STMicroelectronics L9857-TR

Overview

L9857-TR from STMicroelectronics is a high-voltage, non-inverting high-side gate driver IC designed to control N-channel PowerMOSFETs in off-line applications. It supports up to 450 V rail voltage, delivers ±500 mA peak source/sink current, achieves 100 ns rise/fall times with 2.5 nF load, and features CMOS/TTL Schmitt-trigger inputs with hysteresis and pull-down. It is used in industrial AC motor drives for half-bridge high-side switching.

For engineers reviewing the L9857-TR datasheet, L9857-TR pinout, L9857-TR application, or L9857-TR equivalent, key selection criteria include dV/dt immunity (±50 V/ns), under-voltage lockout thresholds (7.2–9.6 V on VCC/VBS), reset timing (0.1–0.8 µs propagation), SO-8 thermal resistance (150 °C/W), and floating supply offset capability (VS up to 300 V).

Technical Context

The L9857-TR integrates dual level shifters ("ON" and "OFF"), break-before-make logic, and independent undervoltage detection on both VCC and VBS rails. Its floating high-side section operates with VB up to 300 V and VS offset up to 300 V, enabling direct drive of N-MOSFETs in high-voltage half-bridges without external bootstrap components.

It uses internal pulse filters and flip-flop latching to suppress noise-induced false triggering, and includes active clamping on VCC and dedicated reset circuitry with negative-logic RES− input tied to open-collector/drain interfaces in multi-driver systems.

Key Specifications

Pinout & Package

Supplied in an industry-standard SO-8 package (ECOPACK® compliant, 1.27 mm pitch), the L9857-TR features eight terminals with one no-connect (NC) pin and integrated level-shifting circuitry for high-side floating operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage high-side gate driver applications.

Compared with IRS21844SPbF and UCC27531D, the L9857-TR uniquely combines 450 V rail tolerance, ±50 V/ns dV/dt immunity, integrated RES− logic, and SO-8 packaging-making it optimal for compact, noise-prone off-line half-bridge systems requiring minimal external components.

Availability

L9857-TR is available at Aetrix Electronics and suitable for industrial AC motor drives, induction cooktop half-bridges, and UPS inverter stages requiring stable component supply across extended temperature ranges (−40 °C to +125 °C) and long production lifecycles.

Supply support for L9857-TR 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, delivering innovative silicon solutions for automotive, industrial, and power management applications.

The L9857-TR belongs to ST's high-voltage gate driver product line, engineered specifically for robust, compact high-side switching in off-line industrial power conversion systems without external isolation or bootstrap components.

FAQ

What is the purpose of the RES− pin, and how should it be interfaced?

The RES− pin is an active-low enable input that forces the HO output low when asserted. It features an internal pull-down resistor (60–300 kΩ) and is designed for direct connection to open-collector or open-drain drivers in multi-driver systems. In practice, it is typically pulled up to 5 V via a 3.8 kΩ resistor and driven low by a bipolar transistor or NMOS switch to ensure fail-safe MOSFET turn-off during faults or startup.

Can the L9857-TR drive a MOSFET directly without external gate resistors?

While the L9857-TR can deliver ±500 mA peak current, external gate resistors are still required for EMI control, ringing suppression, and precise tuning of rise/fall times. The 100 ns switching specification assumes a 2.5 nF capacitive load with appropriate series gate resistance; omitting it risks overshoot, oscillation, and increased EMI in real-world layouts with parasitic inductance.

How does the L9857-TR achieve dV/dt immunity of ±50 V/ns?

This immunity is achieved through internal pulse filtering on the level shifter inputs, combined with optimized layout and BCD process isolation between the floating high-side and low-side domains. The device rejects fast common-mode transients on the VS node by ignoring short-duration spikes (<100 ns) and using hysteresis in its internal comparators-verified across −40 °C to +125 °C per datasheet test conditions.

Is the L9857-TR qualified for automotive applications?

No. The L9857-TR is specified for industrial use only, with operating temperature range −40 °C to +125 °C and no AEC-Q100 qualification. ST explicitly states in the datasheet disclaimer that its products-including the L9857-are not designed or authorized for safety-critical, automotive, aerospace, or medical applications unless expressly designated as such in official product specifications.