LMR36503RS3QRPERQ1 - 65V 0.3A Sync Buck Converter | TI
MPN: LMR36503RS3QRPERQ1 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.35 | $4.35 |
| 10 | $3.92 | $39.20 |
| 100 | $3.48 | $348.00 |
| 500 | $3.13 | $1,565.00 |
| 1,000 | $2.79 | $2,790.00 |
LMR36503RS3QRPERQ1 Overview
A buck (step-down) DC/DC converter is a switched-mode power supply topology that efficiently converts a higher DC input voltage to a lower DC output voltage by chopping the input with a switching element and averaging the result through an LC low-pass filter. The synchronous variant replaces the freewheeling diode with a low-side MOSFET to reduce conduction loss and improve efficiency at light loads. Within the power-management hierarchy, this part sits as a non-isolated point-of-load (PoL) regulator, beneath PMIC and system-rail controllers, and is engineered for distributed power in space-constrained automotive modules.
Key specifications include 4.2 µA quiescent current at no load for low-Iq standby, 65 V absolute maximum input for load-dump survival, AEC-Q100 Grade 1 qualification for -40 °C to +150 °C operation, internal compensation that removes the need for an external compensation network, and a PFM-to-PWM auto-mode transition that optimizes efficiency across the entire load curve. The integrated MOSFETs eliminate external switches, while the RT pin allows external programming of switching frequency when finer EMI control is required.
The HotRod flip-chip package removes bond wires from the critical switching loop, lowering parasitic inductance and reducing switch-node ringing. This architectural choice, combined with frequency dithering and spread-spectrum options, helps the converter meet CISPR 25 Class 5 EMI limits in sensitive automotive radio and sensor modules. Internal soft-start, cycle-by-cycle current limit, and thermal shutdown with auto-retry provide layered fault protection without external supervisor parts.
Typical applications include automotive body electronics and LED lighting drivers, ADAS sensor power rails (camera, radar, lidar front ends), industrial 24 V PLC I/O modules, and always-on battery-connected subsystems that demand low quiescent current during key-off sleep. In all of these use cases the wide Vin tolerance and small footprint allow placement directly beside the load.
When designing with the LMR36503RS3QRPERQ1, choose the inductor so that its ripple current stays in the 20-40% range of the 300 mA load rating, and place both input and bootstrap capacitors within 2 mm of the package to minimize the high-frequency loop area. Verify worst-case thermals at VIN = 60 V and IOUT = 300 mA to ensure the junction stays below the 150 °C AEC-Q100 ceiling.
This page consolidates distributor pricing, pin-compatible TI family variants, and practical design notes (loop-area minimization, RT-pin frequency programming, EMI layout) that are not present together on the manufacturer datasheet.
Drop-in alternatives for LMR36503RS3QRPERQ1 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LMR36503FRPERQ1
✅ Drop-In📋 Reference alternative (not in catalog)
LMR36503RS5QRPERQ1
✅ Drop-In📋 Reference alternative (not in catalog)
LMR36506RPERQ1
✅ Drop-In📋 Reference alternative (not in catalog)
LMR36503RS3QRPERQ1 Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Buck (Step-Down) DC/DC Converter |
| Input Voltage Range | 3 V to 65 V |
| Output Voltage | 3.3 V (Fixed) |
| Maximum Output Current | 300 mA |
| Switching Frequency (Typical) | 2.2 MHz |
| Quiescent Current (No-Load) | 4.2 µA |
| Operating Temperature Range | -40 °C to +150 °C (AEC-Q100 Grade 1) |
| Package | 9-pin VQFN-HR (RPE) 2 mm × 2 mm (HotRod) |
| Mounting Type | Surface Mount |
| Automotive Qualification | AEC-Q100 Grade 1 |
| Internal MOSFETs | Yes (high-side and low-side synchronous) |
| Internal Compensation | Yes (no external compensation network required) |
| Light-Load Operation | PFM-to-PWM auto-mode |
| RT Pin | Yes (external switching-frequency programming) |
| RoHS Status | Compliant |
| Spread-Spectrum / EMI Features | Frequency dithering for CISPR 25 EMI mitigation |
LMR36503RS3QRPERQ1 Pin Configuration
| Pin 1 | VIN — Input supply voltage (3 V to 65 V) |
| Pin 2 | VIN — Input supply voltage (tied to pin 1 for low-impedance input) |
| Pin 3 | EN/UVLO — Enable input and undervoltage lockout threshold programming |
| Pin 4 | RT — Switching-frequency programming resistor to AGND |
| Pin 5 | AGND — Analog ground reference |
| Pin 6 | PGND — Power ground for low-side synchronous MOSFET |
| Pin 7 | SW — Switch-node output to external inductor |
| Pin 8 | BST — Bootstrap capacitor for high-side gate drive |
| Pin 9 | FB/VOUT — Feedback sense / fixed 3.3 V output |
Typical Applications
LMR36503RS3QRPERQ1 is suitable for 6 applications: Automotive Body Electronics and LED Lighting, ADAS Camera and Radar Sensor Power, Industrial 24 V PLC I/O and Sensor Modules, Battery-Connected Always-On Modules, Building Automation 24 V Bus Modules, Portable Battery-Powered Medical Accessories.
Automotive Body Electronics and LED Lighting
The LMR36503RS3QRPERQ1 fits body-control and interior/exterior LED-lighting modules because it accepts the full 3 V to 65 V automotive battery range, tolerating cold-crank drops and 40 V load-dump transients without a TVS clamp. With 80%+ efficiency at 12 V to 3.3 V and only 4.2 µA Iq, it keeps thermal rise minimal in sealed lamp housings. Place it adjacent to the LED driver to power MCU and CAN-transceiver rails; the 2.2 MHz switching frequency pushes ripple outside the AM-band so LED current stays flicker-free.
Recommended
ADAS Camera and Radar Sensor Power
The LMR36503RS3QRPERQ1 is well-suited to ADAS sensor front ends that demand clean 3.3 V rails for image-signal processors and radar MMIC supply pins. Its 2.2 MHz switching and integrated frequency-dithering spectrum-spreading help the converter meet CISPR 25 Class 5 EMI limits, while the VQFN-HR HotRod package keeps the high-frequency switching loop short. Use it to drop the 12 V camera-module battery rail to a low-noise 3.3 V; the 4.2 µA Iq extends key-off parking-surveillance runtime on always-on sensor modules.
Recommended
Industrial 24 V PLC I/O and Sensor Modules
For industrial PLC digital-input cards and 24 V field-sensor modules, the LMR36503RS3QRPERQ1's 65 V input withstands inductive kickback from long cable runs while the internal compensation removes the need for an external compensation network. Its 2.2 MHz switching permits a small 1 µH inductor, enabling a slim module height for DIN-rail packaging. Use it to derive a 3.3 V logic rail from a 24 V bus; the PFM-to-PWM auto-mode keeps standby draw below 10 µA when the PLC is in sleep mode.
Recommended
Battery-Connected Always-On Modules
The LMR36503RS3QRPERQ1's 4.2 µA quiescent current makes it a strong fit for always-on automotive subsystems such as key fob receivers, tire-pressure monitor transmitters, and intrusion-detection modules. It stays alive directly from the 12 V battery during key-off, drawing microamp-level current while continuing to deliver a regulated 3.3 V wake-up rail. The wide Vin range prevents reverse-battery damage, and internal soft-start limits inrush when the module wakes up to scan for activity.
Recommended
Building Automation 24 V Bus Modules
Building-automation HVAC controllers, occupancy sensors, and access-control panels often run from a 24 VAC/DC bus where input surges can exceed 30 V. The LMR36503RS3QRPERQ1's 65 V input tolerates these surges, and its small 2 mm × 2 mm footprint allows direct placement behind screw-terminal connectors. Use it to power a 3.3 V wireless-MCU rail; the 2.2 MHz switching frequency stays above the AM-band and avoids audible interference with building HVAC line-frequency harmonics.
Recommended
Portable Battery-Powered Medical Accessories
For handheld medical-device accessories such as pulse-oximeter probes and portable glucose meters, the LMR36503RS3QRPERQ1 delivers efficient step-down conversion from a 6 V or 12 V battery stack while drawing only 4.2 µA in standby. Its thermally efficient HotRod package allows continuous 300 mA output without a heatsink, and the AEC-Q100 Grade 1 temperature range covers cold-storage environments. Place it near the battery pack to power a precision analog front-end rail; the low-output ripple protects ADC measurement integrity.
Recommended
Recommended Products Summary
Engineering reference data for LMR36503RS3QRPERQ1 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LMR36503FRPERQ1 | LMR36503RS5QRPERQ1 | LMR36506RPERQ1 |
|---|---|---|---|---|
| Package | VQFN-HR (RPE) 2x2 mm | VQFN-HR (RPE) 2x2 mm - same | VQFN-HR (RPE) 2x2 mm - same | VQFN-HR (RPE) 2x2 mm - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Input Voltage Range | 3 V to 65 V | 3 V to 65 V | 3 V to 65 V | 3 V to 65 V |
| Maximum Output Current | 300 mA | 300 mA | 300 mA | 600 mA (+100%) |
| Output Voltage | 3.3 V (fixed) | Adjustable (1 V to 28 V typ) | 5.0 V (fixed) | Adjustable (1 V to 28 V typ) |
| Switching Frequency | 2.2 MHz typ | 2.2 MHz typ | 2.2 MHz typ | 2.2 MHz typ |
| Automotive Grade (AEC-Q100) | Yes (Grade 1) | Yes (Grade 1) | Yes (Grade 1) | Yes (Grade 1) |
Key Differentiators
- Smallest 65 V-tolerant 300 mA automotive synchronous buck in 2x2 mm HotRod package (vs LMR36503ADDAR (SO PowerPAD-8))
- Ultra-low 4.2 µA quiescent current for battery-connected automotive modules (vs LMR36506RPERQ1)
- AEC-Q100 Grade 1 qualified over -40 °C to +150 °C (vs Generic industrial buck (no AEC-Q100))
Design Notes
Place the input ceramic capacitor (≥ 1 µF, X7R 100 V) within 2 mm of the VIN pins and the bootstrap capacitor (≥ 100 nF) directly between BST and SW. The TI datasheet emphasizes that the HotRod flip-chip package depends on a tight high-frequency loop; a wider loop increases switch-node ringing and radiated EMI. Keep the SW trace short and surrounded by a PGND pour on the top layer to minimize antenna-loop area.
Estimated: at VIN = 24 V, VOUT = 3.3 V, IOUT = 300 mA, and 85% efficiency, the LMR36503RS3QRPERQ1 dissipates roughly (24 × 0.3 × 0.15) ≈ 1.1 W. The 2 mm × 2 mm VQFN-HR package has a limited θJA (≈ 60 °C/W on a 1 oz 4-layer board per the datasheet), giving a 66 °C temperature rise over ambient. For continuous high-line operation in sealed enclosures, add thermal vias under the exposed pad to an inner copper plane to stay below the 150 °C AEC-Q100 ceiling.
Do not exceed 65 V on VIN even during transient surges; the datasheet recommends a TVS clamp for load-dump profiles beyond the absolute maximum. Do not leave the RT pin floating - either tie a resistor to AGND for the default 2.2 MHz frequency or to VIN/AGND for the factory-trimmed option. When using the adjustable variant, route the FB trace away from the SW node to avoid noise coupling into the feedback loop.
For CISPR 25 Class 5 compliance, use the built-in spread-spectrum frequency dithering (default enabled on the RT-trimmed variant) and add a small RC snubber (≈ 2 Ω + 1 nF) across the SW node if the second-harmonic peak exceeds the limit. The TI datasheet's EMI-optimized layout keeps the input capacitor return path directly under the PGND pins, which is the single largest contributor to conducted EMI reduction.
Compliance Information
AEC-Q100 Grade 1 qualified per TI LMR36503-Q1 datasheet. RoHS and REACH compliant. Halogen-free status not stated in the verified web data.
