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Analog Devices Inc. LT8705AEFE#TRPBF
- Part No.:
- LT8705AEFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AEFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,399
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Product details
Overview
LT8705AEFE#TRPBF 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 systems. It supports input voltages from 2.8V to 80V and output voltages from 1.3V to 80V, features quad N-channel MOSFET gate drivers, integrated input/output current and voltage feedback loops, and operates in buck, boost, or buck-boost modes using a single inductor - enabling use in solar charge controllers and telecom voltage stabilizers.
For engineers reviewing the LT8705AEFE#TRPBF datasheet, LT8705AEFE#TRPBF pinout, LT8705AEFE#TRPBF application, or LT8705AEFE#TRPBF equivalent, key selection considerations include its 38-lead TSSOP package with exposed pad, –40°C to 125°C operating junction temperature, 100kHz–400kHz synchronizable switching frequency, integrated 3.3V/12mA LDO, and support for Burst Mode®, DCM, or forced CCM via the MODE pin.
Technical Context
The LT8705AEFE#TRPBF implements a current-mode control architecture with four independent feedback loops: input voltage (FBIN), output voltage (FBOUT), input current (IMON_IN), and output current (IMON_OUT). Its VC pin serves as the error amplifier output controlling PWM duty cycle across all operating modes.
It uses external N-channel MOSFETs driven by dedicated top (TG1/TG2) and bottom (BG1/BG2) gate drivers, with BOOST1/BOOST2 pins supplying floating gate drive for high-side switches. The device supports seamless mode transitions and includes dedicated servo outputs (SRVO_FBIN, SRVO_FBOUT, etc.) for loop activity indication - though these are not available in the FE package per Note 5.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports wide-input applications including automotive cold-crank (≥4.5V) and 48V telecom systems. |
| VOUT Range | 1.3V to 80V - enables bidirectional voltage conversion without polarity reversal or additional topology changes. |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; synchronizable to external clock for EMI reduction in multi-rail systems. |
| Operating Temp | –40°C to 125°C junction - qualified for under-hood automotive and industrial environments. |
| Package | 38-lead plastic TSSOP with exposed pad - thermally enhanced for high-power density designs; pin-compatible with QFN variant but excludes SRVO and SWEN pins. |
| Integrated LDO | 3.3V/12mA - powers external circuitry (e.g., sensors, level shifters) without requiring separate regulator. |
| Feedback Loops | 4 independent loops (FBIN, FBOUT, IMON_IN, IMON_OUT) - enables precise regulation of input/output voltage and current for battery charging or constant-power loads. |
Pinout & Package
LT8705AEFE#TRPBF is housed in a 38-lead plastic TSSOP package (FE38 variation) with an exposed thermal pad (Pin 39) that must be soldered to the PCB ground plane. This package lacks SRVO_FBIN, SRVO_IIN, SRVO_IOUT, SRVO_FBOUT, and SWEN pins present in the QFN variant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 4) | Shutdown control input | Pull high ≥1.184V to enable; pull low ≤0.35V to reduce quiescent current to <1µA. |
| FBIN (Pin 8) | Input voltage feedback input | Connects to resistor divider from VIN; regulates input voltage with 1.184V reference (LT8705AE grade). |
| FBOUT (Pin 9) | Output voltage feedback input | Connects to resistor divider from VOUT; regulates output voltage with 1.193V reference (LT8705AE grade). |
| IMON_IN (Pin 3) | Input current monitor output | Sinks current proportional to input current; used for input current limiting or monitoring. |
| IMON_OUT (Pin 10) | Output current monitor output | Sinks current proportional to output current; enables constant-current or overcurrent protection schemes. |
| VC (Pin 11) | Error amplifier output | Drives compensation network; sets peak inductor current threshold via CSP/CSN differential voltage. |
| SYNC (Pin 14) | External clock input | Accepts 0.5V–1.3V logic-level sync signal; overrides internal oscillator for synchronized multi-phase operation. |
| GATEVCC (Pin 18) | Gate driver supply | Must be tied to INTVCC; supplies 6.35V to all gate drivers (TG1/TG2/BG1/BG2). |
| BOOST1 / BOOST2 (Pins 28, 20) | Floating gate drive supplies | Provide bootstrapped voltage for high-side NMOS gates; BOOST1 swings up to VIN + GATEVCC, BOOST2 up to VOUT + GATEVCC. |
| TG1 / TG2 (Pins 26, 21) | Top gate drivers | Drive gates of high-side NMOS switches M1 and M4; require external bootstrap capacitors. |
| BG1 / BG2 (Pins 17, 19) | Bottom gate drivers | Drive gates of low-side NMOS switches M2 and M3; referenced to GND. |
| VIN (Pin 38) | Main input supply | Primary power input; must be locally bypassed with ≥4.7µF ceramic capacitor. |
| INTVCC (Pin 1) | Internal 6.35V regulator | Supplies gate drivers and internal circuitry; powered from VIN or EXTVCC (if >6.4V). |
| LDO33 (Pin 7) | 3.3V auxiliary regulator | Provides regulated 3.3V/12mA output; requires ≥0.1µF ceramic bypass capacitor. |
| MODE (Pin 2) | Operating mode select | 0.4V = forced CCM; floating = Burst Mode®; >2.3V = DCM - enables efficiency optimization across load range. |
| GND (Pins 16, 39) | Power and signal ground | Exposed pad (Pin 39) is GND and must be soldered for thermal and electrical performance. |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor buck-boost topology | Eliminates need for separate buck and boost converters; reduces BOM count and board space in wide-input-range systems. |
| Quad N-channel MOSFET gate drivers | Enables full-synchronous rectification with external NMOS devices, achieving up to 98% efficiency in optimized designs. |
| Four independent regulation loops | Supports complex power management schemes such as input current-limited solar MPPT or output current-regulated battery charging. |
| Synchronizable 100kHz–400kHz oscillator | Allows EMI spread-spectrum control and phase interleaving in multi-converter systems to reduce input ripple current. |
| Integrated 3.3V/12mA LDO | Reduces system component count by powering auxiliary circuitry (e.g., ADC references, microcontroller I/O) without external regulators. |
| –40°C to 125°C operating junction temperature | Qualified for harsh environments including automotive engine compartments and industrial motor drives. |
Applications
| Solar Charge Controller | Automotive DC-DC Converter |
|---|---|
Use Scenario: Regulating variable PV array voltage (20V–80V) to charge 12V/24V/48V battery banks while enforcing maximum input current limits. IC Role / Device Role / Timing Role: Buck-boost controller managing bidirectional energy flow, with FBIN regulating input voltage and IMON_IN enforcing MPPT current limit. Use Value: Enables single-stage conversion from wide-input solar sources to stable battery voltage without intermediate bus stages or topology switching. | Use Scenario: Converting vehicle battery voltage (6V–16V during cold crank or load dump) to stable 5V/12V/48V rails for infotainment, ADAS, or lighting modules. IC Role / Device Role / Timing Role: High-reliability DC-DC controller supporting wide VIN transients and providing precise output voltage regulation under dynamic load steps. Use Value: Maintains regulated output during 4.5V cold-crank and 60V load-dump events, meeting ISO 16750-2 requirements without external protection circuitry. |
| Telecom Voltage Stabilizer | Industrial 48V Power System |
Use Scenario: Stabilizing –48V telecom supply (–36V to –72V range) to deliver tightly regulated +3.3V, +5V, or +12V outputs for line cards and baseband processors. IC Role / Device Role / Timing Role: Negative-input buck-boost controller operating with inverted input polarity; FBOUT regulates output while IMON_OUT enforces current limits. Use Value: Delivers high-efficiency, low-noise power with fast transient response (<2ms recovery) required for sensitive RF and digital circuits. | Use Scenario: Providing isolated or non-isolated 48V-to-12V/24V conversion in factory automation PLCs, where input may vary from 36V–75V due to long cable drops or battery backup. IC Role / Device Role / Timing Role: Wide-input buck-boost controller with programmable MODE pin enabling Burst Mode® at light loads and forced CCM at full load. Use Value: Achieves >94% efficiency across 10mA–10A load range while maintaining <15mV output ripple and ±0.5% regulation accuracy. |
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 38-lead TSSOP package; identical pinout except missing SRVO outputs and CLKOUT; fixed 200kHz/300kHz/400kHz options (no RT adjustment); no integrated LDO33. | Best suited for cost-sensitive, fixed-frequency applications where loop activity monitoring is unnecessary and external 3.3V rail exists. | Select LTC3780EFE#PBF when design prioritizes lower BOM cost and does not require programmable frequency or auxiliary LDO. |
| MPQ4333AGL-AEC1-Z | Monolithic 3.5A buck-boost converter (not controller); integrates MOSFETs; max VIN = 36V; max VOUT = 36V; no input current sensing; AEC-Q100 Grade 1. | Targeted at space-constrained automotive body electronics where full integration and qualification outweigh flexibility needs. | Choose MPQ4333AGL-AEC1-Z only for compact, low-power (<3.5A) automotive applications requiring AEC-Q100 compliance and no external FETs. |
Compared with LTC3780EFE#PBF and MPQ4333AGL-AEC1-Z, the LT8705AEFE#TRPBF offers superior voltage range (80V), full 4-loop regulation, programmable frequency, and integrated LDO - making it optimal for high-flexibility, high-reliability industrial and telecom systems where external FET selection and precision control are critical.
Availability
LT8705AEFE#TRPBF is available at Aetrix Electronics and suitable for solar charge controllers, automotive DC-DC converters, and telecom voltage stabilizers requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT8705AEFE#TRPBF 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, formed through the acquisition of Linear Technology in 2017.
The LT8705A product line delivers high-voltage, high-efficiency buck-boost controllers for demanding power conversion applications in industrial, automotive, and telecommunications infrastructure where wide input/output ranges and precise regulation are essential.
FAQ
What is the maximum input voltage rating for the LT8705AEFE#TRPBF?
The LT8705AEFE#TRPBF has an absolute maximum input voltage rating of 80V on the VIN pin, with recommended operating range from 2.8V to 80V. Exceeding 80V may cause permanent damage. The device is specifically designed for high-voltage applications such as solar arrays and 48V telecom systems, and its robust input stage supports transient conditions like automotive load dump when properly protected externally.
Does the LT8705AEFE#TRPBF support synchronous rectification?
Yes, the LT8705AEFE#TRPBF supports full synchronous rectification via its quad N-channel MOSFET gate drivers (TG1, TG2, BG1, BG2). It controls four external NMOS transistors in a 4-switch buck-boost configuration, eliminating body-diode conduction losses and enabling efficiencies up to 98% in optimized designs. No external Schottky diodes are required when using synchronous MOSFETs with appropriate gate drive timing.
What is the function of the MODE pin on the LT8705AEFE#TRPBF?
The MODE pin on the LT8705AEFE#TRPBF selects the light-load operating mode: <0.4V enables forced continuous conduction mode (FCM), floating enables Burst Mode® operation for ultra-low quiescent current, and >2.3V enables discontinuous conduction mode (DCM). This allows designers to optimize efficiency across the full load range - Burst Mode® achieves <2.65mA quiescent current at no load, while FCM ensures low output ripple at light loads.
Can the LT8705AEFE#TRPBF regulate both input and output current simultaneously?
Yes, the LT8705AEFE#TRPBF integrates independent input current (IMON_IN) and output current (IMON_OUT) regulation loops, each with dedicated amplifiers and reference voltages (1.187V–1.229V). These loops can be configured to enforce hard current limits or provide proportional current monitoring signals. Simultaneous regulation is supported in applications such as solar MPPT (input current limited) with battery charging (output current controlled).
Is the LT8705AEFE#TRPBF pin-compatible with the LT8705A QFN variant?
No, the LT8705AEFE#TRPBF (TSSOP) is not fully pin-compatible with the LT8705AEUHF#TRPBF (QFN). While core power and control pins (VIN, FBIN, FBOUT, TG1, BG1, etc.) align, the TSSOP package omits SRVO_FBIN, SRVO_IIN, SRVO_IOUT, SRVO_FBOUT, and SWEN pins - and repurposes Pin 1 as INTVCC instead of GND. Layout redesign and schematic updates are required when migrating between packages.
LT8705AEFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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#TRPBF FAQ
1.How can I place an order for LT8705AEFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AEFE#TRPBF 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#TRPBF reliable?
The price and inventory of LT8705AEFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AEFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8705AEFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AEFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AEFE#TRPBF?
LT8705AEFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AEFE#TRPBF 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#TRPBF?
For technical support, including LT8705AEFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AEFE#TRPBF requirements.
6.How does Aetrix verify that LT8705AEFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8705AEFE#TRPBF 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#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8705AEFE#TRPBF?
All LT8705AEFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AEFE#TRPBF, 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#TRPBF part is unused and in its original packaging.
Return procedure for LT8705AEFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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