STMicroelectronics L6377D

Overview

L6377D from STMicroelectronics is a high-side intelligent power switch in SO-14L package, designed for industrial load control with programmable current limitation (0.17–1.0 A), non-dissipative short-circuit protection, and integrated diagnostics (undervoltage, overtemperature, overcurrent). It drives inductive, capacitive, or resistive loads in PLC I/O modules and CNC machine interfaces.

For engineers reviewing the L6377D datasheet, L6377D pinout, L6377D application, or L6377D equivalent, this device requires attention to RSC resistor selection for current limit tuning, ON DELAY capacitor sizing to avoid false diagnostics on cold lamp loads, thermal derating per Rth(JA) = 150 °C/W, and diagnostic open-drain pull-up configuration on the DIAG pin.

Technical Context

The L6377D integrates a high-side NDMOS power switch with internal voltage clamping (Vcl = 48–58 V), TTL/CMOS-compatible input with 50–400 mV hysteresis, and asynchronous reset. Its overcurrent protection operates in linear mode with externally set ISC via RSC pin and time-limited retry via CDON on ON DELAY pin.

Thermal shutdown triggers at TJ = 150 °C with 20 °C hysteresis; undervoltage lockout activates below Vsth = 7–8 V with 300–700 mV hysteresis. The DIAG output reports faults as open-drain low-active signals, while internal demagnetization handles inductive kickback up to 50 mJ at TJ = 125 °C.

Key Specifications

Pinout & Package

SO-14L surface-mount package (14-pin small outline, 1.27 mm pitch), RoHS-compliant ECOPACK® grade, with exposed pad for thermal enhancement (not electrically connected).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-side intelligent switch applications.

Compared with VNS3NV04PTR-E and TPS27082LDR, the L6377D uniquely combines adjustable current limit, configurable short-circuit retry timing, integrated diagnostics on one pin, and loss-of-ground protection - making it optimal for complex industrial I/O where reliability and diagnostic granularity are critical.

Availability

L6377D is available at Aetrix Electronics and suitable for programmable logic controllers, CNC machine interfaces, and industrial PC peripheral I/O requiring stable component supply across extended temperature and voltage ranges.

Supply support for L6377D 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 strong analog and smart-power process expertise.

The L6377D belongs to ST's Intelligent Power Switch family, engineered specifically for robust high-side load control in harsh industrial environments - emphasizing fault resilience, diagnostic transparency, and simplified system-level protection.

FAQ

What is the maximum continuous output current the L6377D can deliver without derating?

The L6377D does not specify a fixed maximum continuous current; instead, its output current is programmable via the RSC resistor (ISC = 5/RSC[kΩ] A, range 0.17–1.0 A). Continuous delivery depends on thermal design: with Rth(JA) = 150 °C/W and TJ(max) = 125 °C, sustained 625 mA operation requires ambient ≤ 55 °C and adequate PCB copper area. At 85 °C ambient, continuous current must be reduced to ~400 mA.

How does the ON DELAY pin affect short-circuit behavior?

The ON DELAY pin sets the tON duration during overcurrent events using an external capacitor (CDON). tON = 1.28 μs/pF (50 pF–2 nF); after tON expires, the device enters tOFF = 64 × tON off-time before retrying. This prevents false DIAG assertions on capacitive inrush or cold-filament lamps. Shorting ON DELAY to GND disables retry (tON = 0), forcing immediate shutdown without cycling.

Can the L6377D drive inductive loads without external components?

Yes - the L6377D includes an internal Zener clamp (Vcl = 48–58 V) that safely demagnetizes inductive loads up to 50 mJ at TJ = 125 °C. For larger energy loads (e.g., >100 mJ) or higher peak currents, ST recommends adding an external Zener + diode network referenced to ground or VS, sized using Vz < Vcl(min) – Vs(max) or Vs(max) < Vz < Vcl(min) respectively.

Is the DIAG output compatible with 3.3 V microcontrollers?

Yes - the DIAG pin is an open-drain output rated for up to 40 V, so it can be pulled up to any logic rail (3.3 V, 5 V, or VS). When active, it sinks ≥5 mA at ≤1.5 V drop, ensuring reliable low-level signaling into standard GPIO inputs. No level-shifting circuitry is required for 3.3 V MCUs, provided the pull-up resistor is selected appropriately (e.g., 10 kΩ to 3.3 V yields ~0.33 mA leakage when inactive).