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Analog Devices Inc. LT8705EFE#PBF
- Part No.:
- LT8705EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) 31 Leads, Exposed Pad
- Datasheet:
-
LT8705EFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,451
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Product details
Overview
LT8705EFE#PBF from Analog Devices (formerly Linear Technology) is a synchronous 4-switch buck-boost DC/DC controller IC designed for wide-input, wide-output voltage regulation in high-reliability industrial and automotive power systems. It supports VIN from 2.8V to 80V and VOUT from 1.3V to 80V, features integrated input/output current and voltage feedback loops, quad N-channel gate drivers, and operates up to 400kHz switching frequency - enabling single-inductor bidirectional conversion in solar charge controllers and telecom voltage stabilizers.
For engineers reviewing the LT8705EFE#PBF datasheet, LT8705EFE#PBF pinout, LT8705EFE#PBF application, or LT8705EFE#PBF equivalent, key selection considerations include its 38-lead TSSOP package with high-voltage pin spacing, dual servo feedback status outputs (SRVO_FBIN/SRVO_FBOUT), programmable current limiting via IMON_IN/IMON_OUT, and compatibility with external MOSFETs rated up to 81V on SW1/SW2 nodes.
Technical Context
The LT8705EFE#PBF implements a current-mode control architecture with four independent error amplifiers (EA1–EA4) that diode-AND at the VC pin to govern duty cycle across buck, boost, and buck-boost regions. Its servo pins (SRVO_FBIN, SRVO_FBOUT, SRVO_IIN, SRVO_IOUT) provide real-time indication of active regulation loops without requiring external logic.
It integrates a 6.35V INTVCC regulator powered from VIN or EXTVCC (≥6.4V), a 3.3V/12mA LDO (LDO33), and synchronized gate drivers with <20ns rise/fall times and controlled dead-time (80–100ns). The controller supports Burst Mode® operation, discontinuous conduction mode (DCM), or forced continuous conduction mode (CCM) via the MODE pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.8V to 80V - supports 12V/24V/48V battery systems, automotive cold-crank (≥4.5V), and telecom -48V backplane inputs. |
| VOUT Range | 1.3V to 80V - enables direct regulation of intermediate rails (e.g., 3.3V, 5V, 12V) or high-voltage outputs (e.g., 48V PoE, 60V EV auxiliary supplies). |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; allows optimization of efficiency vs. size using standard 1–10µH inductors. |
| Current Sense Threshold | Boost mode: 102–132mV (LT8705E); Buck mode: 69–102mV - sets precise overcurrent protection thresholds with ±1% reference accuracy. |
| Gate Drivers | Quad N-channel drivers (TG1/BG1/TG2/BG2) with 20ns switching transitions - drives 3300pF loads directly, supporting >10A MOSFETs with minimal external components. |
| Operating Temp | –40°C to +125°C junction - qualified for under-hood automotive and industrial environments with thermal shutdown at TJ >125°C. |
| Package | 38-lead plastic TSSOP (FE package) with modified layout for high-voltage isolation - creepage/clearance optimized for ≥80V working voltage between adjacent pins. |
Pinout & Package
LT8705EFE#PBF uses a 38-lead plastic TSSOP (FE package), variant FE38(31), with exposed pad (Pin 39) soldered to PCB ground for thermal and EMI performance. Pin spacing and internal routing are modified versus standard TSSOP to support 80V operation with enhanced high-voltage clearance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SHDN (Pin 4) | Shutdown control input | Active-low enable; pulls quiescent current to ≤1µA when grounded - essential for low-power standby in battery systems. |
| CSPIN/CSNIN (Pins 37/36) | Input current sense differential inputs | Measure voltage across RSENSE1 to feed EA2; enable input current limiting and foldback during overvoltage or short-circuit events. |
| CSPOUT/CSNOUT (Pins 34/32) | Output current sense differential inputs | Monitor output current via RSENSE2; used for constant-current regulation in LED drivers or battery charging applications. |
| FBIN/FBOUT (Pins 8/9) | Input/output voltage feedback inputs | Connect to resistor dividers for independent input voltage regulation (e.g., MPPT) or output voltage regulation (e.g., 48V bus stabilization). |
| IMON_IN/IMON_OUT (Pins 3/10) | Current monitor analog outputs | Provide 100µA full-scale proportional current signals - interface directly to ADCs or op-amps for digital current telemetry. |
| TG1/BG1/TG2/BG2 (Pins 26/17/21/19) | N-channel MOSFET gate drivers | Drive external high-side (TG1/TG2) and low-side (BG1/BG2) switches; GATEVCC must be tied to INTVCC (Pin 1). |
| VC (Pin 11) | Error amplifier output | Diode-AND node of EA1–EA4; connects to external compensation network (RC) to stabilize all four regulation loops simultaneously. |
| CLKOUT (Pin 13) | Internal oscillator clock output | Provides 180° out-of-phase clock signal; duty cycle varies linearly with die temperature - enables non-contact thermal monitoring. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous 4-switch topology | Enables single-inductor buck-boost conversion with up to 98% efficiency - eliminates need for separate buck and boost stages in wide-input-range systems. |
| Four independent regulation loops | Simultaneous input voltage (FBIN), output voltage (FBOUT), input current (IMON_IN), and output current (IMON_OUT) control - supports complex power management like solar MPPT + battery charge limiting. |
| Servo status outputs (SRVO_*) | Open-drain pins indicate real-time activation of each loop - simplifies system-level fault diagnostics and state-machine control without external comparators. |
| Programmable operating mode | MODE pin selects Burst Mode® (light-load efficiency), DCM (reduced EMI), or forced CCM (low output ripple) - adaptable to dynamic load profiles. |
| Integrated 3.3V/12mA LDO | Power local bias circuitry (e.g., sensors, level shifters) without external regulators - reduces BOM count and improves startup reliability. |
| High-voltage TSSOP package | FE38(31) variant provides ≥0.3mm creepage between HV pins (VIN, SW1, SW2, BOOST1, BOOST2) - meets IEC 62368-1 reinforced insulation requirements. |
Applications
| Solar Charge Controller | Automotive DC-DC Converter |
|---|---|
|
Use Scenario: Regulating variable PV array output (20–80V) to charge 48V lithium battery bank while maintaining MPPT tracking. IC Role / Device Role / Timing Role: Primary buck-boost controller managing both input voltage regulation (via FBIN) and output current limiting (via IMON_OUT) with servo feedback for MPPT state confirmation. Use Value: Single-chip solution replaces dual-controller architectures; achieves >96% efficiency across 10:1 input range without compromising MPPT accuracy. |
Use Scenario: Converting 9–16V automotive battery supply to stable 12V rail for infotainment and ADAS modules during cold-crank and load-dump transients. IC Role / Device Role / Timing Role: High-voltage buck-boost controller with input UVLO (4.45V) and output overvoltage protection (80V clamp), using SRVO_FBIN to flag input undervoltage events. Use Value: Maintains regulated output down to 4.5V input, eliminating need for pre-regulator stage and reducing system cost by 30% versus discrete solutions. |
| Telecom Voltage Stabilizer | Industrial 24V/48V Power Supply |
|
Use Scenario: Stabilizing –48V telecom backplane to deliver clean +48V output for remote radio units despite ±20% input variation and 0–10A load steps. IC Role / Device Role / Timing Role: Bidirectional controller operating in buck-boost region; uses CLKOUT duty cycle for real-time thermal derating and SYNC pin for multi-rail synchronization. Use Value: Delivers <100mV output deviation during 10A load steps; CLKOUT-based thermal monitoring enables predictive fan control without external sensors. |
Use Scenario: Providing isolated 24V-to-48V step-up for factory automation PLC I/O modules requiring high-current, low-noise auxiliary rails. IC Role / Device Role / Timing Role: Synchronous buck-boost controller with forced CCM mode (MODE = 0V) and external MOSFETs (M1–M4) rated for 100V drain-source breakdown. Use Value: Achieves 97.2% peak efficiency at 5A output; quad gate drivers eliminate need for external driver ICs, reducing layout area by 45%. |
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 | Fixed 200kHz frequency; no IMON_IN/IMON_OUT pins; lacks servo outputs and CLKOUT temperature monitor. | Best suited for simpler fixed-frequency designs where only output voltage regulation is required. | Choose LTC3780EFE#PBF when system complexity is low and cost sensitivity outweighs diagnostic capability. |
| MP2918GL-Z | Integrated MOSFETs (40V max); no high-voltage capability; supports only 4.5–36V input; lacks input voltage regulation loop. | Targeted at consumer-grade 12V/24V systems with lower voltage stress and no MPPT or telecom requirements. | Choose MP2918GL-Z only for space-constrained, low-voltage applications where external FETs are undesirable. |
Compared with LTC3780EFE#PBF and MP2918GL-Z, LT8705EFE#PBF uniquely delivers 80V operation, four independent regulation loops, and real-time servo status - making it the only option for high-reliability solar, automotive, and telecom systems requiring simultaneous input/output control and diagnostics.
Availability
LT8705EFE#PBF is available at Aetrix Electronics and suitable for solar charge controllers, automotive DC-DC converters, and telecom voltage stabilizers requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT8705EFE#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 full product support, documentation, and manufacturing continuity for the LT8705 family.
The LT8705 product line was engineered for high-voltage, wide-range DC-DC conversion in harsh environments - targeting solar energy harvesting, automotive electrification, and telecom infrastructure where reliability, diagnostic visibility, and design flexibility are critical.
FAQ
What is the maximum input voltage rating for LT8705EFE#PBF?
The LT8705EFE#PBF supports an absolute maximum input voltage (VIN) of 80V, with guaranteed operation from 2.8V to 80V. Its SW1 and SW2 pins tolerate up to 81V, and BOOST1/BOOST2 pins handle up to 87V - enabling robust use in 48V battery systems and telecom backplanes subject to transient overvoltages.
Does LT8705EFE#PBF support input voltage regulation (IVR) in addition to output regulation?
Yes, LT8705EFE#PBF includes dedicated FBIN and IMON_IN pins to implement full input voltage regulation and input current limiting. This allows functions such as MPPT in solar chargers or input overvoltage protection in automotive systems - independent of output regulation performed via FBOUT and IMON_OUT.
How does the SRVO_FBIN pin function on LT8705EFE#PBF?
The SRVO_FBIN pin on LT8705EFE#PBF is an open-drain output that pulls low when the input voltage feedback loop (FBIN) is actively regulating. It provides real-time status of the input control path - useful for system-level fault logging or enabling auxiliary circuits only when input conditions are within specification.
Can LT8705EFE#PBF operate in forced continuous conduction mode (CCM)?
Yes, LT8705EFE#PBF supports forced CCM operation when the MODE pin voltage is held below 0.4V. This ensures consistent switching frequency and low output ripple under light loads - critical for noise-sensitive applications like RF power supplies or precision instrumentation rails.
What is the purpose of the CLKOUT pin on LT8705EFE#PBF?
The CLKOUT pin on LT8705EFE#PBF outputs a clock signal 180° out of phase with the internal oscillator or SYNC input. Its duty cycle varies linearly with junction temperature (22.7% at –40°C to 77% at 125°C), enabling accurate die temperature monitoring without external sensors - a key feature for thermal management in sealed enclosures.
LT8705EFE#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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT8705EFE#PBF FAQ
1.How can I place an order for LT8705EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8705EFE#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 LT8705EFE#PBF reliable?
The price and inventory of LT8705EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8705EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8705EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8705EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8705EFE#PBF?
LT8705EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8705EFE#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 LT8705EFE#PBF?
For technical support, including LT8705EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8705EFE#PBF requirements.
6.How does Aetrix verify that LT8705EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8705EFE#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 LT8705EFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8705EFE#PBF?
All LT8705EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8705EFE#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 LT8705EFE#PBF part is unused and in its original packaging.
Return procedure for LT8705EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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