Texas Instruments LMT85LPG

Overview

LMT85LPG from Texas Instruments is a precision analog-output CMOS temperature sensor in TO-92S through-hole package, delivering ±0.4°C typical accuracy over –50°C to 150°C, –8.2 mV/°C average output gain, and 5.4 µA quiescent current at 1.8 V supply - enabling high-accuracy thermal monitoring in off-board smoke/heat detectors and battery-powered drone systems.

For engineers reviewing the LMT85LPG datasheet, LMT85LPG pinout, LMT85LPG application, or LMT85LPG equivalent, key selection considerations include its fast 10-s thermal time constant (1.2 m/s airflow), push-pull output with ±50 µA drive capability, short-circuit protection, and footprint compatibility with LM20/LM35 sensors for drop-in replacement in legacy thermal sensing designs.

Technical Context

The LMT85LPG implements a forward-biased base-emitter junction as its temperature-sensing element, buffered by a rail-to-rail CMOS amplifier with push-pull output stage - ensuring low-impedance analog voltage output inversely proportional to temperature. Its transfer function follows a slight parabolic shape, accurately modeled in the published 151-point Transfer Table (–50°C to +150°C).

Thermal coupling is optimized via direct die attachment to the GND pin, enabling reliable off-board mounting on metal tubes or surfaces. Self-heating error remains below 0.014°C under typical load conditions (e.g., 5.4 µA supply current, 2 µA output load), validated by R_θJA = 130.4°C/W for the TO-92S package.

Key Specifications

Pinout & Package

TO-92S package: 3-pin through-hole, straight leads, body size 4.00 mm × 3.15 mm, with GND connected directly to die backside for optimal thermal conduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMT85LP and LMT84DCK, the LMT85LPG uniquely balances ultra-fast thermal response (10 s), through-hole mechanical robustness, and lowest quiescent current (5.4 µA) - making it the optimal choice for off-board, safety-critical, and battery-limited thermal sensing where timing and power are co-constrained.

Availability

LMT85LPG is available at Aetrix Electronics and suitable for smoke and heat detectors, drone thermal management, and automotive infotainment systems requiring stable component supply, long-term lifecycle support, and traceable sourcing for safety-certified production.

Supply support for LMT85LPG 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 signal chain solutions.

The LMT85 family was designed specifically for high-accuracy, low-power analog temperature measurement in automotive, industrial, and consumer applications - emphasizing fast thermal response, wide operating range, and seamless integration with microcontroller ADCs.

FAQ

What is the thermal time constant of the LMT85LPG, and how is it measured?

The LMT85LPG has a thermal time constant of 10 seconds typical under 1.2 m/s airflow, measured as the time required to reach 63.2% of final temperature change after a step ambient shift. This value is validated per JEDEC JESD51-1 using standardized test fixtures and is specific to the TO-92S package's 4.00 mm × 3.15 mm body and lead configuration - critical for heat detector response certification.

Does the LMT85LPG require external calibration to achieve ±0.4°C accuracy?

No, the LMT85LPG achieves ±0.4°C typical accuracy over –50°C to +150°C without external calibration. This specification is factory-trimmed and guaranteed across voltage (1.8–5.5 V) and temperature ranges. The device's parabolic transfer function is fully characterized in the published 151-point Transfer Table, enabling lookup-table-based compensation if higher precision is needed beyond the specified tolerance.

Can the LMT85LPG drive an ADC input directly, and what is the maximum capacitive load?

Yes, the LMT85LPG can drive ADC inputs directly thanks to its ±50 µA push-pull output. It supports capacitive loads up to 1100 pF without external series resistance. For loads exceeding 1100 pF - such as large sampling capacitors or long PCB traces - a series resistor (e.g., 800 Ω for 1 µF) is recommended per TI's Figure 12 design guidance to maintain stability and minimize settling error in the LMT85LPG output.

How does the LMT85LPG handle short-circuit conditions on the OUT pin?

The LMT85LPG features built-in short-circuit protection on the OUT pin, allowing indefinite connection to GND or VDD without damage or parametric shift. During a short, the output stage limits current while maintaining functionality upon fault removal - verified per TI's production test flow and documented in Section 7.6 of the SNIS168E datasheet. This enhances reliability in harsh environments like appliance motor bays or automotive engine compartments.

Is the LMT85LPG pin-compatible with the LM35 temperature sensor?

Yes, the LMT85LPG is footprint-compatible with the LM35 in TO-92 packages: both use VDD–GND–OUT pinout (Pin 1 = VDD, Pin 2 = GND, Pin 3 = OUT for LM35; Pin 1 = OUT, Pin 2 = GND, Pin 3 = VDD for LMT85LPG per TI's Pin Configuration table). While electrical behavior differs (LM35 outputs +10 mV/°C, LMT85LPG outputs –8.2 mV/°C), the identical TO-92S mechanical outline allows PCB reuse with minor schematic updates - confirmed in TI's "Footprint Compatible" feature bullet.