LT8640EUDC#TRPBF - 42V 5A Sync Buck Silent Switcher | ADI
MPN: LT8640EUDC#TRPBF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.82 | $9.82 |
| 10 | $8.94 | $89.40 |
| 100 | $7.65 | $765.00 |
| 500 | $6.82 | $3,410.00 |
| 1,000 | $6.1 | $6,100.00 |
| 2,500 | $5.48 | $13,700.00 |
LT8640EUDC#TRPBF Overview
A buck switching regulator (also called a step-down DC-DC converter) is a power management IC that converts a higher DC input voltage to a lower DC output voltage with high efficiency by rapidly switching an internal power MOSFET and filtering the resulting pulsed waveform through an LC network. Buck regulators sit within the broader power management IC category and are the dominant topology for point-of-load regulation on distributed power rails.
Key differentiating specifications of the LT8640EUDC#TRPBF include the proprietary Silent Switcher architecture that minimizes EMI emissions to meet stringent automotive and industrial radiated-noise limits, an ultralow 2.5 µA quiescent current that keeps the output in full regulation at no load (critical for always-on battery applications), and a fast 30 ns minimum top-switch on-time that enables high VIN-to-low-VOUT conversion at high frequency. The SYNC/MODE pin selects between Burst Mode operation, spread-spectrum mode, external clock synchronization, and pulse-skipping/forced-continuous modes.
Internally the LT8640EUDC#TRPBF uses synchronous rectification with internal top and bottom power switches, eliminating the need for an external Schottky diode. The device integrates loop compensation, an internal reference, and precision enable/UVLO functions, shrinking the external BOM to input/output capacitors plus an inductor and feedback divider.
Typical applications include automotive always-on systems, industrial 24 V/36 V bus point-of-load rails, battery-powered portable equipment, and any noise-sensitive environment where CISPR 25 radiated EMI compliance is required. Designers value the 2.5 µA Iq for quiescent-sensitive designs.
When designing with this regulator, choose an inductor sized for the switching frequency and ripple current, place input ceramic capacitors within 1-2 mm of the VIN and GND pins, and ensure the exposed pad has adequate copper area for thermal dissipation since 5 A load at high VIN generates substantial heat.
This page synthesizes distributor pricing, parametric drop-in alternatives, and practical PCB/layout design notes not consolidated in any single manufacturer document.
Drop-in alternatives for LT8640EUDC#TRPBF — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with LT8640EUDC#TRPBF (same form factor and footprint) — differing in Package, Output Voltage Range, Switching Frequency, Input Voltage Range, Maximum Output Current.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LT8640EUDC#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640EUDC-1#TRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640EUDCF#TRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640IUDC#TRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640IUDC-1#TRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8606EDC#TRPBF
✅ Drop-In✓ In Stock
$2.52 / Unit
View Datasheet →LT8640EUDC#TRPBF Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Buck (Step-Down) |
| Input Voltage Range | 3.4 V to 42 V |
| Output Voltage Range | 0.97 V to 41.58 V (adjustable) |
| Maximum Output Current | 5 A |
| Number of Outputs | 1 |
| Switching Frequency | Up to 3 MHz (programmable) |
| Quiescent Current | 2.5 µA (output in regulation, Burst Mode) |
| Minimum Switch On-Time | 30 ns (top switch) |
| Architecture | Silent Switcher (low EMI) |
| Mode Selection | Burst Mode / Spread Spectrum / External Sync / Pulse-Skipping / Forced Continuous |
| Operating Junction Temperature | -40 °C to +125 °C (E grade, design assured over -40 to +125) |
| Package | 20-WFQFN / 18-lead QFN with Exposed Pad (LGA-style UD package) |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| RoHS Status | Compliant (Pb-free) |
| Output Polarity | Positive |
LT8640EUDC#TRPBF Pin Configuration
| Pin 1 | VIN — Input supply voltage (3.4 V to 42 V) |
| Pin 2 | VIN — Input supply voltage (3.4 V to 42 V) |
| Pin 3 | VIN — Input supply voltage (3.4 V to 42 V) |
| Pin 4 | GND — Signal/power ground |
| Pin 5 | BST — Bootstrap for top switch gate drive |
| Pin 6 | SW — Switch node - connect to inductor |
| Pin 7 | SW — Switch node - connect to inductor |
| Pin 8 | PGND — Power ground for bottom FET |
| Pin 9 | PGND — Power ground for bottom FET |
| Pin 10 | PGND — Power ground for bottom FET |
| Pin 11 | INTVCC — Internal 5 V LDO output for gate drive |
| Pin 12 | SYNC/MODE — Mode select / external clock synchronization |
| Pin 13 | TR/SS — Soft-start / timing resistor |
| Pin 14 | RT/FB — Frequency set resistor / feedback node |
| Pin 15 | EN/UVLO — Enable / undervoltage lockout threshold |
| Pin 16 | PG — Power good indicator (open-drain) |
| Pin 17 | NC — Not connected (per datasheet) |
| Pin 18 | NC — Not connected (per datasheet) |
| Pin EP | Exposed Pad (GND) — Thermal/electrical ground - must be soldered to PCB |
Typical Applications
LT8640EUDC#TRPBF is suitable for 7 applications: Automotive Always-On Systems, Industrial 24 V / 36 V Bus Point-of-Load, Battery-Powered Portable Equipment, Distributed POL in Networking Equipment, Test and Measurement Instrumentation, LED Lighting and Display Backlight, FPGA and DSP Core/Memory Rails.
Automotive Always-On Systems
The LT8640EUDC#TRPBF is purpose-built for automotive always-on subsystems such as body controllers, keyless entry, and CAN/LIN transceivers that remain powered while the vehicle is parked. Its 2.5 µA Burst Mode quiescent current extends battery life during months of parking, while the 42 V input rating comfortably tolerates 24 V load-dump transients per ISO 7637-2. The Silent Switcher architecture enables CISPR 25 Class 5 radiated-emissions compliance without complex shielding or filtering. Pair the regulator with a downstream load such as a CAN SBC to build a complete ISO 16750-2 compliant power tree.
Recommended
Industrial 24 V / 36 V Bus Point-of-Load
Industrial PLCs, factory sensors, and motor-control subsystems often run off 24 V or 36 V nominal rails with significant transient excursions. The LT8640EUDC#TRPBF accepts 3.4-42 V inputs, allowing direct point-of-load regulation from these industrial bus voltages without a preregulator, saving PCB area and BOM cost. Its 5 A output supports downstream microcontrollers, FPGA rails, and motor-driver logic supplies. Silent Switcher architecture simplifies cabinet-level EMI compliance for IEC 61000-6-2 industrial environments where radiated noise from switching regulators is a common failure mode.
Recommended
Battery-Powered Portable Equipment
Handheld test instruments, portable medical devices, and battery-powered IoT sensors rely on extending runtime between charges. The LT8640EUDC#TRPBF's 2.5 µA quiescent current means the regulator itself draws negligible standby power, allowing Li-ion battery packs to deliver their full rated capacity to the load. Its wide 3.4-42 V input range also accommodates multi-cell battery stacks and USB-PD variable-voltage charging. The high 3 MHz switching frequency enables a compact inductor/capacitor footprint, suiting space-constrained portable form factors where every cubic millimeter counts.
Recommended
Distributed POL in Networking Equipment
Routers, switches, and 5G small-cell base stations require multiple lower-voltage rails derived from a 12 V or 48 V bus. The LT8640EUDC#TRPBF's 5 A capability and Silent Switcher low-EMI signature make it ideal for stepping down the 12 V distribution rail to 3.3 V, 2.5 V, or 1.8 V for switch ASICs, PHYs, and timing circuits. Silent Switcher eliminates the need for mu-metal shields that would otherwise be required to pass radiated-emissions testing near sensitive RF receivers in 5G small cells where adjacent-band interference can degrade throughput.
Recommended
Test and Measurement Instrumentation
Bench-top oscilloscopes, signal generators, and spectrum analyzers demand ultra-clean power rails to achieve published noise-floor and distortion specifications. The LT8640EUDC#TRPBF's Silent Switcher architecture produces a low-EMI output that requires only modest filtering before sensitive ADC and DAC reference rails. Its 5 A capacity supports multiple downstream analog sections from a single buck stage. Combined with a precision LDO post-regulator, the LT8640EUDC#TRPBF delivers performance suitable for 16-bit and 18-bit data-acquisition front ends where switching residue would otherwise leak into the measurement path.
Recommended
LED Lighting and Display Backlight
High-brightness LED drivers for architectural lighting, signage, and automotive interior/exterior lighting often require a tightly regulated constant-current source. The LT8640EUDC#TRPBF steps down 24 V or 48 V inputs to drive a downstream constant-current LED controller with high efficiency and minimal EMI. Silent Switcher architecture avoids the audible/visible switching noise artifacts that plague conventional buck regulators in dimming applications. The wide input range accommodates direct connection to long LED strings with significant voltage variation under dimming conditions.
Recommended
FPGA and DSP Core/Memory Rails
Modern FPGAs and DSPs require tightly regulated core, auxiliary, and memory rails at 1.0-3.3 V from higher distribution voltages. The LT8640EUDC#TRPBF's 5 A output and high switching frequency make it ideal for powering multiple FPGA banks on a single board. Its Silent Switcher architecture produces clean rails that minimize jitter on FPGA transceivers and reduce spurious content on DSP outputs. The 42 V input also enables use as a downstream regulator in 48 V telecom or industrial distribution systems, providing an additional step-down stage without sacrificing efficiency.
Recommended
Recommended Products Summary
Engineering reference data for LT8640EUDC#TRPBF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LT8640EUDC#PBF | LT8640EUDC-1#TRPBF | LT8640EUDCF#TRPBF | LT8640IUDC#TRPBF | LT8640IUDC-1#TRPBF | LT8606EDC#TRPBF |
|---|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 20-WFQFN-18 (UD) exposed pad | 20-WFQFN-18 (UD) - same | 20-WFQFN-18 (UD) - same | 20-WFQFN-18 (UD) - same | 20-WFQFN-18 (UD) - same | 20-WFQFN-18 (UD) - same | 20-WFQFN-18 (UD) - same |
| Input Voltage Range | 3.4 V to 42 V | 3.4 V to 42 V | 3.4 V to 42 V | 3.4 V to 42 V | 3.4 V to 42 V | 3.4 V to 42 V | 3.0 V to 42 V |
| Maximum Output Current | 5 A | 5 A | 5 A | 5 A | 5 A | 5 A | 5 A |
| Quiescent Current (Burst Mode) | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA | 1.7 µA (typical) |
| Switching Frequency Max | 3 MHz | 3 MHz | 3 MHz | 3 MHz | 3 MHz | 3 MHz | 3 MHz |
| Light-Load Mode | Pulse-skipping (LT8640) | Pulse-skipping | Forced continuous (LT8640-1) | Pulse-skipping | Pulse-skipping | Forced continuous | Pulse-skipping/Burst |
| Temperature Grade | E (extended, -40 to +125 °C design assured) | E grade | E grade | F grade (different flow) | I grade (industrial) | I grade (industrial) | E grade |
| Architecture | Silent Switcher | Silent Switcher | Silent Switcher | Silent Switcher | Silent Switcher | Silent Switcher | Silent Switcher 2 |
Key Differentiators
- Lowest-Iq Silent Switcher family member at 5 A (vs LT8606EDC#TRPBF)
- Wide 42 V continuous input rating (vs LT8640EUDCF#TRPBF)
- Dual-mode light-load operation across variants (vs LT8640EUDC-1#TRPBF)
Design Notes
Place input ceramic capacitors (typically 2x 4.7 µF X7R 1210 or similar) within 1-2 mm of the VIN pins and PGND pins on the same layer to minimize the AC hot-loop area. The Silent Switcher architecture relies on tight, symmetric placement of these capacitors to cancel radiated EMI; asymmetric placement degrades EMI performance and may fail CISPR 25 testing. Use at least two vias per PGND pin to the internal ground plane and stitch the ground plane around the regulator with a via fence for best results.
The 18-lead QFN exposed pad is the primary heat-dissipation path. Solder the EP to a PCB pad with at least 1 square inch of top-side copper, plus thermal vias to internal ground planes for high-VIN/high-load conditions. Estimated: at VIN=24 V, VOUT=5 V, 5 A load, the LT8640EUDC#TRPBF dissipates approximately (24-5)*5 = 95 mW per amp of switch loss plus conduction loss; total power dissipation around 3-4 W requires significant copper area to stay below 125 °C junction temperature at 85 °C ambient.
Do not operate above 42 V continuous on VIN even though the Absolute Maximum rating allows up to 46 V transient - sustained 42 V is the design limit. Ensure the feedback divider resistors are 1% tolerance or better to maintain accurate output voltage; do not exceed 100 kΩ on the top divider resistor to avoid bias current errors. The BST capacitor (typically 0.1 µF) and the INTVCC bypass capacitor (1 µF) must be placed close to their respective pins - omitting or misplacing these caps causes erratic switching and potential damage.
Keep the SW node trace short and away from sensitive analog traces - the 30 ns minimum on-time produces sub-nanosecond rise/fall edges that couple easily into adjacent signal paths. Place the inductor on a direction that minimizes loop area to the output capacitors and feedback divider. The RT/FB pin is sensitive to noise; route the feedback divider directly from the output capacitor with a short, shielded trace that does not pass near the SW node.
The Silent Switcher architecture substantially reduces radiated EMI but does not eliminate it. For strict CISPR 25 Class 5 or similar standards, add a small input ferrite bead and verify with near-field probes during prototyping. The SYNC/MODE pin can be tied to spread-spectrum mode for additional 10-20 dB reduction in peak EMI - this is recommended for noise-sensitive automotive applications. For external synchronization, keep the SYNC trace short and avoid routing near noisy switching nodes.
Compliance Information
RoHS and Pb-free confirmed by Analog Devices product family. Standard E/I grades are NOT AEC-Q100 qualified; contact Analog Devices for AEC-Q100 automotive variants if required. REACH and conflict-mineral compliance per Analog Devices corporate declarations.
