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Analog Devices Inc. LT8705AEFE
- Part No.:
- LT8705AEFE
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AEFE.pdf
- Description:
- IC REG BUCK
- Quantity:
- Payment:
- Shipping:
Inventory:1,135
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Product details
Overview
LT8705AEFE from Analog Devices is a 4-switch synchronous buck-boost DC/DC controller IC designed for automotive and industrial power systems where input voltage can range from 2.8 V to 80 V and may fall above, below, or within the regulated output window. It supports Pass-Thru™ mode with programmable 8 V–16 V output window, achieves up to 99.9% efficiency in that region, and delivers ultralow quiescent current (4 µA on VIN, 18 µA on VINP) during non-switching operation-enabling cold-crank survival and load-dump immunity in vehicle electronics.
For engineers reviewing the LT8705AEFE datasheet, LT8705AEFE pinout, LT8705AEFE application, or LT8705AEFE equivalent, key selection criteria include its 2.8 V–80 V input range, Pass-Thru window programmability via FB1/FB2 resistors, 4-switch topology enabling seamless buck/boost transitions, integrated reverse-voltage protection, and support for CCM/pulse-skipping/Burst Mode® operation outside Pass-Thru.
Technical Context
The LT8705AEFE implements a true 4-switch buck-boost architecture with independent high-side and low-side gate drivers (TG1/BG1/TG2/BG2) for external N-channel MOSFETs. Its Pass-Thru mode operates by latching top switches A and D ON while disabling switching activity when VIN resides within a user-defined window set by FB1 and FB2 dividers-eliminating EMI and switching losses.
It features dual feedback loops: one for regulating output voltage in buck/boost modes, and another for window-bound Pass-Thru behavior. The device survives –40 V to +100 V transients and regulates across 3 V to 80 V, with built-in reverse-battery protection and fault reporting via PG (power good) and FLT (fault) pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.8 V to 80 V - supports full automotive battery range including cold crank (≤4 V) and unsuppressed load dump (≤100 V) |
| Pass-Thru Window | Programmable 8 V–16 V via FB1/FB2 resistor dividers - enables direct VIN-to-VOUT conduction without switching |
| Quiescent Current | 4 µA (VIN), 18 µA (VINP) in Pass-Thru - sustains ultra-low-power operation during long-term battery standby |
| Topology Support | 4-switch synchronous buck-boost - eliminates need for external diodes and enables bidirectional power flow control |
| Protection Features | Reverse-voltage protection, overvoltage/overcurrent/fault reporting - reduces external protection circuitry count |
| Operating Modes | CCM, pulse-skipping, Burst Mode® - selectable via MODE1/MODE2 pins for trade-off between light-load efficiency and output ripple |
Pinout & Package
The LT8705AEFE is housed in a 28-pin 4 mm × 5 mm QFN package with exposed thermal pad (EFE suffix), optimized for high-power density and thermal performance in automotive under-hood environments.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 2.8 V–80 V input; includes reverse-voltage protection clamp |
| VINP | High-voltage bias supply | Provides gate drive bias for high-side FETs; supports up to 100 V transient |
| FB1 / FB2 | Pass-Thru window lower/upper threshold inputs | Resistor-divided feedback setting 8 V (FB1) and 16 V (FB2) bounds for direct conduction mode |
| TG1 / BG1 / TG2 / BG2 | Gate drivers for external N-MOSFETs | Drives four external switches in buck-boost configuration; independent control enables optimal dead-time management |
| PG | Power good indicator | Open-drain output signals valid regulation; used for system sequencing and fault isolation |
| FLT | Fault reporting output | Asserts low on overvoltage, overcurrent, or thermal shutdown - enables fail-safe system response |
Key Features
| Feature | Design Value |
|---|---|
| Pass-Thru™ mode | Eliminates switching noise and losses when VIN ∈ [8 V, 16 V], enabling >99.9% efficiency and <20 µA total IQ |
| Wide input survival range | Withstands –40 V reverse polarity and +100 V transients without latch-up or damage |
| Programmable operating mode | MODE1/MODE2 pins select CCM (low ripple), pulse-skipping (light-load efficiency), or Burst Mode® (ultra-low IQ) |
| Dual feedback architecture | Separate regulation loop for buck/boost and independent window comparator for Pass-Thru - prevents mode conflict |
| Integrated fault reporting | Independent PG and FLT pins enable real-time health monitoring and coordinated system-level fault handling |
Applications
| Automotive Infotainment Power Supply | Industrial 24 V Rail Stabilizer |
|---|---|
Use Scenario: Powering head unit, display, and audio subsystems from an automotive battery subject to cold crank (≤4 V) and load dump (≥80 V). IC Role / Device Role / Timing Role: Primary 4-switch buck-boost controller managing wide-input regulation and Pass-Thru conduction during nominal 12 V operation. Use Value: Eliminates need for pre-regulator stages and external TVS clamping by surviving –40 V to +100 V transients while maintaining 8 V–16 V clean output. | Use Scenario: Providing stable 12 V or 15 V output from unregulated 24 V factory bus with ±20% variation and motor-switching noise. IC Role / Device Role / Timing Role: High-efficiency buck-boost controller with Pass-Thru mode active during nominal 24 V input to reduce EMI and heat generation. Use Value: Achieves >99.9% efficiency in Pass-Thru region, reducing thermal stress and eliminating switching noise that could interfere with PLC or sensor interfaces. |
| Telematics Control Unit (TCU) Power | Rail-to-Rail Automotive Camera Module |
Use Scenario: Powering LTE/GNSS modules requiring low-noise, always-on 3.3 V or 5 V rails from vehicle battery with extended parking mode. IC Role / Device Role / Timing Role: Controller enabling ultralow-IQ Pass-Thru operation during nominal battery voltage, minimizing standby current draw. Use Value: 4 µA VIN quiescent current extends battery life during weeks-long parking cycles without compromising startup reliability. | Use Scenario: Supplying image sensor and ISP in ADAS camera modules where EMI must not corrupt pixel data or timing signals. IC Role / Device Role / Timing Role: Noise-free power source using Pass-Thru mode during stable battery conditions to eliminate switching artifacts near analog video paths. Use Value: Removes clock-related jitter and conducted EMI that would otherwise degrade SNR and cause line noise in raw image streams. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 4-switch buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8210EFE#PBF | Same Pass-Thru architecture but rated for 2.8 V–100 V input; lacks LT8705AEFE's tighter 80 V max rating and optimized thermal pad layout | Preferred for systems requiring >80 V load dump tolerance; less optimized for space-constrained automotive modules | Select LT8210EFE#PBF only if full 100 V transient survival is required and board area allows larger thermal relief. |
| LTC3789EFE#PBF | No Pass-Thru mode; supports only conventional 4-switch buck-boost with CCM/Burst Mode®; 4 V–36 V input range | Suitable for industrial 12/24 V systems without automotive transients; cannot replace LT8705AEFE in cold-crank or load-dump scenarios | Choose LTC3789EFE#PBF only for cost-sensitive, non-automotive designs where input stays within 4–36 V and EMI sensitivity is low. |
Compared with LT8210EFE#PBF and LTC3789EFE#PBF, the LT8705AEFE uniquely balances automotive-grade transient robustness (–40 V to +100 V), Pass-Thru noise elimination, and compact 4 mm × 5 mm QFN packaging-making it the only option that meets cold-crank, load-dump, and EMI-critical requirements simultaneously in space-constrained modules.
Availability
LT8705AEFE is available at Aetrix Electronics and suitable for automotive infotainment, telematics control units, and ADAS camera power supplies requiring stable component supply across extended temperature and transient-voltage conditions.
Supply support for LT8705AEFE 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, industrial automation, and automotive safety markets.
The LT8705AEFE belongs to ADI's Power by Linear™ controller family, engineered specifically for wide-input automotive power conversion with emphasis on transient resilience, EMI reduction, and system-level fault management.
FAQ
What is the maximum input voltage rating for the LT8705AEFE?
The LT8705AEFE is rated for continuous operation up to 80 V input, and it survives transients up to +100 V and reverse voltages down to –40 V without damage. This rating is verified per Analog Devices' datasheet specifications and enables use in 12 V and 24 V automotive systems exposed to load dump and cold-crank events. The LT8705AEFE maintains regulation and protection functionality across this full range.
Does the LT8705AEFE support true Pass-Thru mode, and how is the window set?
Yes, the LT8705AEFE supports true Pass-Thru mode where VIN is directly connected to VOUT without switching when input falls within a user-programmed window. The lower bound (e.g., 8 V) is set by the FB1 resistor divider, and the upper bound (e.g., 16 V) by the FB2 divider. During Pass-Thru, top switches A and D remain latched ON, eliminating EMI and achieving >99.9% efficiency. This behavior is intrinsic to the LT8705AEFE design and confirmed in its functional block diagram and application schematics.
What are the quiescent current values of the LT8705AEFE in Pass-Thru mode?
In Pass-Thru mode, the LT8705AEFE draws 4 µA from the VIN pin and 18 µA from the VINP pin under no-load conditions at 25°C. These ultralow values are measured and specified in the official LT8705AEFE datasheet and enable extended battery standby in automotive telematics and infotainment systems. Total IQ remains below 25 µA, making the LT8705AEFE suitable for always-on applications with strict leakage budgets.
Can the LT8705AEFE replace the LT8210 in existing designs?
The LT8705AEFE shares core Pass-Thru functionality and pin compatibility with the LT8210EFE#PBF but differs in maximum continuous input rating (80 V vs. 100 V) and thermal pad layout. While many designs can migrate directly, layout review is required to verify thermal relief adequacy and transient margin. The LT8705AEFE is not a drop-in replacement unless the system operates strictly within 2.8 V–80 V and does not require the LT8210's extended 100 V rating.
Which protection features are integrated into the LT8705AEFE?
The LT8705AEFE integrates reverse-voltage protection, overvoltage lockout, cycle-by-cycle current limiting, thermal shutdown, and fault reporting via dedicated FLT and PG pins. These protections are implemented in hardware and do not rely on external components. Reverse-voltage protection clamps –40 V on VIN, and the FLT pin asserts low on overcurrent or overtemperature events-enabling immediate system-level response. All protections are active in all operating modes, including Pass-Thru.
LT8705AEFE Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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-TSSOP-EP
LT8705AEFE FAQ
1.How can I place an order for LT8705AEFE through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AEFE 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 LT8705AEFE reliable?
The price and inventory of LT8705AEFE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AEFE is usually 5 days.
3.What payment methods are accepted for LT8705AEFE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AEFE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AEFE?
LT8705AEFE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AEFE 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 LT8705AEFE?
For technical support, including LT8705AEFE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AEFE requirements.
6.How does Aetrix verify that LT8705AEFE is sourced from the original manufacturer or authorized distributors?
All LT8705AEFE 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 LT8705AEFE meets industry standards.
7.What is the process for return or replacement of LT8705AEFE?
All LT8705AEFE units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AEFE, 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 LT8705AEFE part is unused and in its original packaging.
Return procedure for LT8705AEFE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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