Automotive 3-V to 65-V, 0.3-A buck converter optimized for size and light load efficiency


Product details


Vin (Min) (V) 3 Vin (Max) (V) 65 Vout (Min) (V) 1 Vout (Max) (V) 28 Iout (Max) (A) 0.3 Iq (Typ) (uA) 4 Switching frequency (Min) (kHz) 200 Switching frequency (Max) (kHz) 2200 Features Enable, Fixed Output, Forced PWM, Frequency Synchronization, Light Load Efficiency, Over Current Protection, Power Good, Pre-Bias Start-Up, Soft Start Fixed, Spread Spectrum, Synchronous Rectification, Wettable Flanks Package Operating temperature range (C) -40 to 150 Rating Automotive Regulated outputs (#) 1 open-in-new Find other Buck converters (integrated switch)

Package | Pins | Size

VQFN-HR (RPE) 9 4 mm² 2 x 2 VQFN-HR (RPE) 9 open-in-new Find other Buck converters (integrated switch)


  • AEC-Q100-qualified for automotive applications:
    • Device temperature grade 1: –40°C to +125°C, TA
  • Functional Safety-Capable
  • >70% efficiency at 5 mA
    • 4 µA IQ (switching) at 24 VIN to 3.3 VOUT (fixed output option)
  • Miniature solution size and low component cost
    • 2-mm × 2-mm HotRod™ package with wettable flanks
    • Internal compensation
  • Designed for automotive applications:
    • Junction temperature range –40°C to +150°C
    • Pseudo-random spread spectrum compatible with CISPR 25 EMI standard
    • Wide input voltage range: 3.0 V (falling threshold) to 65 V
    • Adjustable, 3.3-V and 5-V fixed output voltage options available
    • Synchronizable with MODE/SYNC pin variant
    • Adjustable FSW: 200 kHz to 2.2 MHz with RT pin variant
    • Pin compatible with LMR36506-Q1 (65 V, 600 mA)

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The LMR36503-Q1 is the industry’s smallest 65 V, 0.3 A synchronous step-down DC/DC converter in 2-mm x 2-mm HotRod™ package. This easy-to-use converter can handle input voltage transients up to 70 V, provide excellent EMI performance and support fixed 3.3 V, 5 V and other adjustable output voltages.

The LMR36503-Q1 uses peak current mode control architecture with internal compensation and maintains stable operation with minimal output capacitance. The wide input operating range of the LMR36503-Q1 helps it remain functional during a deep input voltage sag condition, making it an excellent choice for automotive applications withstanding severe cold crank start impulses. The PGOOD flag in the LMR36503-Q1 provides precise indication of the output voltage status, eliminating the requirement for an external supervisor. A seamless transition from FPWM to PFM, with an ultra-low standby quiescent current allows the LMR36503-Q1 to support much higher system efficiency at low output loads. The MODE/SYNC pin variant helps to synchronize the LMR36503-Q1 to an external clock. With the right resistor selection, the LMR36503-Q1 RT pin variant can also be externally programmed to any desired switching frequency of operation. The rich feature set of the LMR36503-Q1 is designed to simplify implementation for a wide range of automotive end equipments.

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NEW LMR36506-Q1 ACTIVE 3-V to 65-V, 0.6-A buck converter optimized for size and light load efficiency Pin-to-pin 600-mA version

Technical documentation

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Type Title Date
* Data sheet LMR36503-Q1 3-V to 65-V, 0.3-A Synchronous Buck Converter Optimized for Size datasheet (Rev. B) Sep. 22, 2020
Selection guide Buck Converter Quick Reference Guide (Rev. B) Apr. 08, 2021
Application note LMR3650x-Q1 Functional Safety, FIT Rate, Failure Mode Distribution and Pin FMA Oct. 26, 2020
User guide LMR36506MSCEVM User’s Guide (Rev. A) May 19, 2020
Technical article Optimizing flip-chip IC thermal performance in automotive designs Dec. 11, 2019
Technical article Minimize the impact of the MLCC shortage on your power application Mar. 29, 2019

Design & development

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Hardware development

document-generic User guide

The LMR36506MSCEVM evaluation module (EVM) is a fully assembled and tested circuit for evaluating the LMR36506-Q1 synchronous step-down converter. The LMR36503-Q1 can also be evaluated with LMR36506MSCEVM.

  • Low minimum on-time
  • Integrated synchronous rectification
  • Low operating quiescent current
  • High efficiency at light loads

Design tools & simulation

SNVMBW4.ZIP (166 KB) - PSpice Model
SNVMC16.ZIP (528 KB) - PSpice Model
SNVMC17.ZIP (530 KB) - PSpice Model
SNVMC26.ZIP (517 KB) - PSpice Model
SNVMC27.ZIP (538 KB) - PSpice Model
SNVMC28.ZIP (524 KB) - PSpice Model
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