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Analog Devices Inc. LT8705AHFE
- Part No.:
- LT8705AHFE
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AHFE.pdf
- Description:
- IC REG BUCK
- Quantity:
- Payment:
- Shipping:
Inventory:2,782
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Product details
Overview
LT8705AHFE from Analog Devices is a 4-switch synchronous buck-boost DC/DC controller supporting Pass-Thru™ mode, operating from 2.8 V to 100 V input, regulating output between programmable 8 V–16 V window, with 4 µA VIN quiescent current and up to 99.9% efficiency in Pass-Thru region-used in automotive battery-supplied systems requiring cold-crank and load-dump resilience.
For engineers reviewing the LT8705AHFE datasheet, LT8705AHFE pinout, LT8705AHFE application, or LT8705AHFE equivalent, key selection considerations include its Pass-Thru voltage window programming via FB1/FB2 resistors, ultralow IQ in non-switching state, reverse-voltage protection, and compatibility with external N-channel MOSFETs for high-efficiency wide-input automotive power rails.
Technical Context
The LT8705AHFE implements a 4-switch buck-boost topology with independent gate drivers for four external N-channel MOSFETs (A/B/C/D), enabling seamless transition between buck, boost, and Pass-Thru modes. Its MODE1/MODE2 pins select CCM, pulse-skipping, or Burst Mode® operation, while FB1 and FB2 set lower and upper bounds of the Pass-Thru window.
Pass-Thru mode activates when VIN falls within the programmed window: top switches A and D remain continuously on, eliminating switching losses and EMI; SNSP1/SNSN1 sense current for overcurrent protection; VINP supports high-side sensing up to 100 V with 18 µA quiescent current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.8 V to 100 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 - output tracks input without switching when VIN is within this band, enabling near-zero EMI and >99.9% efficiency |
| VIN Quiescent Current | 4 µA - enables always-on systems with minimal standby power draw during Pass-Thru operation |
| VINP Quiescent Current | 18 µA - supports high-side input monitoring at up to 100 V with negligible bias current |
| Reverse Voltage Protection | –40 V survival - protects against reverse battery connection without external components |
| Operating Temperature | –40°C to +150°C junction - qualified for under-hood automotive environments |
Pinout & Package
The LT8705AHFE is housed in a 38-lead 5 mm × 7 mm thermally enhanced eTSSOP package with exposed pad (EP).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 2.8 V–100 V; powers internal circuitry and gate drivers; includes –40 V reverse protection |
| VINP | High-side input monitor | Enables accurate high-voltage sensing up to 100 V with dedicated low-IQ bias path |
| FB1, FB2 | Pass-Thru window feedback inputs | Set lower (FB1) and upper (FB2) bounds of Pass-Thru voltage window via resistor dividers |
| TG1, BG1, TG2, BG2 | Gate drivers | Drive external N-channel MOSFETs A/B/C/D; support 5 V–12 V gate drive with fast rise/fall times |
| SNSP1, SNSN1 | Current sense inputs | Differential inputs for high-side current sensing; enable cycle-by-cycle overcurrent protection |
| MODE1, MODE2 | Operating mode select | Configure CCM, pulse-skipping, or Burst Mode®; determine light-load behavior and regulation accuracy |
Key Features
| Feature | Design Value |
|---|---|
| Pass-Thru™ mode | Eliminates switching noise and losses by passing VIN directly to VOUT within user-defined window-critical for EMI-sensitive infotainment and ADAS subsystems |
| Ultralow quiescent current | 4 µA on VIN and 18 µA on VINP in Pass-Thru mode-enables compliance with automotive ISO 16750-2 quiescent current requirements |
| Integrated reverse-battery protection | Withstands –40 V without external diodes or FETs-reduces BOM count and board space in vehicle power distribution units |
| Wide input survival range | Operates from 2.8 V to 100 V, survives transient spikes up to ±100 V-meets ISO 7637-2 and ISO 16750-2 pulse test requirements |
| Independent gate drivers | Four dedicated drivers (TG1/BG1/TG2/BG2) with programmable dead time-enables optimal timing control for high-efficiency 4-switch implementation |
Applications
| Automotive Infotainment Power Supply | ADAS Camera Module Rail |
|---|---|
Use Scenario: Powering head-unit SoCs and displays from 12 V battery subject to cold crank and load dump transients. IC Role / Device Role / Timing Role: Primary buck-boost controller managing wide-input regulation and Pass-Thru mode to maintain stable 12 V rail during engine start. Use Value: Eliminates need for post-regulator LDOs or filters by delivering ultra-low-noise output during Pass-Thru, reducing thermal stress and EMI filtering complexity. | Use Scenario: Supplying image sensor and ISP in rear-view or surround-view cameras mounted in vehicle exterior locations. IC Role / Device Role / Timing Role: High-reliability front-end regulator providing 5 V or 3.3 V from battery with reverse polarity and surge immunity. Use Value: Survives –40 V reverse battery events and 100 V load dumps without latch-off or component damage, ensuring camera uptime during service errors. |
| Body Control Module (BCM) Core Rail | Telematics Control Unit (TCU) Input Stage |
Use Scenario: Generating always-on 5 V or 3.3 V for microcontroller and CAN transceivers in BCMs with extended sleep-mode requirements. IC Role / Device Role / Timing Role: Low-quiescent-current buck-boost controller maintaining regulated output during vehicle off-state with battery voltage as low as 3 V. Use Value: 4 µA VIN IQ enables multi-year battery hold-up without excessive drain-meeting OEM requirements for <100 µA total system sleep current. | Use Scenario: Conditioning 12 V battery input for LTE/V2X modems and GNSS receivers in TCUs exposed to harsh electrical environments. IC Role / Device Role / Timing Role: Wide-input pre-regulator delivering clean, stable intermediate rail before point-of-load converters. Use Value: Pass-Thru mode suppresses switching artifacts that would otherwise corrupt sensitive RF receiver front-ends during nominal battery operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8705AIFE | Same functionality but in 38-lead FE package (exposed pad not connected); 150°C max junction temp vs. 150°C for HFE | Lower thermal performance in high-power density layouts; no exposed thermal pad for PCB heat sinking | Select LT8705AHFE when board-level thermal management requires maximum power dissipation capability |
| LT8210HFE | Successor device with identical Pass-Thru architecture, same pinout, improved startup behavior and tighter FB tolerance (±0.5% vs. ±1%) | Direct drop-in replacement in new designs; supports same 2.8 V–100 V range and 8 V–16 V Pass-Thru window | Choose LT8210HFE for new designs requiring higher output voltage accuracy and faster transient response |
Compared with LT8705AHFE, LT8705AIFE lacks thermal enhancement for high-current operation, while LT8210HFE offers improved precision and responsiveness-making LT8705AHFE optimal for cost-sensitive, thermally constrained legacy automotive platforms requiring proven reliability.
Availability
LT8705AHFE is available at Aetrix Electronics and suitable for automotive infotainment systems, ADAS camera modules, and body control modules requiring stable component supply across extended temperature and voltage stress conditions.
Supply support for LT8705AHFE 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 automotive, industrial, communications, and healthcare markets.
The LT8705A product line delivers robust, wide-input-range DC/DC controllers for automotive power systems-designed specifically to replace discrete solutions in battery-supplied ECUs facing extreme voltage transients and low-IQ demands.
FAQ
What is the primary function of the LT8705AHFE in a power system?
The LT8705AHFE serves as a 4-switch synchronous buck-boost DC/DC controller that regulates output voltage across input voltages ranging from 2.8 V to 100 V. Its defining feature is Pass-Thru™ mode, where it passes input voltage directly to output within a programmable window-eliminating switching noise and losses. The LT8705AHFE is used in automotive systems to maintain stable rails during cold crank and load dump events without external protection components.
How does Pass-Thru mode improve efficiency in the LT8705AHFE?
In Pass-Thru mode, the LT8705AHFE turns on top switches A and D continuously, bypassing active switching entirely when input voltage lies within the programmed window (e.g., 8 V–16 V). This eliminates switching losses, gate drive losses, and EMI generation, achieving up to 99.9% efficiency. The LT8705AHFE draws only 4 µA from VIN in this state-critical for meeting automotive quiescent current specifications.
Can the LT8705AHFE withstand reverse battery connection?
Yes, the LT8705AHFE survives –40 V applied to VIN without damage or latch-up, providing integrated reverse-voltage protection. This eliminates the need for external reverse-polarity protection diodes or MOSFETs in automotive designs. The LT8705AHFE maintains functionality after the fault clears, making it suitable for battery-connected modules where operator error may occur.
What package type is used for the LT8705AHFE, and why is it significant?
The LT8705AHFE uses a 38-lead 5 mm × 7 mm thermally enhanced eTSSOP package with an exposed pad (EP). This package provides superior thermal performance compared to standard TSSOP variants, enabling reliable operation at high ambient temperatures and continuous load currents typical in under-hood automotive applications. The exposed pad must be soldered to a thermal pad on the PCB for optimal junction-to-board thermal resistance.
How is the Pass-Thru voltage window configured on the LT8705AHFE?
The Pass-Thru window is set using two external resistor dividers connected to FB1 (lower bound) and FB2 (upper bound). For example, a window of 8 V–16 V is achieved with 2 MΩ/287 kΩ on FB2 and 2 MΩ/133 kΩ on FB1. The LT8705AHFE monitors these nodes to determine when to enter or exit Pass-Thru mode-no additional ICs or firmware are required for window definition or transition control.
LT8705AHFE 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 ~ 150°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705AHFE FAQ
1.How can I place an order for LT8705AHFE through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AHFE 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 LT8705AHFE reliable?
The price and inventory of LT8705AHFE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AHFE is usually 5 days.
3.What payment methods are accepted for LT8705AHFE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AHFE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AHFE?
LT8705AHFE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AHFE 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 LT8705AHFE?
For technical support, including LT8705AHFE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AHFE requirements.
6.How does Aetrix verify that LT8705AHFE is sourced from the original manufacturer or authorized distributors?
All LT8705AHFE 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 LT8705AHFE meets industry standards.
7.What is the process for return or replacement of LT8705AHFE?
All LT8705AHFE units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AHFE, 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 LT8705AHFE part is unused and in its original packaging.
Return procedure for LT8705AHFE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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