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Texas Instruments LM77CIM-3/NOPB
- Part No.:
- LM77CIM-3/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Analog and Digital Output
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM77CIM-3/NOPB.pdf
- Description:
- SENSOR DIGITAL -55C-125C 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:939
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Product details
Overview
LM77CIM-3/NOPB from Texas Instruments is a 9-bit + sign digital temperature sensor and thermal window comparator with I²C interface, ±2°C accuracy from −25°C to +100°C, 3.0V–5.5V supply range, and dual open-drain outputs (INT and T_CRIT_A) for programmable thermal monitoring in ACPI-compliant PC power management systems.
For engineers reviewing the LM77CIM-3/NOPB datasheet, LM77CIM-3/NOPB pinout, LM77CIM-3/NOPB application, or LM77CIM-3/NOPB equivalent, this page delivers verified specifications, SOIC-8 package mapping, thermal window comparator behavior, fault queue operation, and real-world use cases in system thermal shutdown and HVAC sensing.
Technical Context
The LM77CIM-3/NOPB integrates a band-gap temperature sensor, 10-bit ADC, and digital comparator with user-programmable TLOW (10°C default), THIGH (64°C default), T_CRIT (80°C default), and THYST (2°C default). It supports two interrupt modes-Comparator (auto-reset per conversion) and Event (single-shot)-and features a 4-fault queue to suppress noise-induced false triggers.
Its I²C slave interface uses a fixed 5-bit address prefix "10010" with A0/A1 pins selecting the full 7-bit address. The device operates across −55°C to +125°C, delivers 0.5°C LSB resolution in two's complement format, and enters 5 μA shutdown mode via Configuration register bit D0 without disabling the I²C bus.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 3.0V to 5.5V - Supports direct connection to common logic rails (3.3V or 5V) without level-shifting. |
| Temperature Accuracy | ±2°C max from −25°C to +100°C - Enables reliable thermal trip decisions in PC and office electronics environments. |
| Resolution | 9-bit + sign (10-bit effective), 0.5°C LSB - Provides sufficient granularity for window-based thermal control without oversampling overhead. |
| Conversion Time | 70–125 ms - Determines minimum interval between valid temperature updates; affects response latency in fast-transient scenarios. |
| Quiescent Current | 250 μA typical operating / 5 μA typical shutdown - Allows continuous background monitoring with minimal impact on system power budget. |
| Output Type | Two independent open-drain outputs (INT and T_CRIT_A) - Enables hardware-level critical shutdown (T_CRIT_A) separate from software-handled window alerts (INT). |
| Fault Queue Depth | 4 consecutive faults required to assert outputs - Prevents spurious interrupts in electrically noisy industrial or automotive PCB layouts. |
Pinout & Package
LM77CIM-3/NOPB is housed in an 8-pin SOIC (Package Number D0008A), surface-mount package with standard 1.27 mm pitch, JEDEC MS-012AC compliant footprint, and −55°C to +125°C operating temperature rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SDA | I²C bidirectional data line | Open-drain node requiring external pull-up; shares bus with other I²C slaves; supports repeated start/stop protocols. |
| SCL | I²C clock input | Asynchronous master-driven clock; timing compliant with standard-mode (100 kHz) I²C bus specifications. |
| T_CRIT_A | Critical temperature alarm output | Asserts independently of INT; used for hardware-triggered system shutdown (e.g., PSU disable) when T > 80°C. |
| GND | Power supply ground reference | Must be low-impedance connection to system ground plane to ensure ADC accuracy and thermal measurement stability. |
| INT | Window comparator interrupt output | Active when T < TLOW or T > THIGH; configurable polarity and mode; intended for CPU or microcontroller interrupt servicing. |
| +VS | Positive supply voltage input | Accepts 3.0V–5.5V; internal regulation ensures stable core biasing across rail variation; accuracy degrades ~1°C/V outside nominal. |
| A0, A1 | I²C address select inputs | Binary-encoded LSBs of 7-bit slave address (10010xx); tied to GND or +VS to support up to four devices on one bus. |
Key Features
| Feature | Design Value |
|---|---|
| ACPI-compatible thermal window comparator | Enables direct integration into Advanced Configuration and Power Interface firmware stacks for OS-managed thermal throttling and sleep-state transitions. |
| Separate critical alarm output (T_CRIT_A) | Provides fail-safe hardware shutdown path independent of host processor responsiveness-critical for safety-critical thermal runaway prevention. |
| Configurable interrupt modes | Comparator mode resets INT after each conversion; Event mode latches until next threshold crossing-supports both polling and event-driven architectures. |
| Programmable hysteresis (THYST) | Reduces chattering near trip points by defining distinct turn-on/turn-off thresholds (e.g., TLOW+THYST for release, THIGH−THYST for reset). |
| 4-fault queue filtering | Requires four consecutive out-of-window readings before asserting INT/T_CRIT_A-eliminates false alarms caused by EMI or transient thermal noise. |
| Shutdown mode with active I²C | Reduces current to 5 μA while retaining register accessibility-enables low-power thermal watchdog operation during system standby. |
Applications
| Personal Computer Thermal Management | HVAC Remote Sensing Node |
|---|---|
|
Use Scenario: Monitoring CPU, GPU, and VRM temperatures in desktop and laptop motherboards to trigger fan speed adjustments or OS-initiated throttling. IC Role / Device Role / Timing Role: Primary thermal window comparator feeding ACPI-compliant thermal zone data to BIOS/firmware; INT signals temperature excursions to host controller. Use Value: Eliminates need for external analog comparators and ADCs; reduces BOM count and layout area while enabling precise, software-configurable trip points. |
Use Scenario: Distributed temperature sensing in commercial HVAC ducts or wall-mounted thermostats using 3-wire RS-485 or analog interfaces. IC Role / Device Role / Timing Role: Local digital temperature transducer with I²C output; communicates via isolated level shifter or microcontroller gateway to central controller. Use Value: Delivers ±2°C accuracy over −25°C to +100°C range-sufficient for air temperature control within ASHRAE comfort bands without calibration drift compensation. |
| Industrial Embedded Controller Monitoring | Automotive Cabin Climate Module |
|
Use Scenario: Real-time thermal supervision of FPGA, DSP, or power module junction temperatures in programmable logic controllers and motor drives. IC Role / Device Role / Timing Role: Standalone thermal watchdog with dual outputs: INT for PLC firmware logging/alerting, T_CRIT_A for immediate hardware disable of gate drivers or DC-DC converters. Use Value: Fault queue prevents nuisance trips during EMI-heavy factory floor operation; wide supply range accommodates unregulated 5V rails in legacy industrial designs. |
Use Scenario: Cabin ambient temperature sensing in automotive climate control units where reliability and extended temperature range are mandatory. IC Role / Device Role / Timing Role: Primary cabin air sensor interfacing to HVAC MCU via I²C; T_CRIT_A wired to thermal fuse circuit for emergency blower shutdown above 80°C. Use Value: −55°C to +125°C operating range meets AEC-Q200 Grade 2 requirements; SOIC-8 package supports automated reflow assembly and long-term under-hood stability. |
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 |
|---|---|---|---|
| LM75BIM-3/NOPB | Lacks T_CRIT_A output and fault queue; only single INT output; ±2°C accuracy same range but no critical alarm hardware path. | Suitable for basic temperature monitoring where software-only critical response is acceptable; not ACPI-compliant for hardware shutdown. | Select when cost reduction is prioritized over fail-safe thermal protection and dual-output architecture. |
| MAX31820MUA+ | 1-Wire interface instead of I²C; ±0.5°C accuracy; integrated 12-bit ADC; no programmable window comparator or dedicated T_CRIT output. | Better accuracy for precision sensing, but requires different bus protocol and lacks built-in thermal decision logic-host must implement all comparison. | Choose when board space is constrained and 1-Wire infrastructure already exists; avoid if ACPI compliance or hardware-level shutdown is required. |
Compared with LM77CIM-3/NOPB, LM75BIM-3/NOPB omits critical-alarm hardware independence and noise immunity, while MAX31820MUA+ shifts thermal decision responsibility to firmware and changes physical layer compatibility-making LM77CIM-3/NOPB uniquely suited for ACPI-compliant, dual-path thermal safety systems.
Availability
LM77CIM-3/NOPB is available at Aetrix Electronics and suitable for personal computer thermal management, HVAC remote sensing nodes, and industrial embedded controller monitoring requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.
Supply support for LM77CIM-3/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 leader specializing in analog, embedded processing, and high-reliability components for industrial, automotive, and computing markets.
The LM77 product line was designed specifically for ACPI-compliant thermal monitoring in PCs and embedded systems, delivering integrated window comparison, critical alarm signaling, and I²C interoperability in a single SOIC-8 IC.
FAQ
What is the default temperature window and critical threshold for LM77CIM-3/NOPB at power-up?
At power-up, LM77CIM-3/NOPB initializes with TLOW = 10°C, THIGH = 64°C, T_CRIT = 80°C, and THYST = 2°C. These defaults are hard-coded and apply regardless of supply voltage. The device enters Comparator Interrupt Mode with active-low INT and T_CRIT_A outputs. All registers reset when +VS crosses the voltage threshold shown in Figure 6 of the datasheet.
Does LM77CIM-3/NOPB support both 3.3V and 5V I²C buses?
Yes, LM77CIM-3/NOPB operates from 3.0V to 5.5V and is specified for I²C compatibility at both 3.3V and 5V nominal supplies. Its SDA/SCL input thresholds scale with VS (VIN(1) ≥ 0.7×VS), and it tolerates mixed-voltage bus configurations when used with appropriate pull-up resistors and level-shifting considerations.
How does the fault queue in LM77CIM-3/NOPB prevent false interrupts?
The LM77CIM-3/NOPB fault queue requires four consecutive temperature conversions to exceed the programmed window or critical limit before asserting INT or T_CRIT_A. This eliminates false triggers caused by short-duration noise spikes or thermal transients. The queue is enabled by setting bit D4 in the Configuration register and resets automatically upon successful in-window reading.
Can LM77CIM-3/NOPB be used in automotive under-hood applications?
LM77CIM-3/NOPB is rated for −55°C to +125°C operation and packaged in SOIC-8 (D0008A), making it suitable for non-safety-critical automotive cabin or engine bay locations where ambient temperature remains within spec. However, it is not AEC-Q200 qualified; for certified under-hood use, TI recommends the automotive-grade LM77-Q1 variant.
What happens to the T_CRIT_A output when LM77CIM-3/NOPB is read over I²C?
Reading any register in LM77CIM-3/NOPB resets the T_CRIT_A output until the next temperature conversion completes-even if the temperature remains above T_CRIT. This behavior ensures deterministic timing for critical shutdown sequences and avoids race conditions during host interrogation. The INT output follows the same reset rule in Comparator Mode.
LM77CIM-3/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- 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
LM77CIM-3/NOPB FAQ
1.How can I place an order for LM77CIM-3/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM77CIM-3/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 LM77CIM-3/NOPB reliable?
The price and inventory of LM77CIM-3/NOPB 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/NOPB is usually 5 days.
3.What payment methods are accepted for LM77CIM-3/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM77CIM-3/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM77CIM-3/NOPB?
LM77CIM-3/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM77CIM-3/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 LM77CIM-3/NOPB?
For technical support, including LM77CIM-3/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM77CIM-3/NOPB requirements.
6.How does Aetrix verify that LM77CIM-3/NOPB is sourced from the original manufacturer or authorized distributors?
All LM77CIM-3/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 LM77CIM-3/NOPB meets industry standards.
7.What is the process for return or replacement of LM77CIM-3/NOPB?
All LM77CIM-3/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM77CIM-3/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 LM77CIM-3/NOPB part is unused and in its original packaging.
Return procedure for LM77CIM-3/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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