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Analog Devices Inc. LT8705AEUHF#PBF
- Part No.:
- LT8705AEUHF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LT8705AEUHF#PBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:405
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Product details
Overview
LT8705AEUHF#PBF from Analog Devices (formerly Linear Technology) is a synchronous 4-switch buck-boost DC/DC controller IC designed for high-voltage industrial and automotive power conversion. It supports input voltages from 2.8V to 80V and output voltages from 1.3V to 80V, features quad N-channel MOSFET gate drivers, integrated input/output voltage and current feedback loops, and operates in buck, boost, or buck-boost modes using a single inductor - enabling solar charge controllers, telecom voltage stabilizers, and battery-powered HV systems.
For engineers reviewing the LT8705AEUHF#PBF datasheet, LT8705AEUHF#PBF pinout, LT8705AEUHF#PBF application, or LT8705AEUHF#PBF equivalent, key selection criteria include its 80V absolute max VIN/VOUT rating, 100–400kHz synchronizable switching frequency, MODE pin-selectable light-load operation (Burst Mode®, DCM, or FCM), integrated 3.3V/12mA LDO, and dual current-sense monitoring (IMON_IN/IMON_OUT) with ±100mV differential input range.
Technical Context
The LT8705AEUHF#PBF 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 four loops via diode-AND logic, enabling seamless mode transitions across buck, buck-boost, and boost regions without external mode switching.
It integrates two high-speed NMOS gate driver pairs (TG1/BG1 and TG2/BG2) with <20ns rise/fall times and programmable dead-time control, supporting external 100V+ N-channel MOSFETs. The QFN package includes dedicated pins for synchronous rectification control (SRVO_FBIN/SRVO_FBOUT/SRVO_IIN/SRVO_IOUT), clock output (CLKOUT) usable for die temperature monitoring, and EXTVCC switchover at 6.4V for efficient bias supply management.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports wide-input applications including 24V/48V/72V battery systems and unregulated solar arrays. |
| VOUT Range | 1.3V to 80V - enables direct regulation of high-side loads or low-voltage logic rails from HV sources. |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; synchronizable to external clock for EMI reduction. |
| Current Sense Threshold | ±69mV (buck) / ±102mV (boost) - precise, temperature-stable thresholds for accurate current limiting and monitoring. |
| LDO Output | 3.3V/12mA - powers external circuitry or level-shifters; load-regulated to ±1% over full temperature range. |
| Operating Junction Temp | –40°C to +125°C - qualified for automotive under-hood and industrial ambient environments. |
| Gate Driver Outputs | Quad N-channel drivers (TG1/BG1/TG2/BG2) - drives external high-side and low-side MOSFETs with <100ns propagation delay. |
Pinout & Package
LT8705AEUHF#PBF is housed in a 38-lead (5mm × 7mm) plastic QFN package with exposed thermal pad (Pin 39 = GND). The package supports high-power dissipation (θJA = 34°C/W) and requires soldering of the exposed pad to PCB ground for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 1) | Shutdown Control Input | Active-high enable; pulls quiescent current to ≤1µA when grounded - critical for system-level power sequencing. |
| CSP/CSN (Pins 3/2) | Main Inductor Current Sense Inputs | Differential inputs for RSENSE placed in series with inductor - sets peak current limit and enables cycle-by-cycle control. |
| FBIN/FBOUT (Pins 5/6) | Input & Output Voltage Feedback Inputs | High-impedance (≤15nA bias) error amp inputs - support precision resistive dividers for independent VIN/VOUT regulation. |
| IMON_IN/IMON_OUT (Pins 38/7) | Current Monitor Outputs | Current-source outputs proportional to sensed input/output current - interface directly to ADCs or comparator circuits. |
| TG1/BG1, TG2/BG2 (Pins 22/14, 18/16) | Top/Bottom Gate Drivers | High-current (≥100mA sink/source) drivers with matched timing - eliminate need for external driver ICs in 4-switch topology. |
| CLKOUT (Pin 10) | Temperature-Monitored Clock Output | Free-running or synchronized 100–400kHz clock with duty cycle linearly tracking die temperature - enables real-time thermal diagnostics. |
| SRVO_FBIN, SRVO_FBOUT, etc. (Pins 25–28) | Open-Drain Status Outputs | Individually indicate activation of FBIN, FBOUT, IMON_IN, IMON_OUT loops - used for fault logging or loop prioritization logic. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous 4-switch buck-boost topology | Enables single-inductor VIN > VOUT, VIN < VOUT, or VIN ≈ VOUT operation - eliminates need for separate buck/boost stages in wide-input systems. |
| Integrated quad feedback loops | Simultaneous regulation of input voltage, output voltage, input current, and output current - essential for MPPT solar chargers and battery protection circuits. |
| MODE pin selectable light-load behavior | Configures Burst Mode® (ultra-low IQ), discontinuous conduction mode (DCM), or forced continuous conduction mode (FCM) - optimizes efficiency across 1000:1 load range. |
| On-chip 3.3V/12mA LDO | Powers auxiliary circuitry (e.g., microcontroller I/O, sensor bias) without external regulator - reduces BOM count and layout area. |
| CLKOUT-based die temperature monitoring | Eliminates need for external thermal sensors - CLKOUT duty cycle varies from 22.7% to 77% across –40°C to +125°C junction range. |
| Robust gate driver timing control | Programmable dead time and <20ns edge rates ensure safe commutation of external 100V+ MOSFETs - prevents shoot-through in high-power designs. |
Applications
| Solar Charge Controller | Telecom Voltage Stabilizer |
|---|---|
|
Use Scenario: Regulating variable PV array output (30–80V) to charge 48V battery banks while enforcing maximum power point tracking and overcurrent protection. IC Role / Device Role / Timing Role: Primary buck-boost controller managing both input MPPT and output constant-voltage/constant-current charging profiles. Use Value: Single-chip solution replaces discrete buck + boost stages; 98% peak efficiency minimizes thermal stress in outdoor enclosures. |
Use Scenario: Stabilizing fluctuating -48V telecom distribution bus (–36V to –72V) to deliver clean +48V or +12V for line cards and optical modules. IC Role / Device Role / Timing Role: High-reliability DC/DC controller operating in buck-boost mode with input/output current limiting and remote sense capability. Use Value: 80V absolute rating withstands telecom surge transients; integrated IMON_IN/IMON_OUT enables real-time bus health monitoring. |
| Automotive 12V/48V Dual-Battery System | Industrial HV DC Power Supply |
|
Use Scenario: Bidirectional power transfer between 12V starter battery and 48V mild-hybrid rail during regenerative braking and engine start-stop cycles. IC Role / Device Role / Timing Role: Synchronous 4-switch controller configured for bidirectional operation with fast transient response and reverse-current detection. Use Value: CSP/CSN inputs support bidirectional current sensing; SRVO_IIN/SRVO_IOUT pins provide hardware-level fault signaling for ASIL-B compliance. |
Use Scenario: Converting unregulated 60–80V industrial DC bus (e.g., from rectified 3-phase AC) to stable 24V or 5V for PLC I/O and fieldbus interfaces. IC Role / Device Role / Timing Role: High-voltage primary controller with EXTVCC switchover and robust gate drive for 100V MOSFETs in harsh EMI environments. Use Value: 38-pin QFN package offers superior thermal performance vs. TSSOP; CLKOUT-based thermal monitoring replaces discrete thermistors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3780EUF#PBF | Fixed 100kHz–600kHz frequency; no integrated LDO; only input/output voltage feedback (no current monitor outputs); 40V max VIN. | Lacks IMON_IN/IMON_OUT, SRVO status pins, and CLKOUT temperature monitor - unsuitable for current-loop-critical or thermal-aware designs. | Select LTC3780EUF#PBF only for cost-sensitive, lower-voltage (<40V) applications where current monitoring is handled externally. |
| MPQ4332GJ-AEC1-Z | Integrated 100V MOSFETs; fixed 400kHz frequency; no EXTVCC; no current monitor outputs; AEC-Q100 Grade 1 rated. | Monolithic design eliminates external FETs but sacrifices flexibility and current-sense accuracy; limited to automotive-grade use cases. | Choose MPQ4332GJ-AEC1-Z for space-constrained automotive modules requiring qualification, not for programmable industrial power supplies. |
Compared with LTC3780EUF#PBF and MPQ4332GJ-AEC1-Z, the LT8705AEUHF#PBF uniquely combines 80V operation, dual current monitoring, integrated LDO, and die temperature visibility - making it the only option for high-accuracy, high-voltage, thermally managed buck-boost systems requiring full loop observability.
Availability
LT8705AEUHF#PBF is available at Aetrix Electronics and suitable for solar charge controllers, telecom voltage stabilizers, and automotive 12V/48V dual-battery systems requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT8705AEUHF#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, 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 was designed specifically for high-voltage, wide-input-range DC/DC conversion in solar, telecom, and automotive applications - emphasizing precision current sensing, multi-loop regulation, and robust thermal management.
FAQ
What is the maximum input voltage rating for the LT8705AEUHF#PBF?
The LT8705AEUHF#PBF has an absolute maximum input voltage rating of 80V on the VIN and EXTVCC pins, with SW1 and SW2 pins rated to 81V. This allows direct connection to 48V and 72V battery systems, unregulated solar arrays, and telecom distribution buses without external clamping or pre-regulation.
Does the LT8705AEUHF#PBF support bidirectional power flow?
The LT8705AEUHF#PBF does not natively support bidirectional power flow in a single configuration. However, its 4-switch topology and independent input/output current monitoring (via IMON_IN and IMON_OUT) enable bidirectional control when paired with appropriate external MOSFETs and firmware - commonly implemented in automotive 12V/48V dual-battery systems.
How is the switching frequency set on the LT8705AEUHF#PBF?
The LT8705AEUHF#PBF switching frequency is set by an external resistor connected from the RT pin to ground. With RT = 215kΩ, the typical frequency is 202kHz; RT = 124kΩ yields ~310kHz, and RT = 365kΩ yields ~120kHz. The frequency is also synchronizable to an external clock applied to the SYNC pin (1.3V high, 0.5V low).
What is the function of the CLKOUT pin on the LT8705AEUHF#PBF?
The CLKOUT pin on the LT8705AEUHF#PBF provides a buffered copy of the internal oscillator signal, toggling at the same frequency as the switching node. Its duty cycle varies linearly with junction temperature (22.7% at –40°C to 77% at +125°C), enabling passive die temperature monitoring without additional sensors or ADC channels.
Can the LT8705AEUHF#PBF operate without an external bootstrap capacitor?
No - the LT8705AEUHF#PBF requires external bootstrap capacitors on BOOST1 and BOOST2 pins to drive the high-side N-channel MOSFET gates (TG1 and TG2). Each bootstrap capacitor must be ≥0.22µF ceramic and placed close to the respective BOOST pin and SW node to ensure reliable gate drive voltage during continuous conduction mode.
LT8705AEUHF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-WFQFN 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 ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-QFN (5x7)
LT8705AEUHF#PBF FAQ
1.How can I place an order for LT8705AEUHF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AEUHF#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 LT8705AEUHF#PBF reliable?
The price and inventory of LT8705AEUHF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AEUHF#PBF is usually 5 days.
3.What payment methods are accepted for LT8705AEUHF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AEUHF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AEUHF#PBF?
LT8705AEUHF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AEUHF#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 LT8705AEUHF#PBF?
For technical support, including LT8705AEUHF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AEUHF#PBF requirements.
6.How does Aetrix verify that LT8705AEUHF#PBF is sourced from the original manufacturer or authorized distributors?
All LT8705AEUHF#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 LT8705AEUHF#PBF meets industry standards.
7.What is the process for return or replacement of LT8705AEUHF#PBF?
All LT8705AEUHF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AEUHF#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 LT8705AEUHF#PBF part is unused and in its original packaging.
Return procedure for LT8705AEUHF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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