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Home > Products > Sensors, Transducers > Temperature Sensors > Analog and Digital Output

Texas Instruments LM89-1CIMX

Name: LM89-1CIMX
Brand: Texas Instruments
SKU: LM89-1CIMX
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LM89-1CIMX

Manufacturer:: Texas Instruments

Category:: Analog and Digital Output

Package:: 8-SOIC (0.154", 3.90mm Width)

Datasheet:: LM89-1CIMX.pdf

Description:: SENSOR DIGITAL 0C-85C 8SOIC

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Product details

Overview

LM89-1CIMX from Texas Instruments is an 11-bit remote diode and local digital temperature sensor with SMBus 2.0 interface, ±0.75°C remote accuracy at 30°C/80°C, 0.125°C remote resolution, and dual open-drain ALERT/T_CRIT_A outputs for thermal monitoring of MCUs, GPUs, FPGAs, and ASICs in server and workstation platforms.

For engineers reviewing the LM89-1CIMX datasheet, LM89-1CIMX pinout, LM89-1CIMX application, or LM89-1CIMX equivalent, key selection criteria include remote diode sensing accuracy, SMBus 2.0 TIMEOUT reset behavior, T_CRIT_A hysteresis programmability, and compatibility with multi-sensor thermal management systems requiring distinct slave addresses.

Technical Context

The LM89-1CIMX implements a delta-V_BE remote diode sensing architecture with 10-bit plus sign ADC and programmable offset compensation (RTOLB/RTOHB registers) to correct for diode nonideality factors across diverse IC dies. Its SMBus 2.0 interface supports TIMEOUT reset (25–35 ms low pulse), ALERT masking, and ARA protocol compliance for multi-device alert arbitration.

It features dual independent thermal comparators: one for ALERT (triggered by HIGH/LOW/T_CRIT limit violations) and a dedicated T_CRIT_A output with user-defined hysteresis (TH register), where activation occurs above T_CRIT and deactivation occurs below T_CRIT − TH - applied identically to both local and remote readings.

Key Specifications

Parameter	Value and Actual Design Meaning
Remote Temp Accuracy	±0.75°C max at TA=30°C, TD=80°C - enables precise die-temperature tracking of high-performance processors without software calibration.
Remote Resolution	0.125°C (11-bit) - supports fine-grained thermal throttling decisions in CPU/GPU power management loops.
Local Temp Accuracy	±3.0°C max over 25–125°C - sufficient for ambient or package-level thermal supervision with minimal self-heating impact.
SMBus Clock Range	10–100 kHz - compatible with standard system management bus timing and allows shared bus operation with other PMBus/SMBus devices.
Conversion Time	31.25 ms (fastest setting) - defines minimum interval between valid remote/local temperature updates; independent of SMBus read timing.
T_CRIT Default	85°C for LM89-1CIMX - matches common processor critical thresholds and triggers hardware shutdown via T_CRIT_A without host intervention.
Supply Voltage	3.0 V to 3.6 V - aligns with 3.3V auxiliary rail domains, eliminating need for dedicated LDO in typical server motherboard implementations.

Pinout & Package

LM89-1CIMX is housed in an 8-pin VSSOP (DGK) package measuring 3.0 mm × 3.0 mm, optimized for space-constrained thermal sensor placement near high-power ICs.

Pin/Terminal	Circuit Role	Design Meaning
VDD	Positive supply input	Accepts 3.0–3.6 V; requires 0.1 µF + 100 pF bypass capacitors placed adjacent to pin to suppress switching noise affecting ADC accuracy.
D+	Diode current source	Drives 110–315 µA into remote diode anode; mandates 2.2 nF capacitor placed between D+ and D− pins to filter high-frequency noise from diode junction.
D−	Diode return sink	Completes remote diode bias path; voltage limited to ≤0.7 V to prevent forward-biasing parasitic ESD diodes that corrupt measurements.
T_CRIT_A	Critical temperature alarm	Open-drain, active-low output with built-in hysteresis; asserts when local or remote temp exceeds programmed T_CRIT limit and remains asserted until temp falls below T_CRIT − TH.
GND	Power ground reference	Common return for analog and digital circuitry; must be connected to low-impedance system ground plane to minimize measurement offset.
ALERT	General thermal alert	Open-drain, active-low output triggered by any violation of HIGH/LOW/T_CRIT limits; supports comparator, interrupt, or SMBus ARA modes via configuration register.
SMBData	SMBus bidirectional data	Open-drain I/O with 5 pF input capacitance; requires external pull-up; supports SMBus 2.0 TIMEOUT reset when held low ≥25 ms.
SMBCLK	SMBus clock input	Input-only clock line; accepts 10–100 kHz; rise/fall times ≤1 µs/0.3 µs ensure reliable communication under noisy board conditions.

Key Features

Feature	Design Value
Remote diode offset calibration	Two 8-bit offset registers (RTOLB/RTOHB) enable per-device correction of diode nonideality (e.g., 1.0021 factor) without host software overhead.
Programmable T_CRIT hysteresis	Hysteresis register (TH) sets temperature delta between T_CRIT assertion and deassertion - prevents chatter during thermal transients near critical threshold.
SMBus TIMEOUT reset	Holding SMBData/SMBCLK low >25 ms resets internal state machine, recovering from bus lockup without power cycle - essential for unattended server deployments.
Three ALERT operating modes	Configurable as standalone comparator, interrupt flag (mask-on-read), or SMBus ARA responder - adapts to host firmware architecture without hardware change.
Pin/register compatibility	Identical pinout and register map with LM86/LM90/LM99/ADM1032/MAX6657/8 - simplifies migration and multi-vendor BOM strategies in thermal subsystem design.

Applications

Server CPU Thermal Monitoring	Laptop GPU Die Sensing
Use Scenario: Real-time die temperature acquisition from Intel Xeon or AMD EPYC processor thermal diodes in 1U rack servers. IC Role / Device Role / Timing Role: Remote diode sensor interfacing directly to CPU's on-die diode; performs 31.25 ms conversions synchronized to system thermal policy engine. Use Value: ±0.75°C accuracy ensures reliable activation of dynamic frequency scaling and fan control before thermal throttling impacts compute throughput.	Use Scenario: Compact thermal feedback for NVIDIA GeForce or AMD Radeon mobile GPUs in thin-and-light notebooks. IC Role / Device Role / Timing Role: Local + remote sensor co-located on GPU power delivery PCB; uses VSSOP footprint to minimize trace length to diode pins. Use Value: 2.2 nF D+/D− bypass capacitor placement guideline ensures stable remote readings despite high dv/dt noise from GPU VRMs.
FPGA Accelerator Board Management	Workstation ASIC Thermal Guard
Use Scenario: Monitoring Xilinx Versal or Intel Agilex FPGA junction temperature in AI inference accelerators with multiple thermal zones. IC Role / Device Role / Timing Role: One LM89-1CIMX per FPGA die; SMBus address 1001101 enables daisy-chaining up to eight sensors on single bus. Use Value: T_CRIT_A output drives hardware reset logic independently of host OS, preventing FPGA configuration corruption during overtemperature events.	Use Scenario: Protecting custom ASICs in medical imaging or test equipment where thermal runaway risks component failure. IC Role / Device Role / Timing Role: Local sensor monitors ambient PCB temperature while remote channel tracks ASIC junction; ALERT triggers fan ramp-up before T_CRIT_A initiates shutdown. Use Value: Dual-limit comparison (HIGH/LOW) enables predictive cooling - not just fail-safe - extending ASIC lifetime under cyclic thermal loads.

Server CPU Thermal Monitoring

Laptop GPU Die Sensing

Use Scenario: Real-time die temperature acquisition from Intel Xeon or AMD EPYC processor thermal diodes in 1U rack servers.

IC Role / Device Role / Timing Role: Remote diode sensor interfacing directly to CPU's on-die diode; performs 31.25 ms conversions synchronized to system thermal policy engine.

Use Value: ±0.75°C accuracy ensures reliable activation of dynamic frequency scaling and fan control before thermal throttling impacts compute throughput.

Use Scenario: Compact thermal feedback for NVIDIA GeForce or AMD Radeon mobile GPUs in thin-and-light notebooks.

IC Role / Device Role / Timing Role: Local + remote sensor co-located on GPU power delivery PCB; uses VSSOP footprint to minimize trace length to diode pins.

Use Value: 2.2 nF D+/D− bypass capacitor placement guideline ensures stable remote readings despite high dv/dt noise from GPU VRMs.

FPGA Accelerator Board Management

Workstation ASIC Thermal Guard

Use Scenario: Monitoring Xilinx Versal or Intel Agilex FPGA junction temperature in AI inference accelerators with multiple thermal zones.

IC Role / Device Role / Timing Role: One LM89-1CIMX per FPGA die; SMBus address 1001101 enables daisy-chaining up to eight sensors on single bus.

Use Value: T_CRIT_A output drives hardware reset logic independently of host OS, preventing FPGA configuration corruption during overtemperature events.

Use Scenario: Protecting custom ASICs in medical imaging or test equipment where thermal runaway risks component failure.

IC Role / Device Role / Timing Role: Local sensor monitors ambient PCB temperature while remote channel tracks ASIC junction; ALERT triggers fan ramp-up before T_CRIT_A initiates shutdown.

Use Value: Dual-limit comparison (HIGH/LOW) enables predictive cooling - not just fail-safe - extending ASIC lifetime under cyclic thermal loads.

Equivalent & Alternatives

The following parts are listed as comparable options for similar remote diode temperature sensing applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LM90CIMX	Same 8-pin VSSOP package and SMBus interface; ±0.75°C remote accuracy; but lacks T_CRIT_A output - uses ALERT only with programmable hysteresis.	No dedicated critical-temperature shutdown signal; requires host firmware to interpret ALERT and assert system reset.	Select LM90CIMX only if T_CRIT_A hardware interrupt is unnecessary and SMBus bandwidth permits polling-based critical threshold handling.
MAX6657ESA+	Pin-compatible 8-pin SOIC; ±1.0°C remote accuracy; 0.25°C resolution; SMBus 1.1 compliant (no TIMEOUT reset or ARA support).	Lower accuracy and no TIMEOUT recovery increases risk of bus hang in dense thermal sensor networks.	Choose MAX6657ESA+ only for legacy designs where SOIC footprint is mandated and SMBus 2.0 features are unused.

Compared with LM90CIMX and MAX6657ESA+, the LM89-1CIMX uniquely delivers both high-accuracy remote sensing (±0.75°C) and a dedicated, hysteresis-configurable T_CRIT_A output - enabling autonomous hardware-level thermal shutdown without host dependency, critical for server-grade reliability.

Availability

LM89-1CIMX is available at Aetrix Electronics and suitable for server thermal management, laptop GPU monitoring, FPGA accelerator board control, and workstation ASIC protection requiring stable component supply and long-term industrial lifecycle support.

Supply support for LM89-1CIMX 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 company specializing in analog and embedded processing technologies, with leadership in precision analog sensing and system management ICs.

The LM89 product line delivers high-accuracy, SMBus-compatible thermal sensors for real-time die-temperature monitoring in computing infrastructure - designed specifically to meet the reliability, accuracy, and bus robustness requirements of enterprise servers and high-performance workstations.

FAQ

What is the default SMBus slave address for LM89-1CIMX?

The LM89-1CIMX has a fixed SMBus slave address of 1001101 (0x4D in hexadecimal), which differs from LM89C (0x4C) and LM89-1DIMX (0x4D with 105°C T_CRIT). This unique address allows multiple LM89 variants to coexist on the same SMBus without address conflict, enabling scalable thermal monitoring in multi-processor systems using the LM89-1CIMX.

How does the LM89-1CIMX handle remote diode nonideality compensation?

The LM89-1CIMX provides two 8-bit offset registers (RTOLB and RTOHB) that allow direct hardware compensation for diode nonideality factors - such as the 1.0021 factor typical of Pentium 4 or modern GPU thermal diodes. This compensation is applied automatically to the raw remote temperature reading before storage in the temperature register, eliminating the need for host software correction and ensuring consistent ±0.75°C accuracy across different process nodes when using the LM89-1CIMX.

Can LM89-1CIMX operate with a 3.3V supply derived from an auxiliary rail?

Yes, the LM89-1CIMX operates within a 3.0 V to 3.6 V supply range and is explicitly designed to accept 3.3V derived from an auxiliary supply, as confirmed in the functional block diagram and power recommendations section of the datasheet. Its quiescent current of 0.8–1.7 mA at 16 Hz conversion rate and 315 µA in shutdown mode make it compatible with low-noise auxiliary rails commonly used for system management ICs - a key design feature of the LM89-1CIMX.

What is the purpose of the 2.2 nF capacitor required between D+ and D− pins of LM89-1CIMX?

The 2.2 nF capacitor between D+ and D− pins of the LM89-1CIMX filters high-frequency noise generated by nearby switching regulators or high-speed digital circuits, which would otherwise couple into the remote diode measurement path and degrade temperature accuracy. The datasheet mandates placing this capacitor as close as possible to the D+ and D− pins with matched traces - a critical layout requirement to maintain the ±0.75°C remote accuracy specification of the LM89-1CIMX in electrically noisy environments like server motherboards.

Does LM89-1CIMX support SMBus 2.0 TIMEOUT reset, and how is it implemented?

Yes, the LM89-1CIMX fully supports SMBus 2.0 TIMEOUT reset: holding either SMBData or SMBCLK low for 25–35 ms forces a complete reset of the internal SMBus state machine, returning both lines to high-impedance. This feature recovers the device from bus lockup conditions without requiring a power cycle - a critical reliability enhancement for unattended systems. The TIMEOUT behavior is intrinsic to the LM89-1CIMX silicon and requires no configuration, distinguishing it from earlier SMBus 1.1–compliant alternatives.

LM89-1CIMX Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 8-SOIC (0.154", 3.90mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Sensor Type:: Digital, Local/Remote

Sensing Temperature - Local:: 0°C ~ 85°C

Sensing Temperature - Remote:: 0°C ~ 85°C

Output Type:: SMBus

Voltage - Supply:: 3V ~ 3.6V

Resolution:: 7 b (Local), 10 b (Remote)

Features:: One-Shot, Output Switch, Programmable Limit, Shutdown Mode, Standby Mode

Accuracy - Highest (Lowest):: ±3°C

Test Condition:: 25°C ~ 125°C

Operating Temperature:: 0°C ~ 125°C

Mounting Type:: Surface Mount

Grade:: -

Qualification:: -

Supplier Device Package:: 8-SOIC

LM89-1CIMX FAQ

1.How can I place an order for LM89-1CIMX through Aetrix?

Please submit a Request for Quotation (RFQ) for LM89-1CIMX 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 LM89-1CIMX reliable?

The price and inventory of LM89-1CIMX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM89-1CIMX is usually 5 days.

3.What payment methods are accepted for LM89-1CIMX?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM89-1CIMX transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LM89-1CIMX?

LM89-1CIMX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LM89-1CIMX 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 LM89-1CIMX?

For technical support, including LM89-1CIMX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM89-1CIMX requirements.

6.How does Aetrix verify that LM89-1CIMX is sourced from the original manufacturer or authorized distributors?

All LM89-1CIMX 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 LM89-1CIMX meets industry standards.

7.What is the process for return or replacement of LM89-1CIMX?

All LM89-1CIMX units undergo pre-shipment inspection (PSI). If there is an issue with LM89-1CIMX, 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 LM89-1CIMX part is unused and in its original packaging.

Return procedure for LM89-1CIMX:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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