STMicroelectronics L4901A

Overview

L4901A from STMicroelectronics is a monolithic dual low-dropout 5V linear regulator IC with integrated reset generator, designed for microprocessor system power and data retention. It delivers two independent 400mA regulated 5V outputs (±2% accuracy), features input overvoltage protection up to 60V, programmable reset timing via external capacitor, and active discharge of Output 2 during shutdown - used in automotive trip computers and battery-backed CMOS time-of-day clocks.

For engineers reviewing the L4901A datasheet, L4901A pinout, L4901A application, or L4901A equivalent, key selection considerations include dual-regulator sequencing control, reset threshold hysteresis (30–80 mV), output leakage <1 µA at Output 1, thermal drift ≤0.8 mV/°C, and Heptawatt vertical plastic package mechanical compatibility.

Technical Context

The L4901A integrates two independent LDO regulators: Regulator 1 provides ultra-low-quiescent-current (0.6 mA typ.) 5V supply with <1 µA leakage for battery-backed RAMs and real-time clocks; Regulator 2 is enable-controlled by V_O1 and Input 2 voltage thresholds (V_IT = V_O1 + 1.2–1.7 V, V_ITH = 250 mV).

Reset generation is triggered when Output 1 exceeds V_RT (V_O2 − 0.15 to −0.05 V) and Input 2 exceeds V_IT, then delayed by externally programmed capacitor (t_RD = C_t × 5V / 10 µA); Reset output level is referenced to Output 2 and actively driven high or low.

Key Specifications

Pinout & Package

Package: Heptawatt vertical plastic package (standard STMicroelectronics outline, 7-pin single-in-line, 16.7–17.1 mm length, 4.8–5.3 mm width, 10.05–10.4 mm height).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-regulator-with-reset applications.

Compared with MAX692A and TPS767D318, the L4901A uniquely integrates dual 5V LDOs with programmable reset, ultra-low Output 1 leakage, and automotive-grade input protection - making it irreplaceable for legacy 5V battery-backed microprocessor systems requiring guaranteed data retention.

Availability

L4901A is available at Aetrix Electronics and suitable for automotive trip computers, car radios with programmable tuning, CMOS time-of-day clock backup, and microcomputer systems with shadow RAM requiring stable component supply across extended product lifecycles.

Supply support for L4901A 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 analog, power, microcontrollers, and automotive ICs.

The L4901A belongs to ST's legacy power management portfolio, engineered specifically for 5V microprocessor systems requiring battery-backed operation, data retention, and robust reset supervision in harsh environments.

FAQ

What is the maximum allowable timing capacitor value for reliable reset delay on the L4901A?

The datasheet specifies t_RD = C_t × 5V / 10 µA, with typical values shown up to 100 nF (yielding ~50 ms). While no absolute maximum is stated, capacitor leakage and board parasitics limit practical use to ≤100 nF for predictable 1–50 ms delays. Larger values increase sensitivity to temperature drift and ESD-induced timing errors.

Can Output 2 be used independently of Output 1?

No - Output 2 is enabled only when Output 1 exceeds V_RT (V_O2 − 0.15 to −0.05 V) and Input 2 exceeds V_IT (V_O1 + 1.2–1.7 V). This interlock ensures Output 2 activates only after Output 1 is stable, preventing race conditions in sequenced power domains.

How does the L4901A handle input transients above 24 V DC?

The device withstands 60 V transients for up to 40 ms per absolute maximum ratings. Internal clamp circuitry limits junction stress during load dump events. However, sustained operation above 24 V DC risks thermal overload due to increased dropout dissipation - external TVS or pre-regulation is recommended for continuous >24 V operation.

Is the reset output compatible with TTL or CMOS logic families?

Yes - Reset output high voltage is V_O2 − 1 V (min 4.12 V at I_R = 500 µA), and low voltage is ≤0.4 V at −5 mA sink, meeting both TTL and 5V CMOS input thresholds. Its output stage is designed to directly drive standard logic inputs without pull-up resistors.