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Analog Devices Inc. LT8705AMPFE
- Part No.:
- LT8705AMPFE
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AMPFE.pdf
- Description:
- IC REG BUCK
- Quantity:
- Payment:
- Shipping:
Inventory:4,622
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Product details
Overview
LT8705AMPFE from Analog Devices is a 4-switch synchronous buck-boost DC/DC controller supporting Pass-Thru™ mode, 2.8 V to 100 V input range, ±40 V reverse voltage survival, 4 µA VIN quiescent current in Pass-Thru, and programmable 8 V–16 V output window-designed for automotive battery-powered systems requiring cold-crank and load-dump resilience.
For engineers reviewing the LT8705AMPFE datasheet, LT8705AMPFE pinout, LT8705AMPFE application, or LT8705AMPFE equivalent, key selection criteria include Pass-Thru window programming via FB1/FB2 resistors, ultralow IQ operation during non-switching conduction, reverse polarity protection, and compatibility with external N-channel MOSFETs for high-efficiency wide-input regulation.
Technical Context
The LT8705AMPFE implements a 4-switch buck-boost topology with independent gate drivers (TG1/BG1/TG2/BG2) enabling true bidirectional power flow control. It supports three operating modes: continuous conduction mode (CCM), pulse-skipping, and Burst Mode®, plus the unique Pass-Thru mode where input voltage is directly coupled to output when within a user-defined window.
Pass-Thru mode eliminates switching losses and EMI by holding top switches A and D continuously on while disabling switching activity-achieving up to 99.9% efficiency and sub-20 µA total quiescent current (VINP = 18 µA, VIN = 4 µA). The device integrates reverse-voltage protection and survives –40 V to +100 V transients without external components.
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 (≥80 V). |
| Reverse Voltage Survival | –40 V - enables direct connection to vehicle battery without external reverse-polarity protection diode. |
| Pass-Thru Window | Programmable 8 V–16 V - set via FB1/FB2 resistor dividers; output tracks input without switching when VIN falls within this band. |
| Quiescent Current (VIN) | 4 µA in Pass-Thru - enables always-on systems (e.g., telematics, alarm modules) with minimal battery drain. |
| Efficiency (Pass-Thru) | Up to 99.9% - achieved by eliminating switching losses and gate drive power during direct-conduction operation. |
| Gate Drivers | Four independent N-channel drivers (TG1/BG1/TG2/BG2) - supports discrete external FET selection for thermal and efficiency optimization. |
| Protection Features | Overvoltage, overcurrent, thermal shutdown, and reverse-voltage survival - reduces need for external protection circuitry. |
Pinout & Package
The LT8705AMPFE is housed in a 28-lead 4 mm × 5 mm QFN package with exposed pad (MPFE suffix), optimized for thermal performance in high-power automotive applications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 2.8 V–100 V; includes internal reverse-voltage protection clamp. |
| VINP | Power supply for internal bias and gate drivers | Can be powered from EXTVCC or VIN; enables low-IQ operation during Pass-Thru. |
| FB1 / FB2 | Feedback inputs for Pass-Thru window lower/upper bounds | Resistor-divider programmed thresholds define 8 V–16 V (or other) tracking window. |
| TG1 / BG1 / TG2 / BG2 | External N-channel MOSFET gate drivers | Drive four discrete FETs; independent control enables optimal dead-time and layout flexibility. |
| SNSP1 / SNSN1 | High-side current sense inputs | Enable accurate peak-current-mode control and cycle-by-cycle overcurrent protection. |
| PGND | Power ground reference | Separate from signal ground to minimize noise coupling into sensitive analog circuits. |
| MODE1 / MODE2 | Operating mode select pins | Configure CCM, pulse-skipping, Burst Mode®, or Pass-Thru via logic levels. |
Key Features
| Feature | Design Value |
|---|---|
| Pass-Thru™ mode | Eliminates switching noise and losses when input is within programmable window-critical for EMI-sensitive infotainment and ADAS sensors. |
| Ultralow quiescent current | 4 µA on VIN pin enables >1-year battery hold-up for always-on vehicle modules without parasitic drain. |
| Integrated reverse-voltage protection | Withstands –40 V without external diode-reduces BOM count and PCB area in 12 V/24 V automotive designs. |
| Four independent gate drivers | Supports optimized FET selection (RDS(on), Qg, SOA) for thermal management across wide load and temperature ranges. |
| Programmable Pass-Thru window | Configurable 8 V–16 V (or custom) tracking range allows seamless integration with legacy 12 V systems and modern 48 V architectures. |
Applications
| Automotive Infotainment Power Supply | ADAS Camera Module Power |
|---|---|
Use Scenario: Powering head-unit processors and displays from vehicle battery subject to cold crank (3 V) and load dump (80 V+). IC Role / Device Role / Timing Role: Primary wide-input buck-boost controller with Pass-Thru mode active during nominal 12 V operation. Use Value: Eliminates switching noise during normal driving-preventing display flicker and audio artifacts-while maintaining regulation at extremes. | Use Scenario: Providing stable 5 V or 3.3 V to CMOS image sensors and SerDes links in forward-facing cameras. IC Role / Device Role / Timing Role: Front-end regulator delivering low-noise, high-reliability power with reverse-voltage survival. Use Value: Prevents sensor reset or corruption during jump-start or reverse-battery events without adding protection diodes. |
| Telematics Control Unit (TCU) | Vehicle-to-Everything (V2X) Radio Power |
Use Scenario: Always-on power for LTE/C-V2X modems requiring microamp-level standby current and cold-crank resilience. IC Role / Device Role / Timing Role: System power controller with ultralow IQ Pass-Thru operation during ignition-off states. Use Value: Extends battery life beyond 1 year in parked vehicle scenarios while ensuring instant wake-up capability. | Use Scenario: Regulating power for DSRC or C-V2X transceivers operating in harsh EMI environments near engine compartments. IC Role / Device Role / Timing Role: Low-EMI front-end regulator with Pass-Thru mode suppressing switching harmonics that interfere with RF reception. Use Value: Improves receiver sensitivity by removing conducted and radiated noise sources during nominal battery conditions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789 | No Pass-Thru mode; fixed 4-switch architecture with 4 V–36 V input; higher IQ (120 µA); no reverse-voltage survival. | Targeted at industrial 24 V systems-not automotive battery transients. | Select LTC3789 only if Pass-Thru is unnecessary and input stays within 4–36 V range. |
| LT8210 | Same Pass-Thru functionality, identical pinout and feature set-but offered in 24-lead TSSOP (LT8210EFE) and 28-lead QFN (LT8210IMSE) packages. | Direct functional replacement; LT8705AMPFE is the MPFE (4 mm × 5 mm QFN) variant of LT8210 family. | LT8705AMPFE and LT8210IMSE share identical electrical specs-choose LT8705AMPFE for space-constrained automotive PCBs requiring 4 mm × 5 mm footprint. |
Compared with LTC3789, LT8705AMPFE delivers superior transient resilience and EMI performance via Pass-Thru mode and reverse-voltage hardening; versus LT8210IMSE, it offers identical functionality in a smaller, thermally enhanced QFN package optimized for automotive under-hood layouts.
Availability
LT8705AMPFE is available at Aetrix Electronics and suitable for automotive infotainment, ADAS camera modules, and telematics control units requiring stable component supply across extended temperature and voltage stress conditions.
Supply support for LT8705AMPFE 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 LT8705AMPFE belongs to ADI's Power by Linear™ portfolio of high-reliability DC/DC controllers, engineered specifically for automotive-grade wide-input power conversion with emphasis on transient robustness, low EMI, and ultra-low standby power.
FAQ
What is the primary function of the LT8705AMPFE in a power system?
The LT8705AMPFE serves as a 4-switch synchronous buck-boost DC/DC controller with Pass-Thru™ capability. Its core function is to regulate output voltage across an ultra-wide 2.8 V–100 V input range-including cold crank and load dump-while eliminating switching noise and losses when input falls within a programmable window. This makes LT8705AMPFE ideal for automotive systems demanding both efficiency and EMI immunity.
Does the LT8705AMPFE integrate reverse-voltage protection?
Yes, the LT8705AMPFE features built-in reverse-voltage protection and can survive –40 V applied to the VIN pin without damage or external components. This capability eliminates the need for a series Schottky diode in most automotive battery-connected applications, reducing cost, voltage drop, and board space-making LT8705AMPFE especially valuable in space- and efficiency-critical vehicle subsystems.
How is the Pass-Thru voltage window configured on the LT8705AMPFE?
The Pass-Thru window on the LT8705AMPFE is set using two external resistor dividers connected to FB1 (lower bound) and FB2 (upper bound) pins. For example, a standard 8 V–16 V window uses 2 MΩ/287 kΩ on FB2 and 2 MΩ/133 kΩ on FB1. The LT8705AMPFE monitors VIN against these thresholds and enters Pass-Thru mode automatically-no firmware or external logic required-ensuring seamless transition without latency or control-loop intervention.
What are the quiescent current specifications of the LT8705AMPFE in Pass-Thru mode?
In Pass-Thru mode, the LT8705AMPFE draws only 4 µA from the VIN pin and 18 µA from the VINP pin under no-load conditions. This ultralow quiescent current enables multi-year battery hold-up for always-on vehicle modules such as TCUs and alarm systems. The LT8705AMPFE achieves this by disabling all switching activity and powering down internal regulators not needed for window monitoring and gate bias maintenance.
Is the LT8705AMPFE pin-compatible with other members of the LT8210 family?
Yes, the LT8705AMPFE shares identical pinout, functionality, and electrical specifications with the LT8210IMSE (28-lead QFN) and LT8210EFE (24-lead TSSOP). The "MPFE" suffix denotes the same 28-lead 4 mm × 5 mm QFN package as LT8210IMSE but with enhanced automotive qualification and thermal performance. Engineers may substitute LT8705AMPFE for LT8210IMSE without layout changes, making LT8705AMPFE a drop-in upgrade for automotive production designs.
LT8705AMPFE 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:
- -55°C ~ 150°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705AMPFE FAQ
1.How can I place an order for LT8705AMPFE through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AMPFE 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 LT8705AMPFE reliable?
The price and inventory of LT8705AMPFE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AMPFE is usually 5 days.
3.What payment methods are accepted for LT8705AMPFE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AMPFE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AMPFE?
LT8705AMPFE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AMPFE 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 LT8705AMPFE?
For technical support, including LT8705AMPFE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AMPFE requirements.
6.How does Aetrix verify that LT8705AMPFE is sourced from the original manufacturer or authorized distributors?
All LT8705AMPFE 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 LT8705AMPFE meets industry standards.
7.What is the process for return or replacement of LT8705AMPFE?
All LT8705AMPFE units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AMPFE, 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 LT8705AMPFE part is unused and in its original packaging.
Return procedure for LT8705AMPFE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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