LT8640IUDC-1 - 42V, 5A Sync Buck Silent Switcher | Analog Devices
MPN: LT8640IUDC-1 ✓ نشطLT8640IUDC-1 نظرة عامة
An LDO (low-dropout linear regulator) and buck (step-down) DC-DC converter are two distinct topologies in the power-management IC family tree. Both belong to the broader category of voltage regulators, but an LDO uses a series pass element to dissipate VIN-VOUT as heat, while a buck converter switches an inductor to deliver power with much higher efficiency. The LT8640IUDC-1 is a monolithic synchronous buck converter that integrates the high-side and low-side MOSFETs, eliminating the external Schottky diode typical of older buck designs and reducing BOM count.
Key features of the LT8640IUDC-1 include Analog Devices' Silent Switcher architecture, which minimizes EMI emissions by containing the high-dV/dt switching node loops, enabling compliance with CISPR 224 likely-class radiated and conducted limits without a shield. It delivers 5A continuous output at high efficiency, has a 30ns minimum on-time that allows high-frequency step-down at high VIN to low VOUT, and offers Burst Mode operation, spread-spectrum modulation, and external clock synchronization through the SYNC/MODE pin. The -1 suffix designates forced-continuous operation, in contrast to the standard LT8640 which uses pulse-skipping at light loads.
The LT8640IUDC-1 is particularly well-suited to automotive and industrial applications where the input rail can see load-dump transients up to 42V and where EMI compliance is critical. Typical use cases include 24V industrial sensor rails, automotive infotainment, point-of-load supplies downstream of a 12V or 24V bus, and battery-powered systems where 2.5µA quiescent current dramatically extends standby life. A 10µF minimum output capacitor with low ESR is required to keep the control loop stable.
When designing with this part, ensure the input capacitor is ceramic and placed close to the VIN and PGND pads, and that the exposed pad is soldered to a sufficiently large copper pour for thermal dissipation - at 5A load with large VIN-VOUT, the LT8640IUDC-1 can dissipate several watts. This page synthesizes distributor pricing, drop-in alternatives including the AEC-Q100 automotive-grade variant and the 3.5A 65V LT8641, and practical design notes not found in the manufacturer datasheet.
بدائل مباشرة لـ LT8640IUDC-1 — نفس الحزمة، متوافق دبوس بدبوس. تُستثنى القطع ذات الحزم المختلفة التي تتطلب تعديل PCB.
الطرازات في هذه السلسلة
طرازات من نفس السلسلة متوافقة تمامًا مع LT8640IUDC-1 (نفس عامل الشكل والبصمة) — يختلف في Architecture, Operating Junction Temperature, Package, Quiescent Current, RoHS Status.
LT8640IUDC#PBF
✅ بديل مباشر📋 بديل مرجعي (غير موجود في الكتالوج)
LT8640IUDC-1#TRPBF
✅ بديل مباشر📋 بديل مرجعي (غير موجود في الكتالوج)
LT8640EUDC#TRPBF
✅ بديل مباشرتواصل لمعرفة السعر
عرض ورقة البيانات ←LT8640EUDC-1#TRPBF
✅ بديل مباشر📋 بديل مرجعي (غير موجود في الكتالوج)
LT8641HUDC#PBF
✅ بديل مباشر📋 بديل مرجعي (غير موجود في الكتالوج)
LT8640IUDC-1 الحدود القصوى والخصائص الكهربائية
| البنية الطوبولوجية | Synchronous Buck (Step-Down) |
| نطاق جهد الدخل | 3.4 V to 42 V |
| نطاق جهد الخرج | 0.97 V to 41.58 V (adjustable) |
| أقصى تيار خرج | 5 A |
| تردد التبديل | 200 kHz to 3 MHz (programmable) |
| تيار السكون | 2.5 µA (Burst Mode, output in regulation) |
| Architecture | Silent Switcher (integrated MOSFETs) |
| Minimum Top Switch On-Time | 30 ns |
| Light-Load Operation | Forced continuous mode (LT8640-1) |
| SYNC/MODE Pin Functions | Burst Mode, spread spectrum, external SYNC, forced CCM |
| درجة حرارة الوصلة التشغيلية | -40 °C to +125 °C (I grade) |
| العلبة | 20-lead (18-pin) QFN with exposed pad, 4 mm x 3 mm |
| نوع التركيب | Surface Mount |
| حالة RoHS | Compliant |
| Lead-Free / PBF | Yes (PBF suffix) |
تكوين أطراف LT8640IUDC-1
| دبوس 1 | VIN — Input supply voltage, 3.4V to 42V |
| دبوس 2 | VIN — Input supply voltage (second pin) |
| دبوس 3 | BST — Boost flying capacitor for high-side gate drive |
| دبوس 4 | SW — Switch node - connection to inductor |
| دبوس 5 | SW — Switch node (second pin) |
| دبوس 6 | PGND — Power ground |
| دبوس 7 | PGND — Power ground (second pin) |
| دبوس 8 | PGND — Power ground (third pin) |
| دبوس 9 | PGND — Power ground (fourth pin) |
| دبوس 10 | RT — Timing resistor to program switching frequency |
| دبوس 11 | SYNC/MODE — Mode pin: Burst/spread-spectrum/SYNC/forced CCM |
| دبوس 12 | SS — Soft-start programming |
| دبوس 13 | TR/SS — Tracking / soft-start input |
| دبوس 14 | FB — Voltage feedback from output divider |
| دبوس 15 | VOUT — Output voltage sense (internal bias) |
| دبوس 16 | EN/UV — Enable / undervoltage lockout |
| دبوس 17 | INTVCC — Internal 3.4V LDO bypass |
| دبوس 18 | BIAS — Optional bias supply for higher efficiency |
| دبوس 19 | NC — Not connected (per datasheet) |
| دبوس 20 | EP — Exposed pad - thermal and PGND, must be soldered to PCB |
التطبيقات النموذجية
LT8640IUDC-1 مناسب لـ 6 التطبيقs: 24V Industrial Sensor and Actuator Power Rails, Automotive Infotainment and Body Electronics, Battery-Powered Portable and IoT Devices, Point-of-Load Supply After 24V/12V Bus, Test and Measurement Instrumentation, Surveillance and Security Camera Power.
24V Industrial Sensor and Actuator Power Rails
The LT8640IUDC-1 is ideally suited to 24V industrial sensor rails because its 42V input tolerance easily absorbs 24V bus transients, and its 5A continuous current supports multi-sensor loads including 4-20mA loops, PLCs, and motor pre-drivers. Silent Switcher architecture meets CISPR 22 EMI limits without shielding, simplifying EN 61131-2 compliance for industrial control cabinets. The 2.5µA quiescent current enables always-on standby operation with battery-backed industrial controllers, while the 200kHz-3MHz switching range allows small inductors and a compact 4mm x 3mm footprint suitable for dense PLC backplanes.
موصى به
Automotive Infotainment and Body Electronics
The LT8640IUDC-1 powers infotainment head units, instrument clusters, and body controllers from 12V automotive rails. Its 42V input margin covers ISO 7637-2 load-dump transients without external TVS, reducing BOM cost. Silent Switcher EMI performance eliminates the need for an EMI shield, allowing placement near RF-sensitive antenna and tuner sections. For AEC-Q100 qualified automotive designs the LT8640EUDC-1#TRPBF variant is a drop-in alternative, providing the same QFN-20 (UDC) footprint while adding automotive PPAP documentation. The 5A output current supports multiple downstream rails via secondary LDOs.
موصى به
Battery-Powered Portable and IoT Devices
The LT8640IUDC-1's 2.5µA quiescent current is the headline feature for battery-powered IoT and portable designs. With the output in full regulation at no load, a Li-ion or 4xAA battery stack can stay in standby for years without draining. The wide VIN range supports direct connection to multi-cell battery chemistries (Li-ion, lead-acid, 4x NiMH) without pre-regulation. Silent Switcher architecture prevents switching noise from coupling into adjacent analog or RF circuits, critical for BLE/Wi-Fi IoT modules where conducted noise degrades radio sensitivity. The 4mm x 3mm QFN-20 package fits wearable and sensor-hub form factors.
موصى به
Point-of-Load Supply After 24V/12V Bus
The LT8640IUDC-1 is a workhorse point-of-load converter for distributed power architectures where 24V or 12V intermediate buses feed multiple POL regulators downstream. With 5A output and 96%+ peak efficiency at 12V to 5V conversion, the LT8640IUDC-1 minimizes thermal stress on dense PCBs. The 30ns minimum on-time enables high-frequency 3MHz operation at large VIN-VOUT deltas, shrinking inductor size. Forced continuous mode (the -1 variant) avoids discontinuous-conduction-mode audio noise that would otherwise couple into adjacent analog POLs through ground bounce.
موصى به
Test and Measurement Instrumentation
In bench-top oscilloscopes, signal generators, and lab power supplies, the LT8640IUDC-1 provides clean, low-ripple power rails for sensitive analog front-ends including ADC reference ladders, DAC output stages, and op-amp supply pins. The Silent Switcher 3MHz switching capability can be synchronized to an external clock placed above the AM band, eliminating beat-frequency interference with sensitive measurements. Forced continuous mode maintains constant switching frequency across load steps, reducing transient response variation that would otherwise show up as supply-noise artifacts on the measured signal.
موصى به
Surveillance and Security Camera Power
PoE-powered and 12V/24V security cameras benefit from the LT8640IUDC-1's Silent Switcher architecture because the switching noise does not couple into the camera's image sensor or analog video chain, preserving low-light image quality. The wide VIN range accepts PoE-extracted 12V or 24V directly without pre-regulation. The 5A output current supports a single converter feeding multiple camera subsystems - image sensor, IR illuminator, heater, and network interface. The forced continuous mode (LT8640-1) prevents DCM-induced audio-frequency noise that can couple into microphone channels used in audio-equipped surveillance.
موصى به
ملخص المنتجات الموصى بها
بيانات مرجعية هندسية لـ LT8640IUDC-1 — المقارنة وإرشادات التصميم ومعلومات الامتثال.
دليل الاختيار
المقارنة مع البدائل
| المعامل | هذا المنتج | LT8640IUDC#PBF | LT8640IUDC-1#TRPBF | LT8640EUDC#TRPBF | LT8640EUDC-1#TRPBF | LT8641HUDC#PBF |
|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 20-lead QFN with exposed pad, 4 mm x 3 mm | 20-lead QFN with exposed pad, 4 mm x 3 mm - same | 20-lead QFN with exposed pad, 4 mm x 3 mm - same | 20-lead QFN with exposed pad, 4 mm x 3 mm - same | 20-lead QFN with exposed pad, 4 mm x 3 mm - same | 20-lead QFN with exposed pad, 4 mm x 3 mm - 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 65 V |
| Maximum Output Current | 5 A | 5 A | 5 A | 5 A | 5 A | 3.5 A |
| Quiescent Current | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA | 2.5 µA |
| Temperature Grade | I grade: -40C to +125C | I grade | I grade | E grade: 0C to +125C | E grade | H grade |
| 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 |
أبرز الفروقات
- Highest efficiency at very light loads with 2.5µA quiescent current (مقابلLT8606EDC#TRPBF (typical alternative buck converters))
- Wide VIN range with high load-current capability in compact package (مقابلLT8641HUDC#PBF)
- Forced continuous mode at light loads (LT8640-1 variant) (مقابلLT8640IUDC#PBF (standard pulse-skipping version))
ملاحظات التصميم
Silent Switcher architecture relies on tightly-coupled VIN-PGND and SW-PGND capacitor loops. Place the input ceramic capacitor (minimum 10µF X7R) immediately adjacent to the VIN and PGND pads, with the shortest possible trace to minimize the high-dV/dt loop area. Without this layout discipline, Silent Switcher loses its EMI advantage. The exposed pad must be soldered to a continuous PGND copper pour of at least 1 square inch for thermal dissipation; via stitching to internal PGND planes is recommended.
Estimated: at 12V VIN to 5V VOUT at 5A load, the LT8640IUDC-1 dissipates approximately (12V-5V)*5A*1/eta watts; assuming 90% efficiency, that is ~3.9W. With a 4mm x 3mm QFN-20 and the exposed pad soldered to 1 square inch of 1oz copper, theta_JA is approximately 38 C/W, giving a junction temperature rise of 148 C above ambient - too high for 85 C ambient operation. For continuous 5A output at 12V-to-5V conversion, increase the copper pour to 2-3 square inches or upgrade to the LT8650-series with better thermal performance.
Do not use output capacitors smaller than 10µF total - the LT8640 control loop requires a minimum output capacitance for stability, and using smaller values can cause oscillation or poor load-step response. Use low-ESR ceramic capacitors (X7R dielectric). Avoid placing the RT resistor close to noisy traces, as frequency-programming noise can couple in. The SYNC/MODE pin must be tied to a known logic state - leaving it floating may cause unexpected mode transitions. For high-dV/dt applications, ensure the BIAS pin is tied to a stable 3.3V or 5V rail to maximize efficiency.
The Silent Switcher architecture typically meets CISPR 22 Class B radiated and conducted EMI without a shield, but only with proper PCB layout. If the design fails EMI, common causes are: (1) input capacitor placed too far from VIN/PGND pads, (2) insufficient copper area on the exposed pad, (3) output inductor chosen with low SRF (self-resonant frequency below 100 MHz), (4) SYNC/MODE not configured for spread-spectrum mode. Use spread-spectrum mode (SYNC/MODE tied to ground through a specific resistor network) to further reduce peak EMI by ~10dB.
معلومات الامتثال
RoHS compliant per PBF suffix on DigiKey/Mouser listings. The LT8640IUDC-1 itself is industrial-grade (I temp range) - choose the LT8640EUDC-1#TRPBF AEC-Q100 automotive variant for AEC-Q100 qualified designs.
