Texas Instruments LM77CIM-5

Overview

LM77CIM-5 from Texas Instruments is a 9-bit + sign digital temperature sensor and thermal window comparator with I²C interface, operating at +5 V ±10%, featuring ±1.5°C accuracy from −10°C to +65°C, programmable THYST/TLOW/THIGH/T_CRIT thresholds, and dual open-drain outputs (INT and T_CRIT_A) for ACPI-compliant system thermal management in PCs and embedded controllers.

For engineers reviewing the LM77CIM-5 datasheet, LM77CIM-5 pinout, LM77CIM-5 application, or LM77CIM-5 equivalent, this page delivers verified specifications, SOIC-8 package mapping, I²C timing compliance, default threshold behavior, fault queue configuration, and real-world thermal shutdown use cases - all tied explicitly to the LM77CIM-5 variant.

Technical Context

The LM77CIM-5 integrates a band-gap temperature sensor, 10-bit ADC, and digital comparator logic enabling independent monitoring of three user-programmable thresholds: TLOW (default 10°C), THIGH (64°C), and T_CRIT (80°C), with hysteresis (THYST = 2°C) applied asymmetrically-added to TLOW and subtracted from THIGH/T_CRIT. Its I²C slave address is fixed at "10010" with A0/A1 pins selecting LSBs.

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 event), with both INT and T_CRIT_A outputs operating as open-drain, active-low by default, and independently configurable for polarity and fault queue depth (up to 4 consecutive faults).

Key Specifications

Pinout & Package

LM77CIM-5 is housed in an 8-pin SOIC package (Package Number D0008A), surface-mount, with 1.27 mm pitch and JEDEC MS-012AC compliant footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM75BIM-5, LM77CIM-5 adds critical alarm hardware signaling and fault-tolerant interrupt logic; versus MAX6625ASA+, it trades absolute accuracy for I²C compatibility, lower system integration effort, and built-in thermal window functionality - making LM77CIM-5 optimal for cost-sensitive, standards-aligned thermal management.

Availability

LM77CIM-5 is available at Aetrix Electronics and suitable for PC motherboard thermal management, industrial PLC overtemperature protection, and HVAC zone sensing requiring stable component supply across extended product lifecycles.

Supply support for LM77CIM-5 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 sensing, power management, and interface solutions.

The LM77 product line was designed specifically for ACPI-compliant thermal monitoring in personal computers and embedded systems, delivering integrated window comparison, dual-alert outputs, and I²C simplicity in a single SOIC-8 device.

FAQ

What is the nominal supply voltage for LM77CIM-5 and how does variation affect accuracy?

The LM77CIM-5 is specified for +5 V ±10% operation. Per the datasheet, accuracy degrades approximately 1°C per volt deviation from nominal +5 V - meaning operation at 4.5 V or 5.5 V may increase worst-case error by up to ±0.5°C within the −10°C to +65°C range. LM77CIM-5 maintains full functionality across 3.0 V to 5.5 V, but accuracy guarantees apply strictly at its rated nominal voltage.

Does LM77CIM-5 support multiple devices on the same I²C bus, and how is addressing managed?

Yes, LM77CIM-5 supports up to four devices on a single I²C bus using pin-strapped addressing. Pins A1 and A0 determine the two least significant bits of the 7-bit slave address (base "10010xx"), allowing unique addresses 0x48–0x4F. This eliminates address conflicts in multi-sensor thermal monitoring systems without requiring external multiplexers or software arbitration.

How does the fault queue in LM77CIM-5 prevent false interrupts?

The LM77CIM-5 fault queue requires up to four consecutive temperature violations before asserting INT or T_CRIT_A - configurable via bit D4 of the Configuration register. This ensures transient noise, EMI bursts, or momentary thermal spikes do not trigger erroneous shutdowns or alerts, enhancing reliability in electrically noisy environments like motor drives or switch-mode power supplies.

What are the default power-up thresholds and hysteresis settings for LM77CIM-5?

At power-up, LM77CIM-5 initializes with TLOW = 10°C, THIGH = 64°C, T_CRIT = 80°C, and THYST = 2°C. Hysteresis is applied asymmetrically: added to TLOW (e.g., 10°C + 2°C = 12°C release point) and subtracted from THIGH/T_CRIT (e.g., 64°C − 2°C = 62°C release point). These defaults comply with ACPI thermal zone definitions and require no initial programming.

Can LM77CIM-5 operate in shutdown mode while retaining I²C accessibility?

Yes, LM77CIM-5 enters shutdown mode when bit D0 of the Configuration register is set, reducing supply current to 5 μA typical. Crucially, the I²C interface remains fully functional - registers can be read and written, thresholds reprogrammed, and shutdown disabled - enabling low-power background supervision without bus disconnection or system wake-up overhead.