LM5146 - 100V Synchronous Buck DC/DC Controller | Texas Instruments
MPN: LM5146 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.2 | $3.20 |
| 10 | $2.92 | $29.20 |
| 100 | $2.55 | $255.00 |
| 500 | $2.25 | $1,125.00 |
| 1,000 | $1.95 | $1,950.00 |
LM5146 Overview
A synchronous buck controller is a type of DC-DC switching regulator that uses external MOSFETs to step down a higher input voltage to a lower regulated output voltage. Within the broader power management hierarchy, it sits above LDO regulators on the conversion efficiency vs. noise trade-off curve: synchronous buck controllers achieve 90-95% efficiency at high VIN/VOUT ratios, while LDOs trade efficiency for ultra-low output noise. The LM256 belongs to the voltage regulator -> power management IC -> semiconductor taxonomy.
Key features include a 100-V rated bootstrap gate driver, dual-channel random spread spectrum for EMI mitigation, ultra-low quiescent current in standby, and SYNCIN/SYNCOUT pins for frequency synchronization. The integrated high-side and low-side gate drivers feature low impedance to drive large die-size or paralleled MOSFETs with correspondingly large gate charge (QG), enabling multi-amp output current capability.
The LM5146 architecture uses peak current-mode control with an internal 0.8 V reference, internal slope compensation, and adjustable switching frequency up to 1 MHz. The wide duty-cycle capability allows the converter to maintain regulation through severe input transients, such as automotive cold-crank or industrial load-dump events. Synchronous rectification eliminates the lossy external Schottky diode, improving thermal behavior at full load.
Typical applications include 48-V telecom point-of-load converters, industrial PLC and motor-control auxiliary rails, battery-powered robotics with 24-72 V battery stacks, and high-voltage LED driver front ends. The wide input range also supports solar MPPT charge controllers and e-mobility auxiliary supplies. The 20-pin VQFN (4.5x3.5 mm) package (RGY) is optimized for compact designs.
When designing with the LM5146, select the external MOSFETs based on the maximum input voltage (100 V drain-source rating with adequate margin) and the desired output current. Use the WEBENCH Power Designer tool to size the inductor and capacitors, and follow the layout recommendations in the datasheet for the BOOT, SW, and VIN traces to minimize parasitic inductance. The SYNCIN pin should be tied to GND if unused.
Drop-in alternatives for LM5146 — 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:
LM5146-Q1
✅ Drop-In📋 Reference alternative (not in catalog)
LM5145
✅ Drop-In📋 Reference alternative (not in catalog)
LM25145
✅ Drop-In📋 Reference alternative (not in catalog)
LV5144
✅ Drop-In📋 Reference alternative (not in catalog)
LM5146QRGYTQ1
✅ Drop-In📋 Reference alternative (not in catalog)
LM5146 Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Buck Controller |
| Input Voltage Range | 5.5 V to 100 V |
| Output Voltage Range | 0.8 V to VIN (down to approx) |
| Duty Cycle Range | Wide (near 100% at low VIN dips) |
| Control Mode | Peak Current Mode |
| Gate Driver | Integrated high-side and low-side, 100-V rated bootstrap |
| Synchronization | SYNCIN/SYNCOUT pins |
| Spread Spectrum | Dual Random Spread Spectrum |
| Operating Temperature | -40C to +125C |
| Package | 20-pin VQFN (4.5x3.5 mm) RGY |
| Mounting Type | Surface Mount |
| Quiescent Current | Ultra-low IQ |
| RoHS Status | Compliant |
LM5146 Pin Configuration
| Pin 1 | EN — Enable input (active high) |
| Pin 2 | RT — Timing resistor for switching frequency |
| Pin 3 | AGND — Analog ground |
| Pin 4 | FB — Voltage feedback |
| Pin 5 | COMP — Compensation network node |
| Pin 6 | SS/TRK — Soft-start / tracking |
| Pin 7 | PGOOD — Power-good indicator (open-drain) |
| Pin 8 | VCC — Internal LDO output (5V typical) |
| Pin 9 | VIN — Input supply voltage (5.5V to 100V) |
| Pin 10 | BOOT — Bootstrap supply for high-side driver |
| Pin 11 | HB — High-side bootstrap rail |
| Pin 12 | SW — Switch node (to external inductor) |
| Pin 13 | HO — High-side gate drive output |
| Pin 14 | LO — Low-side gate drive output |
| Pin 15 | PGND — Power ground |
| Pin 16 | SYNCIN — Synchronization input |
| Pin 17 | SYNCOUT — Synchronization output |
| Pin 18 | NC — Not connected (per datasheet) |
| Pin 19 | NC — Not connected (per datasheet) |
| Pin 20 | NC — Not connected (per datasheet) |
Typical Applications
LM5146 is suitable for 6 applications: 48V Telecom Point-of-Load Converters, Industrial PLC and Motor Control Auxiliary Rails, Battery-Powered Robotics with 24-72V Battery Stacks, High-Voltage LED Driver Front Ends, Solar MPPT Charge Controllers, Automotive 48V Mild-Hybrid Auxiliary Supplies.
48V Telecom Point-of-Load Converters
The LM5146's 100 V input rating and 5.5 V minimum make it ideal for 48 V telecom POL converters that must survive 100 V surge events on the bus. Place the LM5146 between the 48 V backplane rail and downstream step-down converters feeding ASICs and FPGAs. The 100 V bootstrap gate driver handles transients while dual random spread spectrum reduces conducted EMI on the bus, simplifying compliance with telecom EMC standards.
Recommended
Industrial PLC and Motor Control Auxiliary Rails
The LM5146 is well suited for industrial PLC auxiliary power rails and motor control gate-driver supplies that require 24 V to 72 V input. Its wide duty-cycle range maintains regulation during large load transients from motor inrush currents. With 100 V VIN rating the LM5146 tolerates inductive kickback from motor windings. The 20-pin VQFN (4.5x3.5 mm) RGY footprint enables compact DIN-rail mounted designs.
Recommended
Battery-Powered Robotics with 24-72V Battery Stacks
Mobile robots and AGVs using 24 V to 72 V battery stacks benefit from the LM5146's 100 V input rating and low-IQ standby for sleep modes. The wide duty-cycle range allows the converter to ride through brownout events as battery voltage sags under heavy load. At 1 MHz switching frequency, the LM5146 supports compact inductors and capacitors, critical for weight-sensitive mobile designs where every gram matters.
Recommended
High-Voltage LED Driver Front Ends
High-bay and industrial LED fixtures with high-string-count designs use the LM5146 as a PFC front-end or constant-voltage front stage. The 100 V input allows long wire runs from the AC-DC stage without derating. Dual random spread spectrum reduces EMI peaks that would otherwise require bulky inductors and Y-capacitors, lowering BOM cost and shrinking the fixture profile.
Recommended
Solar MPPT Charge Controllers
Solar MPPT charge controllers use the LM5146 as the buck stage that regulates the panel voltage down to battery voltage. The 100 V input handles 72V nominal panel strings with margin for open-circuit voltage at cold temperatures. The near 100% duty cycle keeps the converter regulating even when the panel voltage approaches the battery voltage, maximizing energy harvest during low-irradiance morning and evening hours.
Recommended
Automotive 48V Mild-Hybrid Auxiliary Supplies
The LM5146-Q1 variant with AEC-Q100 certification is ideal for 48 V mild-hybrid auxiliary supplies that must tolerate 100 V load-dump transients on the 48 V bus. Use it to generate 12 V or 5 V rails for infotainment, ADAS, and lighting ECUs. The wide duty-cycle range maintains output during cold-crank when the 48 V bus sags to 30 V, ensuring ECU operation through cranking events.
Recommended
Recommended Products Summary
Engineering reference data for LM5146 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM5146-Q1 | LM5145 | LM25145 | LV5144 |
|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | VQFN-20 (RGY) 4.5x3.5 mm | VQFN-20 (RGY) 4.5x3.5 mm - same | VQFN-20 (RGY) 4.5x3.5 mm - same | VQFN-20 (RGY) 4.5x3.5 mm - same | VQFN-20 (RGY) 4.5x3.5 mm - same |
| Input Voltage Range | 5.5 V to 100 V | 5.5 V to 100 V | 5.5 V to 100 V | 6 V to 42 V | 5.5 V to 95 V |
| Gate Driver | Integrated high-side and low-side, 100V rated | Integrated HS/LS, 100V rated | Integrated HS/LS, 100V rated | Integrated HS/LS, 42V rated | Integrated HS/LS, 95V rated |
| Control Mode | Peak Current Mode | Peak Current Mode | Peak Current Mode | Peak Current Mode | Peak Current Mode |
Key Differentiators
- Highest VIN rating in TI 100V synchronous buck controller family (vs LM25145)
- Integrated SYNCIN/SYNCOUT for multi-rail synchronization (vs LM5145)
- Dual random spread spectrum for EMI compliance (vs LM5145)
Design Notes
The LM260 is in a 20-pin VQFN (4.5x3.5 mm) RGY package with an exposed thermal pad (pin 21). Solder the exposed pad to a large PCB power-ground copper pour to provide thermal dissipation for the internal LDO and gate drivers. Keep the BOOT and HB traces short and away from the SW node to minimize parasitic capacitance that would otherwise couple switching noise into the bootstrap rail.
Route the high-di/dt loop (VIN, high-side MOSFET, SW, low-side MOSFET, PGND) as small and tight as possible to minimize parasitic inductance that causes ringing and EMI. Place input ceramic capacitors as close as possible to the VIN and PGND pins. The SW node trace should be short and wide; avoid routing sensitive analog traces (FB, COMP) near the SW node.
Enable dual random spread spectrum on the LM5146 to spread switching energy across a wider frequency band, reducing peak EMI emissions by typically 10-15 dB. For additional EMI reduction, place a small RC snubber across the low-side MOSFET or use a ferrite bead on the input. The SYNCIN pin can be tied to GND if external synchronization is not used; do not leave it floating.
Estimated: at VIN=48 V, VOUT=5 V, IOUT=5 A, and 90% efficiency, the LM5146 dissipates approximately 2.7 W through the exposed thermal pad. With a 4-layer PCB and standard thermal vias, theta_JA is approximately 35 C/W, yielding a junction temperature rise of 95 C above ambient. For higher-power designs, use additional copper area or thermal vias to the internal ground plane.
Do not exceed the absolute maximum VIN rating of 100 V; use a TVS diode or transient suppressor on the VIN pin for automotive load-dump protection. The BOOT capacitor must be a low-ESR ceramic (X7R or X5R) and must be sized to provide sufficient charge for the high-side MOSFET gate. Do not connect SYNCIN to a clock signal faster than the internal oscillator maximum frequency.
Compliance Information
LM5146 is RoHS-compliant. The -Q1 variant (LM5146-Q1) is AEC-Q100 qualified for automotive. Standard LM5146 is for industrial/consumer use.
