Texas Instruments LM71CIMFX

Overview

LM71CIMFX from Texas Instruments is a low-power, high-resolution digital temperature sensor with SPI/MICROWIRE-compatible three-wire serial interface, 14-bit delta-sigma ADC, ±1.5°C accuracy from −10°C to +65°C, 0.03125°C resolution, and operates over −40°C to +150°C - used for real-time thermal monitoring in embedded microcontroller systems.

For engineers reviewing the LM71CIMFX datasheet, LM71CIMFX pinout, LM71CIMFX application, or LM71CIMFX equivalent, key selection considerations include its SOT-23-5 package, 2.65V–5.5V supply range, 300 µA typical operating current, 200 ms max conversion time, and compatibility with host processors via CS/SC/SI/O signaling.

Technical Context

The LM71CIMFX integrates a silicon diode-based temperature sensing element with a 14-bit delta-sigma A/D converter delivering two's complement output at 0.03125°C LSB. Its serial interface uses chip-select (CS), slave clock (SC), and bidirectional serial I/O (SI/O) with Schmitt-trigger inputs and tri-state output capability.

It supports two operational modes - continuous conversion (default on power-up) and shutdown - controlled via an 8-bit write command (00h or FFh) to a write-only configuration register. The device also includes a read-only manufacturer ID register (0x800F) and outputs temperature data in a 16-bit frame with MSB-first transmission.

Key Specifications

Pinout & Package

LM71CIMFX is housed in a 5-pin SOT-23 package (DBV), measuring 2.9 mm × 1.6 mm × 1.15 mm, with gull-wing leads and RoHS-compliant CU-SN finish (Level-1 MSL).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX31820 and ADT7320, the LM71CIMFX offers the best balance of wide temperature range (−40°C to +150°C), moderate resolution (0.03125°C), ultra-low quiescent current (300 µA), and simple 3-wire SPI compatibility - making it ideal for cost-sensitive, thermally demanding embedded systems where robustness and ease of integration outweigh extreme precision needs.

Availability

LM71CIMFX is available at Aetrix Electronics and suitable for industrial motor drives, automotive cabin controllers, medical infusion pumps, and server thermal management requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM71CIMFX 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 connectivity technologies, with over 90 years of innovation in precision analog ICs and industrial-grade sensors.

The LM71CIMFX belongs to TI's precision analog temperature sensor product line, designed specifically for high-reliability thermal monitoring in harsh environments where wide operating range, low power, and simple digital interfacing are essential.

FAQ

What is the absolute maximum supply voltage for the LM71CIMFX?

The LM71CIMFX has an absolute maximum supply voltage of 6.0V. Exceeding this limit may cause permanent damage. Its recommended operating range is 2.65V to 5.5V, and operation below ~1.6V places the device in powered-down state. Always use a 0.1 µF ceramic capacitor between V+ and GND to ensure stable ADC performance and noise immunity in the LM71CIMFX.

Does the LM71CIMFX require external calibration for accurate temperature readings?

No, the LM71CIMFX does not require external calibration. It is factory-trimmed for ±1.5°C accuracy from −10°C to +65°C and ±2.0°C from −40°C to +85°C. Accuracy degrades slightly at extremes (e.g., +3/−2°C from −40°C to +150°C), but all specifications are guaranteed without user calibration. The LM71CIMFX achieves this via on-die trimming of the delta-sigma ADC and temperature sensor elements during final test.

How does the LM71CIMFX handle multiple sensor readouts on a shared SPI bus?

The LM71CIMFX uses dedicated chip select (CS) per device, enabling true multi-drop SPI configuration. Each LM71CIMFX must have its own CS line asserted low during communication; other devices remain in tri-state on SI/O. No address byte or software addressing is needed. This ensures deterministic timing and avoids bus collisions - critical when reading multiple LM71CIMFX sensors in parallel for thermal mapping applications.

Can the LM71CIMFX operate in shutdown mode while retaining its device identity?

Yes. When the LM71CIMFX enters shutdown mode (via 0xFF write command), it continues to respond to read requests with its fixed Manufacturer/Device ID register value (0x800F). The SI/O pin remains active and tri-state capable, allowing host firmware to verify presence and identity without waking the sensor - useful for inventory enumeration or fault-isolation diagnostics in multi-sensor systems using LM71CIMFX.

What is the thermal resistance (θJA) of the LM71CIMFX in its SOT-23 package?

The LM71CIMFX in the SOT-23-5 (DBV) package has a junction-to-ambient thermal resistance (θJA) of 250°C/W when mounted on a standard PCB with 2 oz. copper foil. This value reflects heat dissipation through the package leads into the PCB; it does not include heatsinking or airflow effects. For high-power ambient environments, thermal design must ensure die temperature stays within −40°C to +150°C - the specified operating range of the LM71CIMFX.