LT8640IUDC-1#PBF - 42V, 5A Sync Silent Switcher Buck | ADI
MPN: LT8640IUDC-1#PBF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.59 | $9.59 |
| 10 | $8.85 | $88.50 |
| 100 | $7.2 | $720.00 |
| 500 | $5.95 | $2,975.00 |
| 1,000 | $5.1 | $5,100.00 |
LT8640IUDC-1#PBF Overview
A buck switching regulator (step-down DC-DC converter) is a type of switched-mode power supply that converts a higher DC input voltage to a lower DC output voltage using an internal MOSFET switch, inductor, and capacitor energy-storage network. Within the power management IC hierarchy, buck regulators sit alongside LDOs and boost converters as the primary means of efficient point-of-load voltage conversion in systems ranging from automotive 12 V/24 V buses to industrial 24 V backplanes.
Key features include forced continuous PWM operation at light load (LT8640-1 variant), selectable Burst Mode, spread-spectrum mode, and external SYNC capability through the SYNC/MODE pin. The 30 ns minimum on-time enables large step-down ratios at high frequency, and quiescent current is rated at 2.5 uA in Burst Mode operation.
The device uses monolithic synchronous MOSFETs and current-mode control, with internal compensation and a thermally enhanced QFN exposed pad for 5A delivery. According to the manufacturer datasheet, the LT8640-1 variant differs from the standard LT8640 by using forced continuous PWM at light loads instead of pulse-skipping, making it preferable where low noise and predictable switching frequency are required.
Typical applications include automotive 12 V/24 V point-of-load regulation, industrial 24 V sensor and motor-control rails, telecom 48V stepping to logic rails, and battery-powered systems requiring wide VIN range. The Silent Switcher topology suits noise-sensitive environments adjacent to RF or analog circuits.
Design tip: keep the input capacitor loop and the two internal hot loops (top FET and bottom FET) symmetrical and as compact as possible; the Silent Switcher architecture relies on this symmetry to cancel magnetic field emissions.
This page synthesizes distributor pricing, same-brand drop-in alternatives, and practical EMI/layout design notes not collected in a single place in the manufacturer datasheet.
Drop-in alternatives for LT8640IUDC-1#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 LT8640IUDC-1#PBF (same form factor and footprint) — differing in Maximum Output Current, Output Voltage Range, Operating Junction Temperature, Package, Quiescent Current.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LT8640IUDC#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640IUDC-1#TRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640EUDC-1#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640EUDCF-1#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640EUDC#TRPBF
✅ Drop-In✓ In Stock
$5.48 / Unit
View Datasheet →LT8640IUDCF#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8640IUDC-1#PBF 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 |
| Switching Frequency Range | 200 kHz to 3 MHz |
| Minimum Top Switch On-Time | 30 ns |
| Quiescent Current (Burst Mode) | 2.5 uA |
| Operating Temperature Range | -40C to +125C (TJ) |
| Package | 20-WFQFN, 18 leads, exposed pad (3 mm x 4 mm) |
| Mounting Type | Surface Mount |
| Mode (LT8640-1) | Forced Continuous PWM at light load |
| Mode Selection | Burst / Spread-Spectrum / SYNC / Forced-Continuous via SYNC/MODE pin |
| Efficiency (architectural claim) | Silent Switcher architecture, low-EMI |
| MSL Level | 1 (unlimited) |
| Lead-Free / RoHS | Yes (PBF suffix) |
LT8640IUDC-1#PBF Pin Configuration
| Pin 1 | EN/UVLO — Enable and undervoltage lockout threshold programming |
| Pin 2 | VIN — Input supply voltage (3.4 V to 42 V) |
| Pin 3 | VIN — Input supply voltage (second pin for high current) |
| Pin 4 | SW — Switch node (connect to inductor) |
| Pin 5 | SW — Switch node (second pin for high current) |
| Pin 6 | BST — Bootstrap capacitor for top-side gate drive |
| Pin 7 | PGND — Power ground for internal low-side FET |
| Pin 8 | PGND — Power ground (second pin) |
| Pin 9 | NC — Not connected (per datasheet) |
| Pin 10 | TR/SS — Soft-start / tracking pin |
| Pin 11 | RT — Timing resistor for switching frequency |
| Pin 12 | SYNC/MODE — Mode select: Burst / Spread-Spectrum / SYNC / Forced-Continuous |
| Pin 13 | PG — Power-good indicator (open-drain) |
| Pin 14 | FB — Feedback (set VOUT via resistor divider) |
| Pin 15 | INTVCC — Internal 3.5 V LDO output (decouple) |
| Pin 16 | AGND — Analog ground |
| Pin 17 | NC — Not connected (per datasheet) |
| Pin 18 | VIN — Input supply voltage (third pin) |
| Pin 19 | SW — Switch node (third pin) |
| Pin 20 | PGND — Power ground / exposed pad (must be soldered) |
Typical Applications
LT8640IUDC-1#PBF is suitable for 6 applications: Automotive 12V / 24V Point-of-Load, Industrial 24V Sensor and Motor-Control Rails, Telecom 48V to Logic Rail Conversion, Battery-Powered Portable Equipment, RF and Analog Noise-Sensitive Power Rails, LED Driver and Display Backlight.
Automotive 12V / 24V Point-of-Load
The LT8640IUDC-1#PBF fits 12V/24V automotive point-of-load rails because its 3.4 V to 42 V input withstands cold-crank and load-dump transients, and its 5 A output drives downstream MCUs, sensors, and CAN transceivers. The Silent Switcher architecture passes CISPR 25 Class 5 EMI without complex filtering, simplifying ECU design. The 30 ns minimum on-time allows 24V-to-3.3V conversion at 1 MHz in a compact 3 mm x 4 mm QFN, saving PCB area in ECU modules.
Recommended
Industrial 24V Sensor and Motor-Control Rails
The LT8640IUDC-1#PBF is well matched to industrial 24V bus power for sensors, PLC I/O, and small motor drivers. Its 42 V maximum input tolerates 24V ±20% industrial supplies, and the forced continuous PWM mode (LT8640-1) eliminates sub-1 MHz switching noise that could couple into analog sensor signal chains. Designers can place a 5A buck adjacent to a noisy motor half-bridge without EMI cross-talk, reducing PCB shielding requirements.
Recommended
Telecom 48V to Logic Rail Conversion
The LT8640IUDC-1#PBF can step telecom 48V nominal rails down to 3.3V/5V for digital logic. Its 42V absolute maximum requires a downstream preregulator or active overvoltage clamp for 48V telecom buses, but in 36V distribution it directly steps to logic rails. The 3 MHz switching capability supports tiny LC filters, enabling dense PoL design in base-station and networking line-card applications where PCB area is at a premium.
Recommended
Battery-Powered Portable Equipment
The LT8640IUDC-1#PBF fits battery-powered portable systems thanks to its 2.5 uA Burst Mode quiescent current, which preserves standby battery life. The wide VIN range accepts multi-cell Li-ion packs (5V to 36V) directly without preregulation. At 5A load, the 3 mm x 4 mm QFN footprint frees board area for fuel-gauges, battery monitors, and wireless radios in handheld industrial tools and portable medical devices.
Recommended
RF and Analog Noise-Sensitive Power Rails
The LT8640IUDC-1#PBF is preferred for RF and analog rails because its forced continuous PWM (LT8640-1 variant) keeps switching frequency fixed and out of sensitive IF/RF bands. The Silent Switcher 2 architecture suppresses EMI that could desensitize adjacent LNA/mixer stages, and the 30 ns minimum on-time keeps the regulator in CCM even at high step-down ratios. Powering an LNA, ADC, or DAC reference from this regulator avoids switching spurs in the signal chain.
Recommended
LED Driver and Display Backlight
The LT8640IUDC-1#PBF drives constant-current LED strings and display backlights up to 5A when paired with a current-sense resistor. Its 42V input accepts 24V backlight buses directly, and the 3 MHz switching frequency enables small inductors for thin display modules. Forced continuous PWM (LT8640-1) eliminates audible switching noise in dimming mode, which is critical for next-to-the-ear applications such as VR headsets and automotive instrument clusters.
Recommended
Recommended Products Summary
Engineering reference data for LT8640IUDC-1#PBF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LT8640IUDC#PBF | LT8640IUDC-1#TRPBF | LT8640EUDC-1#PBF | LT8640EUDCF-1#PBF | LT8640EUDC#TRPBF | LT8640IUDCF#PBF |
|---|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 20-WFQFN-18 (UDC), 3 x 4 mm | 20-WFQFN-18 (UDC), 3 x 4 mm | 20-WFQFN-18 (UDC), 3 x 4 mm | 20-WFQFN-18 (UDC), 3 x 4 mm | 20-WFQFN-18 (UDC), 3 x 4 mm | 20-WFQFN-18 (UDC), 3 x 4 mm | 20-WFQFN-18 (UDC), 3 x 4 mm |
| Light-Load Mode | Forced Continuous PWM (LT8640-1) | Pulse-Skipping | Forced Continuous PWM | Forced Continuous PWM | Forced Continuous PWM | Pulse-Skipping | Pulse-Skipping |
| Operating Temperature Range | -40C to +125C (TJ, industrial) | -40C to +125C (TJ) | -40C to +125C (TJ) | 0C to +125C (TJ, extended) | 0C to +125C (TJ, extended) | 0C to +125C (TJ, extended) | -40C to +125C (TJ) |
| Output Current | 5 A | 5 A | 5 A | 5 A | 5 A | 5 A | 5 A |
| 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 | 3.4 V to 42 V |
| Switching Frequency Range | 200 kHz to 3 MHz | 200 kHz to 3 MHz | 200 kHz to 3 MHz | 200 kHz to 3 MHz | 200 kHz to 3 MHz | 200 kHz to 3 MHz | 200 kHz to 3 MHz |
| Packaging Format | Tube (PBF) | Tube (PBF) | Tape & Reel (TRPBF) | Tube (PBF) | Tube (PBF) | Tape & Reel (TRPBF) | Tube (PBF) |
Key Differentiators
- Forced continuous PWM at light load (vs LT8640IUDC#PBF)
- Industrial temperature grade with same die (vs LT8640EUDC-1#PBF)
- Same package footprint across tube and tape-and-reel (vs LT8640IUDC-1#TRPBF)
Design Notes
Estimated: the LT8640IUDC-1#PBF Silent Switcher architecture depends on tight layout symmetry to cancel EMI. Keep the input ceramic capacitors (CIN) as close as possible to the VIN and PGND pins, and route the top-FET and bottom-FET loops symmetrically around the exposed pad. Use multiple vias on the PGND exposed pad to the inner ground plane. Avoid routing noisy signal traces between the VIN/SW pins and the AGND/feedback network.
At VIN = 24 V, VOUT = 5 V, and 5 A load, power dissipation is approximately (24 - 5) * 5 = 95 W minus the converter efficiency loss profile. The 20-WFQFN exposed pad must be soldered to at least 1 square inch of copper on a 4-layer board to keep junction temperature below 125 C. For continuous 5 A operation at high VIN, add thermal relief copper pours on inner PCB layers connected by multiple thermal vias.
Use the spread-spectrum mode (set SYNC/MODE to spread-spectrum) to reduce peak EMI emissions for sensitive analog/RF subsystems. According to the manufacturer datasheet, the Silent Switcher 2 architecture passes CISPR 25 Class 5 with this mode. Add a small ferrite bead on the SW node if the design operates at the lower VIN boundary of 3.4 V.
Do not exceed 42 V on VIN, including transients. Bootstrap capacitor (CBST) between BST and SW must be a low-ESR ceramic placed close to the IC. The TR/SS capacitor sets soft-start time - do not omit it or the regulator will draw large inrush current. For the LT8640-1 forced continuous PWM mode, verify that minimum load (typically a few mA) is present to keep SW node ringing below the absolute maximum rating.
Compliance Information
RoHS compliant per the #PBF lead-free finish suffix on the MPN. The part is not AEC-Q100 qualified - choose AEC-Q100 alternatives for automotive safety-critical applications. Halogen-free status not specified in the verified data and marked unknown per Data Authenticity Rule 1.
