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Analog Devices Inc. LT8705AHFE#PBF
- Part No.:
- LT8705AHFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705AHFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:264
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Product details
Overview
LT8705AHFE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage synchronous 4-switch buck-boost DC/DC controller IC designed for wide-input, wide-output voltage regulation in automotive, solar, and telecom power systems. It supports 2.8V–80V input and 1.3V–80V output, integrates quad N-channel gate drivers, features four independent feedback loops (VIN, VOUT, IIN, IOUT), and operates up to 150°C junction temperature.
For engineers reviewing the LT8705AHFE#PBF datasheet, LT8705AHFE#PBF pinout, LT8705AHFE#PBF application, or LT8705AHFE#PBF equivalent, key selection criteria include its 38-pin TSSOP package with exposed pad, –40°C to 150°C operating range, 100kHz–400kHz synchronizable switching frequency, integrated 3.3V/12mA LDO, and support for burst mode, DCM, and forced CCM operation.
Technical Context
The LT8705AHFE#PBF implements a current-mode control architecture with dual-path sensing: CSP/CSN for inductor current, CSPIN/CSNIN for input current, and CSPOUT/CSNOUT for output current. Its VC pin serves as the error amplifier output controlling all four regulation loops via diode-AND logic.
It uses a proprietary 4-switch buck-boost topology enabling seamless transition between buck, boost, and buck-boost regions without external mode switching. Gate drivers (TG1/BG1/TG2/BG2) support fast switching with 20ns rise/fall times and controlled dead-time delays (e.g., TG1 off to BG1 on = 100ns), ensuring robust synchronous rectification up to 98% efficiency.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports 12V/24V/48V automotive, 48V telecom, and 60–80V solar arrays without pre-regulation. |
| VOUT Range | 1.3V to 80V - enables single-stage conversion from battery or PV input directly to high-voltage loads like LED strings or industrial rails. |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; allows optimization of size vs. EMI, with external synchronization capability. |
| Junction Temp Range | –40°C to 150°C - rated for under-hood automotive and high-ambient industrial environments; includes overtemperature protection. |
| Gate Drivers | Quad N-channel (TG1/BG1/TG2/BG2) - drives external MOSFETs with 20ns edge speeds and defined dead-time delays to prevent shoot-through. |
| LDO Output | 3.3V/12mA - powers auxiliary circuitry (e.g., sensors, level shifters) without requiring external regulator. |
| Feedback Loops | 4 independent loops (VIN, VOUT, IIN, IOUT) - enables precise input current limiting, output voltage regulation, and bidirectional power monitoring. |
Pinout & Package
LT8705AHFE#PBF is housed in a 38-lead plastic TSSOP package (FE38 variation) with exposed thermal pad (Pin 39 = GND). The package measures standard TSSOP dimensions and is 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 - critical for low-power standby in battery systems. |
| CSP/CSN (Pins 6/5) | Inductor Current Sense Inputs | Differential pair measuring RSENSE voltage; sets peak current limit in buck/boost modes via VC pin and internal offsets. |
| FBIN/FBOUT (Pins 8/9) | Input/Output Voltage Feedback Inputs | High-impedance inputs (10nA bias) for resistive dividers; regulate VIN or VOUT independently with 1.205V/1.207V reference thresholds. |
| IMON_IN/IMON_OUT (Pins 3/10) | Current Monitor Outputs | Current-source outputs proportional to IIN/IOUT (100µA full-scale); used for analog monitoring or fault detection without ADC. |
| MODE (Pin 2) | Operating Mode Select | Voltage-controlled selection: <0.4V = forced CCM, 1.0–1.7V = Burst Mode®, >2.3V = DCM - enables dynamic efficiency optimization. |
| TG1/BG1/TG2/BG2 (Pins 26/17/21/19) | N-Channel MOSFET Gate Drivers | Drive external high-side/low-side FETs; TG1/TG2 swing referenced to SW1/SW2 nodes; BG1/BG2 referenced to GND. |
| BOOST1/BOOST2 (Pins 28/20) | Floating Bootstrap Supplies | Provide gate drive above SW1/SW2; BOOST1 swings up to VIN + GATEVCC, BOOST2 up to VOUT + GATEVCC - enables high-side NMOS drive. |
| CLKOUT (Pin 13) | Temperature-Monitored Clock Output | Free-running or synchronized clock with duty cycle linearly varying vs. die temperature - enables passive thermal monitoring without sensor. |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor buck-boost topology | Eliminates need for separate buck/boost stages or coupled inductors - reduces BOM count and PCB area in wide-VIN applications. |
| Synchronous rectification support | Enables >98% peak efficiency by driving both high-side and low-side MOSFETs - critical for high-current telecom and EV charging designs. |
| Integrated 4-loop regulation | Allows simultaneous enforcement of input voltage/current limits and output voltage/current targets - essential for MPPT solar chargers and battery protection circuits. |
| 150°C guaranteed operation (H-grade) | Validated performance at full spec across –40°C to 150°C - suitable for engine compartment, industrial motor drives, and enclosed power supplies. |
| 3.3V/12mA LDO and CLKOUT thermal monitor | Reduces external component count while providing system-level diagnostics - simplifies design of compact, self-monitoring power modules. |
Applications
| Automotive 12V/48V Dual-Battery Systems | Solar Microinverter DC-Link Regulation |
|---|---|
Use Scenario: Bidirectional power transfer between 12V starter battery and 48V mild-hybrid rail during regenerative braking and load leveling. IC Role / Device Role / Timing Role: Buck-boost controller regulating 48V rail from 12V input or vice versa; manages input/output current limits to protect batteries. Use Value: Enables single-chip solution for voltage translation with 98% efficiency and 150°C operation - eliminates need for discrete DC-DC stages and thermal derating. | Use Scenario: Stabilizing variable PV array output (30–80V) to fixed DC-link voltage (e.g., 400V) before inversion in microinverters. IC Role / Device Role / Timing Role: High-voltage buck-boost controller with input current monitoring for MPPT algorithm integration and output voltage regulation. Use Value: Supports wide input range and precise IIN/VOUT regulation - improves energy harvest under partial shading and extends inverter uptime. |
| Telecom 48V Backup Power Supply | Industrial HV Battery Charger |
Use Scenario: Maintaining stable 48V output from lithium-titanate or lead-acid backup batteries (36–60V) during grid outage in base station power systems. IC Role / Device Role / Timing Role: Input-voltage-regulated buck-boost controller with programmable input current limit to prevent battery over-discharge. Use Value: Delivers regulated 48V at up to 5A with <100mV line/load regulation - ensures uninterrupted operation of RF amplifiers and baseband units. | Use Scenario: Charging 60V–80V industrial Li-ion stacks from 24V/48V factory power rails with constant-current/constant-voltage profiles. IC Role / Device Role / Timing Role: Output-current-regulated buck-boost controller with isolated current sense interface and thermal monitoring via CLKOUT. Use Value: Provides accurate CC/CV charging with real-time die temperature feedback - enhances safety and cycle life in high-reliability manufacturing equipment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EFE#PBF | Same 38-pin TSSOP package, but rated only to 125°C; lacks IMON_IN/IMON_OUT pins and SRVO logic outputs. | Not suitable for 150°C environments or designs requiring independent input/output current monitoring. | Select LT8705AHFE#PBF when extended temperature rating and full 4-loop monitoring are required. |
| MPQ4332GSD-AEC1-Z | Automotive-grade 4-switch buck-boost controller in QFN; max VIN = 40V, no integrated LDO, no CLKOUT thermal monitor. | Restricted to lower-voltage automotive applications; requires external bias supply and thermal sensor. | Choose LT8705AHFE#PBF for >40V input, integrated 3.3V LDO, and passive die temperature monitoring. |
Compared with LTC3789EFE#PBF and MPQ4332GSD-AEC1-Z, the LT8705AHFE#PBF uniquely combines 80V operation, 150°C rating, four independent regulation loops, and integrated thermal monitoring - making it the only option for high-voltage, high-temperature, multi-parameter regulated power systems.
Availability
LT8705AHFE#PBF is available at Aetrix Electronics and suitable for automotive power management, solar energy conversion, telecom backup systems, and industrial battery charging requiring stable component supply across extended temperature ranges.
Supply support for LT8705AHFE#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 power management portfolio with rigorous qualification standards.
The LT8705A product line delivers high-voltage, multi-loop buck-boost controllers optimized for solar, automotive, and industrial applications where input and output voltages widely vary and reliability under extreme conditions is mandatory.
FAQ
What is the maximum operating junction temperature for the LT8705AHFE#PBF?
The LT8705AHFE#PBF is fully specified and guaranteed over a junction temperature range of –40°C to 150°C. This H-grade rating is validated per manufacturer test data and enables use in under-hood automotive, industrial motor drives, and enclosed power supplies where ambient temperatures exceed 105°C. The device includes overtemperature protection that activates above 150°C to prevent damage.
Does the LT8705AHFE#PBF support synchronization with external clock sources?
Yes, the LT8705AHFE#PBF supports external synchronization via its SYNC pin (Pin 14). A clock signal with high level >1.3V and low level <0.5V can be applied to lock the switching frequency to an external source. The internal oscillator operates from 100kHz to 400kHz and remains synchronizable across this full range, enabling EMI reduction and multi-phase interleaving in complex power systems.
How does the MODE pin configure operating modes on the LT8705AHFE#PBF?
The MODE pin (Pin 2) configures three distinct light-load behaviors: forced continuous conduction mode (CCM) when voltage <0.4V, Burst Mode® operation when floating or biased within 1.0–1.7V, and discontinuous conduction mode (DCM) when voltage >2.3V. These thresholds are guaranteed over temperature and allow designers to optimize efficiency versus output ripple based on load profile without changing hardware.
Can the LT8705AHFE#PBF regulate both input and output parameters simultaneously?
Yes, the LT8705AHFE#PBF integrates four independent regulation loops - input voltage (FBIN), output voltage (FBOUT), input current (IMON_IN), and output current (IMON_OUT) - allowing simultaneous enforcement of multiple constraints. For example, it can hold VOUT at 48V while limiting IIN to 10A and IOUT to 5A, making it ideal for MPPT solar chargers and battery protection circuits where multiple boundaries must be maintained.
What is the function of the CLKOUT pin on the LT8705AHFE#PBF?
The CLKOUT pin (Pin 13) provides a free-running or synchronized clock output whose duty cycle varies linearly with junction temperature (22.7% at –40°C to 77% at 125°C). This enables passive die temperature monitoring without external sensors. It also serves as a synchronization source for other regulators and supports capacitive loads up to 200pF, making it useful for timing-critical multi-rail power systems.
LT8705AHFE#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
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705AHFE#PBF FAQ
1.How can I place an order for LT8705AHFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705AHFE#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 LT8705AHFE#PBF reliable?
The price and inventory of LT8705AHFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705AHFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8705AHFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705AHFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705AHFE#PBF?
LT8705AHFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705AHFE#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 LT8705AHFE#PBF?
For technical support, including LT8705AHFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705AHFE#PBF requirements.
6.How does Aetrix verify that LT8705AHFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8705AHFE#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 LT8705AHFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8705AHFE#PBF?
All LT8705AHFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705AHFE#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 LT8705AHFE#PBF part is unused and in its original packaging.
Return procedure for LT8705AHFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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