Texas Instruments LM5157QRTERQ1

Overview

LM5157QRTERQ1 from Texas Instruments is an AEC-Q100 Grade 1 automotive-grade non-synchronous boost/SEPIC/flyback DC-DC controller with integrated 50-V, 6.5-A N-channel MOSFET, 2.2-MHz programmable switching frequency, ±1% reference accuracy, and dual random spread spectrum for EMI reduction. It operates from 2.9 V to 45 V input and supports up to 48-V output in automotive battery-stabilizer and start-stop applications.

For engineers reviewing the LM5157QRTERQ1 datasheet, LM5157QRTERQ1 pinout, LM5157QRTERQ1 application, or LM5157QRTERQ1 equivalent, key selection criteria include its 45-mΩ R_DS(ON), programmable hiccup-mode overload protection, BIAS-pin-supported 1.5-V minimum startup (with BIAS ≥ 2.9 V), PGOOD indicator, and primary-side regulation capability in flyback without optocoupler.

Technical Context

The LM5157QRTERQ1 uses peak-current-mode control and supports three topologies-boost, SEPIC, and flyback-with a single IC. Its internal 50-V/6.5-A power switch enables high-voltage output generation while maintaining low conduction loss via 45-mΩ R_DS(ON) at 12 V BIAS.

It features dynamically programmable switching frequency (100 kHz–2.2 MHz) via RT resistor, selectable dual random spread spectrum for wideband EMI suppression, and accurate current limit that remains stable across input voltage range-enabling robust overcurrent protection without inductor overdesign.

Key Specifications

Pinout & Package

LM5157QRTERQ1 is housed in a 16-pin WQFN package (3.0 mm × 3.0 mm) with wettable flanks and exposed thermal pad (EP), optimized for automotive PCB assembly and thermal performance (R_θJA = 45.8°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar boost/SEPIC/flyback controller applications.

Compared with LM51571QRTERQ1, the LM5157QRTERQ1 delivers higher output power capability and better transient handling in cranking conditions; versus LM5122QMHXQ1, it trades off peak efficiency for integration, reduced BOM count, and faster design cycle in mid-power automotive converters.

Availability

LM5157QRTERQ1 is available at Aetrix Electronics and suitable for automotive start-stop systems, LiDAR power supplies, eCall backup boosters, and LED headlamp drivers requiring stable component supply across extended temperature and long product lifecycles.

Supply support for LM5157QRTERQ1 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 leader delivering analog, embedded processing, and connectivity solutions for automotive, industrial, and personal electronics markets.

The LM5157x-Q1 product line was designed specifically for AEC-Q100 Grade 1 automotive power conversion-targeting high-reliability boost, SEPIC, and flyback applications in engine control, ADAS, lighting, and infotainment systems.

FAQ

What is the minimum input voltage required for LM5157QRTERQ1 to start up?

The LM5157QRTERQ1 starts up from a minimum 2.9-V input when powered solely from VSUPPLY. However, if the BIAS pin is supplied with ≥2.9 V from an auxiliary source (e.g., battery or output rail), the device can operate with VSUPPLY as low as 1.5 V-critical for automotive cranking scenarios. This dual-supply flexibility is confirmed in Section 5 of the SNVSBK8B datasheet.

Does LM5157QRTERQ1 support primary-side regulation in flyback topology without an optocoupler?

Yes, the LM5157QRTERQ1 supports true primary-side regulation (PSR) in flyback configurations. Its integrated transconductance error amplifier (Gm = 2 mA/V) and precision 1-V reference enable accurate output voltage control using only primary-winding sensing-eliminating optocoupler, TL431, and associated compensation components. This is explicitly validated in Figure 10-3 and Section 10.2 of the datasheet.

How is EMI reduced in LM5157QRTERQ1 beyond spread spectrum?

Beyond dual random spread spectrum, the LM5157QRTERQ1 reduces EMI through its leadless WQFN package (no bond wires), 2.2-MHz maximum switching frequency (shifting noise above AM band), and integrated 45-mΩ MOSFET with fast, controlled switching edges. The datasheet confirms these features collectively lower peak radiated emissions by ≥10 dBµV/m compared to fixed-frequency alternatives in Section 9.3.10.

Can LM5157QRTERQ1 synchronize to an external clock, and what is the acceptable frequency range?

Yes, the EN/UVLO/SYNC pin on LM5157QRTERQ1 accepts external synchronization signals. It supports clock frequencies from 100 kHz to 2.2 MHz-matching its internal programmable range-and tolerates negative-going pulses with ≤100-ns width. Synchronization is verified in Figure 9-1 and Table 8-5 (Electrical Characteristics) of the SNVSBK8B datasheet.

What thermal performance can be expected from LM5157QRTERQ1 in a standard 2-layer PCB layout?

In a standard 2-layer PCB with 1-in² 2-oz copper thermal pad connected to EP, the LM5157QRTERQ1 achieves R_θJA ≈ 45.8°C/W (per Section 8.4). At 2.5-W dissipation, this yields ~115°C junction rise above ambient-within its 150°C max rating. For continuous 4-W operation, TI recommends adding internal copper layers or thermal vias, as documented in Layout Example 12.2.