Texas Instruments LM5109BMA/NOPB

Overview

LM5109BMA/NOPB from Texas Instruments is a high-voltage, 1-A peak half-bridge gate driver IC designed to independently control high-side and low-side N-channel MOSFETs in synchronous buck and half-bridge power converters. It supports HB rail voltages up to 108 V DC, delivers 1.0-A sink/source output current per channel, and achieves 30-ns typical propagation delay with ≤2-ns matching between channels. It is used in industrial motor drives and isolated DC-DC converters requiring robust level-shifting and UVLO protection.

For engineers reviewing the LM5109BMA/NOPB datasheet, LM5109BMA/NOPB pinout, LM5109BMA/NOPB application, or LM5109BMA/NOPB equivalent, key selection considerations include bootstrap voltage tolerance (up to 108 V), independent TTL/CMOS-compatible HI/LI inputs, dual-rail undervoltage lockout (VDD and VHB–HS), thermal performance in WSON-8 package (R_θJB = 19.3°C/W), and fast 15-ns rise/fall times into 1000-pF loads.

Technical Context

The LM5109BMA/NOPB integrates a floating high-side driver with robust level-shift architecture referenced to HS, enabling clean logic-to-HO signal translation without cross-conduction risk. Its dual UVLO circuitry independently monitors VDD–VSS (6.7-V rising threshold) and VHB–HS (6.6-V rising threshold), each with built-in hysteresis (0.5 V and 0.4 V respectively) to prevent oscillation during supply transients.

Each output stage features matched 1-A peak sink/source capability, low R_DS(on)-equivalent drive impedance, and operates across –40°C to +125°C junction temperature. The device requires external bootstrap diode and capacitor for high-side supply generation and mandates low-ESR/low-ESL decoupling at VDD–VSS and HB–HS pins to maintain stability under 500-kHz switching.

Key Specifications

Pinout & Package

LM5109BMA/NOPB is packaged in an 8-pin thermally enhanced WSON (NGT) package (4.00 mm × 4.00 mm), with exposed thermal pad soldered to PCB ground plane for optimal heat dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IRS21844PbF and UCC27211DRCR, LM5109BMA/NOPB offers optimal balance of 108-V HB rating, 1-A drive, tight 2-ns delay matching, and compact WSON-8 thermal performance-making it ideal for space-constrained, medium-power half-bridge applications where precision timing and thermal efficiency are prioritized over maximum current.

Availability

LM5109BMA/NOPB is available at Aetrix Electronics and suitable for industrial motor drives, isolated DC-DC converters, and solid-state relay designs requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM5109BMA/NOPB 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

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in power management, signal chain, and high-reliability IC design.

LM5109BMA/NOPB belongs to TI's high-voltage gate driver product line, engineered for robust half-bridge and synchronous buck power stages in industrial, telecom, and automotive off-battery applications demanding precision timing and thermal resilience.

FAQ

What is the maximum allowable voltage on the HB pin of the LM5109BMA/NOPB?

The LM5109BMA/NOPB supports a maximum HB-to-VSS voltage of 108 V DC, as specified in its Absolute Maximum Ratings. This allows the high-side driver to operate with HS node voltages up to 90 V while maintaining 18 V of headroom for the bootstrap capacitor. Exceeding 108 V risks permanent damage, and proper PCB layout with low-inductance HB–HS decoupling is essential to sustain this rating under transient conditions.

Does the LM5109BMA/NOPB integrate a bootstrap diode?

No, the LM5109BMA/NOPB does not integrate a bootstrap diode. It requires an external Schottky diode (e.g., 1N5819 or equivalent) connected between VDD and HB to charge the bootstrap capacitor during low-side conduction. TI recommends selecting a diode with low forward voltage (<0.5 V) and fast recovery to minimize losses and ensure reliable high-side gate drive across temperature and frequency ranges.

How does the dual UVLO function in the LM5109BMA/NOPB affect output behavior?

The LM5109BMA/NOPB implements independent UVLO on VDD–VSS (6.7-V rising threshold) and VHB–HS (6.6-V rising threshold). If VDD falls below UVLO, both HO and LO are forced low. If only VHB–HS drops below its threshold, only HO is disabled while LO remains fully controllable. This enables graceful degradation in fault conditions and supports asymmetric power rail architectures common in isolated converters.

What is the thermal performance difference between the SOIC and WSON packages of the LM5109BMA/NOPB?

The LM5109BMA/NOPB WSON-8 package (used in LM5109BMA/NOPB) achieves R_θJB = 19.3°C/W, significantly lower than the SOIC-8 variant's R_θJB = 58.1°C/W. This 67% improvement in junction-to-board thermal resistance allows the WSON version to dissipate ~1.5 W continuously with standard 2-oz copper, making it suitable for higher ambient temperature and higher-frequency applications where thermal headroom is critical.

Can unused HI or LI inputs be left floating on the LM5109BMA/NOPB?

No, unused HI or LI inputs on the LM5109BMA/NOPB must be tied to VSS (ground); they must never be left floating. The datasheet explicitly states that floating inputs may cause unpredictable output behavior due to noise susceptibility and internal biasing limitations. Pulling unused inputs to VSS ensures deterministic low-state output and prevents unintended switching or increased quiescent current.