STMicroelectronics L5987TR

Overview

L5987TR from STMicroelectronics is a 3 A synchronous step-down switching regulator with integrated P-channel MOSFET, designed for point-of-load DC-DC conversion in space-constrained systems. It operates from 2.9 V to 18 V input, delivers adjustable output down to 0.6 V, features 250 kHz–1 MHz programmable switching frequency, and supports 100% duty cycle for low-dropout operation in 3.3 V bus applications.

For engineers reviewing the L5987TR datasheet, L5987TR pinout, L5987TR application, or L5987TR equivalent, key selection criteria include thermal resistance (40 °C/W in HSOP8), soft-start duration (7.4–9.1 ms), overcurrent protection behavior (hiccup vs. constant-current modes), and voltage feedforward implementation for line transient stability.

Technical Context

The L5987TR implements voltage-mode PWM control with an internal 0.6 V reference and sawtooth oscillator whose slope is dynamically adjusted via voltage and frequency feedforward-ensuring stable PWM gain across input voltage and switching frequency variations. Its error amplifier provides 100 dB open-loop gain and 4.5 MHz GBWP for robust loop compensation.

Synchronization is supported via the SYNCH pin, enabling master/slave operation with 180° phase shift between devices; external clock synchronization is possible with zero-phase-shift locking. Overcurrent protection uses blanking time (~200 ns) and adaptive pulse-skipping during soft-start, transitioning to hiccup mode under sustained overload at regulation.

Key Specifications

Pinout & Package

Available in HSOP8 and VFQFPN 3×3 mm packages, both with exposed thermal pads for enhanced heat dissipation. The HSOP8 variant achieves lower R_thJA (40 °C/W), while VFQFPN offers compact footprint (3×3 mm) at 60 °C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2315DJ-LF-Z and TPS54331DR, the L5987TR uniquely combines voltage feedforward, programmable frequency with SYNC capability, and 2.9 V minimum input-making it optimal for low-voltage, multi-phase, and high-transient industrial and networking power rails.

Availability

L5987TR is available at Aetrix Electronics and suitable for consumer audio, FPGA power delivery, DSL modem DC-DC modules, and optical storage drive applications requiring stable component supply, long-term manufacturability, and automotive-grade reliability screening.

Supply support for L5987TR 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 L5987TR belongs to ST's high-efficiency monolithic DC-DC regulator product line, engineered for compact, thermally efficient point-of-load conversion in space- and performance-constrained embedded systems.

FAQ

What is the maximum duty cycle supported by the L5987TR?

The L5987TR supports 100% duty cycle operation, enabling dropout-free regulation when V_OUT approaches V_IN. This is critical for 3.3 V bus applications where input may dip near output voltage. The internal P-channel MOSFET architecture eliminates the need for an external freewheeling diode and permits continuous conduction down to zero voltage difference.

How does the SYNCH pin function in master/slave configurations?

When two L5987TR devices have their SYNCH pins connected, the higher-frequency unit becomes the master and the other synchronizes with zero phase shift. If both run at identical frequencies, they automatically adopt 180° phase opposition-halving input capacitor RMS current. No external logic or timing controller is required; the behavior is fully autonomous and hardware-defined.

Can the L5987TR operate with zero load current?

Yes-the L5987TR maintains regulation with zero output load. Its control architecture disables switching pulses during light-load conditions while preserving feedback loop integrity and output voltage accuracy. Quiescent current drops to 20–30 µA in INH-disabled standby, but regulation remains active even at no load in normal operation.

What compensation network type is recommended for ceramic output capacitors?

For low-ESR ceramic output capacitors, a Type II compensation network is recommended. This configuration introduces one pole and one zero to counteract the LC double-pole and provide adequate phase margin. The L5987TR's error amplifier characteristics-including 100 dB DC gain and 4.5 MHz GBWP-support stable Type II design across 250 kHz–1 MHz operating frequencies.