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Analog Devices Inc. LT8705HFE#PBF
- Part No.:
- LT8705HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705HFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,179
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Product details
Overview
LT8705HFE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage synchronous 4-switch buck-boost DC/DC controller designed for wide-input, wide-output applications requiring VIN above, below, or equal to VOUT. It supports 2.8V–80V input and 1.3V–80V output ranges, integrates quad N-channel gate drivers, and delivers up to 98% efficiency in telecom voltage stabilizers and solar charge controllers.
For engineers reviewing the LT8705HFE#PBF datasheet, LT8705HFE#PBF pinout, LT8705HFE#PBF application, or LT8705HFE#PBF equivalent, key selection considerations include its –40°C to 150°C operating junction temperature, integrated input/output current monitoring, programmable 100kHz–400kHz switching frequency, and servo feedback loop status indication for system-level fault diagnostics.
Technical Context
The LT8705HFE#PBF 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 topology enables seamless transition between buck, boost, and buck-boost regions without mode switching artifacts.
It features synchronized fixed-frequency operation via RT resistor or external SYNC clock, onboard 6.35V INTVCC regulator and 3.3V/12mA LDO, and dedicated servo pins (SRVO_FBIN, SRVO_FBOUT, SRVO_IIN, SRVO_IOUT) that actively indicate which feedback loop is regulating. The H-grade variant guarantees full performance across –40°C to 150°C junction temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports automotive cold-crank, industrial 48V systems, and solar MPPT inputs without pre-regulation |
| VOUT Range | 1.3V to 80V - enables single-stage conversion from battery or rectified AC to diverse load rails |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor or external SYNC signal for EMI optimization and magnetics sizing |
| Operating Junction Temp | –40°C to 150°C - qualified for under-hood automotive, high-ambient industrial, and telecom base station environments |
| Gate Drivers | Quad N-channel drivers (TG1/BG1/TG2/BG2) - drives external MOSFETs with 20ns rise/fall times and <100ns dead-time control |
| Current Monitoring | Input & output current sense amplifiers with 1.208V regulation reference - enables precise overcurrent protection and power telemetry |
| Efficiency | Up to 98% - achieved via synchronous rectification and low-loss gate drive architecture in continuous conduction mode |
Pinout & Package
LT8705HFE#PBF is housed in a 38-lead plastic TSSOP package (FE38 variant) with exposed pad (Pin 39) soldered to PCB ground for thermal management and EMI reduction. The package is modified for improved high-voltage operation and rated for 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 |
| CSP/CSN (Pins 6/5) | Inductor current sense differential pair | Measures bidirectional inductor current for peak-current-mode control and reverse-current detection |
| FBIN/FBOUT (Pins 8/9) | Input & output voltage feedback inputs | Connect to resistor dividers for independent VIN and VOUT regulation loops |
| IMON_IN/IMON_OUT (Pins 10/3) | Current monitor outputs | Current-source outputs proportional to sensed input/output current (1.208V reference) |
| VC (Pin 11) | Error amplifier output | Diode-AND node of EA1–EA4; connects to external compensation network for loop stability |
| SYNC (Pin 14) | External clock synchronization input | Accepts 0.5V–1.3V logic levels to lock switching frequency to external source |
| TG1/BG1/TG2/BG2 (Pins 26/17/21/19) | N-channel MOSFET gate drivers | Drive top/bottom switches of two synchronous half-bridges with bootstrap supply support |
| BOOST1/BOOST2 (Pins 28/20) | Floating gate driver supplies | Provide boosted voltage for high-side gate drive referenced to SW1/SW2 nodes |
| SW1/SW2 (Pins 24/22) | Switch node connections | Connect to external MOSFET sources; tolerate up to 81V transient voltage |
| EXTVCC (Pin 30) | External bias supply input | Enables INTVCC sourcing from external 6.4V+ supply to reduce VIN loading |
| GND (Pin 16 & Exposed Pad 39) | Power and signal ground | Exposed pad must be soldered to PCB ground plane for thermal and electrical integrity |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous 4-switch buck-boost topology | Enables single-inductor conversion with VIN > VOUT, VIN < VOUT, or VIN ≈ VOUT - eliminates need for separate buck/boost stages |
| Four independent feedback loops | Simultaneous regulation of input voltage, output voltage, input current, and output current - ideal for battery charging and power-limiting applications |
| Servo status outputs (SRVO_xxx) | Open-drain pins indicate real-time active feedback loop - simplifies system-level fault logging and adaptive control |
| Programmable operating mode | MODE pin selects forced continuous, Burst Mode®, or discontinuous conduction - optimizes light-load efficiency vs. ripple trade-off |
| Integrated 3.3V/12mA LDO | Provides regulated auxiliary supply for sensors or level-shifters - reduces BOM count and external regulators |
| CLKOUT temperature monitor | Duty cycle varies linearly with junction temperature - enables real-time thermal telemetry without external sensor |
Applications
| Solar MPPT Charge Controller | Automotive 12V/48V Bidirectional Converter |
|---|---|
Use Scenario: Regulates battery charging from variable PV array output under partial shading or temperature drift. IC Role / Device Role / Timing Role: Buck-boost controller managing bidirectional power flow with input voltage tracking and output current limiting. Use Value: Maintains >95% efficiency across 20V–80V PV input range while enforcing constant-current/constant-voltage battery profiles. |
Use Scenario: Enables energy recovery during regenerative braking and stable 12V rail generation from 48V mild-hybrid bus. IC Role / Device Role / Timing Role: High-reliability DC/DC controller with extended temperature grade and robust gate drive for dual-rail automotive systems. Use Value: Operates continuously at 150°C junction temperature with integrated current monitoring for ISO 26262-compliant fault response. |
| Telecom 48V Voltage Stabilizer | Industrial Battery Backup System |
Use Scenario: Stabilizes fluctuating -48V telecom rectifier output to deliver clean, regulated +48V for RF amplifiers and baseband units. IC Role / Device Role / Timing Role: Input-voltage-regulated buck-boost controller with fast line-transient response and programmable UVLO. Use Value: Achieves <500µs recovery from ±20% VIN step with <100mV VOUT deviation - meets GR-1089 immunity requirements. |
Use Scenario: Provides seamless switchover between AC mains and lithium-ion backup battery in UPS and PoE injectors. IC Role / Device Role / Timing Role: Dual-loop controller regulating both battery discharge current and output voltage during transition events. Use Value: Uses IMON_IN and FBOUT feedback simultaneously to prevent battery over-discharge while maintaining tight VOUT regulation. |
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 | Lower max VIN (40V), no integrated input current loop, 105°C max junction temp | Not suitable for 80V solar or telecom inputs; lacks IMON_IN for input power limiting | Select only for ≤40V systems where input current regulation is unnecessary |
| MPQ4333GSD-AEC1 | Integrated MOSFETs (40V max), fixed 300kHz freq, AEC-Q100 qualified, no servo outputs | Lower voltage rating and no independent feedback loop status - limits use in high-voltage industrial designs | Prefer for space-constrained automotive modules where external FETs are undesirable |
Compared with LTC3780EFE#PBF and MPQ4333GSD-AEC1, the LT8705HFE#PBF uniquely supports 80V operation, four independent feedback loops with real-time servo status, and guaranteed 150°C operation - making it the only option for high-temperature, high-voltage, multi-loop regulated systems.
Availability
LT8705HFE#PBF is available at Aetrix Electronics and suitable for solar MPPT charge controllers, automotive 48V/12V bidirectional converters, and telecom voltage stabilizers requiring stable component supply across extended temperature and voltage ranges.
Supply support for LT8705HFE#PBF 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 its high-performance analog and power management IC portfolio with rigorous qualification standards.
The LT8705HFE#PBF belongs to Linear's high-voltage buck-boost controller product line, engineered for demanding applications including photovoltaic systems, industrial power supplies, and automotive electrification where wide VIN/VOUT range and multi-parameter regulation are critical.
FAQ
What is the maximum input voltage supported by the LT8705HFE#PBF?
The LT8705HFE#PBF supports an absolute maximum input voltage of 80V on the VIN pin, with operational functionality across 2.8V to 80V. This rating is validated for continuous operation and includes margin for transients per the Absolute Maximum Ratings table. The device maintains regulation and protection features across this full range, making it suitable for 48V telecom, solar array, and heavy-duty vehicle applications where input surges occur.
Does the LT8705HFE#PBF include integrated MOSFETs?
No, the LT8705HFE#PBF is a controller-only IC and does not integrate power MOSFETs. It provides quad N-channel gate drivers (TG1/BG1/TG2/BG2) to drive external discrete MOSFETs in a 4-switch buck-boost configuration. This architecture allows designers to select optimal FETs for voltage, current, RDS(on), and thermal requirements - unlike monolithic converters with fixed internal switches.
How does the LT8705HFE#PBF handle thermal monitoring?
The LT8705HFE#PBF uses its CLKOUT pin for junction temperature monitoring: CLKOUT duty cycle varies linearly with die temperature (22.7% at –40°C to 77% at 125°C). This enables real-time thermal telemetry without external sensors. The LT8705HFE#PBF also includes overtemperature protection that disables switching if junction temperature exceeds safe limits, safeguarding the device during overload conditions.
What is the purpose of the SRVO_FBIN and SRVO_FBOUT pins on the LT8705HFE#PBF?
The SRVO_FBIN and SRVO_FBOUT pins on the LT8705HFE#PBF are open-drain logic outputs that indicate real-time activity of the input and output voltage feedback loops. When pulled low, they signal that the respective loop (FBIN or FBOUT) is actively regulating. These servo outputs enable system-level diagnostics, adaptive control algorithms, and fault logging - a capability not found in standard buck-boost controllers.
Can the LT8705HFE#PBF operate with input voltage below 2.8V?
No, the LT8705HFE#PBF requires a minimum input voltage of 2.8V for normal operation when EXTVCC = 0V. If EXTVCC is supplied ≥6.4V, the minimum functional VIN drops to 5.5V due to internal regulator constraints. Operation below these thresholds is not guaranteed and may result in improper startup, loss of regulation, or undefined behavior - as specified in the Electrical Characteristics table.
LT8705HFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Packaging:
- Tube
- 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 (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705HFE#PBF FAQ
1.How can I place an order for LT8705HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705HFE#PBF 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 LT8705HFE#PBF reliable?
The price and inventory of LT8705HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705HFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8705HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705HFE#PBF?
LT8705HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705HFE#PBF 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 LT8705HFE#PBF?
For technical support, including LT8705HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705HFE#PBF requirements.
6.How does Aetrix verify that LT8705HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8705HFE#PBF 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 LT8705HFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8705HFE#PBF?
All LT8705HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705HFE#PBF, 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 LT8705HFE#PBF part is unused and in its original packaging.
Return procedure for LT8705HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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