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Texas Instruments LM77CIMX-3
- Part No.:
- LM77CIMX-3
- Manufacturer:
- Texas Instruments
- Category:
- Analog and Digital Output
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM77CIMX-3.pdf
- Description:
- SENSOR DIGITAL -55C-125C 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,155
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Product details
Overview
LM77CIMX-3 from Texas Instruments is a 9-bit + sign digital temperature sensor and thermal window comparator with I²C interface, operating from 3.0V to 5.5V supply, delivering ±1.5°C accuracy from −10°C to +65°C, and featuring separate open-drain INT and T_CRIT_A outputs for programmable window and critical shutdown functions in PC thermal management systems.
For engineers reviewing the LM77CIMX-3 datasheet, LM77CIMX-3 pinout, LM77CIMX-3 application, or LM77CIMX-3 equivalent, key selection considerations include its dual-comparator architecture (TLOW/THIGH window + independent T_CRIT threshold), fault queue support, shutdown mode (5 μA typ), and SOIC-8/VSSOP-8 package compatibility with ACPI-compliant thermal control designs.
Technical Context
The LM77CIMX-3 integrates a band-gap temperature sensor, 10-bit ADC, and digital comparator logic with user-programmable TLOW (10°C default), THIGH (64°C default), T_CRIT (80°C default), and THYST (2°C default) registers. Its I²C slave interface uses a fixed 5-bit address prefix "10010" plus A0/A1 pins for up to four devices on one bus.
It supports two interrupt modes: Comparator Mode (output resets after each read and reasserts if condition persists) and Event Mode (output latches until next threshold crossing). The T_CRIT_A output operates exclusively in comparator mode and drives hardware shutdown circuitry independently of host software response.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 3.0V to 5.5V - Enables direct use with 3.3V or 5V system rails without level-shifting. |
| Temperature Accuracy | ±1.5°C max (−10°C to +65°C) - Sufficient for ACPI-compliant PC thermal monitoring where ±2°C is typical requirement. |
| Resolution | 9-bit + sign (0.5°C LSB) - Provides fine-grained thermal feedback for dynamic fan speed or power throttling control. |
| Quiescent Current | 250 μA typ (active), 5 μA typ (shutdown) - Supports low-power thermal monitoring during system sleep states. |
| Conversion Time | 70–125 ms - Determines minimum interval between valid temperature updates for real-time response. |
| Fault Queue Depth | 4 consecutive faults required - Reduces false interrupts in electrically noisy environments like server chassis or motor drives. |
| I²C Address Options | 4 unique addresses via A0/A1 pins - Allows multi-sensor thermal mapping on single bus without address conflict. |
Pinout & Package
LM77CIMX-3 is available in SOIC-8 (D0008A) and VSSOP-8 (DGK0008A) packages - both 8-pin surface-mount formats with identical pinout and thermal resistance profiles (200°C/W and 250°C/W respectively).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SDA | I²C bidirectional data line | Open-drain output requiring external pull-up; enables register reads/writes and configuration updates over shared bus. |
| SCL | I²C clock input | Asynchronous timing reference from host controller; no internal clock generation. |
| T_CRIT_A | Critical temperature alarm output | Open-drain signal asserting when temperature exceeds T_CRIT; used for hardware-level system shutdown independent of CPU. |
| GND | Power supply ground | Reference node for analog sensing and digital logic; must be low-impedance connection to minimize measurement error. |
| INT | Window comparator interrupt output | Open-drain signal active when temperature falls below TLOW or rises above THIGH; configurable polarity and mode. |
| +VS | Positive supply voltage input | Accepts 3.0V–5.5V DC; powers internal sensor, ADC, comparator, and I²C interface logic. |
| A0, A1 | Slave address select inputs | Digital inputs setting two LSBs of 7-bit I²C address; grounded or tied to +VS to select among four device addresses. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent alarm outputs | Separate INT (window) and T_CRIT_A (critical) open-drain signals enable concurrent software alerting and hardware fail-safe shutdown. |
| Programmable hysteresis | THYST register adjusts hysteresis applied to TLOW (additive) and THIGH/T_CRIT (subtractive), preventing oscillation near trip points. |
| ACPI-compliant operation | Default thresholds (TLOW=10°C, THIGH=64°C, T_CRIT=80°C, THYST=2°C) and interrupt behavior align with Advanced Configuration and Power Interface thermal management requirements. |
| Configurable interrupt mode | Comparator Mode (auto-reset per conversion) or Event Mode (latched until next threshold crossing) selected via Configuration Register bit D1. |
| Shutdown mode control | Bit D0 in Configuration Register disables temperature conversions and reduces current to 5 μA while preserving I²C accessibility for remote wake-up or status polling. |
Applications
| Server CPU Thermal Monitoring | Laptop Battery Pack Protection |
|---|---|
Use Scenario: Real-time core temperature tracking in dual-socket x86 servers with dynamic fan control and graceful throttling. IC Role / Device Role / Timing Role: Primary thermal sensor feeding BMC firmware; provides 0.5°C-resolution readings every 125 ms to trigger PWM fan adjustments or CPU frequency scaling. Use Value: Dual-interrupt architecture allows immediate hardware shutdown at 80°C (T_CRIT_A) while maintaining software-managed window alerts (INT) between 10°C–64°C for predictive cooling. | Use Scenario: Overtemperature cutoff in Li-ion battery packs for ultrabooks, preventing thermal runaway during fast charging. IC Role / Device Role / Timing Role: Standalone safety monitor interfacing directly with protection IC or microcontroller; asserts T_CRIT_A at 65°C to disable charge FETs within <100 ms. Use Value: Fault queue prevents spurious shutdowns from transient noise on battery pack PCBs, while 3.3V-compatible supply eliminates need for auxiliary LDO. |
| Industrial PLC Cabinet Control | Automotive Infotainment SoC Throttling |
Use Scenario: Ambient temperature supervision inside sealed industrial control cabinets housing programmable logic controllers. IC Role / Device Role / Timing Role: System-level thermal watchdog; monitors enclosure air temperature via external thermistor trace and triggers forced-air cooling or process halt. Use Value: −55°C to +125°C operating range ensures reliability across wide ambient conditions; SOIC-8 package withstands vibration and conformal coating. | Use Scenario: Die temperature monitoring for application processors in automotive head units, enabling adaptive performance scaling under high ambient load. IC Role / Device Role / Timing Role: Secondary thermal sensor co-located with SoC; communicates via I²C to vehicle MCU to adjust GPU/CPU clocks before reaching critical junction limits. Use Value: Programmable TLOW/THIGH window (e.g., 45°C–75°C) enables granular thermal zoning; Event Mode prevents repeated interrupts during sustained high-load operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar digital temperature sensor and thermal window comparator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM75BIMM-3 | Single-window comparator only (no T_CRIT_A output); 12-bit resolution; same SOIC/VSSOP-8 footprint. | Lacks dedicated critical shutdown output - requires host MCU to poll and assert external shutdown signal. | Select when cost-sensitive designs require basic thermal alerting without hardware-level fail-safe capability. |
| MAX6625ASA+ | Higher accuracy (±1°C over 0°C–70°C); integrated 10-bit ADC; SPI interface only (no I²C). | Requires SPI host interface and additional GPIO for interrupt handling; no native ACPI-compliant defaults. | Select when higher precision is needed and system already uses SPI peripherals, accepting added software complexity for critical alarm logic. |
Compared with LM77CIMX-3, LM75BIMM-3 omits the independent T_CRIT_A hardware shutdown path and fault queue, while MAX6625ASA+ trades I²C compatibility and ACPI-ready defaults for improved accuracy and SPI-only communication - making LM77CIMX-3 uniquely suited for ACPI-compliant, dual-alarm thermal architectures requiring minimal host intervention.
Availability
LM77CIMX-3 is available at Aetrix Electronics and suitable for server thermal management, laptop battery protection, industrial PLC cabinet control, and automotive infotainment SoC throttling requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LM77CIMX-3 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 headquartered in Dallas, Texas, specializing in analog, embedded processing, and connectivity technologies for industrial, automotive, and computing markets.
The LM77 product line delivers ACPI-compliant digital temperature sensing with dual-interrupt architecture, designed specifically for reliable thermal monitoring and hardware-assisted shutdown in personal computers, servers, and embedded systems demanding robustness across −55°C to +125°C.
FAQ
What is the operating temperature range of the LM77CIMX-3?
The LM77CIMX-3 operates from −55°C to +125°C. Its temperature accuracy is specified as ±1.5°C maximum over −10°C to +65°C, ±2.0°C over −25°C to +100°C, and ±3.0°C over the full range. Prolonged operation above +125°C is not recommended per TI's operating ratings.
Does the LM77CIMX-3 support I²C bus addressing for multiple devices?
Yes, the LM77CIMX-3 supports up to four devices on a single I²C bus using pins A0 and A1 to configure the two least significant bits of its 7-bit slave address (prefix "10010"). This allows distinct addresses 0x48–0x4B without external address translators or multiplexers.
How does the fault queue function in the LM77CIMX-3?
The LM77CIMX-3 fault queue requires four consecutive out-of-range temperature readings before asserting INT or T_CRIT_A outputs. Enabled via bit D4 in the Configuration Register, it suppresses false alarms caused by electrical noise or transient thermal spikes - especially valuable in high-noise industrial or automotive environments.
What are the default temperature thresholds at power-up for the LM77CIMX-3?
At power-up, the LM77CIMX-3 initializes with TLOW = 10°C, THIGH = 64°C, T_CRIT = 80°C, and THYST = 2°C. It also defaults to Comparator Interrupt Mode, active-low polarity for both outputs, and disabled fault queue - providing immediate ACPI-compliant behavior without configuration.
Can the LM77CIMX-3 operate from a 3.3V supply?
Yes, the LM77CIMX-3 is fully specified for 3.3V operation (±10%), as confirmed in its Electrical Characteristics tables. Its supply voltage range is 3.0V to 5.5V, and all key parameters - including accuracy, quiescent current, and I²C timing - are validated at 3.3V nominal, making it compatible with modern low-voltage embedded systems.
LM77CIMX-3 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
- Sensing Temperature - Local:
- -55°C ~ 125°C
- Sensing Temperature - Remote:
- -
- Output Type:
- I2C
- Voltage - Supply:
- 3V ~ 5.5V
- Resolution:
- 9 b
- Features:
- Output Switch, Programmable Limit, Shutdown Mode
- Accuracy - Highest (Lowest):
- ±1.5°C (±3°C)
- Test Condition:
- -10°C ~ 65°C (-55°C ~ 125°C)
- Operating Temperature:
- -55°C ~ 125°C
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 8-SOIC
LM77CIMX-3 FAQ
1.How can I place an order for LM77CIMX-3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM77CIMX-3 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 LM77CIMX-3 reliable?
The price and inventory of LM77CIMX-3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM77CIMX-3 is usually 5 days.
3.What payment methods are accepted for LM77CIMX-3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM77CIMX-3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM77CIMX-3?
LM77CIMX-3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM77CIMX-3 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 LM77CIMX-3?
For technical support, including LM77CIMX-3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM77CIMX-3 requirements.
6.How does Aetrix verify that LM77CIMX-3 is sourced from the original manufacturer or authorized distributors?
All LM77CIMX-3 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 LM77CIMX-3 meets industry standards.
7.What is the process for return or replacement of LM77CIMX-3?
All LM77CIMX-3 units undergo pre-shipment inspection (PSI). If there is an issue with LM77CIMX-3, 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 LM77CIMX-3 part is unused and in its original packaging.
Return procedure for LM77CIMX-3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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