Texas Instruments LMT85LPGM

Overview

LMT85LPGM 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, 5.4 µA quiescent current, and 10-s thermal time constant (1.2 m/s airflow), used for off-board thermal monitoring in smoke detectors and heat-sensing modules.

For engineers reviewing the LMT85LPGM datasheet, LMT85LPGM pinout, LMT85LPGM application, or LMT85LPGM equivalent, key selection criteria include its fast thermal response, low-voltage 1.8-V operation, push-pull output drive capability, SC70/TO-92 footprint compatibility with LM20/LM35, and verified accuracy across automotive and industrial ambient ranges.

Technical Context

The LMT85LPGM uses a forward-biased base-emitter junction as its sensing element, buffered by a rail-to-rail CMOS amplifier with push-pull output stage-enabling ±50 µA sourcing/sinking into dynamic ADC input capacitors. Its transfer function exhibits slight parabolic nonlinearity, accurately modeled by TI's published Transfer Table (−50°C to 150°C) and linearized via two-point approximation.

Thermal coupling is optimized by direct die attachment to GND pin; self-heating error remains ≤0.014°C under typical load (2 µA), validated by R_θJA = 130.4°C/W (TO-92S). Output voltage shift due to V_DD–V_OUT ≈ 1 V is monotonic and fully included in ±2.7°C max accuracy spec.

Key Specifications

Pinout & Package

TO-92S (3-pin, through-hole, 4.00 mm × 3.15 mm body) with straight leads; pin 1 = OUT, pin 2 = GND, pin 3 = V_DD. GND pin thermally connects to die backside for optimal thermal conduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMT84DCKR and LM20LPG, the LMT85LPGM delivers tighter accuracy (±0.4°C vs ±2.5°C), steeper gain (−8.2 vs −11.5 mV/°C), and lower quiescent current (5.4 µA vs 6.5 µA), making it optimal for battery-powered safety-critical thermal monitoring where precision and responsiveness are prioritized.

Availability

LMT85LPGM is available at Aetrix Electronics and suitable for smoke detectors, automotive powertrain monitoring, and drone thermal management requiring stable component supply, long-lifecycle assurance, and traceable sourcing.

Supply support for LMT85LPGM 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 high-reliability ICs for industrial, automotive, and consumer markets.

The LMT85LPGM belongs to TI's LMT8x precision analog temperature sensor family, designed specifically for high-accuracy, low-power, and fast-response thermal measurement in safety-critical and battery-operated systems.

FAQ

What is the thermal time constant of the LMT85LPGM and how is it measured?

The LMT85LPGM 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. This value is validated per JEDEC JESD51-1 using standardized test fixtures and is critical for applications like UL-listed smoke detectors where rapid thermal response is mandated. The TO-92S package geometry and direct die-to-GND thermal path enable this performance.

Does the LMT85LPGM require external decoupling capacitors on VDD or OUT?

No, the LMT85LPGM does not require external decoupling on V_DD or OUT under standard conditions. Its 5.4 µA quiescent current and robust internal design eliminate need for bypass caps unless operating in extremely noisy environments (>100 mVpp supply ripple) or driving capacitive loads >1100 pF. In those cases, a 100 nF ceramic capacitor within 5 cm of V_DD is recommended-per TI's layout guidelines in SNIS168E.

How does the LMT85LPGM achieve ±0.4°C typical accuracy across –50°C to 150°C?

The LMT85LPGM achieves ±0.4°C typical accuracy through factory-trimmed CMOS process compensation, calibrated against NIST-traceable reference standards across temperature and supply voltage. Its accuracy specification includes line regulation, output voltage shift, and parabolic nonlinearity-fully characterized in TI's Transfer Table (Table 3, SNIS168E). No external calibration is needed for most applications meeting ±0.4°C requirement.

Can the LMT85LPGM be powered directly from a microcontroller GPIO pin?

Yes, the LMT85LPGM can be powered directly from a microcontroller GPIO pin due to its ultra-low 5.4 µA quiescent current and 1.8-V minimum supply. When the GPIO is driven high, the LMT85LPGM powers on with 0.7-ms turn-on time; when pulled low, it shuts down completely. This enables precise software-controlled thermal sampling in battery-powered devices-verified in Figure 15–19 of the LMT85LPGM datasheet.

Is the LMT85LPGM pin-compatible with the LM35 or LM20 temperature sensors?

The LMT85LPGM is footprint-compatible-not pin-compatible-with the LM35 and LM20 in TO-92S form factor. While all three share identical 3-pin TO-92S mechanical outline and lead spacing, the LMT85LPGM pinout is OUT/GND/V_DD (pin 1/2/3), whereas LM35 uses V_CC/OUT/GND and LM20 uses V_CC/GND/OUT. Direct replacement requires PCB trace modification or adapter layout.