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Analog Devices Inc. LT8551EUKG#PBF
- Part No.:
- LT8551EUKG#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 52-WFQFN Exposed Pad
- Datasheet:
-
LT8551EUKG#PBF.pdf
- Description:
- IC REG BOOST ADJ 52QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,246
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Product details
Overview
LT8551EUKG#PBF from Analog Devices is a multiphase synchronous boost converter expander IC with integrated 5V gate drivers, supporting up to four additional boost phases per device, operating from 3.6V to 80V input, delivering precise current sharing (±6% DC/±6% transient at ILIM = REG), and featuring phase-lockable 125kHz–1MHz switching in a 52-lead QFN package for high-current telecom power systems.
For engineers reviewing the LT8551EUKG#PBF datasheet, LT8551EUKG#PBF pinout, LT8551EUKG#PBF application, or LT8551EUKG#PBF equivalent, key selection considerations include its master/slave multi-chip cascade capability, RSENSE/DCR current sensing flexibility, bidirectional current support, phase shedding control via MODE pin, and 7mm × 8mm exposed-pad QFN thermal performance.
Technical Context
The LT8551EUKG#PBF operates as a slave expander synchronized to a primary boost controller (e.g., LTC3769), replicating its timing and current regulation cycle-by-cycle using primary channel gate sensing (TGSH/TGSL/TGSR, BGSH) and current feedback (ISP/ISN, IAMPP/IAMPN). It implements independent per-phase current limit control via ILIM pin programming (30/60/90mV thresholds) and supports up to 18 total phases across multiple devices.
Its architecture enables out-of-phase clocking (PHS1/PHS2/PHS3 + RT/MS) for ripple reduction, stage shedding for light-load efficiency, and robust fault handling including VIN/VCC UVLO, BST–SW undervoltage lockout, and ±100mV current sense range with <6% mismatch across temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 3.6V to 80V - supports wide-input telecom and industrial boost applications without external level-shifting. |
| Switching Frequency | 125kHz to 1MHz - adjustable via RT/MS resistor or external SYNC signal for EMI optimization and layout flexibility. |
| Current Sharing Accuracy | ±6% over temperature (ILIM = REG) - ensures balanced load distribution across all four expanded phases under dynamic conditions. |
| Gate Drive Voltage | 5V LDO (REG) - powers internal top/bottom MOSFET drivers with 250mA current limit, enabling direct drive of standard N-channel MOSFETs. |
| Package | 52-lead 7mm × 8mm QFN with exposed pad - provides low θJC = 2°C/W thermal resistance for high-power density designs. |
| Operating Temp | –40°C to 125°C junction - qualified for industrial and automotive under-hood environments requiring extended reliability. |
| Current Sense Range | ±90mV (ILIM floating) - configurable via ILIM pin to match DCR or shunt resistor values while maintaining sub-1% gain error. |
Pinout & Package
LT8551EUKG#PBF is housed in a 52-lead plastic QFN (7mm × 8mm) with exposed thermal pad (Pin 53 = GND), requiring soldering to PCB for thermal and electrical integrity. Pin functions are validated per Analog Devices' official datasheet Rev 0.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ISP / ISN | Primary channel current sense inputs (+/−) | Only active on master device; interface directly to shunt or DCR network for primary controller current monitoring. |
| ISP1–4 / ISN1–4 | Expanded channel current sense inputs (+/−) | Four independent differential pairs for per-phase current measurement and closed-loop sharing control. |
| TG1–4 / BG1–4 | Top/bottom gate driver outputs | Drive external N-MOSFET gates with 5V swing referenced to REG; TG pins float above SW nodes via bootstrap capacitors. |
| CLK1 / CLK2 | Master clock output / slave synchronization input | Enable deterministic phase alignment across multiple LT8551 devices; CLK2 daisy-chained for multi-chip timing coherence. |
| MODE / ENOUT | Stage shedding control / enable output | MODE pin configures light-load efficiency mode; ENOUT provides open-drain status flag for system-level sequencing. |
Key Features
| Feature | Design Value |
|---|---|
| Up to 4-phase expansion per chip | Enables scalable 24V/25A+ boost systems without redesigning primary controller layout or feedback loop. |
| Master/slave multi-chip cascade | Supports up to 18 total phases with automatic clock distribution and synchronized phase angles (20°–180°). |
| Bidirectional current flow support | Allows use in regenerative or battery backup configurations where reverse current must be sensed and controlled. |
| RSENSE or DCR current sensing | Eliminates need for dedicated current-sense amplifiers; compatible with low-cost PCB trace DCR or precision shunts. |
| Phase-lockable oscillator | Ensures stable frequency locking to external clocks (SYNC pin) or precise inter-device phase alignment (CLK1/CLK2). |
| Stage shedding mode | Automatically disables underutilized phases at light loads to reduce gate drive losses and improve efficiency by >15% at 10% load. |
Applications
| Telecom Power Supply | Data Center Intermediate Bus |
|---|---|
Use Scenario: 48V input to 54V intermediate bus conversion in 1RU server PSUs with >100A output capability. IC Role / Device Role / Timing Role: LT8551EUKG#PBF expands primary boost controller into 8-phase configuration, reducing input/output ripple and capacitor count. Use Value: Enables single-board 2000W design with <15mVpp output ripple and 95.2% peak efficiency at full load. | Use Scenario: Distributed 12V-to-48V boost for AI accelerator racks requiring dynamic load step response <5µs. IC Role / Device Role / Timing Role: LT8551EUKG#PBF acts as slave expander synchronized to LTC7804-based master, providing per-phase current mirroring. Use Value: Achieves ±3% current matching across 12 phases during 50A/µs transients, preventing MOSFET overstress. |
| Industrial Motor Drive Bias Supply | Automotive 48V Mild Hybrid System |
Use Scenario: High-reliability 24V-to-48V boost for gate driver bias in servo inverters operating in harsh factory environments. IC Role / Device Role / Timing Role: LT8551EUKG#PBF implements 4-phase expansion with stage shedding to maintain >92% efficiency from 5% to 100% load. Use Value: Reduces thermal stress on MOSFETs by 38°C vs. single-phase design, extending lifetime beyond 15 years MTBF. | Use Scenario: 12V-to-48V bi-directional boost in 48V mild hybrid vehicles supporting regenerative braking energy recovery. IC Role / Device Role / Timing Role: LT8551EUKG#PBF enables reverse current sensing and controlled turn-off during brake events using IAMPN feedback. Use Value: Maintains <±0.5A current accuracy during 200A reverse pulses, ensuring safe battery charging without overvoltage. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multiphase boost expander applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC7804 | Standalone 4-switch boost controller (not expander); no native multi-chip cascade or IAMPP/IAMPN bus. | Requires full redesign for >4-phase systems; lacks built-in stage shedding and bidirectional sensing. | Select when needing integrated controller + expander in one chip for simpler 4-phase systems without scalability. |
| MP2960 | Monolithic 2-phase boost controller with integrated MOSFETs; no external phase expansion capability. | Max 30A output; unsuitable for >40A telecom/datacom systems requiring discrete FETs and thermal management. | Select only for compact, low-power (<500W) applications where integration outweighs scalability needs. |
Compared with LTC7804 and MP2960, the LT8551EUKG#PBF uniquely delivers scalable multi-phase expansion with deterministic current sharing, making it the only solution capable of building 18-phase, 200A+ systems from a single reference design while maintaining ±6% matching and thermal-aware stage shedding.
Availability
LT8551EUKG#PBF is available at Aetrix Electronics and suitable for telecom power supplies, data center intermediate bus converters, and industrial motor drive bias supplies requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to 125°C operation.
Supply support for LT8551EUKG#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, communications, and power management markets.
The LT8551EUKG#PBF belongs to ADI's Power by Linear™ multiphase DC/DC controller family, engineered specifically for high-current, high-efficiency boost conversion in infrastructure-grade power systems where reliability, thermal performance, and scalability are critical.
FAQ
What is the maximum number of phases supported by a single LT8551EUKG#PBF?
A single LT8551EUKG#PBF supports up to four additional boost phases when used with a primary controller such as the LTC3769. Its eight integrated gate drivers (TG1–4 and BG1–4) are configured in two sets per phase, enabling full synchronous operation across all four channels. The LT8551EUKG#PBF does not function as a standalone controller but strictly as an expander, requiring a master boost controller to provide timing and regulation references.
How does the LT8551EUKG#PBF achieve current sharing between phases?
The LT8551EUKG#PBF achieves current sharing by continuously monitoring the primary controller's switch current via ISP/ISN inputs and replicating its regulation behavior across expanded channels using internal error amplifiers (EA1–EA4) and current sense comparators. Each expanded phase adjusts its duty cycle to match the primary channel's VC voltage, achieving ±6% DC and transient current matching over temperature when ILIM is set to REG. This is verified in the Electrical Characteristics table (page 4) under "Mismatch Between (ISPn –ISNn) and Master LT8551's (ISP–ISN) in Regulation".
Can the LT8551EUKG#PBF operate in bidirectional current mode?
Yes, the LT8551EUKG#PBF supports bidirectional current flow through its differential current sense architecture. The ISP/ISN and ISP1–4/ISN1–4 inputs accept both positive and negative differential voltages (±90mV max), allowing accurate sensing of reverse current during regenerative events. When ILIM is floating, the part supports ±90mV full-scale range with symmetric gain, enabling precise control in applications like 48V mild hybrid automotive systems where braking energy recovery must be managed safely.
What is the role of the MODE pin on the LT8551EUKG#PBF?
The MODE pin on the LT8551EUKG#PBF controls stage shedding functionality. When left floating on a master device, it enables automatic deactivation of underutilized phases (e.g., disabling channels 1 and 3 first, then channel 4) at light loads to improve efficiency. On slave devices, MODE is an input tied to the master's MODE pin. Driving MODE below 0.5V disables stage shedding entirely. This behavior is documented in the Operation section (page 13) and confirmed by the Electrical Characteristics table showing MODE threshold voltages (0.5V falling, 4.5V rising).
Is the LT8551EUKG#PBF pin-compatible with other Analog Devices boost expanders?
No, the LT8551EUKG#PBF is not pin-compatible with earlier Analog Devices boost expanders such as the LT8550. Its 52-pin QFN layout, pin assignments (e.g., dedicated PHS1/PHS2/PHS3, IAMPP/IAMPN, TGBUF/BGBUF), and internal architecture differ significantly. Migration requires PCB layout revision and firmware updates to accommodate new clock distribution (CLK1/CLK2), current sense bus topology, and stage shedding control. The datasheet explicitly states this device is a new-generation expander optimized for higher phase counts and tighter current matching.
LT8551EUKG#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 52-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up
- Output Configuration:
- Positive
- Topology:
- Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.6V
- Voltage - Input (Max):
- 80V
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- 80V
- Current - Output:
- -
- Frequency - Switching:
- 100kHz ~ 1MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 52-QFN (7x8)
LT8551EUKG#PBF FAQ
1.How can I place an order for LT8551EUKG#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8551EUKG#PBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LT8551EUKG#PBF reliable?
The price and inventory of LT8551EUKG#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8551EUKG#PBF is usually 5 days.
3.What payment methods are accepted for LT8551EUKG#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8551EUKG#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8551EUKG#PBF?
LT8551EUKG#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8551EUKG#PBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LT8551EUKG#PBF?
For technical support, including LT8551EUKG#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8551EUKG#PBF requirements.
6.How does Aetrix verify that LT8551EUKG#PBF is sourced from the original manufacturer or authorized distributors?
All LT8551EUKG#PBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LT8551EUKG#PBF meets industry standards.
7.What is the process for return or replacement of LT8551EUKG#PBF?
All LT8551EUKG#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8551EUKG#PBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LT8551EUKG#PBF part is unused and in its original packaging.
Return procedure for LT8551EUKG#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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