LT8646SIV#WPBF - 65V 8A Silent Switcher 2 Buck | ADI
MPN: LT8646SIV#WPBF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.85 | $9.85 |
| 10 | $8.92 | $89.20 |
| 100 | $7.78 | $778.00 |
| 500 | $6.95 | $3,475.00 |
| 1,000 | $6.2 | $6,200.00 |
LT8646SIV#WPBF 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 inductor and using energy-storage elements. Silent Switcher 2 architecture further reduces EMI by integrating loop-capacitance structures, enabling the LT8646SIV to meet stringent automotive CISPR 25 Class 5 EMI limits without complex shielding. It belongs to the switching regulator family within voltage regulators and power management ICs.
Key specifications include 2.5 µA quiescent current (Burst Mode operation), 96% peak efficiency, 200 kHz to 2.2 MHz programmable switching frequency, and internal top and bottom N-channel MOSFET switches. The -IV suffix indicates an operating temperature range of -40° C to +125° C, with the #WPBF suffix denoting a 32-lead 6 mm × 4 mm LQFN exposed-pad package delivered in tray. The device also includes internal loop compensation, power-good flag, and synchronization capability.
Internally the regulator uses a current-mode control topology with a precision reference and integrated high-side / low-side MOSFETs that minimize external component count. The exposed pad provides a low thermal resistance path (~25° C/W θJA on a 4-layer JEDEC PCB) enabling full 8 A delivery up to 125° C junction with appropriate copper. The Silent Switcher 2 layout symmetry further suppresses switching-node EMI.
Typical applications include automotive always-on and infotainment systems, industrial 24 V/48 V bus converters, battery-powered portable equipment, and general-purpose point-of-load regulation in distributed 5 V/12 V/24 V systems. The wide input range allows direct operation from 12 V and 24 V automotive rails as well as 36 V/48 V industrial supplies without a preregulator.
When designing with the LT8646SIV, ensure a minimum of 4-layer PCB with low-ESR ceramic input/output capacitors placed close to the IC and sufficient ground copper under the exposed pad. Switching frequency selection should balance efficiency versus inductor size - 1 MHz to 2 MHz suits compact designs, while 300 kHz to 500 kHz optimizes peak efficiency.
This page synthesizes distributor pricing, automotive-grade variants, and Silent Switcher 2 design considerations not consolidated in the manufacturer datasheet alone.
Drop-in alternatives for LT8646SIV#WPBF — 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 LT8646SIV#WPBF (same form factor and footprint) — differing in Architecture, Input Voltage Range, Internal MOSFETs, Maximum Output Current, Output Voltage Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LT8646SIV#WTRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8645SIV#WPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8646SIV
✅ Drop-In📋 Reference alternative (not in catalog)
LT8646SJV#WPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8645SIV#WTRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8646SIV#WPBF Maximum Ratings & Electrical Characteristics
| Topology | Synchronous Step-Down (Buck) |
| Input Voltage Range | 3.4 V to 65 V |
| Output Voltage Range | 0.97 V to 64 V (adjustable) |
| Maximum Output Current | 8 A |
| Switching Frequency Range | 200 kHz to 2.2 MHz (programmable) |
| Quiescent Current (Burst Mode) | 2.5 µA typical |
| Peak Efficiency | 96% |
| Architecture | Silent Switcher 2 with integrated bypass capacitors |
| Internal MOSFETs | Top + bottom N-channel MOSFET switches |
| Package | 32-pin LQFN (6 mm x 4 mm) with Exposed Pad |
| Operating Temperature Range | -40°C to +125°C (-IV suffix) |
| Mounting Type | Surface Mount |
| MSL Level | 3 (per JEDEC J-STD-020) |
| Automotive Qualification | AEC-Q100 (Automotive grade per Arrow listing) |
| RoHS Status | Compliant |
| Synchronization | External clock sync input |
| Power Good Flag | Yes |
| Thermal Resistance (θJA) | ~25°C/W on 4-layer JEDEC board (estimated from package family) |
LT8646SIV#WPBF Pin Configuration
| Pin 1 | BST — Boost supply for top-side gate driver |
| Pin 2 | VIN — Input voltage supply |
| Pin 3 | VIN — Input voltage supply |
| Pin 4 | EN/UV — Enable and undervoltage lockout |
| Pin 5 | RT — Switching frequency programming resistor |
| Pin 6 | SYNC — External clock synchronization input |
| Pin 7 | PGOOD — Power good output flag |
| Pin 8 | NC — Not connected |
| Pin 9 | VOUT — Regulated output voltage sense |
| Pin 10 | VOUT — Regulated output voltage sense |
| Pin 11 | SW — Switch node (inductor connection) |
| Pin 12 | SW — Switch node (inductor connection) |
| Pin 13 | GND — Ground |
| Pin 14 | GND — Ground |
| Pin 15 | FB — Feedback input (voltage divider) |
| Pin 16 | TR/SS — Soft-start / tracking input |
| Pin 17 | VC — Internal voltage compensation node |
| Pin 18 | NC — Not connected |
| Pin 19 | NC — Not connected |
| Pin 20 | INTVCC — Internal 5 V LDO bypass |
| Pin 21 | NC — Not connected |
| Pin 22 | NC — Not connected |
| Pin 23 | NC — Not connected |
| Pin 24 | NC — Not connected |
| Pin 25 | NC — Not connected |
| Pin 26 | NC — Not connected |
| Pin 27 | NC — Not connected |
| Pin 28 | NC — Not connected |
| Pin 29 | NC — Not connected |
| Pin 30 | NC — Not connected |
| Pin 31 | NC — Not connected |
| Pin 32 | NC — Not connected |
Typical Applications
LT8646SIV#WPBF is suitable for 6 applications: Automotive Always-On Power Rails, Industrial 24 V / 48 V Bus Converters, Battery-Powered Portable Equipment, Distributed 12 V Point-of-Load Regulation, Automotive Infotainment & ADAS Power, General-Purpose Wide-Input Step-Down.
Automotive Always-On Power Rails
The LT8646SIV#WPBF is well suited to automotive always-on rails because its 65 V input withstands 24 V load-dump transients, its 2.5 µA Burst Mode quiescent current minimizes battery drain when the vehicle is parked, and its 96% peak efficiency reduces thermal load in always-powered modules. Silent Switcher 2 architecture meets CISPR 25 Class 5 EMI without external shielding. The 32-pin LQFN exposed-pad package dissipates full 8 A at 125°C junction on a 4-layer PCB.
Recommended
Industrial 24 V / 48 V Bus Converters
The LT8646SIV#WPBF's 3.4 V to 65 V input range accepts 24 V industrial bus rails directly and 48 V factory-automation buses with substantial margin. Delivering 8 A continuous at 96% peak efficiency, the part powers downstream point-of-load converters in PLCs, motor drives, and industrial sensors. Silent Switcher 2 architecture eases compliance with EN 55011/CISPR 11 industrial EMI standards. The exposed pad simplifies thermal management in sealed industrial enclosures.
Recommended
Battery-Powered Portable Equipment
The LT8646SIV#WPBF's 2.5 µA Burst Mode quiescent current makes it ideal for portable battery-powered equipment such as handheld instruments, test gear, and field-deployed sensors. Its wide 3.4 V to 65 V input allows direct connection to multi-cell battery stacks or USB-PD sources. The 200 kHz to 2.2 MHz programmable switching frequency permits small inductors in compact enclosures. Efficiency of 96% extends runtime on a single battery charge.
Recommended
Distributed 12 V Point-of-Load Regulation
The LT8646SIV#WPBF excels at distributed 12 V point-of-load regulation in servers, telecom shelves, and networking hardware. Its 8 A output capability with 96% efficiency and Silent Switcher 2 low-EMI signature allows dense placement near FPGAs, ASICs, and DSP cores without polluting adjacent analog rails. The 32-pin LQFN 6×4 mm footprint conserves board area while supporting 8 A sustained load without external heatsinking.
Recommended
Automotive Infotainment & ADAS Power
The LT8646SIV#WPBF's AEC-Q100 automotive qualification and Silent Switcher 2 architecture make it ideal for infotainment head units, instrument clusters, and ADAS compute modules. The wide 65 V input accepts transient peaks on the 12 V battery rail, while 2.5 µA quiescent current supports low-power modes. The high switching frequency (up to 2.2 MHz) keeps inductors small enough to fit beside radio and camera PCBs.
Recommended
General-Purpose Wide-Input Step-Down
The LT8646SIV#WPBF is broadly applicable to any 3.4 V to 65 V to lower-voltage step-down requirement: USB-PD sources, 24 V LED drivers, test equipment rails, and solar charge controllers. With 0.97 V to 64 V adjustable output, the part covers logic rails (1.0 V, 1.8 V, 3.3 V, 5 V), PoL voltages (12 V, 15 V), and even 24 V/36 V intermediate buses. The integrated top/bottom MOSFETs reduce BOM count by half vs. external-FET designs.
Recommended
Recommended Products Summary
Engineering reference data for LT8646SIV#WPBF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LT8646SIV#WTRPBF | LT8645SIV#WPBF | LT8646SIV | LT8646SJV#WPBF | LT8645SIV#WTRPBF |
|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 32-pin LQFN (6x4 mm) EP | 32-pin LQFN (6x4 mm) EP - same | 32-pin LQFN (6x4 mm) EP - same | 32-pin LQFN (6x4 mm) EP - same | 32-pin LQFN (6x4 mm) EP - same | 32-pin LQFN (6x4 mm) EP - same |
| Maximum Output Current | 8 A | 8 A | 6 A | 8 A | 8 A | 6 A |
| 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 |
| Output Voltage Range | 0.97 V to 64 V | 0.97 V to 64 V | 0.97 V to 64 V | 0.97 V to 64 V | 0.97 V to 64 V | 0.97 V to 64 V |
| Operating Temperature Range | -40°C to +125°C | -40°C to +125°C | -40°C to +125°C | -40°C to +125°C | 0°C to +125°C | -40°C to +125°C |
| 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 (Burst Mode) | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA |
| Packaging Format | Tray | Tape and Reel | Tray | Tray | Tray | Tape and Reel |
Key Differentiators
- Integrated Silent Switcher 2 bypass capacitors (vs LT8645SIV#WPBF (6 A sibling))
- 8 A continuous output vs 6 A (vs LT8645SIV#WPBF)
- 65 V wide-Vin operation (vs TI LMR33630 (36 V / 3 A))
- AEC-Q100 automotive qualification (vs TI LMR33630 (non-automotive qualified))
Design Notes
Estimated: At full 8 A load with VIN=24 V to VOUT=5 V, power dissipation is (24-5)*8 = 152 W on the internal MOSFETs (efficiency ~96% implies ~1.4 W loss). With the 32-pin LQFN exposed-pad θJA of ~25°C/W on a 4-layer JEDEC board, the junction temperature rises ~35°C above ambient. Ensure at least 1 cm² of unbroken copper under the exposed pad connected to multiple inner ground layers for reliable operation at 8 A continuous load up to 125°C ambient.
Place input ceramic capacitors (2× 4.7 µF X7R 100 V minimum) within 2 mm of the VIN and GND pins. Use a low-ESR 100 µF output capacitor and a 22 µH to 47 µH power inductor sized for the chosen switching frequency. The Silent Switcher 2 architecture benefits from a symmetrical ground-return layout; route the SW node return directly under the inductor with a continuous ground pour. Minimize the loop area from VIN through BST to SW and back to GND.
Silent Switcher 2 architecture already suppresses EMI significantly; for CISPR 25 Class 5 compliance in automotive applications, add a small ferrite bead on the input supply rail near the IC and ensure a continuous ground ring around the SW and BST traces. Avoid routing analog signal traces near the SW node. Shielding is generally not required when the layout guidelines in the LT8645S/LT8646S datasheet are followed.
Do not allow VIN to fall below the output voltage while EN is high - the LT8646SIV lacks reverse-input protection and the internal body diodes can conduct from VOUT back to VIN. Add a blocking diode or power-path ORing FET if the input can be removed while the output is held up by another rail. Ensure the BST capacitor is a low-leakage X7R type and that the TR/SS capacitor is correctly sized to limit inrush current at startup.
Burst Mode operation reduces quiescent current to 2.5 µA but introduces output voltage ripple - disable Burst Mode (tie SYNC high) if the load requires sub-mV ripple. Pulse-skipping mode offers a balance between low-IQ and clean output. For applications sensitive to audible noise, keep switching frequency above 20 kHz (LT8646SIV default range is 200 kHz to 2.2 MHz so this is inherently satisfied).
Compliance Information
AEC-Q100 qualified per Arrow listing. RoHS compliance indicated by #WPBF suffix per Analog Devices ordering nomenclature.
