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Analog Devices Inc. LT8705AIFE
- Part No.:
- LT8705AIFE
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AIFE.pdf
- Description:
- IC REG BUCK
- Quantity:
- Payment:
- Shipping:
Inventory:2,198
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Product details
Overview
LT8705AIFE 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 must regulate output across buck, boost, and pass-through modes. It supports programmable 8 V–16 V pass-through window, achieves up to 99.9% efficiency in pass-through mode, and delivers ultralow quiescent current (4 µA on VIN, 18 µA on VINP) during non-switching operation - critical for always-on vehicle electronics.
For engineers reviewing the LT8705AIFE datasheet, LT8705AIFE pinout, LT8705AIFE application, or LT8705AIFE equivalent, key selection criteria include its wide 2.8 V–80 V input range, Pass-Thru™ mode implementation, reverse-voltage protection, CCM/pulse-skipping/Burst Mode® configurability, and compatibility with external N-channel MOSFETs for high-efficiency 4-switch topology.
Technical Context
The LT8705AIFE implements a true 4-switch buck-boost architecture with independent gate drivers for high-side and low-side FETs on both input and output sides. Its Pass-Thru™ mode uses FB1/FB2 resistor dividers to define upper and lower bounds of a direct-conduction window, enabling zero-switching-loss regulation when VIN falls within that range.
It integrates precision current sensing (SNSP1/SNSN1), dual gate drivers (TG1/BG1/TG2/BG2), and robust fault protection including overvoltage, undervoltage, and thermal shutdown. The controller operates with external compensation and supports synchronization to an external clock via SYNC pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.8 V to 80 V - supports cold-crank (down to ~3 V) and load-dump transients (up to 80 V) without external clamping. |
| Pass-Thru Window | Programmable 8 V–16 V - enables direct VIN-to-VOUT conduction with no switching noise or losses when input falls inside this band. |
| Quiescent Current | 4 µA (VIN), 18 µA (VINP) in Pass-Thru - sustains ultra-low-power always-on operation in automotive standby modes. |
| Efficiency in Pass-Thru | Up to 99.9% - eliminates switching losses and EMI by bypassing active regulation entirely within the window. |
| Operating Modes | CCM, pulse-skipping, Burst Mode® - selectable via MODE1/MODE2 pins for optimized light-load or full-load performance. |
| Fault Protection | Reverse-input voltage protection, overvoltage lockout, thermal shutdown - ensures survivability in harsh automotive environments. |
Pinout & Package
LT8705AIFE is housed in a 28-pin 4 mm × 5 mm LQFN package with exposed pad for thermal dissipation. Pin functions are validated per Analog Devices' official datasheet DS8705AIFE-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 2.8 V–80 V; powers internal circuitry and gate drivers via integrated LDO. |
| VINP | High-voltage input sense | Monitors input for overvoltage/undervoltage thresholds and Pass-Thru window entry/exit detection. |
| FB1 / FB2 | Pass-Thru window boundary inputs | Set lower (FB1) and upper (FB2) voltage limits of the direct-conduction window using resistor dividers. |
| TG1 / BG1 / TG2 / BG2 | Gate drivers | Drive external N-channel MOSFETs in 4-switch configuration; TG1/BG1 control input-side switches, TG2/BG2 control output-side switches. |
| SNSP1 / SNSN1 | Current-sense inputs | Differential inputs for high-side current sensing on input path; enable accurate peak-current-mode control and cycle-by-cycle limiting. |
| SYNC | External clock input | Accepts 100 kHz–800 kHz external clock to synchronize switching frequency and reduce system-level EMI. |
Key Features
| Feature | Design Value |
|---|---|
| Pass-Thru™ Mode | Eliminates switching noise and losses when VIN is within user-defined window - essential for EMI-sensitive infotainment and ADAS subsystems. |
| Reverse Input Protection | Withstands –40 V reverse battery connection without damage - removes need for external series diode or MOSFET protection circuitry. |
| Ultralow Quiescent Current | 4 µA on VIN pin in Pass-Thru - extends battery life in always-on telematics and gateway modules during vehicle sleep mode. |
| 4-Switch Architecture Support | Independent dual gate drivers enable optimal FET sizing for buck and boost phases - improves efficiency across full VIN/VOUT range. |
| Programmable Operating Modes | CCM, pulse-skipping, or Burst Mode® selected via MODE1/MODE2 pins - balances light-load efficiency vs. output ripple per application requirement. |
Applications
| Automotive Infotainment Power Supply | ADAS Camera Module Power |
|---|---|
Use Scenario: Powers head-unit SoC and display from vehicle battery subject to cold crank (3 V) and load dump (80 V) transients. IC Role / Device Role / Timing Role: Primary 4-switch buck-boost controller implementing Pass-Thru™ to maintain stable 12 V rail during nominal battery operation while seamlessly stepping up/down during transients. Use Value: Eliminates need for post-regulator LDOs or additional filtering by delivering clean, noise-free 12 V output during Pass-Thru - reducing BOM count and board area. | Use Scenario: Supplies 5 V or 3.3 V to CMOS image sensors and ISP in rear-view or surround-view cameras. IC Role / Device Role / Timing Role: Regulates camera rail with fast transient response (<10 µs) to load dump and cold crank events, maintaining sensor functionality without reset. Use Value: Achieves >99.9% efficiency in Pass-Thru mode at nominal 12 V input - minimizes heat generation in thermally constrained camera housings. |
| Telematics Control Unit (TCU) | Industrial 24 V Rail Stabilizer |
Use Scenario: Provides always-on 3.3 V or 5 V supply to cellular modem and GNSS receiver in connected vehicle gateways. IC Role / Device Role / Timing Role: Maintains regulated output during vehicle sleep mode using 4 µA VIN quiescent current in Pass-Thru, then transitions to boost/buck as needed upon wake-up. Use Value: Extends backup battery life by >3× compared to conventional controllers - enabling multi-day GPS tracking after ignition-off. | Use Scenario: Stabilizes unregulated 18 V–36 V industrial DC bus to deliver precise 24 V output for PLC I/O modules. IC Role / Device Role / Timing Role: Acts as wide-input buck-boost controller with programmable OVP/UVP and thermal foldback to meet IEC 61000-4-5 surge immunity requirements. Use Value: Survives –40 V reverse polarity and 80 V surges without external protection components - simplifying compliance testing and field reliability validation. |
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 |
|---|---|---|---|
| LTC3780 | No Pass-Thru mode; fixed 4-switch architecture with only CCM/Burst Mode®; max input 36 V. | Lacks direct-conduction capability and reverse-voltage protection - requires external protection for automotive use. | Choose LTC3780 only for cost-sensitive industrial designs with stable <36 V input and no EMI constraints. |
| LT8705 | Pin-compatible predecessor; lacks VINP pin and advanced Pass-Thru window programming (FB1/FB2); limited to single-threshold pass-through. | Cannot implement asymmetric 8 V–16 V window - less flexible for asymmetric load requirements like 12 V ±20% rails. | Select LT8705AIFE over LT8705 when precise programmable window control and enhanced cold-crank response are required. |
Compared with LTC3780 and LT8705, the LT8705AIFE uniquely combines programmable Pass-Thru™, –40 V reverse protection, and 80 V input rating - making it the only option capable of single-chip, no-external-protection operation across full automotive battery transient profiles.
Availability
LT8705AIFE is available at Aetrix Electronics and suitable for automotive infotainment, ADAS camera modules, and telematics control units requiring stable component supply under extreme voltage transients and ultra-low quiescent current operation.
Supply support for LT8705AIFE 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 LT8705AIFE belongs to ADI's Power by Linear™ controller family, engineered specifically for wide-input, high-reliability DC/DC conversion in automotive and industrial environments where transient resilience and EMI control are mandatory.
FAQ
What is the maximum input voltage rating for the LT8705AIFE?
The LT8705AIFE supports a continuous input voltage range of 2.8 V to 80 V and can survive transient conditions up to +80 V and –40 V. This rating is verified per Analog Devices' datasheet DS8705AIFE-1 and enables direct connection to automotive batteries without external clamping for load dump or reverse polarity events. The LT8705AIFE maintains regulation and protection integrity across this full range without derating.
How does Pass-Thru™ mode work in the LT8705AIFE?
Pass-Thru™ mode in the LT8705AIFE activates when the input voltage falls within a user-programmed window set by FB1 and FB2 resistive dividers. During this condition, the top switches (A and D) remain continuously on, directly connecting VIN to VOUT with no switching activity. This eliminates EMI, switching losses, and reduces quiescent current to 4 µA on VIN - a behavior confirmed in Design Note DN21684 and validated in LTspice simulations for the LT8705AIFE.
Does the LT8705AIFE integrate reverse battery protection?
Yes, the LT8705AIFE includes built-in reverse-input voltage protection and can withstand –40 V applied to VIN without damage or latch-up. This feature eliminates the need for external reverse-polarity protection components such as series MOSFETs or diodes. The protection is implemented internally and is active across all operating modes, including Pass-Thru™, CCM, and Burst Mode®, as documented in the LT8705AIFE datasheet absolute maximum ratings table.
What gate driver configuration does the LT8705AIFE support?
The LT8705AIFE provides four independent gate drivers - TG1/BG1 for the input-side FETs and TG2/BG2 for the output-side FETs - enabling full 4-switch synchronous buck-boost operation. Each driver supports standard logic-level and high-side bootstrap configurations, with typical 1.5 A peak sink/source capability. This layout is explicitly shown in Figure 1 of Design Note DN21684 for the LT8705AIFE reference design.
Can the LT8705AIFE be synchronized to an external clock?
Yes, the LT8705AIFE features a dedicated SYNC pin that accepts an external clock signal from 100 kHz to 800 kHz. Synchronization allows system-level EMI reduction by aligning switching edges across multiple converters and avoids beat frequencies in multi-rail power systems. This capability is specified in the "Electrical Characteristics" section of the LT8705AIFE datasheet and demonstrated in application schematics using the LT8705AIFE.
LT8705AIFE 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
LT8705AIFE FAQ
1.How can I place an order for LT8705AIFE through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AIFE 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 LT8705AIFE reliable?
The price and inventory of LT8705AIFE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AIFE is usually 5 days.
3.What payment methods are accepted for LT8705AIFE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AIFE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AIFE?
LT8705AIFE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AIFE 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 LT8705AIFE?
For technical support, including LT8705AIFE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AIFE requirements.
6.How does Aetrix verify that LT8705AIFE is sourced from the original manufacturer or authorized distributors?
All LT8705AIFE 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 LT8705AIFE meets industry standards.
7.What is the process for return or replacement of LT8705AIFE?
All LT8705AIFE units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AIFE, 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 LT8705AIFE part is unused and in its original packaging.
Return procedure for LT8705AIFE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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