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

Texas Instruments LM77CIM-3-TI

Name: LM77CIM-3-TI
Brand: Texas Instruments
SKU: LM77CIM-3-TI
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LM77CIM-3-TI

Manufacturer:: Texas Instruments

Category:: Analog and Digital Output

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

Datasheet:: LM77CIM-3-TI.pdf

Description:: SERIAL SWITCH/DIGITAL SENSOR, 10

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Product details

Overview

LM77CIM-3-TI from Texas Instruments is a 9-bit + sign digital temperature sensor and thermal window comparator with I²C interface, designed for ACPI-compliant thermal management. It features dual open-drain outputs (INT and T_CRIT_A), programmable thresholds (TLOW=10°C, THIGH=64°C, T_CRIT=80°C, THYST=2°C at power-up), ±1.5°C accuracy from −10°C to +65°C, and operates from 3.0V to 5.5V supply - ideal for PC motherboard thermal monitoring.

For engineers reviewing the LM77CIM-3-TI datasheet, LM77CIM-3-TI pinout, LM77CIM-3-TI application, or LM77CIM-3-TI equivalent, key selection considerations include its two-wire I²C compatibility, critical alarm hardware shutdown capability, programmable hysteresis, fault queue support, and SOP-8 package with A0/A1 address configuration.

Technical Context

The LM77CIM-3-TI integrates a band-gap temperature sensor, 10-bit ADC, and digital comparator logic enabling simultaneous window (TLOW/THIGH) and critical (T_CRIT) temperature monitoring. Its INT output supports both comparator and event interrupt modes, while T_CRIT_A operates exclusively in comparator mode with active-low open-drain assertion.

It uses a fixed 7-bit I²C slave address (10010xx) where bits A1–A0 are user-configurable via external connections, allowing up to four devices on one bus. Internal registers include read-only Temperature (0x00), and configurable THYST (0x02), T_CRIT (0x03), TLOW (0x04), THIGH (0x05), and Configuration (0x01) - all accessible over I²C with 16-bit register addressing and two's complement temperature data (LSB = 0.5°C).

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage	3.0V to 5.5V - compatible with 3.3V systems (LM77CIM-3 variant); no level-shifting needed for standard I²C hosts.
Temperature Accuracy	±1.5°C max (−10°C to +65°C) - sufficient for system-level thermal throttling and fan control without calibration.
Output Resolution	9-bit + sign (two's complement), LSB = 0.5°C - enables precise granularity for ACPI-compliant window reprogramming.
Conversion Time	70 ms typical - ensures timely updates for dynamic thermal response without excessive polling overhead.
Quiescent Current	250 μA typical operating / 5 μA typical shutdown - supports low-power thermal monitoring in standby states.
Fault Queue Depth	4 consecutive faults required to assert outputs - suppresses false triggers in electrically noisy environments like PC chassis.
I²C Address Options	4 unique addresses via A0/A1 pins (00–11) - allows multi-sensor deployment on shared bus without address conflict.

Pinout & Package

LM77CIM-3-TI is housed in an 8-pin SOP package (NS M08A, JEDEC MS-012AA), 3.9mm × 4.9mm body, 1.75mm height, with 1.27mm pitch. Pin 1 is SDA (serial data), Pin 2 is SCL (clock), Pin 3 is T_CRIT_A (critical alarm output), Pin 4 is GND, Pin 5 is INT (interrupt output), Pins 6–7 are A1/A0 (address inputs), and Pin 8 is +VS (supply voltage).

Pin/Terminal	Circuit Role	Design Meaning
SDA (Pin 1)	I²C bidirectional data line	Open-drain; requires external pull-up; supports standard/fast-mode I²C communication with host controller.
SCL (Pin 2)	I²C clock input	Input only; synchronizes data transfer; no internal clock generation; driven by host master.
T_CRIT_A (Pin 3)	Critical temperature alarm output	Open-drain, active-low; directly drives hardware shutdown circuitry independent of processor state.
GND (Pin 4)	Power supply ground reference	Primary return path for analog and digital sections; must be low-impedance connection to system ground plane.
INT (Pin 5)	Thermal window interrupt output	Open-drain, active-low; signals temperature excursions outside TLOW/THIGH window; configurable as comparator or event mode.
A1, A0 (Pins 6–7)	I²C slave address inputs	User-set binary address bits; tied to GND (0) or +VS (1) to select one of four possible device addresses on shared bus.
+VS (Pin 8)	Positive supply voltage input	Accepts 3.0V–5.5V DC; powers internal band-gap sensor, ADC, comparator, and I²C interface logic.

Key Features

Feature	Design Value
ACPI-compliant window comparison	Enables direct integration into Advanced Configuration and Power Interface thermal management stacks without custom firmware logic.
Separate critical alarm output (T_CRIT_A)	Provides hardware-level system shutdown path independent of CPU responsiveness - essential for fail-safe thermal protection.
Programmable hysteresis (THYST)	Prevents oscillation near trip points; default 2°C adds stability to fan control and throttling decisions in dynamic thermal loads.
Configurable interrupt modes	Comparator mode resets INT after each read; Event mode latches first threshold crossing until next event - simplifies interrupt handling in resource-constrained hosts.
Fault queue (4-cycle validation)	Requires four consecutive out-of-window readings before asserting outputs - eliminates spurious interrupts caused by transient noise or measurement glitches.

Applications

Personal Computer Thermal Management	Industrial HVAC Sensor Node
Use Scenario: Monitoring CPU, GPU, and VRM temperatures on ATX motherboards to trigger fan speed changes or OS-level throttling per ACPI spec. IC Role / Device Role / Timing Role: Primary thermal window comparator feeding SMBus/I²C host; provides real-time status flags and hardware-triggered critical shutdown. Use Value: Eliminates need for discrete comparators and ADCs; reduces BOM count while meeting strict ACPI 2.0/3.0 thermal event timing requirements.	Use Scenario: Remote ambient temperature sensing in duct-mounted HVAC controllers with local alarm activation and bus reporting. IC Role / Device Role / Timing Role: Standalone digital temperature node with dual alert outputs - INT for microcontroller polling, T_CRIT_A for direct relay or power-cut activation. Use Value: Enables single-chip solution for both supervisory alerts and safety-critical cutoff, reducing wiring complexity and field failure risk.
Automotive Cabin Climate Control	Office Equipment Overtemperature Protection
Use Scenario: Cabin air temperature feedback in automotive HVAC modules requiring robust operation across −40°C to +125°C ambient range. IC Role / Device Role / Timing Role: High-accuracy thermal sensor with extended range support (±3°C max error from −55°C to +125°C) and fault-tolerant I²C interface. Use Value: Meets AEC-Q200 stress test requirements when used with appropriate board layout; supports fail-safe cabin heating/cooling logic.	Use Scenario: Thermal supervision of laser printer fuser assemblies and copier power supplies to prevent overheating damage during high-duty cycles. IC Role / Device Role / Timing Role: Critical temperature monitor with dedicated T_CRIT_A output wired to hardware latch that disables high-voltage power stage. Use Value: Provides deterministic, sub-100ms thermal cutoff independent of firmware execution - prevents fire hazard and component degradation.

Personal Computer Thermal Management

Industrial HVAC Sensor Node

Use Scenario: Monitoring CPU, GPU, and VRM temperatures on ATX motherboards to trigger fan speed changes or OS-level throttling per ACPI spec.

IC Role / Device Role / Timing Role: Primary thermal window comparator feeding SMBus/I²C host; provides real-time status flags and hardware-triggered critical shutdown.

Use Value: Eliminates need for discrete comparators and ADCs; reduces BOM count while meeting strict ACPI 2.0/3.0 thermal event timing requirements.

Use Scenario: Remote ambient temperature sensing in duct-mounted HVAC controllers with local alarm activation and bus reporting.

IC Role / Device Role / Timing Role: Standalone digital temperature node with dual alert outputs - INT for microcontroller polling, T_CRIT_A for direct relay or power-cut activation.

Use Value: Enables single-chip solution for both supervisory alerts and safety-critical cutoff, reducing wiring complexity and field failure risk.

Automotive Cabin Climate Control

Office Equipment Overtemperature Protection

Use Scenario: Cabin air temperature feedback in automotive HVAC modules requiring robust operation across −40°C to +125°C ambient range.

IC Role / Device Role / Timing Role: High-accuracy thermal sensor with extended range support (±3°C max error from −55°C to +125°C) and fault-tolerant I²C interface.

Use Value: Meets AEC-Q200 stress test requirements when used with appropriate board layout; supports fail-safe cabin heating/cooling logic.

Use Scenario: Thermal supervision of laser printer fuser assemblies and copier power supplies to prevent overheating damage during high-duty cycles.

IC Role / Device Role / Timing Role: Critical temperature monitor with dedicated T_CRIT_A output wired to hardware latch that disables high-voltage power stage.

Use Value: Provides deterministic, sub-100ms thermal cutoff independent of firmware execution - prevents fire hazard and component degradation.

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital temperature sensor and thermal comparator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LM75BIM-3/NOPB	Lacks T_CRIT_A output and fault queue; only single INT output; no critical alarm hardware shutdown capability.	Suitable for basic temperature monitoring but not for safety-critical thermal cutoff scenarios requiring independent hardware response.	Select LM77CIM-3-TI when dual-alert architecture (window + critical) and fault immunity are required.
MAX6625ASA+	Higher accuracy (±1°C), SPI interface only, no I²C support; different pinout and register map; no built-in hysteresis programming.	Better for precision lab equipment where SPI is preferred and critical alarm is handled in software.	Choose LM77CIM-3-TI for I²C-based ACPI systems needing integrated hardware shutdown and configurable hysteresis.

Compared with LM75BIM-3/NOPB, LM77CIM-3-TI adds critical-alarm hardware independence and noise-immune fault queuing; versus MAX6625ASA+, it offers native I²C compatibility, simpler address configuration, and direct ACPI window-comparator implementation - making it optimal for PC, server, and industrial thermal control where bus simplicity and fail-safe response are mandatory.

Availability

LM77CIM-3-TI is available at Aetrix Electronics and suitable for personal computer thermal management, industrial HVAC sensor nodes, automotive cabin climate control, office equipment overtemperature protection, and electronic test equipment requiring stable component supply and long-term lifecycle support.

Supply support for LM77CIM-3-TI 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 acquired National Semiconductor in 2011 and maintains full technical and manufacturing continuity for legacy precision analog products including the LM77 series.

The LM77CIM-3-TI belongs to TI's precision temperature sensing portfolio, engineered specifically for ACPI-compliant thermal monitoring and hardware-fail-safe shutdown in computing, industrial, and automotive platforms.

FAQ

What is the default I²C address of the LM77CIM-3-TI at power-up?

The LM77CIM-3-TI defaults to I²C slave address 0x48 (1001000b) when both A0 and A1 pins are grounded. The five most significant address bits are hardwired as "10010", and A1/A0 set the two LSBs - so grounding both yields 1001000. This address is confirmed in the LM77CIM-3-TI datasheet Section 1.3 and applies regardless of supply voltage (3.3V or 5V).

Does the LM77CIM-3-TI support both 3.3V and 5V I²C buses?

Yes, the LM77CIM-3-TI operates from 3.0V to 5.5V and supports standard I²C logic levels across that range. Its VIN(1) threshold is +VS × 0.7, so at 3.3V it accepts ≥2.31V as high, and at 5V ≥3.5V - fully compatible with both 3.3V and 5V I²C masters without level shifters. This is specified in the LM77CIM-3-TI Logic Electrical Characteristics table.

How does the fault queue function in the LM77CIM-3-TI?

The LM77CIM-3-TI fault queue requires four consecutive temperature conversions to exceed a set threshold before asserting INT or T_CRIT_A. Enabled via bit D4 of the Configuration register, it prevents false alarms from electrical noise or transient spikes - especially valuable in PC chassis or motor-drive environments. This behavior is documented in Section 1.7 and verified in the LM77CIM-3-TI Absolute Maximum Ratings table.

Can the LM77CIM-3-TI operate in shutdown mode while retaining I²C accessibility?

Yes, the LM77CIM-3-TI supports full I²C register access in shutdown mode (enabled by setting bit D0 of the Configuration register). Supply current drops to 5 μA typical, conversions halt, and INT/T_CRIT_A are reset - yet the device remains addressable, allowing configuration updates and status reads without waking the sensor. This is explicitly defined in Section 1.5 of the LM77CIM-3-TI datasheet.

What is the temperature resolution and data format of the LM77CIM-3-TI?

The LM77CIM-3-TI provides 9-bit + sign temperature data in two's complement format, with 0.5°C per LSB. The Temperature Register (0x00) returns a 16-bit word where bits D3–D15 contain the signed value - e.g., 0x032 = +25°C, 0x3CE = −25°C. This resolution and encoding are confirmed in Section 1.4 and Table 1 of the LM77CIM-3-TI datasheet.

LM77CIM-3-TI Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

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

Packaging:: Bulk

Product Status:: Active

Sensor Type:: Digital

Sensing Temperature - Local:: -55°C ~ 125°C

Sensing Temperature - Remote:: -

Output Type:: 2-Wire Serial, I2C/SMBUS

Voltage - Supply:: 3V ~ 5.5V

Resolution:: 10 b

Features:: Programmable Limit, Shutdown Mode

Accuracy - Highest (Lowest):: ±0.3°C

Test Condition:: 25°C

Operating Temperature:: -55°C ~ 125°C

Mounting Type:: Surface Mount

Grade:: -

Qualification:: -

Supplier Device Package:: 8-SOIC

LM77CIM-3-TI FAQ

1.How can I place an order for LM77CIM-3-TI through Aetrix?

Please submit a Request for Quotation (RFQ) for LM77CIM-3-TI 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 LM77CIM-3-TI reliable?

The price and inventory of LM77CIM-3-TI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM77CIM-3-TI is usually 5 days.

3.What payment methods are accepted for LM77CIM-3-TI?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM77CIM-3-TI transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LM77CIM-3-TI?

LM77CIM-3-TI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LM77CIM-3-TI 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 LM77CIM-3-TI?

For technical support, including LM77CIM-3-TI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM77CIM-3-TI requirements.

6.How does Aetrix verify that LM77CIM-3-TI is sourced from the original manufacturer or authorized distributors?

All LM77CIM-3-TI 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 LM77CIM-3-TI meets industry standards.

7.What is the process for return or replacement of LM77CIM-3-TI?

All LM77CIM-3-TI units undergo pre-shipment inspection (PSI). If there is an issue with LM77CIM-3-TI, 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 LM77CIM-3-TI part is unused and in its original packaging.

Return procedure for LM77CIM-3-TI:

1.Submit a request within 90 days.

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

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