STMicroelectronics L4995AK

Overview

L4995AK from STMicroelectronics is an AEC-Q100 qualified automotive 5 V, 500 mA low-dropout linear voltage regulator in PowerSSO-24 package, featuring integrated programmable reset, watchdog timer, and enable input. It operates from 5.6 V to 31 V DC supply, delivers ±2% output voltage tolerance, maintains regulation under 40 V transients, and supports junction temperatures from –40 °C to 150 °C - deployed in engine control units for stable microprocessor power delivery.

For engineers reviewing the L4995AK datasheet, L4995AK pinout, L4995AK application, or L4995AK equivalent, key selection criteria include its 500 mV dropout at 400 mA, 3 µA quiescent current with regulator disabled, externally programmable reset delay (via Vcr), watchdog period tuning (via Vcw), and dual-capacitor-configurable timing functions critical for automotive safety-critical subsystems.

Technical Context

The L4995AK implements a p-channel MOSFET pass element enabling low-dropout operation independent of input transients up to 40 V. Regulation relies on a pre-trimmed internal reference, achieving ±2% output accuracy across temperature and load.

Its integrated supervisory functions include a reset circuit sensing output voltage down to 1 V, a watchdog timer monitoring external clock frequency at Wi pin, and an enable input controlling regulator, reset, and watchdog activation simultaneously - all configurable via external capacitors on Vcr and Vcw pins.

Key Specifications

Pinout & Package

Package: PowerSSO-24 (exposed pad), thermally enhanced surface-mount package with 24 terminals and integrated heat slug for high-power dissipation in automotive under-hood applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar automotive LDO with supervision applications.

Compared with NCP380LSN33T2G and TPS7B6950QDCYRQ1, the L4995AK uniquely integrates programmable reset, watchdog, and enable in a single AEC-Q100 Grade 0 package - eliminating external supervision components while supporting full under-hood thermal and electrical requirements.

Availability

L4995AK is available at Aetrix Electronics and suitable for engine control units, body control modules, transmission control units, and ADAS camera ECUs requiring stable component supply with automotive-grade qualification and long-term lifecycle support.

Supply support for L4995AK 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The L4995AK belongs to ST's automotive power management portfolio, engineered specifically to consolidate voltage regulation and functional safety supervision into single-chip solutions for ASIL-B compatible systems.

FAQ

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

The L4995AK maintains regulation down to 5.6 V input at 500 mA load, with a maximum dropout voltage of 500 mV. At 400 mA, typical dropout is 270 mV, meaning regulation holds with input as low as 5.27 V - critical for automotive cold-crank operation where battery voltage may dip to 6 V.

How is the watchdog timeout period set, and what is its tolerance?

The watchdog period is set by a capacitor connected between Vcw (Pins 22–24) and GND; with 47 nF, typical Twop is 40 ms (range 20–80 ms). Tolerance depends on capacitor accuracy and temperature drift - at 13.5 V supply and Tj = 25 °C, variation is ±50% over full operating range per datasheet Table 7.

Can the L4995AK be used without connecting the En pin?

Yes - the En pin can be tied directly to VS to permanently enable the regulator, reset, and watchdog functions. If unused, ST recommends connecting En to VS; leaving it floating is not advised due to potential noise-induced misoperation in automotive EMI environments.

What thermal performance can be expected with standard PCB layout?

With a 77 mm × 86 mm FR4 double-layer PCB (1.6 mm thick, 3 cm² copper area, thermal vias), Rthj-amb is 38 °C/W for PowerSSO-24. At 500 mA and 13.5 V input, power dissipation is ~4.25 W, resulting in ~161 °C junction rise above ambient - requiring careful heatsinking or derating above 85 °C ambient to stay within 150 °C Tj limit.