Texas Instruments LM86CIMM

Overview

LM86CIMM from Texas Instruments is an 11-bit remote/local digital temperature sensor with SMBus 2.0 interface, ±0.75°C remote diode accuracy at 30°C–80°C, 0.125°C remote resolution, and dual alert outputs (ALERT and T_CRIT_A) for thermal management in computing systems.

For engineers reviewing the LM86CIMM datasheet, LM86CIMM pinout, LM86CIMM application, or LM86CIMM equivalent, this page delivers verified technical context, exact pin functions, real-world thermal monitoring use cases, and two validated alternative sensors with documented functional differences.

Technical Context

The LM86CIMM implements a delta-V_BE sensing architecture for both local die and external diode junctions, using a 10-bit plus sign ΔΣ ADC. It supports programmable conversion rates (up to 16 Hz), on-chip offset compensation for diode nonideality (e.g., 1.008 factor for Pentium III), and independent high/low/critical limit registers for local and remote channels.

Its SMBus 2.0 slave interface operates at 10–100 kHz, features timeout reset capability (25–35 ms low time), and supports three ALERT operating modes: comparator, interrupt flag, and SMBus ARA protocol. The T_CRIT_A output provides hysteresis-controlled critical shutdown signaling with user-defined TH register value.

Key Specifications

Pinout & Package

LM86CIMM is housed in an 8-pin VSSOP package (3.0 mm × 3.0 mm, 0.65 mm pitch), optimized for space-constrained PCB layouts in portable and server applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar remote/local digital temperature sensing applications.

Compared with ADM1032ARQZ and MAX6657ESA+, the LM86CIMM delivers superior remote diode accuracy (±0.75°C), integrated T_CRIT_A hardware shutdown signaling, and robust diode fault detection - making it optimal for high-reliability computing thermal management where precision and fail-safe response are mandatory.

Availability

LM86CIMM is available at Aetrix Electronics and suitable for laptop thermal protection, server blade fan control, workstation GPU monitoring, and industrial embedded controller applications requiring stable component supply and long-term lifecycle support.

Supply support for LM86CIMM 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies, with decades of heritage in precision sensing and power management ICs.

The LM86CIMM belongs to TI's System Monitor family, designed specifically for real-time thermal supervision in compute-intensive platforms where reliability, SMBus interoperability, and sub-degree accuracy are critical.

FAQ

What is the remote diode accuracy specification for LM86CIMM under typical operating conditions?

The LM86CIMM achieves ±0.75°C maximum remote diode temperature accuracy when ambient temperature (TA) is 30°C and remote diode junction temperature (TD) is 80°C - a condition representative of mobile CPU thermal monitoring. This accuracy is factory trimmed for the 1.008 nonideality factor of Intel Pentium III thermal diodes. At wider ranges (e.g., TA = 0°C–85°C, TD = 25°C–125°C), accuracy degrades to ±3.0°C maximum, as specified in the SNIS114E datasheet.

Does LM86CIMM support both local and remote temperature sensing simultaneously?

Yes, the LM86CIMM performs sequential local and remote temperature conversions in a round-robin fashion, completing both measurements every 31.25 ms at the fastest conversion rate. Local sensing uses an on-die thermal diode; remote sensing uses external diode-connected transistors (e.g., 2N3904) or ASIC thermal diodes. Each channel has independent HIGH, LOW, and T_CRIT limit registers, and status bits in the Status Register (02h) indicate which channel triggered an alert.

How does the T_CRIT_A output function in LM86CIMM, and what determines its hysteresis?

The T_CRIT_A output of LM86CIMM is an active-low, open-drain comparator that asserts when either local or remote temperature exceeds its respective T_CRIT setpoint register value. Hysteresis is controlled by the TH register (address 20h): T_CRIT_A remains asserted until temperature falls below (T_CRIT − TH). For example, with RCS = 95°C and TH = 2°C, T_CRIT_A deasserts only when remote temperature drops below 93°C. This prevents oscillation during critical thermal transitions.

Can LM86CIMM detect faults in the remote diode connection, and how is this indicated?

Yes, LM86CIMM includes built-in diode fault detection. If D+ is floating or shorted to VDD, the Remote Temperature registers load +127°C and the OPEN bit (D2) in the Status Register is set. If D+ is shorted to GND or D−, the registers load −128°C and OPEN remains clear. Neither condition triggers ALERT unless the corresponding limit registers are configured below +127°C or above −128°C. These fault codes enable robust system diagnostics without external circuitry.

What SMBus protocols and timing features does LM86CIMM implement, and is clock stretching supported?

The LM86CIMM fully complies with SMBus 2.0 specifications, supporting START/STOP, repeated START, ARA (Alert Response Address), and timeout reset (25–35 ms low time on SMBCLK or SMBData). It operates at 10–100 kHz clock frequency and includes input hysteresis (400 mV) and defined rise/fall times. Crucially, LM86CIMM does not support clock stretching - SMBCLK is strictly an input, and the device never holds the clock line low. This simplifies bus arbitration but requires master-side timing compliance.