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Analog Devices Inc. LT8705AHFE#TRPBF
- Part No.:
- LT8705AHFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AHFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,667
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Product details
Overview
LT8705AHFE#TRPBF from Analog Devices (formerly Linear Technology) is a high-voltage synchronous 4-switch buck-boost DC/DC controller with integrated input/output voltage and current feedback loops, 2.8V–80V input range, 1.3V–80V output range, and quad N-channel MOSFET gate drivers. It operates in buck, boost, or buck-boost modes using a single inductor and supports telecom voltage stabilization, solar MPPT, and automotive battery systems.
For engineers reviewing the LT8705AHFE#TRPBF datasheet, LT8705AHFE#TRPBF pinout, LT8705AHFE#TRPBF application, or LT8705AHFE#TRPBF equivalent, key selection criteria include its –40°C to 150°C junction temperature rating, 100kHz–400kHz synchronizable switching frequency, MODE pin selectable operation (Burst/DCM/FCM), integrated 3.3V/12mA LDO, and dual current monitor outputs (IMON_IN/IMON_OUT) for precise power management.
Technical Context
The LT8705AHFE#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)-each referenced to a 1.205V–1.229V internal bandgap. Its quad-gate driver stage delivers 20ns rise/fall times and includes dead-time control (TG1/BG1 delay ≤100ns) to prevent shoot-through in high-side/low-side NMOS configurations.
It features a programmable oscillator via RT pin (100–400kHz), CLKOUT pin with linear junction temperature correlation (duty cycle shifts from 22.7% to 77% across –40°C to 125°C), and SRVO logic outputs (SRVO_FBIN/SRVO_FBOUT etc.) that indicate active regulation loops-though these are not implemented in the FE package per Note 5.
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 battery stacks without external pre-regulation. |
| VOUT Range | 1.3V to 80V - enables direct regulation from low-voltage rails or high-voltage sources such as photovoltaic arrays or industrial supplies. |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; allows optimization of efficiency vs. size trade-offs in magnetics and EMI filtering. |
| Junction Temp Range | –40°C to 150°C - rated for harsh environments including under-hood automotive and industrial power conversion where thermal derating is critical. |
| Gate Drivers | Quad N-channel - drives external high-side and low-side MOSFETs (TG1/BG1/TG2/BG2) with 20ns switching transitions and built-in shoot-through protection. |
| LDO Output | 3.3V/12mA - powers auxiliary circuitry (e.g., sensors, level shifters) without requiring an external regulator. |
| Current Sense Accuracy | ±1.5% max offset error (IMON_IN/IMON_OUT) - enables precise input/output current limiting and telemetry in safety-critical applications. |
Pinout & Package
LT8705AHFE#TRPBF uses a 38-lead plastic TSSOP package (FE38 variation) with exposed pad (Pin 39 = GND). The package measures standard TSSOP dimensions and supports surface-mount reflow assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 2) | Shutdown Control | Active-low enable: <0.3V disables IC, reducing quiescent current to ≤1µA; must be tied high or grounded-no floating allowed. |
| FBIN (Pin 8) | Input Voltage Feedback Input | Connects to resistor divider from VIN; regulates input voltage with 1.182–1.226V reference; used in input-limited or MPPT applications. |
| FBOUT (Pin 9) | Output Voltage Feedback Input | Connects to resistor divider from VOUT; regulates output voltage with 1.191–1.222V reference; primary loop for constant-voltage operation. |
| IMON_IN (Pin 3) | Input Current Monitor Output | Sink current proportional to input current (100µA full-scale); used for input overcurrent protection and telemetry. |
| IMON_OUT (Pin 10) | Output Current Monitor Output | Sink current proportional to output current (100µA full-scale); enables output current limiting and load monitoring. |
| MODE (Pin 2) | Operating Mode Select | Voltage-selectable: <0.4V = forced continuous mode; 1.0–1.7V = Burst Mode®; >2.3V = discontinuous conduction mode. |
| RT (Pin 15) | Oscillator Timing | Resistor-to-ground sets free-running frequency (100–400kHz); enables synchronization via SYNC pin. |
| VIN (Pin 38) | Main Power Input | Primary supply rail (2.8–80V); requires local 4.7µF ceramic bypass to GND; powers internal regulators when EXTVCC is inactive. |
| EXTVCC (Pin 30) | External Bias Supply | Optional 6.15–6.6V input; takes priority over VIN for INTVCC generation when >6.4V, improving efficiency at high input voltages. |
| GATEVCC (Pin 18) | Gate Driver Supply | Must be connected directly to INTVCC; powers all gate drivers; not user-supplied externally. |
| TG1/BG1/TG2/BG2 | Top/Bottom Gate Outputs | Drive external N-MOSFET gates; TG1/TG2 swing above SW1/SW2 nodes; BG1/BG2 referenced to GND; dead-time controlled internally. |
| SW1/SW2 (Pins 24,22) | Switch Node Terminals | Connect to source terminals of bottom MOSFETs (M2/M4) and drain terminals of top MOSFETs (M1/M3); tolerate up to 81V. |
| BOOST1/BOOST2 (Pins 28,20) | Floating Bootstrap Supplies | Connect to (+) terminals of bootstrap capacitors; BOOST1 swings up to VIN + GATEVCC; BOOST2 up to VOUT + GATEVCC. |
| CSPIN/CSNIN (Pins 37,36) | Input Current Sense Inputs | Differential pair measuring voltage across RSENSE1; common-mode range 1.5–80V; used for input current regulation. |
| CSPOUT/CSNOUT (Pins 34,32) | Output Current Sense Inputs | Differential pair measuring voltage across RSENSE2; common-mode range 0–80V; used for output current regulation. |
| VC (Pin 11) | Error Amplifier Output | Compensation node for all four control loops; connects external RC network to set loop bandwidth and stability. |
| SS (Pin 12) | Soft-Start Timing | Charged by 13–25µA current to 2.5V; controls ramp-up of output voltage and prevents inrush current. |
| CLKOUT (Pin 13) | Temperature-Monitored Clock | Outputs toggling signal at fOSC; duty cycle varies linearly with die temperature (22.7–77% from –40°C to 125°C); drives ≤200pF loads. |
| SYNC (Pin 14) | External Clock Input | Accepts 0.5–1.3V logic levels; synchronizes switching frequency to external clock; falling edge triggers phase alignment. |
| LDO33 (Pin 7) | 3.3V Regulated Output | Supplies 12mA max; requires ≥0.1µF ceramic bypass; undervoltage lockout at 2.96–3.12V ensures clean reset behavior. |
| INTVCC (Pin 1) | Internal 6.35V Regulator | Output of internal LDO; powers gate drivers and analog circuitry; must connect to GATEVCC; bypass with ≥4.7µF ceramic capacitor. |
| GND (Pins 16,39) | Ground Reference | Power and signal ground; exposed pad (Pin 39) must be soldered to PCB ground plane for thermal and electrical performance. |
Key Features
| Feature | Design Value |
|---|---|
| Four Independent Feedback Loops | Simultaneous regulation of input voltage, output voltage, input current, and output current enables complex power management schemes like solar MPPT with battery charge control. |
| Single-Inductor Buck-Boost Topology | Eliminates need for separate buck and boost converters; reduces BOM count, board space, and magnetic losses while supporting VIN = VOUT, VIN < VOUT, and VIN > VOUT operation. |
| 150°C Junction-Rated TSSOP Package | Enables deployment in high-temperature environments (e.g., automotive engine compartments, industrial motor drives) without derating or heatsinking penalties. |
| Programmable Light-Load Operation | MODE pin selects Burst Mode® (ultra-low IQ), discontinuous conduction mode (reduced switching loss), or forced continuous mode (lowest output ripple). |
| Integrated 3.3V LDO and 6.35V Regulator | Reduces external component count; LDO33 powers aux circuits; INTVCC powers gate drivers-both regulated from VIN or EXTVCC with automatic switchover. |
| Current Monitor Outputs with ±1.5% Accuracy | IMON_IN and IMON_OUT provide calibrated current telemetry for system-level monitoring, fault logging, and closed-loop current limiting without external amplifiers. |
Applications
| Telecom Voltage Stabilizer | Solar Charge Controller |
|---|---|
Use Scenario: Maintaining stable 48V output from fluctuating -48V telecom rectifier inputs during brownouts or surges. IC Role / Device Role / Timing Role: Synchronous 4-switch buck-boost controller regulating output voltage while limiting input current to protect upstream rectifiers. Use Value: Enables seamless transition between buck and boost modes without output interruption; achieves >94% efficiency at 5A load with 36–72V input range. | Use Scenario: Charging 48V lithium-ion battery banks from variable-output photovoltaic arrays (20–80V). IC Role / Device Role / Timing Role: MPPT-enabled buck-boost controller using FBIN and FBOUT loops to maximize energy harvest while enforcing battery voltage and current limits. Use Value: Dual-loop regulation maintains optimal array operating point while delivering precise constant-current/constant-voltage charging profiles. |
| Automotive Start-Stop System | Industrial 24V/48V Power Supply |
Use Scenario: Providing regulated 12V or 48V output during engine cranking when battery voltage drops to 6V. IC Role / Device Role / Timing Role: High-reliability buck-boost controller with 150°C rating and robust input UVLO to sustain critical ECUs during cold cranking events. Use Value: Operates down to 2.8V input with no dropout; integrated IMON_IN protects against alternator overload; extended temperature grade ensures long-term reliability. | Use Scenario: Converting unregulated 36–72V industrial DC bus to stable 24V or 48V for PLC I/O modules and sensors. IC Role / Device Role / Timing Role: Programmable-frequency buck-boost controller with synchronized CLKOUT for noise-sensitive measurement subsystems. Use Value: 100–400kHz frequency tuning avoids EMI bands; SRVO outputs signal active regulation states for system diagnostics and redundancy management. |
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, but rated only to 125°C junction; lacks IMON_OUT and SRVO outputs; no CLKOUT temperature monitor. | Lower-cost alternative for non-automotive applications where 150°C rating and dual current monitoring are unnecessary. | Select LTC3780EFE#PBF if thermal margin is sufficient and only input current monitoring is required. |
| LT8714IFE#TRPBF | Successor device with integrated MOSFET drivers optimized for higher efficiency; adds digital interface (I²C) and enhanced light-load performance; same 38-pin TSSOP footprint. | Supports smart power management with telemetry and remote configuration; suitable for next-gen designs requiring firmware-upgradable control. | Choose LT8714IFE#TRPBF for new designs needing digital control, improved light-load efficiency, and future-proofing. |
Compared with LTC3780EFE#PBF and LT8714IFE#TRPBF, the LT8705AHFE#TRPBF uniquely combines 150°C operation, dual current monitors (IMON_IN/IMON_OUT), and analog-only control-making it ideal for safety-critical, high-temperature analog power systems where digital interfaces add complexity or risk.
Availability
LT8705AHFE#TRPBF is available at Aetrix Electronics and suitable for telecom voltage stabilizers, solar charge controllers, automotive start-stop systems, and industrial 24V/48V power supplies requiring stable component supply, extended temperature operation, and high-voltage buck-boost capability.
Supply support for LT8705AHFE#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 LT8705A product line delivers high-voltage synchronous buck-boost controllers designed for demanding applications requiring wide input/output ranges, multiple regulation loops, and operation in extreme thermal environments.
FAQ
What is the maximum operating junction temperature for LT8705AHFE#TRPBF?
The LT8705AHFE#TRPBF is guaranteed over the full –40°C to 150°C operating junction temperature range per manufacturer specifications. This rating is confirmed in the Absolute Maximum Ratings table and distinguishes it from lower-grade variants (e.g., LT8705AE/FE rated to 125°C). Thermal design must ensure the exposed pad (Pin 39) is soldered to a thermally robust PCB ground plane to maintain reliability at 150°C.
Does LT8705AHFE#TRPBF support synchronization with external clock sources?
Yes, the LT8705AHFE#TRPBF supports synchronization via its SYNC pin (Pin 14), which accepts logic-level clocks with high threshold ≥1.3V and low threshold ≤0.5V. The internal oscillator can be overridden to match an external frequency from 100kHz to 400kHz, enabling EMI reduction through frequency dithering or deterministic timing alignment across multiple power stages in complex systems.
Can LT8705AHFE#TRPBF regulate both input and output voltage simultaneously?
Yes, the LT8705AHFE#TRPBF integrates independent input voltage (FBIN) and output voltage (FBOUT) feedback loops, each with dedicated error amplifiers and 1.205V–1.226V references. This allows simultaneous regulation-for example, holding VOUT at 48V while limiting VIN to 60V in a solar MPPT application-without external circuitry or microcontroller intervention.
What are the key differences between LT8705AHFE#TRPBF and LT8705AEFE#TRPBF?
The LT8705AHFE#TRPBF and LT8705AEFE#TRPBF share identical pinout, functionality, and electrical characteristics except for their guaranteed operating junction temperature ranges: LT8705AHFE#TRPBF is specified from –40°C to 150°C, while LT8705AEFE#TRPBF is rated from –40°C to 125°C. Both use the same 38-lead TSSOP (FE) package and have identical marking (LT8705AFE), differentiated only by part number suffix and temperature screening.
Is the CLKOUT pin on LT8705AHFE#TRPBF usable for temperature monitoring?
Yes, the CLKOUT pin on LT8705AHFE#TRPBF provides a temperature-correlated signal: its duty cycle varies linearly from 22.7% at –40°C to 77% at 125°C, enabling accurate die temperature estimation without external sensors. This feature is documented in the Typical Performance Characteristics section (Figure G16) and applies across the full operating range of the LT8705AHFE#TRPBF.
LT8705AHFE#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 ~ 150°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705AHFE#TRPBF FAQ
1.How can I place an order for LT8705AHFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AHFE#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 LT8705AHFE#TRPBF reliable?
The price and inventory of LT8705AHFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AHFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8705AHFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AHFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AHFE#TRPBF?
LT8705AHFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AHFE#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 LT8705AHFE#TRPBF?
For technical support, including LT8705AHFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AHFE#TRPBF requirements.
6.How does Aetrix verify that LT8705AHFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8705AHFE#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 LT8705AHFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8705AHFE#TRPBF?
All LT8705AHFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AHFE#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 LT8705AHFE#TRPBF part is unused and in its original packaging.
Return procedure for LT8705AHFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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