STMicroelectronics LF85ABPT-TR

Overview

LF85ABPT-TR from STMicroelectronics is a 8.5 V fixed-output, very low dropout (LDO) linear voltage regulator in PENTAWATT-5 package with logic-controlled shutdown, delivering up to 500 mA output current, 0.45 V typical dropout at 200 mA, ±1% output voltage accuracy at 25°C, and operation across –40°C to +125°C junction temperature. It serves as a local power supply for microcontroller core rails in portable instrumentation.

For engineers reviewing the LF85ABPT-TR datasheet, LF85ABPT-TR pinout, LF85ABPT-TR application, or LF85ABPT-TR equivalent, key selection criteria include dropout voltage at full load, shutdown quiescent current (<100 µA), output voltage tolerance (±1%), thermal resistance (R_thJC = 3°C/W), and minimum required output capacitance (2.2 µF).

Technical Context

The LF85ABPT-TR implements a PNP pass transistor architecture enabling ultra-low dropout performance and stable regulation with only 2.2 µF ceramic output capacitance (ESR 0.1–10 Ω). Its TTL-compatible enable input (Pin 2) allows precise system-level power sequencing and standby mode control.

Internal protection includes current limiting and thermal shutdown. Supply voltage rejection reaches 80 dB at 120 Hz and remains >60 dB up to 10 kHz, supporting noise-sensitive analog and mixed-signal loads such as ADC reference supplies and sensor signal chains.

Key Specifications

Pinout & Package

PENTAWATT-5 (vertical mount, 5-pin) package with integrated heatsink tab. Pin 1: Input, Pin 2: Enable (TTL-compatible), Pin 3: Ground, Pin 4: Output, Pin 5: Bypass/Noise Reduction (connected to 0.1 µF capacitor to ground per datasheet).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LDO regulator applications.

Compared with LDL112PU33R and LD3985M85R, the LF85ABPT-TR uniquely combines 8.5 V output, 500 mA capability, logic-enable functionality, and PENTAWATT-5 thermal performance - making it the only option among the three that satisfies simultaneous requirements for high-voltage LDO, active power management, and robust thermal delivery.

Availability

LF85ABPT-TR is available at Aetrix Electronics and suitable for portable medical sensors, industrial PLC I/O modules, automotive body control units, and test & measurement equipment requiring stable component supply across extended temperature and long product lifecycles.

Supply support for LF85ABPT-TR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The LF00 series was developed specifically for low-noise, low-power local regulation in battery-operated and thermally constrained systems - emphasizing ultra-low dropout, micropower shutdown, and minimal external component count.

FAQ

What is the minimum input voltage required for regulation at full 500 mA load?

The minimum input voltage is calculated as V_O + V_DROP(MAX). For LF85ABPT-TR, V_O = 8.5 V and maximum dropout is 0.7 V at 500 mA (per Table 9), so VI ≥ 9.2 V is required. Below this, the device enters dropout and output voltage drops linearly with input.

Can the bypass (Pin 5) terminal be left unconnected?

No. Pin 5 must be connected to a 0.1 µF ceramic capacitor between BP and GND, as specified in the schematic diagram and electrical characteristics tables. Omitting this capacitor degrades high-frequency PSRR and may cause instability under transient load conditions.

Is the enable pin (Pin 2) 5 V tolerant when used with a 5 V microcontroller GPIO?

Yes. The enable pin accepts VIH ≥ 2.0 V and tolerates up to 6 V (per Table 3), making it fully compatible with standard 5 V CMOS logic outputs. Input current is limited to ≤10 µA, imposing negligible loading on the driving GPIO.

Does the ±1% output voltage tolerance apply over the full –40°C to +125°C range?

No. The ±1% tolerance (AB grade) is specified at T_A = 25°C only. Over –40°C to +85°C, total variation is ±1.5% (e.g., 8.37–8.63 V for LF85AB); full –40°C to +125°C data is not provided in the datasheet, but thermal drift is bounded by load/line regulation specs (≤15 mV).