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Analog Devices Inc. LT8705AMPFE#TRPBF
- Part No.:
- LT8705AMPFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AMPFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,262
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Product details
Overview
LT8705AMPFE#TRPBF from Analog Devices (formerly Linear Technology) is a high-performance synchronous 4-switch buck-boost DC/DC controller designed for wide-input, wide-output voltage conversion 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 deployed in telecom voltage stabilizers and high-voltage solar charge controllers requiring precise input/output current limiting.
For engineers reviewing the LT8705AMPFE#TRPBF datasheet, LT8705AMPFE#TRPBF pinout, LT8705AMPFE#TRPBF application, or LT8705AMPFE#TRPBF equivalent, key selection criteria include its –55°C to 150°C extended temperature grade, integrated input/output current monitoring (IMON_IN/IMON_OUT), MODE pin-selectable operation modes (Burst/DCM/FCM), and compatibility with external MOSFETs for high-power industrial converters.
Technical Context
The LT8705AMPFE#TRPBF implements a proprietary 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 all switching states via PWM duty cycle modulation across buck, boost, and buck-boost regions.
It features synchronized fixed-frequency operation (100–400 kHz) set by an external RT resistor, onboard 3.3V/12mA LDO, and clock output (CLKOUT) usable for both synchronization and die temperature monitoring. The device uses dual bootstrap supplies (BOOST1/BOOST2) to drive top-gate MOSFETs with rail-to-rail swing referenced to SW1/SW2 nodes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports automotive cold-crank (≥2.8V) and telecom 48V/60V systems without pre-regulation |
| VOUT Range | 1.3V to 80V - enables single-controller solutions for battery charging, LED drivers, and HVDC distribution |
| Switching Frequency | 100 kHz to 400 kHz - adjustable via RT pin; allows optimization of size vs. EMI in industrial power supplies |
| Efficiency | Up to 98% - achieved via synchronous rectification and low-loss gate drivers reducing conduction losses |
| Operating Temp | –55°C to 150°C - qualified for aerospace, downhole, and military applications requiring extreme thermal resilience |
| Gate Drivers | Quad N-channel (TG1/BG1/TG2/BG2) - drives external high-side and low-side MOSFETs with 20ns rise/fall times |
| Current Monitoring | IMON_IN & IMON_OUT pins - provide proportional analog current signals for real-time system-level protection and telemetry |
Pinout & Package
LT8705AMPFE#TRPBF is housed in a 38-lead plastic TSSOP package (FE38 variation) with exposed pad (Pin 39) soldered to PCB ground for thermal management. θJA = 25°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 4) | Shutdown control input | Logic-high (>1.184V) enables IC; logic-low disables switching and reduces quiescent current to ≤1µA |
| CSP/CSN (Pins 6/5) | Inductor current sense inputs | Differential pair measuring RSENSE voltage; sets peak current limit in buck/boost modes |
| FBIN/FBOUT (Pins 8/9) | Input/output voltage feedback inputs | Connect to resistor dividers for closed-loop regulation of VIN or VOUT independently |
| IMON_IN/IMON_OUT (Pins 3/10) | Analog current monitor outputs | Current-source outputs proportional to input/output current; used for OCP, telemetry, or loop coordination |
| MODE (Pin 2) | Operating mode selector | Voltage <0.4V → FCM; 1.0–1.7V → Burst Mode; >2.3V → DCM - enables light-load efficiency tuning |
| SYNC/CLKOUT (Pins 14/13) | Frequency sync I/O | SYNC accepts external clock (0.5–1.3V thresholds); CLKOUT provides phase-inverted oscillator signal + temp monitoring |
| TG1/BG1/TG2/BG2 (Pins 26/17/21/19) | N-channel MOSFET gate drivers | Drive external high-side/low-side switches with 20ns edge speeds and controlled dead-time sequencing |
| BOOST1/BOOST2 (Pins 28/20) | Floating gate drive supplies | Provide bootstrapped voltage rails referenced to SW1/SW2 nodes for high-side NMOS gate drive |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous 4-switch topology | Enables single-inductor buck-boost conversion without polarity reversal or external diodes, reducing BOM count and losses |
| Four independent feedback loops | Allows simultaneous regulation of input voltage, output voltage, input current, and output current - critical for solar MPPT and battery charge control |
| Integrated 3.3V/12mA LDO | Provides local bias for external circuitry (e.g., sensors, ADCs) without requiring separate regulator IC |
| CLKOUT temperature monitoring | Linear duty-cycle shift vs. junction temperature eliminates need for external thermal sensor in sealed enclosures |
| Extended temperature grade (–55°C to 150°C) | Validated for operation in aerospace avionics, oilfield electronics, and defense systems where commercial-grade parts fail |
Applications
| Telecom Voltage Stabilizer | Solar Charge Controller |
|---|---|
Use Scenario: Maintaining stable 48V output from fluctuating -48V telecom rectifier bus under load transients and brownouts. IC Role / Device Role / Timing Role: Primary buck-boost controller regulating VOUT while monitoring input current to prevent upstream breaker tripping. Use Value: Integrated IMON_IN enables real-time input current limiting; 80V absolute max rating withstands telecom surge events per GR-1089. | Use Scenario: Charging 48V lithium battery banks from variable PV arrays (20–80V) with MPPT and constant-current/constant-voltage profiles. IC Role / Device Role / Timing Role: Core DC/DC controller executing MPPT algorithm via FBIN/FBOUT/IMON_IN coordination and adaptive frequency sweep. Use Value: Four feedback loops allow simultaneous tracking of panel voltage, battery voltage, and charge current - eliminating need for external DACs or microcontrollers. |
| Industrial HVDC Power Supply | Automotive 12V/48V Bi-Directional Converter |
Use Scenario: Converting 380V DC bus to regulated 24V for PLC I/O modules in factory automation systems with strict EMC requirements. IC Role / Device Role / Timing Role: Isolation-free buck-boost controller operating in continuous conduction mode at 200kHz to minimize conducted EMI. Use Value: Synchronizable frequency (via SYNC pin) enables multi-phase interleaving with other LT8705A units to reduce input ripple current by >70%. | Use Scenario: Bidirectional power transfer between 12V starter battery and 48V mild-hybrid system during regenerative braking and engine start-stop cycles. IC Role / Device Role / Timing Role: Dual-direction buck-boost controller using same external FETs for both charging and discharging paths. Use Value: Pin-compatible upgrade from LT8705 enables seamless integration into existing 48V architectures with improved light-load transition and cold-temperature IMON offset stability. |
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; 4–36V input range; no IMON_IN/IMON_OUT; lower max VOUT (36V) | Limited to mid-voltage industrial supplies; lacks dual current monitoring required for solar/battery systems | Select only when input voltage stays below 36V and current telemetry is unnecessary |
| MPQ4333AGL-AEC1-Z | Automotive AEC-Q100 qualified; 3.5–36V input; integrated MOSFETs; no external gate drivers or IMON pins | Targeted at automotive infotainment; not suitable for >36V or discrete high-power designs | Choose for cost-sensitive 12V/24V automotive modules where integration outweighs flexibility |
Compared with LTC3780EFE#PBF and MPQ4333AGL-AEC1-Z, LT8705AMPFE#TRPBF uniquely supports 80V operation, dual current monitoring, and extended temperature range - making it the only option for high-reliability, high-voltage, telemetry-enabled buck-boost systems.
Availability
LT8705AMPFE#TRPBF is available at Aetrix Electronics and suitable for telecom voltage stabilizers, solar charge controllers, industrial HVDC power supplies, and automotive 12V/48V bi-directional converters requiring stable component supply across extended temperature ranges.
Supply support for LT8705AMPFE#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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for the LT® portfolio.
The LT8705A product line was engineered for high-voltage, high-reliability DC/DC conversion in mission-critical infrastructure - emphasizing precision current/voltage regulation, robust thermal performance, and flexible topology configuration.
FAQ
What is the maximum input voltage rating for LT8705AMPFE#TRPBF?
The LT8705AMPFE#TRPBF has an absolute maximum input voltage rating of 80V on the VIN pin, as specified in the Absolute Maximum Ratings table. This allows direct interface with 48V telecom systems, 60V solar arrays, and industrial HVDC buses without external clamping or pre-regulation stages. Operation above 80V risks permanent damage.
Does LT8705AMPFE#TRPBF support bidirectional power flow?
The LT8705AMPFE#TRPBF does not natively support true bidirectional power flow. It operates as a unidirectional buck-boost controller - delivering power from VIN to VOUT only. However, its architecture permits reverse current detection (via SRVO_FBIN/SRVO_IIN) and can be used in bi-directional converter designs when paired with external control logic and complementary FETs, as seen in automotive 12V/48V systems.
How does the MODE pin affect efficiency at light loads in LT8705AMPFE#TRPBF?
The MODE pin selects among Burst Mode® (floating), discontinuous conduction mode (DCM, >2.3V), or forced continuous conduction mode (FCM, <0.4V). At light loads, Burst Mode minimizes switching losses by pulsing the controller on/off, achieving highest efficiency. DCM reduces gate drive losses but increases ripple; FCM maintains regulation at expense of higher quiescent loss - enabling trade-offs based on noise, transient response, and efficiency targets.
Can LT8705AMPFE#TRPBF operate without an external microcontroller?
Yes, LT8705AMPFE#TRPBF is a fully autonomous analog controller. All regulation (FBIN, FBOUT), current limiting (IMON_IN, IMON_OUT), and mode selection (MODE) are implemented internally without firmware or digital intervention. It requires only passive components (resistors, capacitors, inductors, MOSFETs) to form a complete, self-contained buck-boost power stage - ideal for safety-critical or radiation-hardened applications.
What is the purpose of the CLKOUT pin on LT8705AMPFE#TRPBF?
The CLKOUT pin on LT8705AMPFE#TRPBF serves two functions: (1) it outputs a phase-inverted copy of the internal oscillator or SYNC signal for synchronizing multiple converters, and (2) its duty cycle varies linearly with junction temperature (22.7% at –40°C to 77% at 125°C), enabling contactless die temperature monitoring without external sensors - a key feature for sealed or inaccessible installations.
LT8705AMPFE#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 ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705AMPFE#TRPBF FAQ
1.How can I place an order for LT8705AMPFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AMPFE#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 LT8705AMPFE#TRPBF reliable?
The price and inventory of LT8705AMPFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AMPFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8705AMPFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AMPFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AMPFE#TRPBF?
LT8705AMPFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AMPFE#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 LT8705AMPFE#TRPBF?
For technical support, including LT8705AMPFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AMPFE#TRPBF requirements.
6.How does Aetrix verify that LT8705AMPFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8705AMPFE#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 LT8705AMPFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8705AMPFE#TRPBF?
All LT8705AMPFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AMPFE#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 LT8705AMPFE#TRPBF part is unused and in its original packaging.
Return procedure for LT8705AMPFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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