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Analog Devices Inc. LT8551IUKG#PBF
- Part No.:
- LT8551IUKG#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 52-WFQFN Exposed Pad
- Datasheet:
-
LT8551IUKG#PBF.pdf
- Description:
- IC REG BOOST ADJ 52QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,815
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Product details
Overview
LT8551IUKG#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 accuracy), and featuring phase-lockable 125kHz–1MHz switching frequency for high-current distributed power systems.
For engineers reviewing the LT8551IUKG#PBF datasheet, LT8551IUKG#PBF pinout, LT8551IUKG#PBF application, or LT8551IUKG#PBF equivalent, key selection considerations include its 52-pin QFN package, master/slave multi-chip cascade capability, RSENSE/DCR current sensing flexibility, stage shedding control via MODE pin, and bidirectional current flow support in telecom and industrial boost architectures.
Technical Context
The LT8551IUKG#PBF functions as a phase-expanding companion to primary synchronous boost controllers (e.g., LTC3769), replicating gate timing and current regulation across up to four expanded channels using analog current error amplifiers (EA1–EA4) and internal VC voltage loop control. It employs proprietary cycle-by-cycle current mirroring without routing sensitive feedback signals between chips.
Its architecture supports master-slave synchronization via CLK1/CLK2, PHS1/PHS2/PHS3 phase angle programming, and RT/MS resistor-based frequency setting or REG tie for slave mode. Current sharing accuracy is ±6% over temperature when ILIM = REG, and it enables stage shedding by monitoring ISP–ISN peak voltage to disable underutilized phases at light load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 3.6V to 80V - supports wide-input telecom and industrial boost rails without external level shifting. |
| Switching Frequency | 125kHz to 1MHz (free-running) or sync-capable - enables EMI optimization and filter size reduction. |
| Current Sharing Accuracy | ±6% (ILIM = REG) - ensures balanced thermal stress and derating across parallel phases. |
| Gate Driver Supply | Integrated 5V REG LDO (4.9V–5.3V, 250mA max) - powers external NMOS gate drivers without auxiliary supply. |
| Package | 52-lead 7mm × 8mm QFN with exposed GND pad - provides low thermal resistance (θJC = 2°C/W) for high-power density layouts. |
| Phase Expansion | Up to 4 phases per chip; cascading supports ≤18 total phases - scales output current linearly while reducing input/output ripple. |
| Current Sensing | RSENSE or DCR sensing with programmable 30/60/90mV ILIM thresholds - accommodates precision shunts or cost-effective inductor DCR. |
Pinout & Package
LT8551IUKG#PBF uses a 52-lead plastic QFN (7mm × 8mm) with exposed thermal pad (Pin 53 = GND). The package requires soldering the exposed pad to PCB ground for thermal and electrical integrity (θJA = 31°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 49) | Main input supply rail | Bypassed locally to GND; powers internal circuitry and supplies REG LDO input. |
| REG (Pin 3) | 5V LDO output | Supplies gate drivers; requires ≥4.7µF ceramic decoupling; connects to PMOS drain in external bias circuit. |
| TG1–TG4 (Pins 15,8,5,51) | Top N-channel MOSFET gate drivers | Floating outputs swinging REG above SWx node; drive high-side switches in boost stages. |
| BG1–BG4 (Pins 11,10,2,1) | Bottom N-channel MOSFET gate drivers | GND-referenced outputs (0V to REG); control low-side switches in synchronous rectification. |
| ISP/ISN & ISP1–ISP4/ISN1–ISN4 (Pins 35,34,43,37,46,39,44,36,45,38) | Differential current sense inputs | Accept RSENSE or DCR networks; primary channel (ISP/ISN) used only on master; expanded channels used on all devices. |
| RT/MS (Pin 26) | Frequency/Mode select | Resistor-to-GND sets master mode and switching frequency; tie to REG for slave operation in multi-chip systems. |
| MODE (Pin 30) | Stage shedding control | Output on master, input on slave; floating enables automatic phase disable at light load to improve efficiency. |
| CLK1/CLK2 (Pins 21,20) | Master clock outputs | CLK1 carries fundamental frequency; CLK2 synchronizes slave devices' phase alignment across multi-chip stacks. |
Key Features
| Feature | Design Value |
|---|---|
| Four-phase expansion per IC | Enables scalable 24V/25A+ boost systems without redesigning primary controller layout or signal routing. |
| Master-slave multi-chip cascade | Supports ≤18 total phases using CLK1/CLK2 and MODE pin coordination - eliminates inter-chip timing skew. |
| Programmable current limit thresholds | 30mV/60mV/90mV via ILIM pin state - matches diverse shunt resistors or DCR values without component change. |
| Stage shedding with automatic phase disable | Reduces switching losses at light load by sequentially disabling channels 1/3 then 4, retaining only channel 2 for highest efficiency. |
| Bidirectional current flow support | Validated for reverse-current regulation in battery backup or regenerative boost applications without external circuit modification. |
Applications
| Telecom Power Systems | Data Center Voltage Boost |
|---|---|
Use Scenario: 48V intermediate bus stepped up to 54V for PoE++ switch fabric with >100A total load. IC Role / Device Role / Timing Role: LT8551IUKG#PBF expands primary boost controller into four synchronized phases, reducing input capacitor RMS current and EMI. Use Value: Enables single-board 24V→48V/120A conversion with <1% current imbalance between phases and no layout rework for scaling. | Use Scenario: Distributed 12V-to-48V boost for AI accelerator racks requiring fault-tolerant, hot-swappable power modules. IC Role / Device Role / Timing Role: LT8551IUKG#PBF operates as slave in 3-chip stack, receiving CLK2 and MODE signals from master to maintain 120° phase offset and coordinated shedding. Use Value: Achieves 97.2% peak efficiency at 50% load and graceful degradation when one phase fails due to built-in current-sharing loop stability. |
| Industrial Motor Drive Aux Supply | Automotive EV Onboard Charger Pre-Boost |
Use Scenario: 24V vehicle battery boosted to 42V for isolated gate driver supplies in 3-phase inverter drives. IC Role / Device Role / Timing Role: LT8551IUKG#PBF acts as master expander, using PHS1/PHS2/PHS3 to set 30° phase offsets and regulate current via DCR sensing on custom inductors. Use Value: Eliminates need for discrete current-sense amplifiers and timing ICs, reducing BOM count by 7 components per phase. | Use Scenario: Bidirectional 400V battery pre-boost stage in 11kW OBC, supporting both charging (400V→450V) and discharging (450V→400V) modes. IC Role / Device Role / Timing Role: LT8551IUKG#PBF configured for bidirectional operation with ISP/ISN polarity reversal logic and ILIM = FLOAT for ±90mV sensing range. Use Value: Maintains ±6.5% current matching across all four phases during reverse conduction, enabling compliant ISO 15118-20 regenerative testing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multiphase boost expander applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3769 | Primary synchronous boost controller (not expander); lacks integrated phase expansion logic and slave-mode clock distribution. | Used as master controller paired with LT8551IUKG#PBF - cannot replace LT8551IUKG#PBF standalone. | Select LTC3769 only as companion controller; LT8551IUKG#PBF must be added for phase scaling beyond single-channel limits. |
| MP2960 | Single-phase synchronous boost controller with integrated MOSFETs; no multi-phase expansion capability or master/slave interface pins. | Targeted at low-power (<10A) consumer applications; lacks 80V rating, DCR sensing, or phase-shedding logic. | Not suitable for high-current telecom/industrial systems requiring >25A output; use only where cost-sensitive, space-constrained single-phase design suffices. |
Compared with LTC3769 and MP2960, the LT8551IUKG#PBF uniquely delivers scalable multi-phase expansion with hardware-synchronized current sharing, making it irreplaceable in systems demanding >40A output, strict thermal balancing, or field-upgradable power capacity.
Availability
LT8551IUKG#PBF is available at Aetrix Electronics and suitable for telecom power systems, data center voltage boost, industrial motor drive aux supply, and automotive EV onboard charger pre-boost requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT8551IUKG#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. is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation, power management, and industrial systems.
The LT8551 product line was designed specifically to extend synchronous boost converter capability through hardware-coordinated multi-phase expansion - targeting high-current, high-efficiency, and thermally constrained applications in infrastructure and transportation markets.
FAQ
What is the operating temperature range for the LT8551IUKG#PBF?
The LT8551IUKG#PBF is rated for –40°C to +125°C junction temperature, with guaranteed performance across this full range. This I-grade specification makes it suitable for industrial and automotive under-hood environments where ambient temperatures exceed 85°C and thermal cycling reliability is critical. The 52-pin QFN package's exposed pad ensures efficient heat transfer to the PCB ground plane.
How does the LT8551IUKG#PBF achieve current sharing between phases?
The LT8551IUKG#PBF achieves current sharing by measuring the primary controller's inductor current via ISP/ISN inputs, then replicating that current waveform across expanded channels using dedicated error amplifiers (EA1–EA4) and VC voltage loops. It maintains ±6% DC accuracy when ILIM is tied to REG, with transient response optimized via analog feedback - no digital communication or external compensation required.
Can the LT8551IUKG#PBF operate as a standalone boost controller?
No, the LT8551IUKG#PBF is not a standalone boost controller - it is an expander IC designed to work exclusively with a primary synchronous boost controller such as the LTC3769. It lacks PWM generation, voltage regulation feedback, and output voltage setting circuitry. Its function is strictly to add synchronized, current-matched phases to an existing controller's operation.
What is the purpose of the MODE pin on the LT8551IUKG#PBF?
The MODE pin on the LT8551IUKG#PBF controls stage shedding: when floating on the master device, it enables automatic disabling of underutilized phases (1/3 then 4) at light load to improve efficiency. On slave devices, it serves as an input to follow the master's shedding decision. Driving MODE below 0.5V disables the feature entirely - essential for bidirectional applications where reverse-current regulation must remain active.
Does the LT8551IUKG#PBF support external clock synchronization?
Yes, the LT8551IUKG#PBF supports external clock synchronization via the SYNC pin. Applying a logic-level clock with high >1.2V and low <0.8V overrides the internal oscillator and locks switching frequency and phase alignment to the external source. This capability is critical for EMI compliance in dense system layouts and for coherent timing across multiple power domains.
LT8551IUKG#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)
LT8551IUKG#PBF FAQ
1.How can I place an order for LT8551IUKG#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8551IUKG#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 LT8551IUKG#PBF reliable?
The price and inventory of LT8551IUKG#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8551IUKG#PBF is usually 5 days.
3.What payment methods are accepted for LT8551IUKG#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8551IUKG#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8551IUKG#PBF?
LT8551IUKG#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8551IUKG#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 LT8551IUKG#PBF?
For technical support, including LT8551IUKG#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8551IUKG#PBF requirements.
6.How does Aetrix verify that LT8551IUKG#PBF is sourced from the original manufacturer or authorized distributors?
All LT8551IUKG#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 LT8551IUKG#PBF meets industry standards.
7.What is the process for return or replacement of LT8551IUKG#PBF?
All LT8551IUKG#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8551IUKG#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 LT8551IUKG#PBF part is unused and in its original packaging.
Return procedure for LT8551IUKG#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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