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

Texas Instruments LM89-1DIMMX/NOPB

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

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Part No.:: LM89-1DIMMX/NOPB

Manufacturer:: Texas Instruments

Category:: Analog and Digital Output

Package:: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)

Datasheet:: LM89-1DIMMX/NOPB.pdf

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

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Product details

Overview

LM89-1DIMMX/NOPB 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 dedicated T_CRIT_A output for hardware thermal shutdown. It monitors die temperature of MCUs, GPUs, FPGAs, and ASICs via external thermal diodes or its on-die sensor in server, workstation, and high-performance computing thermal management systems.

For engineers reviewing the LM89-1DIMMX/NOPB datasheet, LM89-1DIMMX/NOPB pinout, LM89-1DIMMX/NOPB application, or LM89-1DIMMX/NOPB equivalent, key selection criteria include remote diode accuracy under nonideal conditions, T_CRIT_A hysteresis programmability, SMBus timeout reset behavior, and VSSOP-8 package compatibility with high-density DIMM thermal monitoring layouts.

Technical Context

The LM89-1DIMMX/NOPB implements a delta-V_BE remote diode sensing architecture with programmable nonideality compensation via RTOLB/RTOHB offset registers, supporting diodes with series resistance up to 3.64 Ω and nonideality factor 1.0021. Its 10-bit-plus-sign remote ADC delivers 0.125°C resolution, while local sensing uses an 8-bit ADC with 1°C resolution.

It features dual open-drain outputs: ALERT (SMBus 2.0-compliant interrupt with mask control and ARA protocol support) and T_CRIT_A (hardware comparator with user-defined hysteresis TH register), both active-low and independently configurable against local/remote HIGH/LOW/T_CRIT limit registers. Conversion time is fixed at 31.25 ms per full cycle (local + remote).

Key Specifications

Parameter	Value and Actual Design Meaning
Remote Accuracy	±0.75°C max at TA=30°C, TD=80°C - enables precise thermal throttling of high-power processors without software calibration
Remote Resolution	0.125°C - supports fine-grained fan speed control and thermal margining in server DIMM modules
Local Accuracy	±3.0°C max over 25°C–125°C - sufficient for ambient board temperature monitoring with minimal self-heating impact
T_CRIT Default	105°C - higher than standard LM89 variants (85°C), optimized for DDR memory module thermal limits
SMBus Compatibility	SMBus 2.0 compliant with TIMEOUT reset (25–35 ms low pulse) - ensures bus recovery after communication faults without power cycle
Supply Range	3.0 V to 3.6 V - matches standard 3.3V auxiliary rails used on memory modules and motherboard VRMs
Quiescent Current	1.7 mA typical at 16 Hz conversion rate - balances responsiveness and power in always-on thermal monitoring

Pinout & Package

LM89-1DIMMX/NOPB is housed in an 8-pin VSSOP (DGK) package, 3.0 mm × 3.0 mm body size, with exposed pad for thermal enhancement and surface-mount compatibility in space-constrained DIMM and server board layouts.

Pin/Terminal	Circuit Role	Design Meaning
VDD	Positive supply input	Requires 0.1 µF + 100 pF bypass capacitors placed adjacent to pin; bulk 10 µF nearby - critical for noise immunity during remote diode current sourcing
D+	Diode current source	Drives 110–315 µA into remote diode anode; requires 2.2 nF capacitor placed between D+ and D− pins - suppresses high-frequency noise corrupting diode voltage measurement
D−	Diode return current sink	Completes remote diode bias path; must be routed with matched trace length to D+ - maintains measurement integrity under ESD and switching noise
T_CRIT_A	Hardware thermal shutdown output	Open-drain, active-low comparator output with programmable hysteresis - directly drives power supply enable or system reset without MCU intervention
GND	Power ground reference	Common return for VDD, D+, D−, and digital I/O - must connect to solid ground plane to minimize offset errors in remote sensing
ALERT	Configurable interrupt/alert output	Open-drain, SMBus 2.0–compliant; supports comparator, interrupt, and ARA modes - enables flexible integration with host BMC or EC firmware
SMBData	SMBus bidirectional data line	Open-drain I/O with 5 pF input capacitance and 400 mV hysteresis - ensures robust communication on shared bus with multiple sensors
SMBCLK	SMBus clock input	Input-only clock with 4.0 µs minimum high time - supports 10–100 kHz bus speeds; timing reset on >25 ms low pulse

Key Features

Feature	Design Value
Remote Diode Offset Compensation	Two 8-bit offset registers (RTOLB/RTOHB) correct for diode nonideality and series resistance - eliminates need for per-board calibration in volume manufacturing
T_CRIT_A Hardware Comparator	Dedicated output with independent hysteresis register (TH) - provides fail-safe thermal shutdown even if host firmware hangs or SMBus fails
SMBus TIMEOUT Reset	Automatic state machine reset when SMBData/SMBCLK held low >25 ms - recovers bus lockup without requiring system reset or power cycle
105°C Default Local T_CRIT	Factory-programmed threshold specific to LM89-1D variants - aligns with JEDEC DDR4/DDR5 memory module thermal specifications
Three ALERT Operating Modes	Configurable as temperature comparator, interrupt flag, or SMBus ARA responder - adapts to host controller capabilities without hardware change

Applications

Server Memory Thermal Monitoring	Laptop GPU Die Sensing
Use Scenario: Real-time temperature tracking of DDR4/DDR5 DIMM modules in 1U/2U rack servers to prevent thermal throttling and ensure JEDEC compliance. IC Role / Device Role / Timing Role: Remote diode sensor interfacing with memory IC thermal diodes; local sensor monitoring DIMM PCB ambient; T_CRIT_A triggers VRM shutdown at 105°C. Use Value: Enables hardware-enforced thermal safety without BMC polling latency; 0.125°C resolution allows predictive fan control reducing acoustic noise by 3–5 dB(A).	Use Scenario: Direct die temperature measurement of discrete GPU on thin-and-light laptop motherboards with limited airflow. IC Role / Device Role / Timing Role: Remote diode sensor connected to GPU's integrated thermal diode; ALERT signals GPU driver for dynamic clock scaling; SMBus updates every 31.25 ms. Use Value: Achieves ±0.75°C accuracy despite GPU package self-heating and PCB trace impedance - improves thermal margin by 4–6°C versus generic NTC solutions.
Workstation FPGA Thermal Management	Industrial Embedded Controller Board
Use Scenario: Monitoring Xilinx/Intel FPGA die temperature during high-throughput compute workloads in air-cooled workstations. IC Role / Device Role / Timing Role: Remote diode sensor tied to FPGA's thermal diode; local sensor tracks board ambient; T_CRIT_A asserts to FPGA configuration logic for safe reconfiguration. Use Value: Supports FPGA partial reconfiguration based on real-time die temp; 31.25 ms conversion time ensures thermal feedback loop meets <50 ms response requirement.	Use Scenario: Long-life thermal supervision of ARM-based industrial controllers operating in 0°C–70°C extended ambient environments. IC Role / Device Role / Timing Role: Local + remote sensor monitoring SoC die and heatsink; ALERT latched to microcontroller GPIO; SMBus read only during scheduled diagnostics. Use Value: 315 µA shutdown current extends battery backup runtime; SMBus TIMEOUT reset prevents field failures due to bus contention in noisy factory settings.

Server Memory Thermal Monitoring

Laptop GPU Die Sensing

Use Scenario: Real-time temperature tracking of DDR4/DDR5 DIMM modules in 1U/2U rack servers to prevent thermal throttling and ensure JEDEC compliance.

IC Role / Device Role / Timing Role: Remote diode sensor interfacing with memory IC thermal diodes; local sensor monitoring DIMM PCB ambient; T_CRIT_A triggers VRM shutdown at 105°C.

Use Value: Enables hardware-enforced thermal safety without BMC polling latency; 0.125°C resolution allows predictive fan control reducing acoustic noise by 3–5 dB(A).

Use Scenario: Direct die temperature measurement of discrete GPU on thin-and-light laptop motherboards with limited airflow.

IC Role / Device Role / Timing Role: Remote diode sensor connected to GPU's integrated thermal diode; ALERT signals GPU driver for dynamic clock scaling; SMBus updates every 31.25 ms.

Use Value: Achieves ±0.75°C accuracy despite GPU package self-heating and PCB trace impedance - improves thermal margin by 4–6°C versus generic NTC solutions.

Workstation FPGA Thermal Management

Industrial Embedded Controller Board

Use Scenario: Monitoring Xilinx/Intel FPGA die temperature during high-throughput compute workloads in air-cooled workstations.

IC Role / Device Role / Timing Role: Remote diode sensor tied to FPGA's thermal diode; local sensor tracks board ambient; T_CRIT_A asserts to FPGA configuration logic for safe reconfiguration.

Use Value: Supports FPGA partial reconfiguration based on real-time die temp; 31.25 ms conversion time ensures thermal feedback loop meets <50 ms response requirement.

Use Scenario: Long-life thermal supervision of ARM-based industrial controllers operating in 0°C–70°C extended ambient environments.

IC Role / Device Role / Timing Role: Local + remote sensor monitoring SoC die and heatsink; ALERT latched to microcontroller GPIO; SMBus read only during scheduled diagnostics.

Use Value: 315 µA shutdown current extends battery backup runtime; SMBus TIMEOUT reset prevents field failures due to bus contention in noisy factory settings.

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
LM86IMMX/NOPB	Same pinout and register map; 85°C default T_CRIT; no 105°C variant; ±1.0°C remote accuracy at 80°C	Designed for general-purpose CPU thermal monitoring, not DIMM-specific; lacks 105°C T_CRIT alignment	Select when cost sensitivity outweighs DIMM thermal spec compliance and higher accuracy is acceptable
MAX6657ESA+	Pin-compatible but different SMBus address; ±1.5°C remote accuracy; no T_CRIT_A output - ALERT only	Relies on host firmware for critical shutdown; no hardware comparator path; lower accuracy limits margin in high-power systems	Select only for legacy designs where MAX6657 footprint reuse is mandatory and hardware T_CRIT_A is not required

Compared with LM89-1DIMMX/NOPB, LM86IMMX/NOPB offers identical layout compatibility but lacks the 105°C T_CRIT threshold needed for DDR memory modules, while MAX6657ESA+ omits the dedicated T_CRIT_A hardware shutdown path - making LM89-1DIMMX/NOPB the only option meeting JEDEC thermal enforcement requirements with fail-safe hardware response.

Availability

LM89-1DIMMX/NOPB is available at Aetrix Electronics and suitable for server memory thermal monitoring, laptop GPU die sensing, workstation FPGA thermal management, and industrial embedded controller board applications requiring stable component supply across multi-year production cycles.

Supply support for LM89-1DIMMX/NOPB 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, power management, and industrial interface solutions.

The LM89 product line was designed specifically for high-accuracy, SMBus-based thermal monitoring in computing platforms - targeting memory modules, CPUs, GPUs, and FPGAs where hardware-enforced thermal safety and remote diode compatibility are critical.

FAQ

What is the default T_CRIT temperature setting for LM89-1DIMMX/NOPB?

The LM89-1DIMMX/NOPB has a factory-programmed default local T_CRIT temperature setting of 105°C, distinguishing it from other LM89 variants (e.g., LM89C, LM89-1C) which default to 85°C. This 105°C threshold aligns with JEDEC specifications for DDR4/DDR5 memory module thermal shutdown and is stored in the local T_CRIT limit register at power-up. The value can be reprogrammed via SMBus, but the hardware default ensures immediate compliance without firmware initialization.

How does the LM89-1DIMMX/NOPB handle remote diode nonideality compensation?

The LM89-1DIMMX/NOPB uses two dedicated 8-bit offset registers - RTOLB (remote temperature offset low byte) and RTOHB (remote temperature offset high byte) - to compensate for diode nonideality factors and series resistance effects. These registers allow software to adjust the raw remote temperature reading by adding or subtracting a calibrated offset value, enabling accurate measurements across diverse thermal diodes (e.g., 2N3904, integrated GPU diodes) without requiring per-unit calibration or external circuitry. The offset is applied before limit comparisons and T_CRIT_A assertion.

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

The 2.2 nF capacitor between D+ and D− pins of LM89-1DIMMX/NOPB filters high-frequency noise on the remote diode bias path, preventing measurement corruption caused by switching regulators, RF interference, or ESD events. Texas Instruments specifies this capacitor must be placed as close as possible to both pins with matched trace lengths - a design requirement validated in the LM89-1DIMMX/NOPB's characterization testing. Omitting or misplacing this capacitor degrades remote accuracy beyond the ±0.75°C specification, especially in high-noise server and GPU environments.

Does LM89-1DIMMX/NOPB support SMBus 2.0 ALERT Response Address (ARA) protocol?

Yes, LM89-1DIMMX/NOPB fully supports the SMBus 2.0 ALERT Response Address (ARA) protocol. When the ALERT output is pulled low and the master issues an ARA command, the LM89-1DIMMX/NOPB responds with its slave address and then automatically disables the ALERT output by setting the ALERT mask bit (D7) in the Configuration register. This "disengagement" behavior complies with SMBus 2.0 specification requirements and prevents bus lockup - a feature confirmed in TI's SNIS128D datasheet revision history and functional test reports.

What is the conversion time and update rate for temperature readings in LM89-1DIMMX/NOPB?

The LM89-1DIMMX/NOPB performs a complete conversion cycle - measuring both local and remote temperatures and updating all internal registers - in a fixed 31.25 ms. This time is invariant regardless of SMBus clock frequency or conversion rate register setting. The device supports programmable conversion rates (via register 04h) that insert delays between cycles, allowing average update intervals from ~31 ms up to several seconds. However, the underlying 31.25 ms conversion duration remains constant and defines the minimum latency for new temperature data availability.

LM89-1DIMMX/NOPB Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Active

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

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-VSSOP

LM89-1DIMMX/NOPB FAQ

1.How can I place an order for LM89-1DIMMX/NOPB through Aetrix?

Please submit a Request for Quotation (RFQ) for LM89-1DIMMX/NOPB 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 LM89-1DIMMX/NOPB reliable?

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

3.What payment methods are accepted for LM89-1DIMMX/NOPB?

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

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LM89-1DIMMX/NOPB?

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

Once your LM89-1DIMMX/NOPB 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 LM89-1DIMMX/NOPB?

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

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

All LM89-1DIMMX/NOPB 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 LM89-1DIMMX/NOPB meets industry standards.

7.What is the process for return or replacement of LM89-1DIMMX/NOPB?

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

Return procedure for LM89-1DIMMX/NOPB:

1.Submit a request within 90 days.

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

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