Texas Instruments LMR33620ARNXT

Overview

LMR33620ARNXT from Texas Instruments is a synchronous step-down DC/DC converter delivering 2 A output current across 3.8 V to 36 V input, supporting adjustable 1 V to 24 V output with 400 kHz fixed switching frequency in a 12-pin VQFN (3 mm × 2 mm) package. It features peak-current-mode control, 68 ns minimum on-time, –40°C to +125°C junction temperature range, and integrated compensation for industrial motor drive and PLC power supplies.

For engineers reviewing the LMR33620ARNXT datasheet, LMR33620ARNXT pinout, LMR33620ARNXT application, or LMR33620ARNXT equivalent, key selection criteria include its rugged wide-VIN capability, low EMI HotRod™ VQFN layout, precision enable threshold (1.231 V typ), power-good flag timing (60–170 µs glitch filter), and thermal shutdown at 165°C - all critical for factory automation and drone power systems.

Technical Context

The LMR33620ARNXT implements peak-current-mode control with automatic PFM/PWM mode transition: PWM at full load (400 kHz), PFM with diode emulation at light loads to maintain >95% peak efficiency and 25 µA quiescent current. Its architecture supports dropout operation down to VIN – VOUT = 150 mV at 1 A, enabled by short 68 ns minimum on-time and adaptive frequency foldback.

It integrates dual MOSFET drivers (RDS-ON-HS = 75–145 mΩ, RDS-ON-LS = 50–95 mΩ in VQFN), internal 5-V VCC LDO, and analog ground (AGND) separate from PGND for noise isolation. Protection includes cycle-by-cycle current limit, hiccup-mode short-circuit response (94 ms burst interval), thermal shutdown (165°C), and input UVLO (3.8 V).

Key Specifications

Pinout & Package

LMR33620ARNXT uses a 12-pin VQFN package (3.00 mm × 2.00 mm × 0.85 mm) with wettable flanks and exposed thermal pad (AGND). The package enables low-inductance layout, symmetrical VIN/PGND routing for EMI reduction, and compatibility with automated optical inspection (AOI).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMR33620ARNXT, LMR33620BDDA offers smaller solution volume but higher thermal resistance and lower efficiency at 2 A; TPSM53602 trades off PCB area and bill-of-materials simplicity for reduced engineering effort and guaranteed EMI performance - making it ideal for rapid prototyping of industrial HMIs.

Availability

LMR33620ARNXT is available at Aetrix Electronics and suitable for motor drive systems, PLC CPU power, HVAC control boards, and servo amplifier auxiliary rails requiring stable component supply across extended temperature and wide-input voltage ranges.

Supply support for LMR33620ARNXT 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 power management ICs, with decades of industrial-grade reliability validation.

The LMR33620ARNXT belongs to TI's SIMPLE SWITCHER® family - engineered specifically for rugged, wide-input DC/DC conversion in factory automation, motor control, and building infrastructure where long-term supply stability and AEC-Q100-qualified variants are essential.

FAQ

What is the recommended input capacitor for LMR33620ARNXT in a 24-V industrial application?

The LMR33620ARNXT requires a minimum 10-µF X7R ceramic capacitor placed directly between VIN and PGND pins with short, wide traces. For 24-V input, TI recommends paralleling one 10-µF/35-V and two 2.2-µF/35-V capacitors to handle RMS ripple current and improve hold-up during transients. This configuration reduces input voltage droop during 2-A load steps and maintains stability across –40°C to +125°C operation.

Does LMR33620ARNXT support adjustable output voltage, and what is the feedback resistor tolerance requirement?

Yes, LMR33620ARNXT supports adjustable output from 1 V to 24 V using an external resistor divider on the FB pin. The internal 1.0-V reference has ±1.5% tolerance over temperature, so TI specifies ≤1% tolerance for RFBT and RFBB to maintain overall output accuracy within ±2%. A typical 5-V design uses 100-kΩ top and 200-kΩ bottom resistors, with both placed close to FB and AGND to minimize noise pickup.

How does the power-good flag (PG) of LMR33620ARNXT behave during thermal shutdown?

During thermal shutdown, the LMR33620ARNXT pulls the open-drain PG pin low within 10 µs, signaling fault to the host system. The PG remains low until junction temperature falls below 148°C (recovery threshold) and output voltage re-stabilizes within ±5% of target. The 60–170 µs glitch filter prevents false triggering from brief thermal excursions, ensuring reliable reset behavior in servo amplifier thermal protection circuits.

Can LMR33620ARNXT operate in dropout mode, and what is the minimum input-to-output differential?

Yes, LMR33620ARNXT operates in dropout mode with automatic frequency foldback. At 1 A output and 5-V setpoint, the minimum VIN–VOUT differential is 150 mV - verified across –40°C to +125°C. This enables stable 5-V output from a 5.15-V input, critical for maintaining PLC CPU operation during brownout events on 24-V field buses.

What layout guidance is critical for minimizing EMI with LMR33620ARNXT in the VQFN package?

TI mandates symmetrical, short, and wide VIN–PGND copper pours adjacent to pins 2/10 and 1/11 to cancel magnetic fields; the SW pin (12) must connect to an NC pad on PCB to shorten CBOOT routing; and the thermal pad must be fully soldered to a solid AGND plane. These steps reduce peak radiated emissions by ≥10 dB compared to standard layouts - essential for meeting CISPR 11 Class A in motor drive enclosures.