STMicroelectronics L4947PD

Overview

L4947PD from STMicroelectronics is a monolithic 5V/0.5A very low-dropout linear voltage regulator in PowerSO-20 package, featuring integrated power-on reset with externally programmable delay, ±80V load dump protection, reverse voltage protection (–18V), and thermal shutdown with hysteresis-designed for automotive microprocessor supply during cranking (down to 6V input).

For engineers reviewing the L4947PD datasheet, L4947PD pinout, L4947PD application, or L4947PD equivalent, key selection considerations include dropout voltage ≤0.75V at 500mA over –40°C to +125°C, reset threshold hysteresis of 50mV, external capacitor–programmed reset delay (e.g., 10–30ms with 100nF), and compatibility with 20µF minimum output capacitance (ESR <10Ω).

Technical Context

The L4947PD employs a lateral PNP pass transistor enabling ultra-low dropout (0.4V typ. at 25°C, 0.75V max. over full temperature range at 500mA) and stable operation down to 6V input-critical for automotive cranking. Its three-stage regulation loop (error amplifier, driver, PNP) requires external output capacitance (≥47µF, ESR <10Ω) for stability.

The integrated reset circuit monitors V_OUT with precise thresholds: V_RT(on) = V_OUT – 0.04V (power-on high-to-low transition), V_RT(off) = V_OUT – 0.15V (power-off low-to-high transition), yielding 50mV hysteresis. Delay timing is set by an external capacitor (Cd) charging at 20µA, enabling configurable reset assertion windows.

Key Specifications

Pinout & Package

Package: PowerSO-20 (JEDEC MO-166), thermally enhanced exposed slug, R_{th j-case} = 3°C/W - optimized for high-power dissipation in constrained automotive PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV70750PDP and TPS7B6750QPWPRQ1, the L4947PD uniquely delivers ±80V load dump immunity, 500mA output at ≤0.75V dropout, and field-proven thermal hysteresis-making it irreplaceable in legacy ECU designs requiring full ISO 7637-2 compliance without added protection components.

Availability

L4947PD 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 under automotive-grade reliability and transient immunity.

Supply support for L4947PD 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 scale and AEC-Q100 qualification expertise.

The L4947PD belongs to ST's automotive-grade linear regulator family, engineered specifically for harsh-environment microprocessor supply in engine, chassis, and safety-critical systems where cranking resilience and transient immunity are non-negotiable.

FAQ

What is the minimum output capacitance required for stable operation?

The L4947PD requires a minimum 47µF output capacitor with ESR <10Ω across –40°C to +125°C. This value ensures phase margin >45° and prevents oscillation under all load and temperature conditions. Using less capacitance or higher ESR risks instability, especially during fast load transients typical in MCU power domains.

How does the reset function behave during power-off?

At power-off, when V_OUT falls below V_RT(off) = V_OUT – 0.15V (typically ~4.75V), the RESET pin immediately transitions LOW to inhibit the microprocessor. This occurs without delay-unlike the programmable power-on delay-and ensures deterministic shutdown before V_OUT drops into undervoltage lockout.

Can the L4947PD operate with input voltages above 26V?

No. The L4947PD is specified for DC input voltages from 6V to 26V. Voltages between 26V and 37V place the device in non-operational state (no regulation, no reset assertion). Transient spikes up to ±80V are tolerated per ISO 7637-2, but sustained DC above 26V will cause functional failure and potential damage.

Is the PowerSO-20 package RoHS-compliant and lead-free?

Yes. The L4947PD in PowerSO-20 packaging conforms to RoHS Directive 2011/65/EU and is lead-free. The exposed slug is matte tin-plated, and all soldering profiles comply with JEDEC J-STD-020 moisture sensitivity level (MSL) 3 requirements for reflow assembly.