flow feedback and dry-run detection.
Power & Interface
PMBus/SMBus Thermal Management
Thresholds, curves and logs; coordinate with PSU/VRM.
GPIO / Alerts / INT
Fast alarms for over-temp, stall and fan-missing events.
Power Path & Protection
Inrush limiting, reverse blocking, eFuse front-end and QOD.
Acoustics & Reliability
25–30 kHz PWM, slope limits and random spread-spectrum.
Bearings & Lifetime
Ball/fluid bearings, L10 estimates and cold-start torque.
Vibration / Resonance
Avoid chassis modes with stepped RPM searches.
Dust & Stall
Self-cleaning, reverse-blow and current-limited restart windows.
Heatsink & Thermal Path
Heatsink / Heatpipe / Vapor Chamber
Thermal-R networks and consistent mounting pressure.
TIM: Grease / Pad / Phase-Change
Compression, thickness and aging—process matters most.
Airflow Ducting & Pressure Drop
In/outlet openness, filter losses and pressure strategy.
Key Specs & Selection
Sensor Specs
Accuracy, resolution, sampling, remote-diode support and hysteresis.
Controller Specs
PWM channels/resolution, 25–30 kHz, tach capture ranges.
Protection
Stall detection timing, retry policy, hard over-temp and logging.
Power
Rail current capability, inrush, efficiency and thermal budgets.
Interfaces
I²C/PMBus addressing, alert mapping and curve storage.
Application-Focused
Servers / Data Centers
Zone fans + PMBus matrices + DVFS/power-limit + N+1 redundancy.
Telecom / Base Stations
Front/rear flow, HV DC fans, dust/salt proofing and remote logging.
Industrial / Drive Cabinets
In/out ΔT control, filter ΔP sensing and pump coordination.
Automotive Cockpit / Compute
Low-noise strategies, wide-temp, AEC-Q100, crank/brownout tolerance.
Imaging / Laser / Metrology
TEC set-point control + fan assist; compensate optical drift.
Design Hooks & Pitfalls
Single Master Controller
One authority for fans; other controllers only raise alerts.
Sensor Placement
Hotspots + inlet/outlet; differential routing for remote diodes.
EMC Practices
Twisted fan cables + CM chokes; PWM edge-rate control and TVS.
Kick-Start & Minimum Duty
40–60% for 200–500 ms before dropping to target duty.
Tach Validity
Debounce, missing-pulse detect and pulses-per-rev calibration.
Power-Down Strategy
Ramp first, then cut; manage BEMF and align with ALL_OFF events.
Acoustic Experience
RPM slope limits, night curves, and SONE/NC-aware tuning.
Maintenance & Dust
Runtime counters, filter ΔP thresholds and service reminders.
Quick Cheats
Fan Laws
Flow Q∝RPM; pressure ΔP∝RPM²; sound power LW∝RPM⁵ (approx.).
Thermal RC Estimate
ΔT(t) ≈ P·Rθ·(1−e^(−t/(Rθ·Cθ))).
Power vs Noise
Prefer multiple fans at lower RPM vs one at high RPM.
PWM & Tach
25–30 kHz PWM; tach capture ≥ 2× max pulse frequency.
System Hooks
With Power/PMBus
Mutual limits; fan failure → derate or controlled shutdown.
With Sequencer/Rail Monitor
Over-temp → safe power-down; log to black-box.
With Vibration/Structure
Avoid modal RPMs; protect HDD/optical modules.
