STMicroelectronics L4938NPD

Overview

L4938NPD from STMicroelectronics is a dual low-dropout voltage regulator IC designed for automotive microcomputer power systems, featuring a precision 5V ±2% standby output (VO1), a programmable main output (VO2) adjustable from 5V to 20V, 50mA/500mA output current capability, <250µA quiescent current in standby mode, and integrated power-on reset with external capacitor timing.

For engineers reviewing the L4938NPD datasheet, L4938NPD pinout, L4938NPD application, or L4938NPD equivalent, key selection considerations include VO2 tracking accuracy (±25mV), dropout performance (0.4V/0.6V max), enable-controlled VO2 disable, early warning undervoltage sensing, and thermal/short-circuit protection in PowerSO-20 package.

Technical Context

The L4938NPD integrates two independent LDO regulators: VO1 uses an isolated-collector vertical PNP for ultra-low dropout down to 2V input, while VO2 employs the same topology rated for 500mA and configurable via ADJ pin with external resistor divider. Both share a common ground and are optimized for transient immunity up to 40V supply spikes.

A dedicated reset circuit monitors VO1 with 4.7V threshold and user-defined delay (via CT capacitor), and a separate sense comparator (1.23V reference) provides early undervoltage warning via SI/SO pins. Enable logic (VENH ≥2.4V) disables VO2 independently without affecting VO1 operation.

Key Specifications

Pinout & Package

Package: PowerSO-20 (PSO20), thermally enhanced surface-mount package with exposed die pad for improved heat dissipation; RoHS-compliant, JEDEC MO-166 compliant outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-output automotive LDO regulator applications.

Compared with TPS7B7702QPWPRQ1 and MAX16922ATP+T, the L4938NPD uniquely supports VO2 voltage programming, early undervoltage warning via SI/SO, and user-tunable reset delay - making it optimal for automotive systems requiring adaptable rail generation and predictive fault handling.

Availability

L4938NPD is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera modules, and infotainment head units requiring stable component supply across extended temperature and automotive qualification cycles.

Supply support for L4938NPD 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, specializing in automotive, industrial, and power management ICs with broad manufacturing and qualification capabilities.

The L4938NPD belongs to ST's automotive-grade linear regulator product line, engineered specifically for microcontroller-based vehicle subsystems requiring dual-rail power, robust transient immunity, and integrated system supervision functions.

FAQ

What is the maximum allowable input voltage for continuous operation?

The L4938NPD supports continuous DC supply voltage up to 25 V on VS1 and VS2 pins. It tolerates transient overvoltage up to 40 V for durations under 1 second, complying with ISO 7637-2 Pulse 5a for automotive load-dump protection. Operation above 25 V DC risks permanent damage and is outside absolute maximum ratings.

Can VO2 be configured for exactly 5V without external resistors?

Yes. Connecting the ADJ pin directly to VO2 configures VO2 as a fixed 5V output that tracks VO1 within ±25 mV. This eliminates external components while maintaining tight regulation relative to the standby rail, ideal for dual 5V domain applications such as MCU core and I/O supply.

How is the reset delay time calculated and what capacitor value is recommended?

Reset delay tRD is calculated as tRD = CT × 2 V / 2 µA. For a nominal 100 µs delay, use CT = 100 nF. The capacitor must be ceramic with X7R or better dielectric; typical values range from 47 nF (50 µs) to 220 nF (220 µs). CT tolerance directly impacts delay accuracy, so ±10% C0G is preferred for critical timing.

Does the L4938NPD require external capacitors, and what are the minimum values?

Yes. Per the application circuit: CS ≥ 1 µF (input bypass), CO1 ≥ 6 µF (VO1 output), and CO2 ≥ 10 µF (VO2 output), all with ESR < 10 Ω at 10 kHz. Low-ESR tantalum or ceramic capacitors are required; aluminum electrolytics are not recommended due to ESR and lifetime limitations in automotive environments.