Analog Devices Inc./Maxim Integrated MAX6641AUB90+

Overview

The MAX6641AUB90+ from Maxim Integrated is an SMBus-compatible temperature sensor and automatic PWM fan-speed controller that measures both local die temperature and remote junction temperature (e.g., CPU/FPGA emitter-base diode) with ±1°C accuracy over +60°C to +145°C. It delivers digital temperature data via a 2-wire SMBus interface, drives an open-drain PWM output for fan speed control, and provides an active-low OT alarm output. It operates from 3.0V to 5.5V and consumes 500µA typical supply current - ideal for thermal management in automotive-grade embedded systems.

For engineers reviewing the MAX6641AUB90+ datasheet, MAX6641AUB90+ pinout, MAX6641AUB90+ application, or MAX6641AUB90+ equivalent, key selection criteria include its -40°C to +125°C automotive operating range, programmable fan-start duty cycle (40% POR), 33Hz default PWM frequency, ±1°C remote accuracy band, and 10-pin µMAX package compatibility with space-constrained PCB layouts.

Technical Context

The MAX6641AUB90+ integrates dual-sensing capability: a precision on-die thermal sensor and a remote diode interface (DXP/DXN) supporting external PNP transistor junctions. Its SMBus interface implements write byte, read byte, send byte, and receive byte protocols with four selectable slave addresses (1001 000x for MAX6641AUB90+), enabling up to four devices on one bus.

Temperature data feeds a fully programmable PWM generator with configurable spin-up (2s forced high), rate-of-change limiting (0–320s ramp time), step size (2/240 to 30/240 per °C), and frequency selection (20Hz–35kHz). The OT output is open-drain, 5.5V-tolerant, and independently maskable per channel.

Key Specifications

Pinout & Package

MAX6641AUB90+ uses a 10-pin µMAX® package (3mm × 5mm, 0.5mm pitch), specified for -40°C to +125°C operation. Pin 1 and Pin 6 are internally connected to GND and must be externally tied to ground.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar temperature-monitoring-and-fan-control applications.

Compared with LM96163CIMM/NOPB and ADT7470ARQZ, the MAX6641AUB90+ uniquely combines automotive-grade temperature range, ±1°C remote accuracy in the critical +60°C to +145°C band, and hardware-enforced fan spin-up - making it the only option qualified for ASIL-B thermal management in compute-intensive automotive modules.

Availability

MAX6641AUB90+ is available at Aetrix Electronics and suitable for server thermal management, automotive ADAS compute modules, notebook CPU cooling, and industrial PLC controllers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6641AUB90+ 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) designs precision analog, mixed-signal, and power-management ICs for demanding industrial, automotive, and computing applications.

The MAX6641AUB90+ belongs to Maxim's thermal management product line, engineered specifically for SMBus-based closed-loop fan control in space- and reliability-constrained systems where junction temperature accuracy and fail-safe startup behavior are critical.

FAQ

What is the SMBus address of the MAX6641AUB90+?

The MAX6641AUB90+ has a fixed SMBus slave address of 1001 000x (binary), where the 'x' bit is determined by the state of the ADDR pin - not applicable on MAX6641AUB90+ as it uses hardwired U10-2 package coding. This address allows up to four MAX6641 devices on a single SMBus without conflict. The MAX6641AUB90+ responds only to this base address and does not support dynamic address reconfiguration.

Does the MAX6641AUB90+ support remote diode measurement without external components?

The MAX6641AUB90+ requires a 2200pF capacitor between DXP and DXN for stable remote diode measurement - this is explicitly mandated in the datasheet to suppress noise-induced errors. Without it, remote temperature error increases significantly, especially above 100kHz noise frequencies. The MAX6641AUB90+ integrates the current source and A/D converter but relies on this external capacitor for specified ±1°C accuracy.

Can the MAX6641AUB90+ drive a fan directly without a MOSFET?

Yes - the MAX6641AUB90+ PWMOUT pin can directly drive the PWM input of compatible brushless DC fans that accept logic-level signals (e.g., 3.3V/5V-tolerant inputs). In this configuration, the 35kHz PWM frequency setting is recommended. For fans without dedicated PWM inputs, an external MOSFET or bipolar transistor is required, and the MAX6641AUB90+'s open-drain output with external pullup supports both top-side (p-channel) and bottom-side (n-channel) switching.

What is the purpose of the I.C. pins (1 and 6) on the MAX6641AUB90+?

Pins 1 and 6 on the MAX6641AUB90+ are labeled I.C. (Internally Connected) and must be externally connected to GND. These pins provide additional grounding paths for internal bias circuitry and ESD protection structures. Leaving them unconnected violates the absolute maximum ratings and causes unpredictable behavior, including inaccurate temperature readings and failure to assert the OT output. The MAX6641AUB90+ will not function correctly unless both I.C. pins are soldered to the PCB ground plane.

How does the MAX6641AUB90+ handle fan startup under cold conditions?

The MAX6641AUB90+ guarantees fan startup via hardware-enforced spin-up: upon power-on or OT recovery, PWMOUT is forced high for exactly 2 seconds - independent of temperature reading or register settings. This ensures mechanical rotation begins even at sub-zero ambient temperatures where bearing viscosity inhibits initial motion. The MAX6641AUB90+'s spin-up is non-configurable and always active unless disabled via bit 2 of Configuration Register 02h, which is not recommended for automotive or industrial use.