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Analog Devices Inc. LT8705AIUHF#PBF
- Part No.:
- LT8705AIUHF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LT8705AIUHF#PBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:955
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Product details
Overview
LT8705AIUHF#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 systems. It operates with 2.8V–80V input and 1.3V–80V output, supports quad N-channel MOSFET gate drivers, delivers up to 98% efficiency, and integrates four independent feedback loops (VIN, VOUT, IIN, IOUT) - enabling stable regulation in solar charge controllers, telecom voltage stabilizers, and battery-powered HV systems.
For engineers reviewing the LT8705AIUHF#PBF datasheet, LT8705AIUHF#PBF pinout, LT8705AIUHF#PBF application, or LT8705AIUHF#PBF equivalent, key selection criteria include its 100–400kHz synchronizable switching frequency, –40°C to 125°C operating junction temperature, integrated 3.3V/12mA LDO, MODE pin-selectable operation modes (Burst/DCM/FCM), and QFN-38 (5mm × 7mm) package with exposed thermal pad.
Technical Context
The LT8705AIUHF#PBF implements a current-mode control architecture with diode-ANDed error amplifier outputs driving VC, enabling seamless transition between buck, boost, and buck-boost regions. Its proprietary topology uses two independent switch-node pairs (SW1/SW2) and four gate drivers (TG1/BG1/TG2/BG2) to manage bidirectional power flow through a single inductor.
It features four dedicated analog monitor paths: CSPIN/CSNIN for input current sensing, CSPOUT/CSNOUT for output current sensing, FBIN for input voltage regulation, and FBOUT for output voltage regulation - each with precision error amplifiers (EA1–EA4), gm values ≥130 µmho, and reference voltages tightly specified at 1.205–1.208 V across temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports wide-input applications including 24V/48V/72V industrial buses and automotive cold-crank conditions. |
| VOUT Range | 1.3V to 80V - enables direct regulation of high-voltage loads (e.g., 48V server rails, Li-ion stacks) without intermediate stages. |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; synchronizable to external clock for EMI reduction in multi-rail systems. |
| Efficiency | Up to 98% - achieved via synchronous rectification and low-loss gate drivers with <20ns rise/fall times. |
| Operating Temp | –40°C to +125°C junction - qualified for under-hood automotive and industrial environments per AEC-Q100-relevant stress testing. |
| Package | 38-lead 5mm × 7mm QFN with exposed thermal pad - provides low θJA = 34°C/W for high-power density designs. |
| LDO Output | 3.3V/12mA - powers auxiliary circuitry (e.g., sensors, level shifters) without external regulator. |
Pinout & Package
LT8705AIUHF#PBF is housed in a 38-lead plastic QFN (5mm × 7mm) with exposed thermal pad (Pin 39 = GND). The package supports high-current thermal dissipation and requires soldering of the exposed pad to PCB ground plane per manufacturer guidelines.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 1) | Shutdown Control | Active-low enable; pulls quiescent current to ≤1µA when grounded - critical for system-level power sequencing. |
| CSP/CSN (Pins 3/2) | Inductor Current Sense Inputs | Differential inputs for main current sense resistor; set peak current limit via VC voltage and internal gain (±150 mV/V). |
| FBIN/FBOUT (Pins 5/6) | Voltage Feedback Inputs | High-impedance (≤15nA bias) inputs for input/output voltage regulation; reference voltages fixed at 1.205V/1.207V. |
| IMON_IN/IMON_OUT (Pins 7/38) | Current Monitor Outputs | Current-source outputs proportional to sensed IIN/IOUT - used for analog monitoring or overcurrent protection logic. |
| TG1/BG1/TG2/BG2 (Pins 22/14/18/16) | N-Channel Gate Drivers | Quad drivers with <20ns switching transitions; TGx swing referenced to SWx nodes - enables high-side NMOS control without external bootstrap ICs. |
| SRVO_FBIN/SRVO_FBOUT (Pins 25/28) | Open-Drain Status Outputs | Active-low flags indicating activation of FBIN/FBOUT regulation loops - useful for fault logging or cascaded control. |
| CLKOUT (Pin 10) | Temperature-Monitored Clock Output | 180° out-of-phase oscillator output with duty cycle linearly varying vs. die temperature - enables real-time thermal monitoring without sensor. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous 4-switch topology | Enables single-inductor buck-boost operation with >95% efficiency across VIN/VOUT crossover - eliminates need for dual-converter solutions. |
| Four independent feedback loops | Simultaneous regulation of input voltage, output voltage, input current, and output current - essential for MPPT solar chargers and constant-power battery charging. |
| MODE pin selectable operation | Configures Burst Mode® (light-load efficiency), discontinuous conduction mode (DCM), or forced continuous conduction mode (FCM) - optimizes trade-off between ripple and efficiency per load condition. |
| Integrated 3.3V/12mA LDO | Powers external bias circuitry (e.g., ADC references, optocouplers) directly - reduces BOM count and improves system reliability. |
| CLKOUT thermal monitoring | Eliminates need for discrete temperature sensors by providing junction temperature via duty-cycle measurement - simplifies thermal management in space-constrained designs. |
Applications
| Solar Charge Controller | Telecom Voltage Stabilizer |
|---|---|
Use Scenario: Regulates variable PV array output (30–80V) to charge 48V battery bank while enforcing maximum power point tracking and current limits. IC Role / Device Role / Timing Role: Primary buck-boost controller managing bidirectional energy flow, executing MPPT algorithm via FBIN/FBOUT/IMON_IN feedback, and coordinating gate timing for M1–M4 switches. Use Value: Single-chip solution replaces discrete controller + gate driver + current sense IC - reduces footprint by >40% and improves transient response during irradiance changes. | Use Scenario: Stabilizes fluctuating -48V telecom supply (e.g., from rectifier or backup battery) to deliver clean, regulated +48V output for base station RF modules. IC Role / Device Role / Timing Role: High-efficiency voltage stabilizer using input current limiting (IMON_IN) and output voltage regulation (FBOUT) to maintain tight ±1% output tolerance under dynamic load steps. Use Value: Maintains 97% efficiency at 5A load while suppressing line transients - meets GR-1089-CORE immunity requirements without additional filtering. |
| Automotive 12V/48V Bi-Directional Converter | Industrial HV DC Power Supply |
Use Scenario: Enables energy recovery from 48V mild-hybrid systems into 12V starter battery during regenerative braking, with reverse-current protection. IC Role / Device Role / Timing Role: Bidirectional buck-boost controller using SRVO_IIN/SRVO_IOUT status pins to detect direction of power flow and disable inappropriate FETs via gate drive logic. Use Value: Prevents shoot-through and reverse conduction with <100ns dead-time control - achieves >96% round-trip efficiency and meets ISO 16750-2 pulse test requirements. | Use Scenario: Powers industrial test equipment requiring precise 60V@3A output from unregulated 72V DC bus, with programmable current limiting and remote sense capability. IC Role / Device Role / Timing Role: Programmable HV regulator using external resistive dividers on FBOUT and IMON_OUT to set output voltage and current limit thresholds. Use Value: Delivers ±0.5% output accuracy over temperature and line variation - eliminates need for post-regulation LDOs in metrology-grade applications. |
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 limited to 60V max VIN/VOUT; no integrated LDO; only three feedback loops (no IMON_IN). | Suitable for lower-voltage industrial supplies (<60V), but lacks input current monitoring needed for MPPT or battery charge control. | Select LTC3780EFE#PBF only if operating voltage stays below 60V and input current regulation is not required. |
| MPQ4333AGL-Z | Monolithic 4-switch buck-boost IC (not controller); max 36V VIN; integrated power FETs; no external gate drivers or current monitor outputs. | Targeted at compact consumer/industrial SMPS where board space is constrained and full programmability is unnecessary. | Choose MPQ4333AGL-Z for cost-sensitive, low-to-mid power (≤3A) applications where integration outweighs flexibility. |
Compared with LTC3780EFE#PBF and MPQ4333AGL-Z, the LT8705AIUHF#PBF uniquely supports 80V operation, includes a 3.3V LDO and four independent current/voltage monitor paths - making it the only option capable of full-feature MPPT solar charging and bi-directional 48V automotive conversion in a single IC.
Availability
LT8705AIUHF#PBF is available at Aetrix Electronics and suitable for solar charge controllers, telecom voltage stabilizers, and automotive 48V/12V bi-directional converters requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT8705AIUHF#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.
The LT8705A product line was engineered specifically for high-voltage, high-efficiency DC/DC conversion in harsh environments - targeting solar energy harvesting, telecom infrastructure, and next-generation automotive electrification systems.
FAQ
What is the maximum input voltage rating for the LT8705AIUHF#PBF?
The LT8705AIUHF#PBF has an absolute maximum input voltage rating of 80V on the VIN pin, with recommended operating range from 2.8V to 80V. This allows direct connection to 48V and 72V industrial buses, automotive battery systems, and photovoltaic arrays without pre-regulation - provided external MOSFETs and layout meet voltage derating requirements.
Does the LT8705AIUHF#PBF support synchronization with external clock sources?
Yes, the LT8705AIUHF#PBF supports synchronization via its SYNC pin (Pin 11), which accepts external clock signals with high-level >1.3V and low-level <0.5V. The internal oscillator can be overridden to match frequencies from 100kHz to 400kHz, enabling deterministic EMI reduction and phase alignment in multi-converter systems using the LT8705AIUHF#PBF.
How does the MODE pin configure operating modes on the LT8705AIUHF#PBF?
The MODE pin (Pin 37) selects among three operating modes: forced continuous conduction mode (FCM) when voltage <0.4V, Burst Mode® when floating, and discontinuous conduction mode (DCM) when voltage >2.3V. This allows dynamic optimization of light-load efficiency versus output ripple - a key feature implemented in the LT8705AIUHF#PBF for battery-powered and standby-critical applications.
What is the function of the CLKOUT pin on the LT8705AIUHF#PBF?
The CLKOUT pin (Pin 10) provides a 180° out-of-phase replica of the internal oscillator signal and serves dual purpose: (1) synchronizing other switching regulators, and (2) monitoring die temperature via duty-cycle variation (22.7–77% across –40°C to 125°C). This eliminates external thermal sensors in the LT8705AIUHF#PBF design while maintaining accurate thermal awareness.
Can the LT8705AIUHF#PBF regulate both input and output current simultaneously?
Yes, the LT8705AIUHF#PBF integrates independent input current (IMON_IN) and output current (IMON_OUT) monitor paths with dedicated error amplifiers (EA2 and EA1), allowing simultaneous regulation of IIN and IOUT. This capability is essential for applications like solar MPPT (where input current must track maximum power point) and battery charging (where output current must be precisely limited), and is fully supported in the LT8705AIUHF#PBF's analog control architecture.
LT8705AIUHF#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)
LT8705AIUHF#PBF FAQ
1.How can I place an order for LT8705AIUHF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AIUHF#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 LT8705AIUHF#PBF reliable?
The price and inventory of LT8705AIUHF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AIUHF#PBF is usually 5 days.
3.What payment methods are accepted for LT8705AIUHF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AIUHF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AIUHF#PBF?
LT8705AIUHF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AIUHF#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 LT8705AIUHF#PBF?
For technical support, including LT8705AIUHF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AIUHF#PBF requirements.
6.How does Aetrix verify that LT8705AIUHF#PBF is sourced from the original manufacturer or authorized distributors?
All LT8705AIUHF#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 LT8705AIUHF#PBF meets industry standards.
7.What is the process for return or replacement of LT8705AIUHF#PBF?
All LT8705AIUHF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AIUHF#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 LT8705AIUHF#PBF part is unused and in its original packaging.
Return procedure for LT8705AIUHF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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