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Analog Devices Inc. LT8705IFE#TRPBF
- Part No.:
- LT8705IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705IFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,193
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Product details
Overview
LT8705IFE#TRPBF from Analog Devices (formerly Linear Technology) is a synchronous 4-switch buck-boost DC/DC controller IC designed for wide-input, wide-output voltage regulation in high-reliability industrial and telecom power systems. It supports VIN from 2.8V to 80V and VOUT from 1.3V to 80V, integrates quad N-channel gate drivers, and features four independent feedback loops (input/output voltage and current). It is used in solar charge controllers where input voltage varies widely across irradiance conditions.
For engineers reviewing the LT8705IFE#TRPBF datasheet, LT8705IFE#TRPBF pinout, LT8705IFE#TRPBF application, or LT8705IFE#TRPBF equivalent, key selection criteria include its 38-pin TSSOP package with high-voltage isolation enhancements, programmable 100–400 kHz switching frequency, integrated 3.3V/12mA LDO, and servo pins indicating active feedback loop status - all critical for stable bidirectional power conversion in battery backup and telecom rectifier designs.
Technical Context
The LT8705IFE#TRPBF implements a current-mode control architecture with diode-ANDed error amplifiers (EA1–EA4) on the VC pin, enabling seamless transition between buck, boost, and buck-boost operating regions without mode switching artifacts. Its four independent regulation loops-FBIN (input voltage), FBOUT (output voltage), IMON_IN (input current), and IMON_OUT (output current)-allow simultaneous constraint enforcement for overvoltage, overcurrent, and input power limiting.
It uses external N-channel MOSFETs in a 4-switch topology with dedicated top (TG1/TG2) and bottom (BG1/BG2) gate drivers, supporting synchronous rectification up to 98% efficiency. The controller includes programmable UVLO, soft-start via SS pin, clock output (CLKOUT) for temperature monitoring and synchronization, and servo outputs (SRVO_FBIN, SRVO_FBOUT, etc.) that indicate real-time loop activity - all implemented in a single monolithic IC with no external compensation required for basic operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports automotive cold-crank (≥4.5V), 48V telecom, and solar PV arrays (up to 100V open-circuit). |
| VOUT Range | 1.3V to 80V - enables direct regulation of 12V, 24V, 48V, and 60V systems from variable inputs without intermediate stages. |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; allows optimization of size vs. efficiency and EMI filtering requirements. |
| Gate Drivers | Quad N-channel drivers (TG1/BG1/TG2/BG2) - drives external high-side and low-side FETs with 20ns rise/fall times and <100ns dead-time control. |
| Integrated LDO | 3.3V/12mA regulator (LDO33 pin) - powers external circuitry (e.g., ADC reference, level shifters) without auxiliary supply. |
| Feedback Loops | Four independent loops (FBIN, FBOUT, IMON_IN, IMON_OUT) - enables simultaneous input voltage clamping, output regulation, and dual-current limiting. |
| Operating Temp | –40°C to +125°C junction - qualified for industrial and telecom equipment operating in uncontrolled ambient environments. |
Pinout & Package
LT8705IFE#TRPBF is housed in a 38-lead plastic TSSOP package (FE38 variant), modified for improved high-voltage operation with enhanced creepage and internal isolation. The exposed pad (Pin 39) must be soldered to PCB ground for thermal and electrical integrity. Pin count and layout match the QFN variant but with different mechanical footprint and thermal resistance (θJA = 25°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 4) | Shutdown control input | Active-high enable; pulls quiescent current to ≤1µA when grounded - essential for system-level power sequencing. |
| FBIN (Pin 8) | Input voltage feedback input | Connects to resistor divider from VIN; regulates input voltage to prevent source overloading or brownout. |
| FBOUT (Pin 9) | Output voltage feedback input | Connects to resistor divider from VOUT; sets regulated output with ±0.5% typical accuracy at 1.207V internal reference. |
| IMON_IN (Pin 3) | Input current monitor output | Sinks current proportional to input current (1µA/mA typical); used for input current limiting and telemetry. |
| IMON_OUT (Pin 10) | Output current monitor output | Sinks current proportional to output current (1µA/mA typical); enables constant-current CV/CC battery charging profiles. |
| VC (Pin 11) | Error amplifier output | Diode-AND node of EA1–EA4 outputs; controls duty cycle based on dominant active loop - requires external RC compensation. |
| SYNC (Pin 14) | External clock input | Accepts 0.5V–1.3V logic levels; synchronizes switching to external master clock to reduce beat frequencies in multi-rail systems. |
| CLKOUT (Pin 13) | Internal clock output | 180° out-of-phase with internal oscillator; duty cycle linearly tracks die temperature - enables passive thermal monitoring. |
| TG1/BG1 (Pins 26/17) | Top/bottom gate drive for Channel 1 | Drives M1/M2 FETs; BOOST1 supplies floating gate bias - supports high-side N-MOS in buck stage with no bootstrap diode loss. |
| TG2/BG2 (Pins 21/19) | Top/bottom gate drive for Channel 2 | Drives M3/M4 FETs; BOOST2 supplies floating gate bias referenced to VOUT - enables high-side N-MOS in boost stage. |
| CSNIN/CSPIN (Pins 36/37) | Input current sense differential inputs | Measure voltage across RSENSE1 (typically 1–10mΩ); support bidirectional current sensing with ±100mV common-mode range. |
| CSNOUT/CSPOUT (Pins 32/34) | Output current sense differential inputs | Measure voltage across RSENSE2; same architecture as input sense but referenced to VOUT - enables accurate load-current telemetry. |
| MODE (Pin 2) | Operating mode select | Voltage-controlled: <0.4V = forced CCM, 1.0–1.7V = Burst Mode®, >2.3V = DCM - optimizes light-load efficiency per application need. |
| EXTVCC (Pin 30) | External bias supply input | Enables INTVCC sourcing from external 6.4–80V rail - reduces power dissipation when VIN is high (e.g., 72V solar input). |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor buck-boost topology | Eliminates need for separate buck and boost converters - reduces BOM count, board area, and magnetic component cost in 48V/24V hybrid systems. |
| Four independent regulation loops | Enables simultaneous enforcement of input voltage clamp, output voltage regulation, input current limit, and output current limit - critical for solar MPPT and battery protection. |
| Servo status outputs (SRVO_xxx) | Open-drain pins (SRVO_FBIN, SRVO_FBOUT, SRVO_IIN, SRVO_IOUT) signal which loop is actively controlling - simplifies fault diagnostics and loop priority debugging. |
| Programmable 100–400 kHz switching | RT resistor sets frequency; higher frequencies allow smaller magnetics and output capacitors - ideal for space-constrained telecom rectifiers. |
| Integrated 3.3V/12mA LDO | Powers external analog circuitry (e.g., current-sense amps, microcontroller I/O) without requiring a separate LDO - improves system integration density. |
| CLKOUT-based temperature monitoring | CLKOUT duty cycle varies linearly with junction temperature - enables real-time thermal tracking without external sensor or ADC channel. |
Applications
| Solar Charge Controller | Telecom Rectifier |
|---|---|
|
Use Scenario: Regulates variable PV array voltage (20–80V) to charge 48V battery bank while enforcing max input current and output voltage limits. IC Role / Device Role / Timing Role: Primary buck-boost controller managing power flow direction, voltage translation, and dual-loop protection (input current + output voltage). Use Value: Enables single-stage MPPT-capable charging without intermediate DC-DC stages; achieves >95% efficiency across 10–100% load range. |
Use Scenario: Converts –48V telecom distribution bus to isolated +48V output for remote radio units, maintaining tight regulation under dynamic load steps. IC Role / Device Role / Timing Role: High-efficiency non-isolated buck-boost controller providing precise 48V output with fast transient response and input overvoltage shutdown. Use Value: Delivers 98% peak efficiency at full load; CLKOUT-based thermal monitoring prevents derating in sealed outdoor cabinets. |
| Automotive 12V/48V Bi-Directional Converter | Industrial Battery Backup System |
|
Use Scenario: Bidirectionally transfers power between 12V starter battery and 48V mild-hybrid rail during regenerative braking and engine start assist. IC Role / Device Role / Timing Role: Synchronous 4-switch controller with independent input/output current monitoring for precise energy accounting and fault detection. Use Value: Supports reverse current flow with <100ns dead-time control; servo outputs confirm active current-limiting loop during transients. |
Use Scenario: Maintains uninterrupted 24V output during AC mains failure by seamlessly switching from grid to battery input using a single power stage. IC Role / Device Role / Timing Role: Voltage-agile controller regulating output from either 18–36V battery or 30–60V rectified AC, with automatic input switchover. Use Value: Eliminates need for OR-ing diodes or separate buck/boost ICs; FBIN/FBOUT loops enforce both input undervoltage lockout and output overvoltage protection. |
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-pin TSSOP package; supports 4–36V input, 1.2–36V output; lacks input/output current monitoring and servo outputs. | Targeted at lower-voltage industrial DC-DC; not suitable for 80V solar or telecom rectifier applications requiring wide VIN/VOUT. | Select LTC3780EFE#PBF only if input stays below 36V and current-loop telemetry is unnecessary - saves cost in fixed-rail systems. |
| MPQ4333AGL-Z | Monolithic 3.5A 4-switch buck-boost IC in 20-pin QFN; 3.3–40V input, 0.8–36V output; integrates power FETs but no current monitoring or servo outputs. | Designed for compact consumer/industrial point-of-load; limited to ≤36V input and fixed 3.5A output - insufficient for high-power telecom or solar. | Choose MPQ4333AGL-Z for space-constrained, medium-power applications where integrated FETs simplify layout but wide voltage range is not needed. |
Compared with LTC3780EFE#PBF and MPQ4333AGL-Z, the LT8705IFE#TRPBF uniquely delivers 80V input capability, four independent regulation loops with real-time servo status, and high-voltage TSSOP packaging - making it the only option among the three for 48V/60V telecom rectifiers and high-VOC solar charge controllers requiring comprehensive protection telemetry.
Availability
LT8705IFE#TRPBF is available at Aetrix Electronics and suitable for solar charge controllers, telecom rectifiers, and automotive 12V/48V bi-directional converters requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT8705IFE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT8705IFE#TRPBF belongs to Linear's high-voltage buck-boost controller product line, engineered specifically for wide-input industrial power conversion where reliability, precision regulation, and multi-loop protection are mandatory - not just desirable.
FAQ
What is the maximum input voltage supported by the LT8705IFE#TRPBF?
The LT8705IFE#TRPBF supports an absolute maximum input voltage of 80V on the VIN pin, with operational functionality guaranteed from 2.8V to 80V. This makes the LT8705IFE#TRPBF suitable for high-voltage solar arrays, 48V telecom systems, and industrial battery banks where input transients may exceed nominal ratings.
Does the LT8705IFE#TRPBF integrate gate drivers for external MOSFETs?
Yes, the LT8705IFE#TRPBF integrates four independent N-channel gate drivers - TG1/BG1 for Channel 1 and TG2/BG2 for Channel 2 - each capable of driving high-side and low-side FETs with 20ns rise/fall times and programmable dead time. These drivers eliminate the need for external driver ICs in 4-switch buck-boost designs using the LT8705IFE#TRPBF.
Can the LT8705IFE#TRPBF regulate both input and output voltage simultaneously?
Yes, the LT8705IFE#TRPBF features separate FBIN and FBOUT pins connected to independent error amplifiers (EA3 and EA4), allowing simultaneous regulation of input voltage (e.g., to prevent PV array overvoltage) and output voltage (e.g., to maintain battery charging profile). The VC pin performs diode-AND logic to prioritize the most restrictive loop in real time.
What is the purpose of the SRVO_FBIN and SRVO_FBOUT pins on the LT8705IFE#TRPBF?
The SRVO_FBIN and SRVO_FBOUT pins are open-drain logic outputs on the LT8705IFE#TRPBF that go low when their respective feedback loops (input voltage and output voltage) are actively controlling the converter. They provide real-time visibility into which regulation loop dominates - invaluable for debug, telemetry, and fault logging in safety-critical power systems using the LT8705IFE#TRPBF.
Is the LT8705IFE#TRPBF compatible with external clock synchronization?
Yes, the LT8705IFE#TRPBF includes a dedicated SYNC pin (Pin 14) that accepts external TTL/CMOS clock signals from 100kHz to 400kHz. When driven above 1.3V, it synchronizes the internal oscillator to the external clock - reducing EMI interference in multi-rail systems and enabling deterministic timing alignment across multiple LT8705IFE#TRPBF-based power supplies.
LT8705IFE#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 (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705IFE#TRPBF FAQ
1.How can I place an order for LT8705IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705IFE#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 LT8705IFE#TRPBF reliable?
The price and inventory of LT8705IFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705IFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8705IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705IFE#TRPBF?
LT8705IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705IFE#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 LT8705IFE#TRPBF?
For technical support, including LT8705IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705IFE#TRPBF requirements.
6.How does Aetrix verify that LT8705IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8705IFE#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 LT8705IFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8705IFE#TRPBF?
All LT8705IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705IFE#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 LT8705IFE#TRPBF part is unused and in its original packaging.
Return procedure for LT8705IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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