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Analog Devices Inc. LT8705MPFE#TRPBF
- Part No.:
- LT8705MPFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705MPFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,447
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Product details
Overview
LT8705MPFE#TRPBF from Analog Devices (formerly Linear Technology) is a high-voltage synchronous 4-switch buck-boost DC/DC controller IC designed for wide-input, wide-output voltage regulation in harsh environments. 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. It is used in telecom voltage stabilizers, solar charge controllers, and automotive battery management systems where VIN may be above, below, or equal to VOUT.
For engineers reviewing the LT8705MPFE#TRPBF datasheet, LT8705MPFE#TRPBF pinout, LT8705MPFE#TRPBF application, or LT8705MPFE#TRPBF equivalent, key selection considerations include its –55°C to 150°C extended temperature grade, integrated input/output current monitoring with programmable thresholds, servo feedback loop status indication, and compatibility with external MOSFETs for high-reliability industrial power conversion.
Technical Context
The LT8705MPFE#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)-all diode-ANDed at the VC error amplifier output. Its 4-switch topology enables seamless buck-boost transition without discontinuity, supporting continuous conduction mode (CCM), discontinuous conduction mode (DCM), and Burst Mode® operation selectable via the MODE pin.
It features synchronized fixed-frequency operation (100kHz–400kHz) set by an external RT resistor, onboard 6.35V INTVCC regulator and 3.3V/12mA LDO, and dedicated open-drain SRVO pins (QFN-only) indicating active feedback loops. The FE package variant uses TSSOP-38 with modified layout for improved high-voltage isolation and excludes SWEN and SRVO pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V (with EXTVCC > 6.4V) to 80V - supports wide-range inputs including 24V/48V telecom, 12–72V automotive, and unregulated solar arrays. |
| VOUT Range | 1.3V to 80V - enables single-stage regulation across buck, buck-boost, and boost regions without topology change. |
| Switching Frequency | 100kHz to 400kHz (RT-programmable) - balances efficiency, EMI, and magnetics size; synchronizable via SYNC pin. |
| Efficiency | Up to 98% - achieved via synchronous rectification using external N-MOSFETs and low-loss gate drivers. |
| Operating Temp | –55°C to +150°C (MP grade) - qualified for military, aerospace, and under-hood automotive applications. |
| Feedback Loops | 4 integrated loops (FBIN, FBOUT, IMON_IN, IMON_OUT) - enables precise input/output voltage and current limiting, critical for battery charging and fault protection. |
| Package | 38-lead TSSOP (FE) with exposed pad - optimized for high-voltage creepage/clearance and thermal dissipation in industrial PCBs. |
Pinout & Package
LT8705MPFE#TRPBF is housed in a 38-lead plastic TSSOP (FE package), modified for enhanced high-voltage operation and featuring an exposed GND pad (Pin 39) that must be soldered to the PCB for thermal and electrical integrity. Unlike the QFN variant, the FE package omits SWEN and all SRVO pins (SRVO_FBIN, SRVO_FBOUT, SRVO_IIN, SRVO_IOUT), and internally ties SWEN to INTVCC.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 4) | Shutdown control input | Active-low enable; pulls quiescent current to ≤1µA when grounded - essential for system-level power sequencing. |
| FBIN (Pin 8), FBOUT (Pin 9) | Input/output voltage feedback inputs | Differential inputs to dedicated error amplifiers (EA3/EA4); regulate VIN and VOUT independently with 1.205V/1.207V internal references. |
| IMON_IN (Pin 3), IMON_OUT (Pin 10) | Current monitor outputs | Current-source outputs proportional to sensed input/output current; used for programmable OCP and telemetry. |
| VC (Pin 11) | Error amplifier output | Diode-AND node of EA1–EA4 outputs; drives external compensation network to stabilize all four control loops. |
| SYNC (Pin 14), CLKOUT (Pin 13) | Frequency synchronization I/O | SYNC accepts external clock (1.3V–5.5V); CLKOUT provides phase-inverted oscillator signal and linear junction temperature monitoring. |
| BOOST1/BOOST2 (Pins 28/20), TG1/TG2 (Pins 26/21), BG1/BG2 (Pins 17/19) | Gate drive outputs | Quad N-MOSFET drivers with 20ns rise/fall times; BOOST1 swings up to VIN + GATEVCC, BOOST2 up to VOUT + GATEVCC. |
| CSNIN/CSPIN (Pins 36/37), CSNOUT/CSPOUT (Pins 32/34) | Current sense differential inputs | High-side current sensing inputs (±100mV range, 1.5–80V common-mode) - enable accurate input/output current measurement with external shunts. |
| INTVCC (Pin 1), GATEVCC (Pin 18) | Internal supply rails | 6.35V regulated output powering gate drivers; must be connected directly to GATEVCC - no external sourcing allowed. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous 4-switch buck-boost topology | Enables single-inductor VIN-above/below/equal-to-VOUT regulation without mode switching artifacts or output glitches. |
| Integrated 4-loop feedback control | Simultaneous regulation of input voltage, output voltage, input current, and output current - ideal for bidirectional power converters and battery charge/discharge systems. |
| Programmable operating modes | MODE pin selects forced CCM (<0.4V), Burst Mode® (floating), or DCM (>2.3V) - optimizes light-load efficiency across diverse load profiles. |
| High-temperature MP grade qualification | –55°C to +150°C guaranteed operation with lifetime derating beyond 125°C - meets MIL-PRF-38535 Class K and automotive AEC-Q100 stress requirements. |
| Input/output current monitoring with servo status | IMON_IN/IMON_OUT provide analog current telemetry; FE package retains full current loop functionality despite omission of SRVO pins. |
| Robust high-voltage TSSOP package | FE package includes reinforced creepage/clearance, exposed GND pad for thermal management, and pinout optimized for >80V system isolation. |
Applications
| Telecom Voltage Stabilizer | Solar Charge Controller |
|---|---|
|
Use Scenario: Regulating fluctuating -48V telecom plant voltage to stable 54V for remote radio units under varying line/load conditions. IC Role / Device Role / Timing Role: Primary buck-boost controller managing bidirectional power flow and maintaining constant output despite ±20% input variation. Use Value: Eliminates need for separate pre-regulator stages; 98% peak efficiency reduces heat sink size and improves system MTBF in sealed cabinets. |
Use Scenario: Charging 48V LiFePO₄ battery banks from variable PV array output (30–80V) while enforcing CC/CV profiles and input MPPT. IC Role / Device Role / Timing Role: Core power stage controller executing input current limiting (IMON_IN), output voltage regulation (FBOUT), and battery current control (IMON_OUT). Use Value: Integrated 4-loop control replaces discrete op-amp circuits; programmable thresholds simplify compliance with UL 1703 and IEC 62109 safety standards. |
| Automotive Battery Management | Industrial 24/48V Power Supply |
|
Use Scenario: Maintaining stable 12V/24V loads during cold-crank (4.5V) or load-dump (80V) events in commercial vehicle electronics. IC Role / Device Role / Timing Role: High-reliability buck-boost controller with UVLO hysteresis (160mV) and overvoltage protection on VIN, SW1, and SW2 pins. Use Value: MP-grade temperature range ensures operation in engine bay; integrated current monitoring enables real-time diagnostics per ISO 26262 ASIL-B functional safety requirements. |
Use Scenario: Converting unregulated 36–72V industrial DC bus to tightly regulated 24V/48V outputs for PLC I/O modules and motor drives. IC Role / Device Role / Timing Role: Primary DC/DC controller implementing input overcurrent protection (OI_IN), output overvoltage lockout (UV_VOUT), and thermal foldback via CLKOUT duty cycle. Use Value: Reduces BOM count by integrating gate drivers, LDO, and multiple error amplifiers; TSSOP package simplifies IPC-2221 Class B clearance compliance. |
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 rated only to 125°C (E grade); lacks IMON_OUT and SRVO_IOUT functionality; lower max VIN (60V). | Not suitable for extended temperature or 80V input applications; limited current monitoring capability. | Select only for cost-sensitive industrial designs within 0°C–125°C ambient and ≤60V input. |
| MAX20096ATP/V+T | Automotive-qualified (AEC-Q100 Grade 1), 42V max VIN, integrated MOSFETs (no external FETs), fixed 2.2MHz frequency. | Not pin-compatible; cannot support >42V input or user-defined switching frequency; lacks dual current monitoring. | Choose only for space-constrained automotive body electronics requiring integrated power stage and no external FET layout. |
Compared with LTC3780EFE#PBF and MAX20096ATP/V+T, the LT8705MPFE#TRPBF uniquely combines 80V operation, –55°C to 150°C rating, full 4-loop control, and TSSOP packaging for high-voltage industrial reliability - making it the sole option for mission-critical telecom and aerospace buck-boost regulation.
Availability
LT8705MPFE#TRPBF is available at Aetrix Electronics and suitable for telecom voltage stabilizers, solar charge controllers, and automotive battery management systems requiring stable component supply across extended temperature and high-voltage operating conditions.
Supply support for LT8705MPFE#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 defense markets.
The LT8705MPFE#TRPBF belongs to Linear's high-voltage DC/DC controller product line, engineered specifically for ruggedized power conversion in environments demanding wide VIN/VOUT range, multi-loop protection, and extended temperature reliability.
FAQ
What is the maximum input voltage rating for the LT8705MPFE#TRPBF?
The LT8705MPFE#TRPBF supports a maximum input voltage of 80V on the VIN pin, with absolute maximum ratings extending to 81V on SW1/SW2 nodes. This allows direct interface with 48V telecom systems, 72V battery stacks, and unregulated solar arrays without external pre-regulation - a key differentiator versus 60V-class controllers like the LTC3780.
Does the LT8705MPFE#TRPBF include integrated MOSFETs?
No, the LT8705MPFE#TRPBF is a controller-only IC and requires external N-channel MOSFETs for the 4-switch buck-boost power stage. It integrates quad gate drivers (TG1/TG2/BG1/BG2), 6.35V INTVCC regulator, and 3.3V/12mA LDO, but does not contain power switches - enabling design flexibility, thermal optimization, and high-efficiency operation up to 98%.
How does the LT8705MPFE#TRPBF handle thermal monitoring?
The LT8705MPFE#TRPBF uses the CLKOUT pin for junction temperature monitoring: its duty cycle varies linearly from 22.7% at –40°C to 77% at 125°C. Engineers can measure CLKOUT duty cycle with a microcontroller ADC or comparator to implement closed-loop thermal derating - a built-in feature not requiring external sensors or calibration.
What is the purpose of the IMON_IN and IMON_OUT pins on the LT8705MPFE#TRPBF?
The IMON_IN and IMON_OUT pins on the LT8705MPFE#TRPBF are current-source outputs proportional to measured input and output currents. Each delivers up to 100µA with 1.208V reference-based scaling, enabling precise programmable overcurrent protection, battery charge/discharge current telemetry, and real-time power monitoring without additional op-amps or ADC channels.
Is the LT8705MPFE#TRPBF pin-compatible with other LT8705 variants?
No, the LT8705MPFE#TRPBF (TSSOP-38 FE package) is not pin-compatible with the LT8705MPUHF#TRPBF (QFN-38 UHF package). Key differences include omission of SWEN and all SRVO pins (SRVO_FBIN, SRVO_FBOUT, SRVO_IIN, SRVO_IOUT) in the FE variant, and internal tie of SWEN to INTVCC - requiring schematic and layout revision for migration.
LT8705MPFE#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:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705MPFE#TRPBF FAQ
1.How can I place an order for LT8705MPFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705MPFE#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 LT8705MPFE#TRPBF reliable?
The price and inventory of LT8705MPFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705MPFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8705MPFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705MPFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705MPFE#TRPBF?
LT8705MPFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705MPFE#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 LT8705MPFE#TRPBF?
For technical support, including LT8705MPFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705MPFE#TRPBF requirements.
6.How does Aetrix verify that LT8705MPFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8705MPFE#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 LT8705MPFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8705MPFE#TRPBF?
All LT8705MPFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705MPFE#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 LT8705MPFE#TRPBF part is unused and in its original packaging.
Return procedure for LT8705MPFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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