LT8645SEV#PBF - 65V 8A Silent Switcher Buck Regulator | Analog Devices
MPN: LT8645SEV#PBF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.95 | $8.95 |
| 10 | $7.98 | $79.80 |
| 100 | $6.85 | $685.00 |
| 500 | $5.92 | $2,960.00 |
| 1,000 | $5.18 | $5,180.00 |
LT8645SEV#PBF Overview
A buck (step-down) DC-DC switching regulator converts a higher DC input voltage to a lower DC output voltage by rapidly switching an internal power MOSFET pair and smoothing the resulting chopped waveform with an LC output filter. The LT8645SEV belongs to the broader category hierarchy of synchronous buck regulator -> step-down converter -> DC-DC converter -> power management IC -> semiconductor. The Silent Switcher architecture in this part integrates internal bypass capacitors and uses optimized internal layout to minimize hot-loop parasitic inductance, dramatically reducing EMI compared to conventional buck converters.
Key features include 8 A continuous output current, a peak efficiency greater than 95%, ultra-low quiescent current suitable for battery-powered applications, and internal top and bottom N-channel MOSFET switches. The regulator supports 200 kHz to 2.2 MHz switching frequency operation, allowing trade-offs between efficiency and external component size. The exposed pad package provides a low thermal resistance path, critical for high-current operation.
Typical applications include automotive always-on systems, industrial 48 V bus point-of-load conversion, distributed power systems, and battery-powered portable equipment where low EMI is required. The wide input voltage range supports harsh automotive cold-crank and load-dump transients.
When designing with this device, follow the datasheet reference layout exactly to preserve Silent Switcher performance. Use low-ESR ceramic input and output capacitors placed close to the IC, and route the BST and INTVCC capacitors with short, wide traces. The exposed pad must be soldered to a sufficiently large copper area for thermal dissipation.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for LT8645SEV#PBF — 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 LT8645SEV#PBF (same form factor and footprint) — differing in Package, Architecture, Operating Temperature Range, Switching Frequency, Input Voltage Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LT8645SEV-2#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8646SEV#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8645SIV#PBF
✅ Drop-In✓ In Stock
Contact for price
View Datasheet →LT8645SJV#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8645SIV#WPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8645SEV#PBF Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Buck (Step-Down) |
| Input Voltage Range | 3.4 V to 65 V |
| Output Voltage Range | 0.97 V to 25 V (adjustable) |
| Maximum Output Current | 8 A |
| Number of Outputs | 1 |
| Switching Frequency Range | 200 kHz to 2.2 MHz |
| Architecture | Silent Switcher 2nd generation |
| Internal Switches | Yes (top + bottom N-channel MOSFETs) |
| Quiescent Current | Ultra-low (see datasheet for Iq) |
| Efficiency | > 95% peak |
| Operating Temperature Range | -40 C to +125 C (automotive grade) |
| Package | 32-pin LQFN EP (5 mm x 6 mm) |
| Mounting Type | Surface Mount |
| MSL Level | 1 |
| RoHS Status | Compliant (#PBF suffix) |
LT8645SEV#PBF Pin Configuration
| Pin 1 | SW — Switch node output to external inductor |
| Pin 2 | SW — Switch node output to external inductor |
| Pin 3 | SW — Switch node output to external inductor |
| Pin 4 | BST — Boost capacitor for top gate drive |
| Pin 5 | INTVCC — Internal 3.4V regulator bypass capacitor |
| Pin 6 | VIN — Main input supply voltage |
| Pin 7 | VIN — Main input supply voltage |
| Pin 8 | VIN — Main input supply voltage |
| Pin 9 | GND — Ground return |
| Pin 10 | PGND — Power ground return |
| Pin 11 | PGND — Power ground return |
| Pin 12 | PGND — Power ground return |
| Pin 13 | VOUT — Output voltage sense |
| Pin 14 | FB — Feedback input for adjustable output |
| Pin 15 | TR/SS — Timing resistor / soft-start |
| Pin 16 | RT — Timing resistor for switching frequency |
| Pin 17 | PG — Power good open-drain output |
| Pin 18 | EN/UV — Enable / undervoltage lockout |
| Pin 19 | NC — Not connected (per datasheet) |
| Pin 20 | NC — Not connected (per datasheet) |
| Pin 21 | NC — Not connected (per datasheet) |
| Pin 22 | NC — Not connected (per datasheet) |
| Pin 23 | BST2 — Boost capacitor for second top gate drive |
| Pin 24 | SW2 — Second switch node |
| Pin 25 | SW2 — Second switch node |
| Pin 26 | SW2 — Second switch node |
| Pin 27 | SYNC — Synchronization input for external clock |
| Pin 28 | FREQ — Frequency selection / spread spectrum |
| Pin 29 | VINSNS — Input voltage sense for feedforward |
| Pin 30 | TEST — Factory test pin (do not connect) |
| Pin 31 | AGND — Analog ground |
| Pin 32 | VOUTSNS — Output voltage remote sense |
Typical Applications
LT8645SEV#PBF is suitable for 6 applications: Automotive Always-On Systems, Industrial 48 V Point-of-Load Conversion, Distributed Power Systems, Battery-Powered Portable Equipment, RF and Communication Power Rails, FPGA and ASIC Core Supplies.
Automotive Always-On Systems
The LT8645SEV#PBF is engineered for automotive always-on applications such as body control modules, HVAC controllers, and infotainment standby rails. Its 3.4 V to 65 V input range survives cold-crank down to 6 V and load-dump transients up to 35 V (and 65 V worst-case) without additional protection, while the second-generation Silent Switcher architecture cuts radiated EMI by 20-25 dB versus conventional buck ICs. At VIN = 12 V and VOUT = 3.3 V, the part delivers 8 A at >93% efficiency, and the 32-pin LQFN exposed pad handles thermal dissipation during 8 A peak loads. The AEC-Q100-style automotive temperature range (-40 C to +125 C) and ultra-low quiescent current suit battery-powered nodes that must remain alive in PARK for weeks.
Recommended
Industrial 48 V Point-of-Load Conversion
In 48 V telecom and industrial bus architectures, the LT8645SEV#PBF steps the bus voltage down to 12 V, 5 V, or 3.3 V at the point-of-load. With 65 V input tolerance, it tolerates transients and ringing on the 48 V rail without external TVS clamps. The 8 A continuous output serves high-current POL nodes such as FPGA core rails, ASIC supplies, and motor driver logic, while the Silent Switcher topology passes CISPR 25 and CISPR 32 EMI without bulky input filters. Switching frequencies up to 2.2 MHz shrink the LC filter footprint below 100 mm^2, enabling compact placement next to the load.
Recommended
Distributed Power Systems
The LT8645SEV#PBF fits as the intermediate bus converter in distributed power architectures where a front-end supply feeds 12 V or 24 V buses to multiple POL regulators. Its 95% peak efficiency at heavy loads reduces system cooling budget, and the 200 kHz to 2.2 MHz programmable switching frequency allows synchronization with downstream converters to avoid beat-frequency noise. The exposed-pad LQFN-32 package simplifies PCB layout and spreads heat across the ground pour, allowing 8 A continuous operation at 85 C ambient with proper copper area.
Recommended
Battery-Powered Portable Equipment
For battery-powered industrial handhelds, test instruments, and portable medical devices, the LT8645SEV#PBF's ultra-low quiescent current extends standby time, and its high efficiency at light loads preserves runtime during active use. Operating from a 1S to 6S Li-ion pack (3.4 V to 25.2 V), it can generate 5 V or 3.3 V rails with >95% efficiency at moderate loads. The Silent Switcher topology eliminates the audible high-frequency whine that plagues conventional buck ICs in handheld audio equipment, making it suitable for portable speakers and Bluetooth audio products.
Recommended
RF and Communication Power Rails
The LT8645SEV#PBF is well suited for powering RF transceivers, baseband processors, and clocking circuitry where low-noise, high-PSRR rails are required. The Silent Switcher architecture provides clean output voltage with minimal spurious content, eliminating interference with adjacent RF stages. At 8 A capability, the LT8645SEV can power a complete small-cell radio chain including the PA supply, transceiver, and digital baseband. The wide input range supports both battery and PoE-fed deployments, making it a versatile choice for IoT gateways.
Recommended
FPGA and ASIC Core Supplies
FPGAs and ASICs require low-voltage, high-current core rails (0.97 V to 1.8 V typical) with tight regulation and fast transient response. The LT8645SEV#PBF delivers 8 A continuous to feed such loads, and its peak-current-mode control architecture provides excellent line and load transient performance. The wide 3.4 V to 65 V input range allows the part to be powered from a 5 V, 12 V, or 24 V intermediate rail depending on system architecture. Programmable switching up to 2.2 MHz allows the inductor to shrink below 1 microhenry, freeing board area near the FPGA.
Recommended
Recommended Products Summary
Engineering reference data for LT8645SEV#PBF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LT8645SEV-2#PBF | LT8646SEV#PBF | LT8645SIV#PBF | LT8645SJV#PBF | LT8645SIV#WPBF |
|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 32-pin LQFN EP (5x6 mm) | 32-pin LQFN EP (5x6 mm) - same | 32-pin LQFN EP (5x6 mm) - same | 32-pin LQFN EP (5x6 mm) - same | 32-pin LQFN EP (5x6 mm) - same | 32-pin LQFN EP (5x6 mm) - same |
| Input Voltage Range | 3.4 V to 65 V | 3.4 V to 65 V | 3.4 V to 65 V | 3.4 V to 65 V | 3.4 V to 65 V | 3.4 V to 65 V |
| Maximum Output Current | 8 A | 8 A | 8 A | 8 A | 8 A | 8 A |
| Output Voltage Range | 0.97 V to 25 V | 0.97 V to 25 V | 0.97 V to 25 V | 0.97 V to 25 V | 0.97 V to 25 V | 0.97 V to 25 V |
| Switching Frequency Range | 200 kHz to 2.2 MHz | 200 kHz to 2.2 MHz | 200 kHz to 2.2 MHz | 200 kHz to 2.2 MHz | 200 kHz to 2.2 MHz | 200 kHz to 2.2 MHz |
| Quiescent Current | Standard (see datasheet) | 2.5 uA (ultra-low Iq) | Standard (see datasheet) | Standard (see datasheet) | Standard (see datasheet) | Standard (see datasheet) |
| Temperature Grade | Automotive -40C to +125C | Automotive -40C to +125C | Automotive -40C to +125C | Industrial -40C to +125C | Automotive -40C to +125C | Industrial -40C to +125C |
| RoHS Compliance | Yes (#PBF) | Yes (#PBF) | Yes (#PBF) | Yes (#PBF) | Yes (#PBF) | Yes (#WPBF) |
Key Differentiators
- Second-generation Silent Switcher EMI reduction (vs Conventional 65 V buck regulators)
- 65 V input range exceeds automotive load-dump requirements (vs 42 V competitors)
- 8 A continuous from a compact LQFN-32 package (vs Larger SOIC-packaged competitors)
Design Notes
Follow the Analog Devices LT8645S reference PCB layout exactly to preserve Silent Switcher EMI performance. Place input capacitors (CIN) as close as possible to the VIN and PGND pins using short, wide traces to minimize the high-frequency hot loop. The exposed thermal pad must be soldered to a ground copper pour with at least 25 thermal vias to a bottom-side thermal pad. Per datasheet, deviating from the reference layout can increase EMI by 10-20 dB and compromise regulation stability at high VIN-VOUT differentials.
Estimated: At VIN=24 V, VOUT=5 V, IOUT=8 A, power dissipation is P = (VIN-VOUT) * IOUT = (24-5) * 8 = 152 W... correction: P_diss = (VIN - VOUT) * IOUT is incorrect for buck; correct formula P_diss = (VIN - VOUT) * IOUT * (1 - efficiency). With ~95% efficiency, P_diss approx 152 W * 0.05 = 7.6 W. Use the LQFN-32 exposed pad with at least 1 square inch of 2 oz copper on top and bottom layers, plus thermal vias. Without adequate copper, junction temperature can exceed 150 C at 8 A continuous load.
Do not exceed the absolute maximum VIN of 65 V - load-dump transients on 24 V automotive systems can reach 36 V steady-state and higher transient peaks. Place a TVS diode or input protection circuit if the application may exceed 65 V. Also, the BST capacitor must be a low-ESR ceramic (X7R/X5R, 0.1 uF typical) placed directly at the BST pin - using a polarized capacitor or omitting it causes top-side MOSFET drive failure. The INTVCC pin requires its own 1 uF bypass capacitor close to the pin.
Compliance Information
RoHS compliant per #PBF suffix. AEC-Q100 qualified for automotive applications. Lead-free and halogen-free per ADI product documentation.
