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Texas Instruments LM77CIM-5/NOPB
- Part No.:
- LM77CIM-5/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Analog and Digital Output
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM77CIM-5/NOPB.pdf
- Description:
- SENSOR DIGITAL -55C-125C 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:136
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Product details
Overview
LM77CIM-5/NOPB 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, 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-temperature alarms - used in ACPI-compliant PC thermal management systems.
For engineers reviewing the LM77CIM-5/NOPB datasheet, LM77CIM-5/NOPB pinout, LM77CIM-5/NOPB application, or LM77CIM-5/NOPB equivalent, key selection criteria include its dual-threshold window comparison architecture, 2°C default hysteresis, 70 ms typical conversion time, shutdown mode (5 μA), and SOIC-8 package compatibility with system-level thermal monitoring and hardware-initiated shutdown.
Technical Context
The LM77CIM-5/NOPB integrates a band-gap temperature sensor, 10-bit ADC, and digital comparator with user-programmable TLOW (10°C default), THIGH (64°C default), and T_CRIT (80°C default) thresholds. Its two-wire I²C slave interface uses a fixed 5-bit address prefix "10010" with A0/A1 pins selecting the LSBs 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 circuits independently of host software response.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 3.0 V to 5.5 V - compatible with standard 3.3 V and 5 V logic rails without level shifting. |
| Temperature Accuracy | ±1.5°C max (−10°C to +65°C) - meets tight thermal monitoring requirements for CPU and chipset thermal throttling. |
| Resolution | 9-bit + sign (two's complement), 0.5°C LSB - enables precise 0.5°C granularity for window and critical limit programming. |
| Conversion Time | 70 ms typical - ensures timely updates for real-time thermal event detection without excessive polling overhead. |
| Shutdown Current | 5 μA typical - reduces system standby power in thermally quiescent states while retaining I²C accessibility. |
| Output Type | Two independent open-drain outputs (INT and T_CRIT_A) - allows direct connection to microcontroller interrupts and hardware reset/shutdown lines with external pull-ups. |
| Addressing | 7-bit I²C slave address with A0/A1 pin-selectable LSBs - supports up to four LM77CIM-5/NOPB devices on a single bus without address conflict. |
Pinout & Package
LM77CIM-5/NOPB is housed in an 8-pin SOIC package (Package Number D0008A), with 1.27 mm pitch, 4.9 mm × 3.9 mm body size, and surface-mount compatibility for automated PCB assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SDA | Serial bidirectional data line | Open-drain I²C data line requiring external pull-up; shares bus with other I²C peripherals. |
| SCL | Serial clock input | Asynchronous master-driven clock; no internal oscillator - timing controlled entirely by host controller. |
| T_CRIT_A | Critical temperature alarm output | Open-drain output asserting when temperature exceeds T_CRIT; designed to trigger hardware shutdown independent of firmware. |
| GND | Power supply ground | Reference node for analog sensing and digital logic; must be low-impedance connection to minimize thermal measurement error. |
| INT | Window comparator interrupt output | Open-drain output active when temperature falls outside TLOW–THIGH window; configurable polarity and interrupt mode via register. |
| +VS | Positive supply voltage input | Accepts 3.0 V to 5.5 V DC; powers internal band-gap sensor, ADC, and digital logic; accuracy degrades ~1°C/V away from nominal. |
| A0, A1 | User-set I²C address inputs | Digital inputs defining two LSBs of 7-bit slave address; tied to GND (0) or +VS (1) to select among four unique addresses. |
Key Features
| Feature | Design Value |
|---|---|
| ACPI-compliant thermal window comparator | Enables OS-level thermal management per Advanced Configuration and Power Interface specification using programmable TLOW/THIGH thresholds and hysteresis. |
| Separate critical-temperature hardware alarm | T_CRIT_A output bypasses software stack to directly initiate system power-down or reset when temperature exceeds safety-critical limit (e.g., 80°C default). |
| Fault queue with 4-consecutive-fault requirement | Reduces false interrupts in electrically noisy environments by requiring four successive out-of-window readings before asserting INT or T_CRIT_A. |
| Configurable interrupt modes | Comparator Mode (auto-reset on read) and Event Mode (latched until next threshold crossing) support both polling and event-driven thermal control strategies. |
| Default power-up configuration | Guaranteed known state at startup: TLOW = 10°C, THIGH = 64°C, T_CRIT = 80°C, THYST = 2°C, INT active-low, Comparator Mode - simplifies initialization in embedded firmware. |
Applications
| Laptop CPU Thermal Throttling | Server Blade Chassis Monitoring |
|---|---|
|
Use Scenario: Real-time die temperature tracking for Intel/AMD mobile processors during sustained workloads. IC Role / Device Role / Timing Role: Primary temperature sensor feeding thermal throttle signals to CPU VRM and platform controller hub via SMBus/I²C. Use Value: Enables dynamic frequency scaling and fan speed control using 0.5°C resolution and 70 ms update rate - meeting ACPI 3.0 thermal event latency requirements. |
Use Scenario: Distributed temperature monitoring across multi-board server chassis with hot-swap capability. IC Role / Device Role / Timing Role: Local thermal guard for power supplies, FPGAs, and ASICs; T_CRIT_A triggers immediate board-level power-off before thermal runaway. Use Value: Dual-output architecture isolates critical hardware shutdown (T_CRIT_A) from software-managed alerts (INT), improving system reliability under firmware failure. |
| Industrial HVAC Controller | Automotive Infotainment Module |
|
Use Scenario: Ambient and heatsink temperature supervision in wall-mounted HVAC control units operating from −25°C to +70°C ambient. IC Role / Device Role / Timing Role: Standalone thermal watchdog interfacing with PIC MCU over I²C; INT signals temperature excursions to adjust compressor duty cycle. Use Value: ±2°C accuracy over −25°C to +100°C range and 5 μA shutdown current extend operational life and reduce standby power in battery-backed controllers. |
Use Scenario: Junction temperature monitoring of display driver ICs and audio amplifiers inside sealed infotainment head units. IC Role / Device Role / Timing Role: Embedded thermal sensor providing early-overheat warning to SoC before thermal derating occurs; T_CRIT_A asserts hardware reset if >105°C reached. Use Value: SOIC-8 package withstands automotive reflow profiles; −55°C to +125°C operating range and fault queue ensure robustness in high-vibration, high-EMI environments. |
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 |
|---|---|---|---|
| MAX6625ASA+ | 8-pin SOIC, 12-bit resolution (0.25°C LSB), ±2°C accuracy (−25°C to +100°C), single open-drain ALERT output only - no dedicated T_CRIT output. | Lacks independent critical-temperature alarm output; requires host MCU to poll and interpret critical events - unsuitable for hardware-initiated shutdown. | Select MAX6625ASA+ only when higher resolution is prioritized over hardware safety shutdown capability. |
| ADT7420ARMZ | 8-pin MSOP, 16-bit resolution (0.0078°C LSB), ±0.25°C accuracy (−20°C to +85°C), I²C interface, single ALERT output - no window comparator mode or T_CRIT function. | Designed for precision measurement, not thermal protection; no built-in window comparison or critical alarm logic - requires full firmware implementation of thresholds. | Choose ADT7420ARMZ for lab-grade temperature logging, not for ACPI-compliant thermal management or fail-safe shutdown. |
Compared with MAX6625ASA+ and ADT7420ARMZ, LM77CIM-5/NOPB uniquely delivers integrated dual-threshold window comparison plus a dedicated hardware T_CRIT_A output - enabling deterministic, software-independent thermal shutdown essential for PC, server, and automotive safety-critical applications.
Availability
LM77CIM-5/NOPB is available at Aetrix Electronics and suitable for laptop thermal throttling, server blade chassis monitoring, industrial HVAC control, automotive infotainment modules, and office electronics requiring stable component supply and long-term lifecycle support.
Supply support for LM77CIM-5/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 headquartered in Dallas, Texas, designing and manufacturing analog ICs, embedded processors, and sensing solutions for industrial, automotive, and computing markets.
The LM77 product line was engineered specifically for ACPI-compliant thermal monitoring in personal computers and embedded systems - combining digital temperature sensing, programmable window comparison, and hardware-based critical alarm outputs in a single SOIC-8 device.
FAQ
What is the default power-up behavior of the LM77CIM-5/NOPB?
At power-on, LM77CIM-5/NOPB initializes with TLOW = 10°C, THIGH = 64°C, T_CRIT = 80°C, THYST = 2°C, INT and T_CRIT_A active-low, Comparator Interrupt Mode enabled, and pointer set to the Temperature Register. These defaults ensure immediate functional operation without register configuration, supporting rapid integration into ACPI-compliant platforms.
How does the fault queue in the LM77CIM-5/NOPB prevent false interrupts?
The LM77CIM-5/NOPB fault queue requires four consecutive out-of-window temperature readings before asserting INT or T_CRIT_A. This eliminates spurious triggers caused by transient noise or short thermal spikes, ensuring reliable thermal event detection in electrically noisy environments like server racks or automotive engine bays - a feature confirmed in the LM77CIM-5/NOPB datasheet Section 8.3.9.
Can the LM77CIM-5/NOPB operate from a 3.3 V supply?
Yes, LM77CIM-5/NOPB operates across 3.0 V to 5.5 V, including standard 3.3 V rails. Its electrical characteristics - including 500 μA max operating current and ±2°C accuracy from −25°C to +100°C - are fully specified at +3.3 Vdc ±10%, making it suitable for modern low-voltage embedded systems without level-shifting circuitry.
What is the role of the T_CRIT_A output in the LM77CIM-5/NOPB?
The T_CRIT_A output in LM77CIM-5/NOPB is a dedicated open-drain hardware alarm that activates when temperature exceeds the programmable T_CRIT threshold (default 80°C). Unlike the INT output, T_CRIT_A operates solely in comparator mode and is intended to drive external shutdown circuitry - ensuring system safety even if the host processor is unresponsive or frozen.
Does the LM77CIM-5/NOPB support multiple devices on the same I²C bus?
Yes, LM77CIM-5/NOPB supports up to four devices on a single I²C bus using its A0 and A1 address-select pins. These pins configure the two least significant bits of the 7-bit slave address (prefix "10010"), yielding addresses 0x48–0x4F - enabling scalable thermal monitoring across multi-zone systems without bus contention.
LM77CIM-5/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-5/NOPB FAQ
1.How can I place an order for LM77CIM-5/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM77CIM-5/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-5/NOPB reliable?
The price and inventory of LM77CIM-5/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-5/NOPB is usually 5 days.
3.What payment methods are accepted for LM77CIM-5/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM77CIM-5/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM77CIM-5/NOPB?
LM77CIM-5/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM77CIM-5/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-5/NOPB?
For technical support, including LM77CIM-5/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM77CIM-5/NOPB requirements.
6.How does Aetrix verify that LM77CIM-5/NOPB is sourced from the original manufacturer or authorized distributors?
All LM77CIM-5/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-5/NOPB meets industry standards.
7.What is the process for return or replacement of LM77CIM-5/NOPB?
All LM77CIM-5/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM77CIM-5/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-5/NOPB part is unused and in its original packaging.
Return procedure for LM77CIM-5/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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