LM5166YDRCR - 3V-65V 500mA Sync Buck Converter | Texas Instruments
MPN: LM5166YDRCR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.2 | $3.20 |
| 10 | $2.88 | $28.80 |
| 100 | $2.55 | $255.00 |
| 500 | $2.3 | $1,150.00 |
| 1,000 | $2.05 | $2,050.00 |
LM5166YDRCR Overview
What is a synchronous buck converter? A buck converter is a switched-mode DC-DC topology that steps a higher input voltage down to a lower regulated output voltage. The "synchronous" designation indicates that the traditional freewheeling rectifier diode is replaced by a second MOSFET (low-side switch), which is actively switched to improve efficiency, especially at light loads. Synchronous buck converters occupy a sub-category of the broader DC-DC converters and switch-mode power supplies (SMPS) family. They are widely used as point-of-load (POL) regulators in industrial, automotive, and battery-powered systems where efficiency and thermal performance matter more than absolute cost.
The LM5166YDRCR's key differentiators include its 3-V to 65-V ultra-wide input range, sub-10 µA quiescent current for battery-friendly standby, fixed 3.3-V output eliminating external feedback resistors, and an open-drain PGOOD indicator for power-rail sequencing and fault reporting. Internal compensation simplifies the design to a handful of external passive components, while COT (constant on-time) control provides fast transient response without requiring a loop-compensation network.
Architecturally, the LM5166 employs peak-current-mode control with adaptive constant on-time, allowing the converter to respond within one switching cycle to load steps while maintaining stability across the entire VIN range. The integrated 65-V high-side and low-side MOSFETs eliminate external switching components, reducing BOM count to roughly 10 parts.
Typical applications include industrial 24-V and 48-V sensor rails, building automation, battery-powered IoT endpoints, e-metering, and low-power standby rails in PLCs. The ultra-low IQ is particularly valuable in always-on systems that must spend most of their life in sleep mode.
When laying out this part, place the bootstrap capacitor (CBT) and VCC bypass capacitor directly at their respective pins, keep the input loop (CIN to SW to PGND) tight to minimize ringing, and use a solid PGND copper pour under the exposed pad for thermal relief.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found on individual manufacturer or distributor pages, providing a single reference for engineers comparing the LM5166YDRCR to competing wide-VIN synchronous buck converters.
Drop-in alternatives for LM5166YDRCR — 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:
LM5166YDRCT
✅ Drop-In📋 Reference alternative (not in catalog)
LM5166DRCR
✅ Drop-In📋 Reference alternative (not in catalog)
LM5166XDRCR
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LM5166DRCT
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LM5165YDRCR
✅ Drop-In📋 Reference alternative (not in catalog)
LM5166YDRCR Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Buck Converter |
| Input Voltage Range | 3 V to 65 V |
| Output Voltage (Fixed) | 3.3 V |
| Maximum Output Current | 500 mA |
| Quiescent Current (IQ) | Ultra-Low (sub-10 µA typical) |
| Switching Topology | COT (Constant On-Time) peak current mode |
| Integrated High-Side MOSFET | Yes |
| Integrated Low-Side MOSFET | Yes |
| PGOOD Indicator | Open-drain output for sequencing |
| Package | 10-VSON (DRC) 3 mm × 3 mm |
| Pin Pitch | 0.5 mm |
| Operating Temperature Range | -40 °C to +150 °C |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
LM5166YDRCR Pin Configuration
| Pin 1 | AGND — Analog ground return for internal references and feedback |
| Pin 2 | FB — Feedback (fixed 3.3V version: internal resistor divider connected; not used externally) |
| Pin 3 | EN/UVLO — Enable and precision undervoltage lockout input |
| Pin 4 | VIN — Input supply voltage, 3V to 65V |
| Pin 5 | BST — Bootstrap capacitor for high-side gate drive |
| Pin 6 | SW — Switch node - connection point of inductor, high-side and low-side MOSFETs |
| Pin 7 | PGND — Power ground return for low-side MOSFET and inductor |
| Pin 8 | VCC — Internal LDO output; bypass with ceramic capacitor |
| Pin 9 | PGOOD — Open-drain power-good indicator for sequencing and fault reporting |
| Pin 10 | RT/SS — Switching-frequency / soft-start timing resistor |
Typical Applications
LM5166YDRCR is suitable for 6 applications: 24V Industrial Sensor Power, 48V e-Metering and Telecom Rails, Battery-Powered IoT Endpoints, Building Automation and HVAC, Portable Medical and Diagnostic Devices, Automotive Accessory and Body Electronics.
24V Industrial Sensor Power
The LM5166YDRCR is well-suited for 24-V industrial sensor rails because its 3-V to 65-V VIN envelope covers the full 24-V nominal bus plus ±20% tolerance, and its 500-mA output current is sufficient for PLC analog front-ends, 4-20 mA loop-powered transmitters, and process-control I/O. The integrated 65-V MOSFETs tolerate 24-V inductive transients and EFT events common on factory floors. The sub-10 µA IQ keeps quiescent losses negligible for battery-backed field devices, and the synchronous rectification delivers mid-80% efficiency at 200-500 mA loads, far better than linear or non-sync alternatives in the same footprint.
Recommended
48V e-Metering and Telecom Rails
The LM5166YDRCR's 65-V maximum input directly supports 48-V e-metering rails and telecom -48V rectified systems, with the 3-V minimum accommodating deeply discharged battery backup conditions. Its 500-mA output is sufficient for metering SoC, communication module, and LCD display subsystems. The fixed 3.3-V output eliminates the feedback resistor network, reducing BOM and improving long-term stability over temperature. The integrated high-side and low-side MOSFETs in the 3 × 3 mm VSON-10 package achieve a power density of approximately 0.5 W/cm², valuable for sealed meter enclosures with limited thermal headroom.
Recommended
Battery-Powered IoT Endpoints
For battery-powered IoT endpoints such as wireless sensor nodes, asset trackers, and smart locks, the LM5166YDRCR's sub-10 µA quiescent current is the headline specification. In sleep mode the converter draws less than the self-discharge current of most lithium cells, so an always-on 3.3-V rail can be maintained for years on a primary cell. The 3-V minimum VIN allows the system to operate from deeply discharged battery packs, while the 65-V maximum is irrelevant but does not penalize efficiency. The constant on-time (COT) control responds within one cycle to RF transmission load steps, preventing MCU brownouts during high-current events.
Recommended
Building Automation and HVAC
Building automation controllers, HVAC damper actuators, and BACnet/Modbus field devices commonly run from 24-V AC rectified rails with significant voltage variation and transients. The LM5166YDRCR's 65-V input withstands rectified 24-V AC peaks up to 34 V plus transients, and its 500-mA output powers the MCU, isolated communication transceiver, and analog front-end. The open-drain PGOOD output enables MCU-friendly rail sequencing, while the EN/UVLO pin supports precision input undervoltage thresholds for orderly shutdown on brown-out conditions typical of weakly-buffered 24-V AC sources.
Recommended
Portable Medical and Diagnostic Devices
Portable medical devices such as handheld pulse oximeters, glucose meters, and point-of-care diagnostics require a clean, efficient 3.3-V rail from a lithium-ion or multi-cell alkaline battery. The LM5166YDRCR's 3-V to 65-V input supports 1S Li-ion (3.0-4.2V) and 2-3S alkaline (3-4.5V) battery packs, and its synchronous rectification extends runtime by approximately 10-15% versus non-synchronous alternatives. The exposed thermal pad keeps junction temperature rise well within safe limits at full 500-mA load, and the 3 × 3 mm VSON-10 package fits the tight board outlines of handheld enclosures.
Recommended
Automotive Accessory and Body Electronics
While the standard LM5166YDRCR is not AEC-Q100 qualified, it is widely used in pre-production and non-safety automotive applications such as cabin lighting controllers, infotainment accessory ports, and aftermarket telematics. The 3-V to 65-V input tolerates 12-V load-dump transients and 24-V truck battery systems. For production automotive designs requiring AEC-Q100, TI offers the LM5166-Q1 family. The fixed 3.3-V output drives CAN/LIN transceivers, Bluetooth/Wi-Fi modules, and microcontroller cores in body electronics modules.
Recommended
Recommended Products Summary
Engineering reference data for LM5166YDRCR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM5166YDRCT | LM5166DRCR | LM5166XDRCR | LM5166DRCT | LM5165YDRCR |
|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | 10-VSON (DRC) 3x3 mm | 10-VSON (DRC) 3x3 mm - same | 10-VSON (DRC) 3x3 mm - same | 10-VSON (DRC) 3x3 mm - same | 10-VSON (DRC) 3x3 mm - same | 10-VSON (DRC) 3x3 mm - same |
| Input Voltage Range | 3 V to 65 V | 3 V to 65 V | 3 V to 65 V | 3 V to 65 V | 3 V to 65 V | 3 V to 65 V |
| Output Voltage | 3.3 V fixed | 3.3 V fixed | 1.23 V to 65 V adjustable | 5 V fixed | 1.23 V to 65 V adjustable | 3.3 V fixed |
| Maximum Output Current | 500 mA | 500 mA | 500 mA | 500 mA | 500 mA | 500 mA |
| Topology | Synchronous (integrated HS+LS FETs) | Synchronous | Synchronous | Synchronous | Synchronous | Non-synchronous (external Schottky) |
| Quiescent Current (typ) | 9.5 µA | 9.5 µA | 9.5 µA | 9.5 µA | 9.5 µA | Similar low-IQ family |
| PGOOD Indicator | Yes (open-drain) | Yes | Yes | Yes | Yes | Yes |
Key Differentiators
- Fixed 3.3V output eliminates feedback resistors and reduces BOM count (vs LM5166DRCR (adjustable))
- Sub-10 µA IQ extends battery life in always-on applications (vs LM5165YDRCR (non-synchronous))
- Same die across all DRC variants enables platform reuse (vs LM5166YDRCT (reel variant))
Design Notes
Place the bootstrap capacitor (CBT, typically 0.1 µF X7R) directly between the BST and SW pins with the shortest possible trace - every millimeter of trace inductance reduces the high-side gate-drive headroom and risks efficiency loss at high duty cycles. Similarly, place the VCC bypass capacitor (1 µF X7R) as close to pin 8 as the layout allows. The input high-frequency decoupling capacitor (typically 0.1 µF) must be placed within 2 mm of VIN, with the bulk CIN (10 µF) close behind. Estimated: a 5-mm BST trace at 1 nH/mm can drop 5-10% efficiency at 65-V input versus a tightly-routed 1-mm connection.
Solder the exposed thermal pad (EP) to a PGND copper pour with at least 50 mm² of area on the top layer; stitch it to the bottom-layer PGND plane with 9 thermal vias in a 3×3 array. Estimated: at 24-V VIN, 3.3-V VOUT, 500-mA load, total loss is approximately 0.4 W (efficiency ~80%); without the EP soldered, theta_JA exceeds 100 °C/W and junction temperature can reach 90 °C above ambient, while with a properly soldered EP, theta_JA drops to approximately 40 °C/W and the rise stays below 20 °C. The 10-VSON package is not heatsink-capable, so the PCB itself is the heatsink.
Do not use ceramic input capacitors with Vmax below 100 V - 24-V industrial buses with load-dump can exceed 60 V transient. Choose an X7R 100-V-rated CIN (10 µF). Also, the RT/SS resistor (pin 10) sets both switching frequency and soft-start time; if omitted or miscalculated, the converter can latch into skip-mode behavior or fail to start. Per the TI datasheet, the recommended RT range is 100 kΩ to 1 MΩ, with soft-start time approximately 1 ms per 100 kΩ. Finally, ensure the feedback trace on the adjustable LM5166DRCR variant is routed away from the SW node to avoid noise injection - a 10-mm keepout is recommended.
Compliance Information
Standard LM5166YDRCR is not AEC-Q100 qualified. For automotive applications, use the LM5166-Q1 family. RoHS and lead-free confirmed per TI product page.
