STMicroelectronics L4938ND

Overview

L4938ND from STMicroelectronics is a dual low-dropout voltage regulator IC designed for automotive microcomputer power supply systems. It delivers a precision 5V ±2% standby output (VO1, 50mA) and a tracked/adjustable main output (VO2, up to 500mA), with integrated power-on reset, undervoltage warning, enable control, and thermal/short-circuit protection. Its 0.4V/0.6V max dropout and 40V transient tolerance support engine-control unit (ECU) and body-control module (BCM) applications.

For engineers reviewing the L4938ND datasheet, L4938ND pinout, L4938ND application, or L4938ND equivalent, key selection criteria include VO2 tracking accuracy (±25mV), standby quiescent current (<250µA), programmable VO2 range (5–20V), dual overcurrent limits (ILIM1 = 25–200mA, ILIM2 = 550–1700mA), and SO-20 package compatibility with automotive AEC-Q100 stress requirements.

Technical Context

The L4938ND integrates two independent LDO regulators sharing a common ground and input domain: VO1 uses an isolated-collector vertical PNP for ultra-low dropout down to 2V input, while VO2 employs a matched PNP structure with adjustable feedback via ADJ pin. Both regulators operate under a unified thermal shutdown and short-circuit foldback protection scheme.

Its auxiliary functions are tightly coupled to system supervision: the RESET circuit monitors VO1 with 4.7V threshold and user-defined delay (via CT capacitor); the SENSE comparator provides early undervoltage warning using a 1.23V internal reference and external resistor divider on SI/SO pins.

Key Specifications

Pinout & Package

Package: SO-20 (Small Outline, 20-pin, 0.5 mm pitch, JEDEC MO-166 compliant). Body dimensions: 12.6 × 7.4 mm, height ≤1.065 mm. RoHS-compliant, Pb-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLE4275G and TPS7B8133QPWPRQ1, the L4938ND uniquely combines dual LDOs with tracking, integrated reset timing, and undervoltage sensing in one SO-20 package-reducing BOM count by ≥3 components and enabling true single-chip dual-rail automotive power management.

Availability

L4938ND is available at Aetrix Electronics and suitable for engine control units (ECUs), body control modules (BCMs), advanced driver assistance system (ADAS) camera ECUs, and infotainment head units requiring stable component supply across extended temperature and automotive qualification lifecycles.

Supply support for L4938ND 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 over 40 years of automotive qualification expertise.

The L4938ND belongs to ST's automotive-grade dual LDO regulator product line, engineered specifically to consolidate power and supervision functions in microcontroller-based vehicle subsystems while meeting ISO 16750 and AEC-Q100 reliability requirements.

FAQ

What is the maximum allowable input voltage for continuous operation?

The L4938ND supports continuous DC supply voltage from 6 V to 25 V on VS1/VS2 pins. Transient operation up to 40 V is permitted for durations less than 1 second, complying with ISO 7637-2 Pulse 5a load-dump test profiles. Exceeding 25 V continuously risks thermal overload and reduced lifetime.

How is VO2 programmed to a specific voltage like 12V?

VO2 is set using an external resistor divider between VO2, ADJ, and GND. With VO1 = 5.0 V, select R1 and R2 such that VO2 = 5.0 × (1 + R1/R2) = 12 V → R1/R2 = 1.4. For example, R2 = 10 kΩ and R1 = 14 kΩ yields VO2 ≈ 12.0 V. The ADJ pin draws <1 µA, minimizing divider current error.

Does the RESET output require an external pull-up resistor?

Yes. The RESET pin is an open-drain output and must be pulled up to VO1 (or another clean 5V rail) via a 10 kΩ resistor. This ensures proper logic-high level (≥4.5 V) during normal operation and fast low-level assertion (<50 µs) during undervoltage events, as specified in the electrical characteristics table.

Can the SENSE function monitor battery voltage directly?

Yes. Connect the battery positive terminal to SI through a resistor divider (e.g., 1 MΩ + 240 kΩ) to scale battery voltage to 1.23 V at SI when battery = 12.3 V. SO then asserts low when scaled voltage drops below 1.16–1.35 V threshold, providing early warning before VO1 collapses - confirmed in functional description section 5.