STMicroelectronics L7985TR

Overview

L7985TR from STMicroelectronics is a 2 A step-down switching regulator with integrated P-channel MOSFET, designed for DC-DC conversion in mid-power industrial and consumer power rails. It operates from 4.5 V to 38 V input, delivers adjustable output from 0.6 V, features 250 kHz–1 MHz programmable switching frequency, internal soft-start, and supports 100% duty cycle for low-dropout operation in battery-backed or wide-input applications.

For engineers reviewing the L7985TR datasheet, L7985TR pinout, L7985TR application, or L7985TR equivalent, key selection considerations include its voltage-mode control architecture, SYNCH pin phase-shift synchronization capability, FSW-resistor programmability, thermal shutdown hysteresis (30 °C), and dual-package availability (VFDFPN10 and HSOP8) with R_thJA as low as 40 °C/W.

Technical Context

The L7985TR implements voltage-mode PWM control using an internal 0.6 V reference and error amplifier with 100 dB open-loop gain and 4.5 MHz GBWP. Its oscillator provides feed-forward compensation-both voltage-dependent sawtooth slope and frequency-dependent slope adjustment-to maintain constant PWM gain across input voltage and switching frequency variations.

Synchronization is achieved via the SYNCH pin, supporting master/slave interleaving with 180° phase shift when pins are tied together, or external clock locking with zero-phase-shift alignment. Overcurrent protection uses blanked peak-current sensing (200 ns masking time) and adaptive pulse-skipping down to 1/8 nominal frequency to sustain 2.5 A current limit during overload or short-circuit conditions.

Key Specifications

Pinout & Package

Available in VFDFPN10 (3 × 3 × 1.0 mm, exposed pad) and HSOP8 (exposed pad) packages. VFDFPN offers R_thJA = 60 °C/W; HSOP8 achieves 40 °C/W for higher power density.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down switching regulator applications.

Compared with LM5164QDDARQ1 and MP2451DT-LF-Z, the L7985TR uniquely combines 2 A output, 1 MHz programmability, SYNCH-based interleaving, and 30 °C thermal hysteresis - making it optimal for industrial power modules requiring reliability, scalability, and thermal robustness.

Availability

L7985TR is available at Aetrix Electronics and suitable for FPGA core supplies, automotive infotainment rails, and industrial PLC I/O modules requiring stable component supply across extended temperature and long-lifecycle programs.

Supply support for L7985TR 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The L7985TR belongs to ST's high-voltage buck regulator product line, engineered for robust DC-DC conversion in harsh environments - emphasizing thermal resilience, wide VIN range, and flexible system integration via SYNCH and FSW pins.

FAQ

What is the minimum output voltage achievable with the L7985TR?

The L7985TR regulates down to 0.6 V, set by its internal reference voltage. This value is guaranteed over temperature (−40°C to +125°C) with ±1.2% tolerance. To achieve lower voltages, an external resistive divider cannot reduce the feedback voltage below the internal reference - thus 0.6 V is the absolute minimum regulated output.

Can the L7985TR operate with input voltage below 4.5 V?

No. The L7985TR has a defined V_CCON UVLO threshold of 4.5 V (min), with 0.4 V hysteresis. Below this, the device remains disabled and draws only leakage current. It cannot regulate or switch at 4.0 V or lower - attempting operation risks undefined behavior or failure to start.

How does the SYNCH pin behave when left unconnected?

When floating, the SYNCH pin outputs a 180° phase-shifted version of the internal oscillator signal. This allows automatic interleaving when two devices have tied SYNCH pins - the higher-frequency unit becomes master, the other slave - without external clock generation or timing components.

Is the L7985TR RoHS-compliant and halogen-free?

Yes. Per STMicroelectronics' official documentation (DocID022446 Rev 8), the L7985TR is manufactured in full compliance with EU RoHS Directive 2011/65/EU and is halogen-free per IEC 61249-2-21. Both VFDFPN10 and HSOP8 variants carry the "E" suffix indicating halogen-free packaging.