STMicroelectronics L5994

Overview

L5994 from STMicroelectronics is a dual adjustable PWM controller with integrated linear regulator driver and 5V LDO, designed for triple-output power management in mobile computing systems. It delivers 1.9–5.3V (Section 1) and 1.6–3.5V (Section 2) synchronous buck outputs plus a 1A-capable linear driver for PCMCIA or 2.5V-from-5V regulation, achieving up to 96% efficiency and 50µA standby current at 12V input.

For engineers reviewing the L5994 datasheet, L5994 pinout, L5994 application, or L5994 equivalent, key selection criteria include its adaptive anti-shoot-through gate drivers, pulse-skipping light-load optimization, separated RUN1/RUN2 enable control, and dual POWER GOOD signals with 1.25µs overvoltage propagation delay - all critical for notebook I/O rail sequencing and fault-tolerant power supervision.

Technical Context

The L5994 implements two independent current-mode PWM controllers sharing a programmable 200/300 kHz oscillator (via OSC pin) and synchronized by external clock edges. Each section uses slope-compensated error summing with cycle-by-cycle current sensing via low-value sense resistors (37–63 mV overcurrent threshold), enabling fast transient response without external compensation.

Its auxiliary linear regulator driver operates as a PNP base controller (VDRLIN/VFBLIN interface) with 2.5V reference accuracy (±2.5%), while the internal 5V LDO (PREG5) supplies bootstrap circuits and logic. Adaptive anti-cross-conduction timing (50 ns dead time) and "one-shot" shutdown (L5994A only) are embedded in the gate driver architecture for high-current buck stages.

Key Specifications

Pinout & Package

TQFP32 package with exposed thermal pad (R_{TH j-amb} = 60°C/W); pin-compatible with L5994A except for "One Shot" functionality on VDRLIN.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual PWM controller applications.

Compared with TPS51116 and RT8205A, the L5994 uniquely integrates a linear regulator driver and 5V LDO, enabling complete triple-rail power management from a single IC - essential for legacy mobile platforms requiring PCMCIA support and ultra-low standby current.

Availability

L5994 is available at Aetrix Electronics and suitable for notebook I/O power rails, PCMCIA card regulation, internet appliance DC-DC cores, and WordPad system power management requiring stable component supply across extended production lifecycles.

Supply support for L5994 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 specializing in power management, microcontrollers, and analog ICs for automotive, industrial, and consumer applications.

The L5994 belongs to ST's mobile power management controller product line, engineered specifically for multi-rail, high-efficiency power conversion in space-constrained portable computing equipment with stringent standby current and fault-response requirements.

FAQ

What is the functional difference between L5994 and L5994A?

The L5994A adds a "One Shot" shutdown feature triggered by a falling VDRLIN voltage threshold (12.88–14.52 V), generating a 1.5 µs pulse to force immediate system reset during brown-out events. The L5994 lacks this function but shares identical PWM, LDO, and driver specifications - making them pin-compatible except for VDRLIN behavior under fault conditions.

How does the adaptive anti-shoot-through control operate in practice?

It dynamically adjusts dead time by monitoring H1SRC/H2SRC voltage: high-side turn-off is delayed until the source falls below 2V, and low-side turn-on is delayed until gate voltage drops below 0.3V. This prevents simultaneous conduction without fixed timing, reducing heat in high-current buck stages while maintaining >96% efficiency across load ranges.

Can the L5994 regulate 1.2V output for modern processor cores?

No - Section 2's minimum regulated output is 1.6V (typical 1.64V feedback threshold), and Section 1 starts at 1.9V. For sub-1.5V core rails, an external controller or post-regulator is required. The device targets I/O, memory, and peripheral rails, not CPU core voltages, as confirmed by its 1.6–3.5V and 1.9–5.3V specified ranges.

What is the role of the CRST capacitor beyond startup timing?

The CRST capacitor sets both power-good assertion delay (115–180 ms) and shutdown propagation time (identical value). During fault conditions like overvoltage, it also defines the 115–180 ms window before low-side MOSFET activation - ensuring controlled energy discharge and preventing inductive kickback damage to synchronous rectifiers.