Texas Instruments LM536355QRNLTQ1

Overview

LM536355QRNLTQ1 from Texas Instruments is an AEC-Q100 Grade 1 automotive synchronous buck DC-DC converter delivering 5 V fixed output at up to 3.5 A, operating from 3.9 V to 36 V input with 2.1-MHz switching, ±1% output voltage tolerance (–40°C to +125°C), and 15-µA quiescent current at no load - used in automotive head units for stable 5-V rail generation under cold-crank conditions.

For engineers reviewing the LM536355QRNLTQ1 datasheet, LM536355QRNLTQ1 pinout, LM536355QRNLTQ1 application, or LM536355QRNLTQ1 equivalent, key selection considerations include its 3.5-A continuous output capability, wettable-flank VQFN-22 package, spread-spectrum EMI reduction, external frequency synchronization support, and integrated RESET with 3-ms release timer - all validated for automotive telematics and instrumentation cluster power rails.

Technical Context

The LM536355QRNLTQ1 implements peak-current-mode control with adaptive off-time spreading to maintain regulation down to 300-mV dropout at 3.5 A while sustaining 2.1-MHz operation across wide VIN/VOUT ratios - enabling 18 V → 3.3 V conversion without frequency foldback. Its flip-chip HotRod QFN architecture minimizes parasitic inductance, reducing switch-node ringing and radiated EMI.

It integrates a 3.1-V internal LDO (VCC), bootstrap gate driver (CBOOT), open-drain RESET with built-in 12–45 µs glitch filter and 2–4 ms assertion delay, and FPWM pin for forced PWM mode override. The device supports external SYNC input (1.9–2.3 MHz) and features programmable UVLO hysteresis (0.28–0.4 V) and thermal shutdown at 155–175°C with 15°C hysteresis.

Key Specifications

Pinout & Package

VQFN-HR-22 (5.0 mm × 4.0 mm) package with wettable flanks, 0.6-mm pin pitch, exposed thermal pad (PGND-connected), and RoHS-compliant matte-tin finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar automotive buck regulator applications.

Compared with LM536353QRNLTQ1, the LM536355QRNLTQ1 provides identical performance in a 5-V configuration - ideal for legacy 5-V peripherals. Against LM61460-Q1, it trades higher integration (RESET, spread-spectrum) for slightly larger footprint and lower max current, favoring cost-sensitive, safety-critical clusters over miniaturized ADAS nodes.

Availability

LM536355QRNLTQ1 is available at Aetrix Electronics and suitable for automotive telematics, head unit, and instrumentation cluster applications requiring stable component supply, AEC-Q100 compliance, and long-term lifecycle support.

Supply support for LM536355QRNLTQ1 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 specializing in analog, embedded processing, and automotive-grade power management ICs with over 40 years of automotive qualification experience.

The LM536xx-Q1 product line delivers high-efficiency, low-EMI synchronous buck regulators optimized for automotive infotainment, body electronics, and ADAS subsystems - designed to meet stringent AEC-Q100, ISO 26262, and CISPR 25 requirements.

FAQ

What is the minimum input voltage required for LM536355QRNLTQ1 to start and regulate a 5-V output?

The LM536355QRNLTQ1 requires a minimum input voltage of 3.55 V (rising) to initiate regulation of its fixed 5-V output, verified across temperature and load conditions. This enables reliable operation during automotive cold-crank events where battery voltage dips below 6 V. The device maintains regulation down to 300-mV dropout at full 3.5-A load, and the LM536355QRNLTQ1 datasheet specifies 3.9 V as the recommended minimum for full functionality at maximum load.

Does LM536355QRNLTQ1 require external compensation components?

No, the LM536355QRNLTQ1 features fully integrated compensation - no external RC networks or type-II/type-III compensators are needed. Its internal error amplifier and current-mode control architecture are factory-tuned for stability with standard 2.2-µH inductors and ceramic output capacitors. This simplifies design, reduces BOM count, and eliminates tuning effort - a key advantage confirmed in the LM536355QRNLTQ1 functional block diagram and electrical characteristics table.

How does the RESET output of LM536355QRNLTQ1 behave during startup and fault conditions?

The LM536355QRNLTQ1 RESET output is an open-drain signal that remains low until the output reaches 105–110% of nominal 5 V and remains stable for ≥3 ms, then transitions high. It asserts low again during EN deactivation, input UVLO, thermal shutdown (>155°C), or output overvoltage. The internal 12–45 µs glitch filter prevents false triggering from noise - all behavior is documented in the LM536355QRNLTQ1 timing characteristics and functional description sections.

Can LM536355QRNLTQ1 synchronize to an external clock, and what are the valid frequency and duty-cycle ranges?

Yes, the LM536355QRNLTQ1 accepts external synchronization via its SYNC pin, supporting input frequencies from 1.9 MHz to 2.3 MHz with a duty cycle range of 25% to 75%. The device triggers on the rising edge and maintains tight phase alignment. This capability is explicitly specified in the LM536355QRNLTQ1 electrical characteristics table (FSYNC and DSYNC parameters) and enables EMI reduction in multi-rail automotive systems.

What thermal performance can be expected from LM536355QRNLTQ1 in a standard 4-layer PCB layout?

In a standard 4-layer automotive PCB with 2 oz copper, 1-in² thermal pad exposure, and 2000 mm² copper pour under the LM536355QRNLTQ1 VQFN-22 package, the junction-to-board thermal resistance (RθJB) is 5.4°C/W. At 3.5-A load and 13.5-V input, typical power dissipation is ~1.2 W, resulting in ~6.5°C rise above board temperature - well within the –40°C to +125°C junction limit. This RθJB value is measured and published in the LM536355QRNLTQ1 thermal information table.