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Analog Devices Inc. LT8705AEFE#PBF
- Part No.:
- LT8705AEFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AEFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,473
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Product details
Overview
LT8705AEFE#PBF 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 - enabling stable 48V telecom voltage stabilization from 36–80V solar or battery inputs.
For engineers reviewing the LT8705AEFE#PBF datasheet, LT8705AEFE#PBF pinout, LT8705AEFE#PBF application, or LT8705AEFE#PBF equivalent, key selection criteria include its dual feedback loops (input/output voltage and current), MODE pin selectable operation modes (Burst/DCM/FCM), 100–400kHz synchronizable switching frequency, and TSSOP-38 package compatibility with high-temperature industrial designs.
Technical Context
The LT8705AEFE#PBF implements a current-mode control architecture with four independent error amplifiers (EA1–EA4) managing input voltage (FBIN), output voltage (FBOUT), input current (IMON_IN), and output current (IMON_OUT) regulation. Its VC pin serves as the diode-AND of all four amplifier outputs, directly setting peak inductor current via CSP/CSN differential sensing.
It features integrated gate drivers with <20ns rise/fall times, programmable minimum on/off times (260–265ns), and dedicated BOOST1/BOOST2 supplies for high-side NMOS drive. The CLKOUT pin provides both synchronization capability and linear junction temperature monitoring via duty cycle variation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports wide-input systems including 48V telecom, 12–72V automotive, and multi-cell solar arrays without pre-regulation. |
| VOUT Range | 1.3V to 80V - enables buck, boost, and buck-boost operation across single-stage conversion from sub-5V logic rails to high-voltage bus regulation. |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; allows optimization of efficiency vs. size trade-offs in magnetics and EMI filtering. |
| Efficiency | Up to 98% - achieved via synchronous rectification and low-loss gate drivers, reducing thermal load in high-power (>50W) converters. |
| Operating Temp | –40°C to +125°C - qualified for industrial and automotive under-hood applications with guaranteed performance over full range. |
| Package | 38-Lead Plastic TSSOP (FE) - surface-mount package with exposed pad for thermal dissipation; compatible with standard PCB assembly processes. |
| Integrated LDO | 3.3V/12mA - powers external circuitry (e.g., sensors, level shifters) without requiring auxiliary regulators. |
Pinout & Package
LT8705AEFE#PBF uses the FE package: 38-lead plastic TSSOP with exposed thermal pad (Pin 39 = GND). Pin numbering follows standard JEDEC TSSOP layout (top view, Pin 1 at top-left corner).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 4) | Shutdown Control Input | Active-high enable; pulls quiescent current to ≤1µA when grounded - critical for low-power standby modes in battery systems. |
| CSP/CSN (Pins 6/5) | Inductor Current Sense Inputs | Differential pair measuring RSENSE voltage; sets peak current limit in buck/boost modes via VC pin interaction. |
| FBIN/FBOUT (Pins 8/9) | Input & Output Voltage Feedback | High-impedance (≤15nA bias) inputs for precision resistive dividers; enable independent regulation of input and output rails. |
| IMON_IN/IMON_OUT (Pins 3/10) | Current Monitor Outputs | Current-source outputs proportional to sensed input/output current - used for protection, telemetry, or loop coordination. |
| MODE (Pin 2) | Operating Mode Selection | Voltage-controlled selection: <0.4V = FCM, 1.0–1.7V = Burst Mode, >2.3V = DCM - enables dynamic efficiency optimization under light loads. |
| TG1/BG1, TG2/BG2 (Pins 26/17, 21/19) | N-Channel Gate Drivers | Quad drivers with <20ns edge rates and built-in dead-time control - eliminate need for external driver ICs in 4-switch topology. |
| BOOST1/BOOST2 (Pins 28/20) | Floating High-Side Supplies | Bootstrap node connections enabling gate drive above VIN (BOOST1) or VOUT (BOOST2) - essential for NMOS high-side switches. |
| CLKOUT (Pin 13) | Synchronization & Temp Monitor | Provides phase-inverted clock signal for multi-phase sync; duty cycle varies linearly with die temperature (22.7–77% over –40°C to 125°C). |
Key Features
| Feature | Design Value |
|---|---|
| Quad Feedback Loops | Independent regulation of input voltage, output voltage, input current, and output current - enables complex source-sink power management in bidirectional or energy-harvesting systems. |
| Synchronous 4-Switch Topology | Eliminates external Schottky diodes; reduces conduction losses and improves thermal performance in high-current (>5A) applications. |
| Programmable Light-Load Operation | Burst Mode® reduces no-load input current to 2.65mA while maintaining regulation - extends battery runtime in portable telecom equipment. |
| Integrated 3.3V LDO | 12mA output with ±0.5% load regulation - powers auxiliary circuits (e.g., ADC references, microcontroller I/O) without adding discrete regulators. |
| Robust Gate Drive Architecture | 100ns TG→BG and 80ns BG→TG delays prevent shoot-through; 81V SW pin rating supports transient-tolerant designs in 48V automotive systems. |
Applications
| Telecom Voltage Stabilizer | Solar Charge Controller |
|---|---|
Use Scenario: Regulating 48V telecom distribution bus from variable 36–72V input during line transients or backup battery switchover. IC Role / Device Role / Timing Role: Primary buck-boost controller managing bidirectional power flow and maintaining tight output regulation under rapid load steps. Use Value: 98% peak efficiency and 100kHz–400kHz frequency agility minimize heatsink size and simplify EMI filter design for NEBS-compliant systems. | Use Scenario: MPPT-enabled charge controller converting variable PV array output (20–80V) to fixed 54.6V battery charging voltage. IC Role / Device Role / Timing Role: Core DC/DC controller implementing input current limiting and output voltage regulation with real-time telemetry via IMON_IN/IMON_OUT. Use Value: Integrated input/output current monitoring eliminates external sense amplifiers, reducing BOM count and improving measurement accuracy for MPPT algorithms. |
| Automotive Start-Stop System | Industrial 24V/48V Hybrid Bus |
Use Scenario: Maintaining stable 12V/48V rail during engine cranking events where battery voltage dips to 3.5V or surges to 16V. IC Role / Device Role / Timing Role: High-reliability buck-boost controller with –40°C to +125°C operation and robust UVLO thresholds (INTVCC = 4.45–4.85V). Use Value: Dual feedback loops ensure continuous regulation even during extreme input transients, preventing ECU brownouts during cold-cranking. | Use Scenario: Bidirectional power converter interfacing 24V legacy control systems with modern 48V high-efficiency motor drives. IC Role / Device Role / Timing Role: Synchronous 4-switch controller supporting seamless buck/boost transitions without intermediate storage capacitors. Use Value: Single-inductor architecture reduces component count and footprint versus dual-converter solutions, lowering system cost and improving power density. |
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 lacks integrated IMON_IN/IMON_OUT current monitors and SRVO logic outputs; lower max VIN (60V). | Not suitable for input/output current telemetry or coordinated multi-loop protection schemes requiring dedicated monitor pins. | Select only if current monitoring is handled externally and input voltage remains ≤60V. |
| MPQ4332GJ-AEC1-Z | Automotive-grade 4-switch buck-boost controller with AEC-Q100 qualification; narrower VIN range (4–40V); no programmable MODE pin or CLKOUT temp monitor. | Targeted for passenger vehicle infotainment and ADAS; not rated for industrial 80V input or telecom 48V bus stabilization. | Choose for automotive production programs requiring AEC-Q100 compliance and simplified feature set. |
Compared with LTC3780EFE#PBF and MPQ4332GJ-AEC1-Z, the LT8705AEFE#PBF uniquely combines 80V operation, integrated current monitoring, and thermal-aware CLKOUT functionality - making it optimal for high-reliability industrial and telecom systems demanding full parameter visibility and wide input flexibility.
Availability
LT8705AEFE#PBF is available at Aetrix Electronics and suitable for telecom voltage stabilizers, solar charge controllers, automotive start-stop systems, and industrial hybrid bus converters requiring stable component supply across extended temperature ranges and long product lifecycles.
Supply support for LT8705AEFE#PBF 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 full technical and manufacturing continuity for the LT® product family. Linear Technology pioneered high-performance analog ICs for power management, signal conditioning, and RF applications.
The LT8705A product line was designed specifically for high-voltage, high-efficiency buck-boost conversion in mission-critical infrastructure - addressing needs in telecom, renewable energy, and transportation where input voltage variability and reliability are paramount.
FAQ
What is the maximum input voltage rating for the LT8705AEFE#PBF?
The LT8705AEFE#PBF has an absolute maximum input voltage rating of 80V on the VIN pin, with guaranteed operation from 2.8V to 80V. This wide range enables direct interface with unregulated 48V telecom buses, multi-string solar arrays, and 24V/48V automotive systems without pre-regulation stages. The device also tolerates 81V on SW1/SW2 pins during transients, enhancing robustness in noisy environments.
Does the LT8705AEFE#PBF support synchronization with external clock sources?
Yes, the LT8705AEFE#PBF supports external synchronization via its SYNC pin (Pin 14), which accepts TTL/CMOS-compatible clocks from 100kHz to 400kHz. The high-level threshold is 1.3V and low-level threshold is 0.5V, with 20–80% duty cycle tolerance. When synchronized, the internal oscillator locks to the external clock, enabling noise-sensitive multi-rail systems to avoid beat frequencies and simplify EMI filtering.
How does the MODE pin affect operating behavior in the LT8705AEFE#PBF?
The MODE pin (Pin 2) selects among three distinct operating modes: forced continuous conduction mode (<0.4V), Burst Mode® (1.0–1.7V), and discontinuous conduction mode (>2.3V). This enables dynamic efficiency optimization - Burst Mode reduces light-load quiescent current to 2.65mA while maintaining regulation, whereas FCM ensures constant switching frequency for predictable EMI profiles in noise-sensitive applications.
Can the LT8705AEFE#PBF be used in bidirectional power applications?
The LT8705AEFE#PBF supports bidirectional power flow through its dual feedback architecture: FBIN regulates input voltage while FBOUT regulates output voltage, and IMON_IN/IMON_OUT provide directional current telemetry. However, it is not inherently bidirectional - external MOSFET control logic and reverse-polarity protection must be added. Its 4-switch topology and symmetric voltage/current sensing make it well-suited as the core controller in custom bidirectional converters for energy storage or regenerative braking interfaces.
What thermal management considerations apply to the LT8705AEFE#PBF in TSSOP package?
The LT8705AEFE#PBF in FE (TSSOP-38) package has θJA = 25°C/W and requires soldering of the exposed thermal pad (Pin 39) to a solid ground plane for effective heat dissipation. At full load, junction temperature rise can exceed 60°C above ambient; derating is recommended above 85°C ambient. Use of thermal vias under the pad and copper pours on inner layers significantly improves thermal performance, especially in high-efficiency (>95%) designs operating near 125°C junction limit.
LT8705AEFE#PBF 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:
- 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-TSSOP-EP
LT8705AEFE#PBF FAQ
1.How can I place an order for LT8705AEFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AEFE#PBF 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#PBF reliable?
The price and inventory of LT8705AEFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AEFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8705AEFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AEFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AEFE#PBF?
LT8705AEFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AEFE#PBF 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#PBF?
For technical support, including LT8705AEFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AEFE#PBF requirements.
6.How does Aetrix verify that LT8705AEFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8705AEFE#PBF 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#PBF meets industry standards.
7.What is the process for return or replacement of LT8705AEFE#PBF?
All LT8705AEFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AEFE#PBF, 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#PBF part is unused and in its original packaging.
Return procedure for LT8705AEFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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