STMicroelectronics LF85CDT-TRY

Overview

LF85CDT-TRY from STMicroelectronics is a very low-dropout linear voltage regulator with logic-controlled electronic shutdown, delivering 8.5 V output at up to 500 mA. It features 0.45 V dropout (at 200 mA), ±2% output voltage accuracy (C grade), and operates across –40 °C to 125 °C - qualified per AEC-Q100 for automotive applications in DPAK package. It is used as a local regulator in engine control units to power microcontroller I/O rails while enabling board-level standby via TTL-compatible inhibit control.

For engineers reviewing the LF85CDT-TRY datasheet, LF85CDT-TRY pinout, LF85CDT-TRY application, or LF85CDT-TRY equivalent, key selection criteria include dropout voltage at 500 mA, quiescent current in ON/OFF modes, AEC-Q100 qualification status, thermal resistance (R_thJA = 100 °C/W), and minimum 2.2 µF ceramic output capacitance requirement.

Technical Context

The LF85CDT-TRY implements a PNP-based LDO architecture with internal current and thermal limiting, enabling stable regulation under transient load conditions without external compensation. Its 5-pin DPAK configuration includes dedicated INH (inhibit) input (Pin 2), allowing TTL-compatible logic-level control of output enable/disable - critical for power domain sequencing in automotive ECUs.

It supports input voltages from 2.5 V to 16 V, maintains 8.5 V output with ≤15 mV load regulation (5–500 mA) and ≤15 mV line regulation (3.5–16 V), and delivers 80 dB supply voltage rejection at 120 Hz - making it suitable for noise-sensitive analog subsystems powered from noisy battery or alternator sources.

Key Specifications

Pinout & Package

LF85CDT-TRY is housed in a surface-mount DPAK (TO-252-3) package with exposed thermal pad electrically connected to GND. The 5-pin variant includes dedicated INH control, distinguishing it from 3-pin fixed-output variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with NCP1117DT85T3G and TPS7B6750QDDARQ1, LF85CDT-TRY uniquely combines 8.5 V output, AEC-Q100 Grade 0 rating, TTL inhibit control, and 0.45 V dropout in DPAK - making it the only drop-in solution for 8.5 V automotive local regulation with active power gating.

Availability

LF85CDT-TRY is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera ECUs, and transmission control units requiring stable component supply across automotive production lifecycles.

Supply support for LF85CDT-TRY 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, power, microcontroller, and automotive-grade ICs.

LF85CDT-TRY belongs to the LFXX family of very low-dropout regulators engineered specifically for automotive power management - emphasizing AEC-Q100 compliance, wide temperature operation, and minimal external component count.

FAQ

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

The LF85CDT-TRY requires input voltage ≥8.95 V to maintain 8.5 V output at 500 mA, based on maximum dropout of 0.45 V (typical) and 0.7 V (max at 500 mA per automotive-grade specs). Below this, output collapses linearly - verified in Table 6 and Table 13 of the datasheet under "Vd Dropout voltage".

Can the INH pin be left unconnected, or does it require a pull-up/down resistor?

The INH pin must not be left floating: it defaults to ON only if pulled above 2 V (VIH), but leakage or noise may cause erratic enable/disable behavior. STMicroelectronics recommends a 10 kΩ pull-up to VIN for default-ON operation or 10 kΩ pull-down to GND for default-OFF - confirmed in Section 4 Electrical Characteristics (Table 3–17) and Application Note AN2717.

Is the exposed thermal pad on the DPAK package electrically connected, and how should it be routed?

Yes, the exposed thermal pad is electrically connected to GND per Figure 2 (Pin connections, top view) and Package Information section (6.5 DPAK). It must be soldered to a dedicated GND plane with ≥4 thermal vias (0.3 mm diameter) to maximize heat dissipation - critical to achieve R_thJA = 100 °C/W and avoid thermal shutdown at 125 °C ambient.

Does LF85CDT-TRY support ceramic output capacitors with ESR below 0.1 Ω?

No - the datasheet explicitly specifies CO stability range for ESR = 0.1–10 Ω (Table 3–17, "CO Output bypass capacitance"). Using <0.1 Ω ESR (e.g., ultra-low-ESR X7R/X5R) risks oscillation due to insufficient phase margin; STMicroelectronics validates stability only within the stated ESR window.