Texas Instruments LM71CISD/NOPB

Overview

LM71CISD/NOPB from Texas Instruments is a high-accuracy, low-power digital temperature sensor with SPI/MICROWIRE-compatible three-wire serial interface, 14-bit delta-sigma ADC, ±1.5°C max error (−10°C to +65°C), 0.03125°C resolution, and −40°C to +150°C operating range - used for real-time thermal monitoring in embedded control systems.

For engineers reviewing the LM71CISD/NOPB datasheet, LM71CISD/NOPB pinout, LM71CISD/NOPB application, or LM71CISD/NOPB equivalent, key selection considerations include its WSON-6 package thermal performance (θJA = 57.6°C/W), shutdown mode control via 8-bit write, manufacturer ID register access, and compatibility with microcontrollers requiring minimal I/O overhead and sub-1mA quiescent current.

Technical Context

The LM71CISD/NOPB implements a 14-bit two's complement temperature data format with LSB = 0.03125°C, directly outputting die temperature via a synchronous serial interface where SI/O serves as bidirectional data line with Schmitt-trigger inputs on CS and SC. Its internal architecture integrates a precision bandgap sensor, delta-sigma modulator, digital filter, and register map comprising read-only temperature/ID registers and a write-only configuration register.

Communication requires 32 clock cycles per full transaction: first 16 clocks read temperature (MSB-first), next 16 clocks support write commands (e.g., 0x00 for continuous mode, 0xFF for shutdown); CS must be held low across both phases for ID readback, and minimum inter-read interval is 270 ms to ensure valid conversion completion.

Key Specifications

Pinout & Package

LM71CISD/NOPB uses a 6-pin WSON (No-Pull-Back) package (NGG0006A), 2.0 mm × 2.0 mm body, 0.5 mm pitch, exposed thermal pad, moisture sensitivity level 1 (260°C peak reflow). The package enables compact layout and enhanced thermal coupling to PCB copper.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX31875RASD+ and ADT7410TRZ-REEL7, the LM71CISD/NOPB offers SPI/MICROWIRE compatibility, integrated ID verification, and superior thermal resistance in its WSON-6 package - making it optimal for new designs prioritizing MCU GPIO efficiency, counterfeit mitigation, and high-density thermal sensing.

Availability

LM71CISD/NOPB is available at Aetrix Electronics and suitable for industrial PLCs, automotive climate ECUs, server thermal management subsystems, and portable medical devices requiring stable component supply across extended product lifecycles.

Supply support for LM71CISD/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, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets since 1930.

The LM71 series belongs to TI's precision analog temperature sensor product line, designed specifically for high-reliability, low-power digital thermal monitoring in space-constrained embedded systems where SPI interface simplicity and die-temperature fidelity are critical.

FAQ

What is the absolute maximum supply voltage for LM71CISD/NOPB?

The absolute maximum supply voltage for LM71CISD/NOPB is 6.0V. Operation above 5.5V or below 2.65V is outside the specified operating range and may cause undefined behavior or permanent damage. The device is rated for continuous operation from 2.65V to 5.5V, with typical performance characterized at 3.3V and 5.0V. Always use a 0.1 µF ceramic capacitor between V+ and GND close to the package.

How does the LM71CISD/NOPB handle power-up initialization?

LM71CISD/NOPB powers up in continuous conversion mode with internal registers reset to default state. After power application, the first temperature read is invalid until at least 270 ms have elapsed - this is the maximum conversion time. Subsequent reads must also observe ≥270 ms spacing to guarantee accuracy. The device detects power-up when V+ rises above ~1.6V, and remains functional down to 2.65V.

Can LM71CISD/NOPB be used with an I²C host controller?

No, LM71CISD/NOPB does not support I²C protocol. It implements a three-wire SPI/MICROWIRE-compatible interface (CS, SC, SI/O) with specific timing requirements including 32-clock transactions and MSB-first data framing. An I²C host would require external level-shifting and bit-banging logic to emulate the required serial protocol - TI does not validate or recommend such implementation. Use ADT7410 or MAX31875 for native I²C support.

What is the function of the Manufacturer ID register in LM71CISD/NOPB?

The Manufacturer ID register in LM71CISD/NOPB is a read-only 16-bit register (value 0x800F) that identifies the device as a Texas Instruments product. It is accessed automatically when the part is placed in shutdown mode (via 0xFF write), providing hardware-level authenticity verification. This register helps prevent counterfeit components in safety-critical or high-reliability designs and is used during system boot diagnostics to confirm genuine TI silicon.

Does LM71CISD/NOPB require external calibration for accuracy?

No, LM71CISD/NOPB is factory-calibrated and requires no external calibration. Its ±1.5°C max error over −10°C to +65°C and +3/−2°C max over −40°C to +150°C are guaranteed across process, voltage, and temperature variations. The 14-bit ADC and bandgap sensor are trimmed during wafer test. System-level accuracy depends on PCB thermal design - minimize self-heating by avoiding nearby power traces and using adequate copper pour under the exposed thermal pad.

How is shutdown mode activated and verified on LM71CISD/NOPB?

Shutdown mode on LM71CISD/NOPB is activated by writing 0xFF (hex) to the configuration register via the SI/O line during the receive phase of a 32-clock serial transaction. Once active, the device outputs fixed code 0x800F on SI/O - which is the Manufacturer ID - confirming entry into shutdown. Current drops to near-zero, but CS, SC, and SI/O remain functional for status polling. To exit, write 0x00 to resume continuous conversion.