STMicroelectronics L5989DTR

Overview

L5989DTR from STMicroelectronics is a monolithic synchronous step-down DC-DC switching regulator delivering 4 A continuous output current (5 A pulsed), operating from 2.9 V to 18 V input, with programmable 100–1000 kHz switching frequency, 0.6 V feedback reference, and HTSSOP16 package with exposed thermal pad. It serves as a primary power supply for core logic rails in LCD TV, networking routers, and industrial DC-DC modules.

For engineers reviewing the L5989DTR datasheet, L5989DTR pinout, L5989DTR application, or L5989DTR equivalent, key selection criteria include its 200 ns minimum on-time, dual-switch current limiting, pre-bias startup capability, voltage feed-forward control, and multifunction U/O/S pin configuration for UVLO/OVP/sink mode selection.

Technical Context

The L5989DTR implements a voltage-mode control architecture using a sawtooth oscillator and error amplifier comparison-enabling stable regulation at ultra-low duty cycles (e.g., 0.6 V out from 12 V in) without current-sense dependency. Its BCD6 process integrates 35 mΩ NMOS and 50 mΩ PMOS switches, supporting 100% duty cycle operation without external bootstrap.

Protection is implemented via independent high-side/low-side current sensing, latched or non-latched OVP (configurable via U/O/S pin), programmable UVLO thresholds for 3.3 V/5 V/12 V buses, and thermal shutdown with 40°C/W junction-to-ambient thermal resistance in HTSSOP16. The SS/INH pin provides active-low enable and soft-start capacitor charging control.

Key Specifications

Pinout & Package

HTSSOP16 package with exposed thermal pad (R_thJA = 40°C/W), 0.65 mm pitch, 5 mm × 4.4 mm footprint, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2315DJ-LF-Z and TPS54332DDAR, the L5989DTR uniquely combines 4 A continuous current, 0.6 V reference, multifunction pin configurability, and pre-bias startup-making it optimal for space-constrained, multi-rail consumer and industrial systems requiring robust fault management.

Availability

L5989DTR is available at Aetrix Electronics and suitable for LCD TV main logic rails, networking router core supplies, and industrial DC-DC modules requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for L5989DTR 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The L5989DTR belongs to ST's high-current monolithic synchronous buck regulator product line, engineered for compact, thermally efficient point-of-load conversion in space- and reliability-constrained applications such as flat-panel displays and network infrastructure.

FAQ

What is the minimum recommended output capacitance for stable operation?

The L5989DTR is MLCC-compatible and requires ≥22 µF total output capacitance with ≤5 mΩ ESR. ST's evaluation board uses three 10 µF/6.3 V X5R ceramics in parallel. Lower ESR improves transient response and reduces output voltage deviation during 3 A load steps to <50 mV.

How does the U/O/S pin configure UVLO, OVP, and sink modes simultaneously?

The U/O/S pin accepts three distinct voltage thresholds (0–0.2 V, 0.26–0.65 V, 0.71–1.525 V) to select combinations: e.g., 0.4 V enables 3.3 V UVLO + non-latched OVP + sink disabled; 1.2 V enables 12 V UVLO + latched OVP + sink enabled. No external logic is needed-configuration is purely analog.

Can the L5989DTR operate with 100% duty cycle, and what enables this?

Yes-the L5989DTR supports true 100% duty cycle due to its integrated high-side PMOS switch, which eliminates the need for a bootstrap capacitor. This allows seamless dropout operation (e.g., 3.3 V out from 3.6 V in) without loss of regulation or gate drive failure, critical for battery-powered systems near end-of-discharge.

What thermal derating applies above 60°C ambient temperature?

At T_A > 60°C, output current must be linearly derated from 4 A using the formula I_OUT = 4 A × (1 − (T_A − 60)/90), based on 150°C max junction temperature and 40°C/W R_thJA. At 100°C ambient, max continuous current is 2.2 A; forced airflow or PCB copper pour can extend this limit.