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Analog Devices Inc. LT8705AIUHF#TRPBF
- Part No.:
- LT8705AIUHF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LT8705AIUHF#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,645
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Product details
Overview
LT8705AIUHF#TRPBF from Analog Devices (formerly Linear Technology) is a synchronous 4-switch buck-boost DC/DC controller IC designed for high-voltage industrial and automotive power conversion. It supports 2.8V–80V input and 1.3V–80V output, integrates quad N-channel gate drivers, and delivers up to 98% efficiency in synchronous rectification mode. It is used in telecom voltage stabilizers and solar charge controllers where VIN may be above, below, or equal to VOUT.
For engineers reviewing the LT8705AIUHF#TRPBF datasheet, LT8705AIUHF#TRPBF pinout, LT8705AIUHF#TRPBF application, or LT8705AIUHF#TRPBF equivalent, key selection criteria include its 4-switch topology, integrated input/output current monitoring (IMON_IN/IMON_OUT), MODE pin selectable operation modes (Burst/DCM/FCM), and compatibility with wide-input solar and battery systems requiring stable bidirectional voltage regulation.
Technical Context
The LT8705AIUHF#TRPBF implements a proprietary current-mode control architecture with four independent feedback loops: input voltage (FBIN), output voltage (FBOUT), input current (IMON_IN), and output current (IMON_OUT). Its dual-stage gate drive (TG1/BG1/TG2/BG2) enables precise timing control of external N-MOSFETs in buck, boost, and buck-boost regions.
It features a synchronizable fixed-frequency oscillator (100–400 kHz), programmable via RT resistor, and includes an internal 6.35V INTVCC regulator and 3.3V/12mA LDO. The CLKOUT pin provides both clock synchronization and die temperature monitoring via duty-cycle variation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports wide-input sources including 48V telecom, 72V battery stacks, and unregulated solar arrays. |
| VOUT Range | 1.3V to 80V - enables single-controller solutions for both step-up and step-down applications without topology change. |
| Switching Frequency | 100 kHz to 400 kHz - adjustable via RT pin; higher frequencies reduce inductor size but increase switching loss. |
| Gate Drivers | Quad N-channel drivers (TG1/BG1/TG2/BG2) - drives external high-side and low-side MOSFETs with 20 ns rise/fall times and controlled dead-time delays. |
| Efficiency | Up to 98% - achieved via synchronous rectification and optimized gate drive timing, reducing conduction losses in high-current paths. |
| Operating Temp | –40°C to +125°C junction - qualified for automotive under-hood and industrial ambient environments. |
| Package | 38-lead 5mm × 7mm QFN (UHF) with exposed thermal pad - provides low θJA = 34°C/W for high-power density designs. |
Pinout & Package
LT8705AIUHF#TRPBF uses a 38-lead plastic QFN (UHF) package with 5mm × 7mm footprint and exposed GND pad (Pin 39) requiring PCB soldering for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 1) | Shutdown control input | Active-high logic; pulls quiescent current to ≤1 µA when grounded - enables system-level power sequencing. |
| CSP/CSN (Pins 3/2) | Inductor current sense inputs | Differential pair measuring RSENSE voltage; sets peak current limit via VC pin and internal gain (±150 mV/V). |
| FBIN/FBOUT (Pins 5/6) | Input/output voltage feedback inputs | High-impedance error amplifier inputs (10–15 nA bias); regulate VIN and VOUT independently with 1.205V/1.207V reference voltages. |
| IMON_IN/IMON_OUT (Pins 38/7) | Current monitor outputs | Current-source outputs proportional to input/output current; 100 µA full-scale enables analog current limiting and telemetry. |
| TG1/BG1/TG2/BG2 (Pins 22/14/18/16) | N-MOSFET gate drivers | Drive external high-side (TG) and low-side (BG) switches with 100 ns max dead-time control - prevents shoot-through in 4-switch topology. |
| CLKOUT (Pin 10) | Internal oscillator output | 180° out-of-phase clock signal with temperature-dependent duty cycle - usable for multi-phase sync or junction temperature estimation. |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor buck-boost topology | Eliminates need for separate buck and boost converters - reduces BOM count and board area in bidirectional power systems. |
| Four independent feedback loops | Enables simultaneous regulation of input voltage, output voltage, input current, and output current - critical for MPPT solar chargers and battery protection circuits. |
| MODE pin selectable light-load operation | Configures Burst Mode® (low IQ), discontinuous conduction (DCM), or forced continuous conduction (FCM) - optimizes efficiency across load range without external circuitry. |
| Integrated 3.3V/12mA LDO | Provides local bias for external circuitry (e.g., ADC references or level shifters) - eliminates need for discrete LDO in auxiliary rail design. |
| Open-drain SRVO status pins (QFN only) | SRVO_FBIN/SRVO_FBOUT/SRVO_IIN/SRVO_IOUT indicate active feedback loop states - enables real-time fault diagnostics and loop prioritization in safety-critical systems. |
Applications
| Solar Charge Controller | Telecom Voltage Stabilizer |
|---|---|
Use Scenario: Regulates variable PV array output (30–80V) to charge 48V battery bank while maintaining constant current/voltage profiles. IC Role / Device Role / Timing Role: Primary buck-boost controller managing MPPT algorithm interface, input current limiting, and output voltage regulation via FBIN/FBOUT/IMON_IN loops. Use Value: Enables single-stage conversion from wide-input solar sources to stable battery charging voltage without intermediate DC-DC stages. | Use Scenario: Stabilizes -48V telecom supply against line transients and load steps in central office equipment. IC Role / Device Role / Timing Role: High-efficiency buck-boost regulator maintaining ±1% VOUT accuracy despite ±20% VIN variation and 0–10A load swings. Use Value: Delivers >95% efficiency at full load and fast transient response (<2ms recovery) using synchronized CLKOUT and fast current-loop bandwidth. |
| Automotive 12V/48V Bi-Directional Converter | Industrial Battery Backup System |
Use Scenario: Bidirectional power transfer between 12V starter battery and 48V mild-hybrid rail during regenerative braking and engine start. IC Role / Device Role / Timing Role: Synchronous 4-switch controller operating in buck mode (48V→12V) and boost mode (12V→48V) with reverse-current detection via CSP/CSN polarity sensing. Use Value: Supports seamless mode transition and <100 ns dead-time control to prevent cross-conduction in high-power bi-directional topologies. | Use Scenario: Maintains uninterrupted 24V output during AC mains failure by switching from grid to battery input with zero output voltage dip. IC Role / Device Role / Timing Role: Input-voltage regulated buck-boost controller with fast SWEN-controlled enable/disable and IMON_IN-based input current limiting during battery discharge. Use Value: Achieves <50 µs switchover time using internal UVLO hysteresis and dedicated shutdown pin, meeting UL 1778 hold-up requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3780EFE#PBF | Same 4-switch architecture but limited to 60V max VIN/VOUT; no integrated IMON_IN/IMON_OUT; requires external current sense amplifiers. | Less suitable for 80V solar or 72V battery systems; lacks built-in current monitoring for MPPT or battery protection. | Select LTC3780EFE#PBF only if operating below 60V and external current sensing is acceptable. |
| MP2918GL-Z | Monolithic 4-switch buck-boost IC (integrated MOSFETs); 3.5–36V input; fixed 300kHz frequency; no RT programming or multi-loop feedback. | Targeted at compact low-power applications; cannot scale to >10A or >80V; no independent input/output current regulation. | Choose MP2918GL-Z for space-constrained 12V/24V systems where integration outweighs flexibility. |
Compared with LTC3780EFE#PBF and MP2918GL-Z, the LT8705AIUHF#TRPBF offers wider 80V operation, on-chip current monitoring, and programmable frequency - making it uniquely suited for high-voltage industrial and automotive bidirectional power conversion where precision loop control and voltage headroom are critical.
Availability
LT8705AIUHF#TRPBF is available at Aetrix Electronics and suitable for solar charge controllers, telecom voltage stabilizers, and automotive 12V/48V bi-directional converters requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT8705AIUHF#TRPBF 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 acquired Linear Technology in 2017 and maintains its high-performance power management portfolio with rigorous automotive and industrial qualification standards.
The LT8705A product line was designed specifically for high-voltage, high-efficiency buck-boost conversion in solar, telecom, and automotive applications where input voltage may exceed, fall below, or equal the required output voltage.
FAQ
What is the maximum input voltage rating for the LT8705AIUHF#TRPBF?
The LT8705AIUHF#TRPBF has an absolute maximum input voltage (VIN) rating of 80V, with operational input range specified from 2.8V to 80V. This allows direct interfacing with 48V and 72V battery systems, unregulated solar arrays, and telecom -48V supplies without external pre-regulation. Exceeding 80V risks permanent damage per Absolute Maximum Ratings.
Does the LT8705AIUHF#TRPBF support synchronization with external clock sources?
Yes, the LT8705AIUHF#TRPBF supports external clock synchronization via the SYNC pin (Pin 11), which accepts TTL/CMOS-compatible signals with high level ≥1.3V and low level ≤0.5V. When driven, the internal oscillator locks to the external frequency, enabling phase-aligned multi-phase operation or EMI reduction through spread-spectrum clocking.
How does the MODE pin affect light-load efficiency in the LT8705AIUHF#TRPBF?
The MODE pin (Pin 37) selects among three light-load operating modes: forced continuous conduction (FCM) below 0.4V, Burst Mode® when floating, and discontinuous conduction mode (DCM) above 2.3V. Burst Mode® reduces quiescent current to 2.65mA (typical), extending battery runtime in standby; FCM ensures low-noise output but increases light-load losses.
What is the function of the SRVO pins on the LT8705AIUHF#TRPBF?
The SRVO_FBIN, SRVO_FBOUT, SRVO_IIN, and SRVO_IOUT pins (Pins 25–28, QFN-only) are open-drain status outputs that go low when their respective feedback loops (input voltage, output voltage, input current, output current) are actively regulating. They enable real-time loop activity monitoring, fault isolation, and priority arbitration in multi-loop control systems using the LT8705AIUHF#TRPBF.
Can the LT8705AIUHF#TRPBF operate with input voltage below 2.8V?
No, the LT8705AIUHF#TRPBF requires minimum 2.8V VIN for normal operation when EXTVCC = 0V. With EXTVCC ≥6.4V, the minimum VIN drops to 5.5V due to internal switchover behavior. Below these thresholds, the INTVCC regulator cannot sustain gate drive and internal logic, causing undervoltage lockout and shutdown - the LT8705AIUHF#TRPBF will not start or maintain regulation.
LT8705AIUHF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck-Boost
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 2.8V ~ 80V
- Frequency - Switching:
- 100kHz ~ 400kHz
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Enable, Frequency Control, Soft Start
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-QFN (5x7)
LT8705AIUHF#TRPBF FAQ
1.How can I place an order for LT8705AIUHF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AIUHF#TRPBF 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 LT8705AIUHF#TRPBF reliable?
The price and inventory of LT8705AIUHF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AIUHF#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8705AIUHF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AIUHF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AIUHF#TRPBF?
LT8705AIUHF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AIUHF#TRPBF 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 LT8705AIUHF#TRPBF?
For technical support, including LT8705AIUHF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AIUHF#TRPBF requirements.
6.How does Aetrix verify that LT8705AIUHF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8705AIUHF#TRPBF 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 LT8705AIUHF#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8705AIUHF#TRPBF?
All LT8705AIUHF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AIUHF#TRPBF, 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 LT8705AIUHF#TRPBF part is unused and in its original packaging.
Return procedure for LT8705AIUHF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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