STMicroelectronics L9856-LF

Overview

L9856-LF from STMicroelectronics is a high-voltage high-side gate driver IC designed to control N-channel power MOSFETs in half-bridge and high-side switching topologies. It supports up to 160 V floating rail voltage (VB), delivers ±500 mA peak source/sink current at HO, features 100 ns rise/fall times with 2.5 nF load, and includes integrated bootstrap recharge circuitry and under-voltage lockout for VCC and VBS. It is used in industrial motor drives and DC-DC converters requiring robust dV/dt immunity.

For engineers reviewing the L9856-LF datasheet, L9856-LF pinout, L9856-LF application, or L9856-LF equivalent, key selection criteria include its 160 V high-side capability, negative logic IN-/RESET- interface, SO-8 package thermal performance (Rth(j-amb) = 150 °C/W), and guaranteed dV/dt immunity of ±50 V/ns across –40 °C to +125 °C.

Technical Context

The L9856-LF integrates dual level shifters ("ON" and "OFF"), break-before-make logic, and pulse filters to ensure safe high-side gate driving under fast transient conditions. Its internal architecture separates VCC-referenced logic from VS-referenced high-side output stage, enabling operation with VB up to 160 V while maintaining CMOS/TTL-compatible input thresholds and hysteresis.

It implements independent undervoltage lockout (UVLO) on both VCC and VBS rails with hysteresis (0.02–0.6 V), plus dedicated reset circuitry and a controlled recharge path for the external bootstrap capacitor. Propagation delays (e.g., tplhi = 0.1–0.35 µs) and deadtime control (DTHOFF = 3–9 µs, DTHON = 0.1–0.7 µs) are specified across full temperature range.

Key Specifications

Pinout & Package

Package: SO-8, ECOPACK® lead-free, 150 °C/W junction-to-ambient thermal resistance. Pin 6 is NC (no bondwire); all other pins are electrically functional per datasheet Figure 2 and Table 2.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IRS21844PbF and UCC27211DR, the L9856-LF uniquely balances 160 V capability, integrated bootstrap management, and ±50 V/ns dV/dt immunity in an SO-8 package-making it optimal for cost-sensitive, thermally constrained industrial motor and power conversion designs where reliability under electrical stress is paramount.

Availability

L9856-LF is available at Aetrix Electronics and suitable for industrial motor drives, DC-DC converters, solar microinverters, and PLC output modules requiring stable component supply and long-term manufacturability.

Supply support for L9856-LF 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, designing and manufacturing analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The L9856-LF belongs to ST's high-voltage gate driver product line, engineered specifically for robust, high-side N-MOSFET control in industrial power conversion and motor control applications demanding reliability under harsh electrical conditions.

FAQ

What is the maximum allowable dV/dt at the VS pin, and how is it tested?

The L9856-LF guarantees ±50 V/ns dV/dt immunity at the VS pin across its full operating temperature range (–40 °C to +125 °C). This is verified per datasheet Table 4 (Absolute Maximum Ratings) and confirmed by design under repetitive 0.1 µs pulses at –8 V to +150 V offset. No external filtering is required to meet this specification.

Does the L9856-LF require an external bootstrap diode?

No. The L9856-LF integrates a dedicated recharge transistor and control logic (see Figure 1 block diagram and Table 6 timing parameters ton_rech/toff_rech). An external bootstrap diode is unnecessary; only a single ceramic bootstrap capacitor (typically 1 µF) is required between VB and VS.

How does the RESET- pin interact with IN- during normal operation?

RESET- is asynchronous and dominant: when pulled LOW, it forces HO OFF and disables the high-side output regardless of IN- state or UVLO status. When HIGH, normal IN- control resumes. The logic table (Table 7) confirms that RESET- LOW overrides all IN- combinations, providing hardware-level fault containment.

Can the L9856-LF drive a MOSFET with >2.5 nF gate charge?

Yes. While 100 ns rise/fall times are specified with a 2.5 nF capacitive load, the L9856-LF delivers ±500 mA peak current (Table 6), enabling it to drive larger gate charges. For example, a 10 nF load would yield ~400 ns transitions-still compatible with 200 kHz switching, though layout parasitics and gate resistor selection must be optimized per application.