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Analog Devices Inc. LT8708HLWE#PBF
- Part No.:
- LT8708HLWE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 64-LQFP Exposed Pad
- Datasheet:
-
LT8708HLWE#PBF.pdf
- Description:
- 80V SYNCHRONOUS 4-SWITCH BUCK-BO
- Quantity:
- Payment:
- Shipping:
Inventory:4,691
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Product details
Overview
LT8708HLWE#PBF from Analog Devices is a high-voltage synchronous 4-switch buck-boost DC/DC controller with bidirectional power flow capability, operating from 2.8V to 80V input and regulating output from 1.3V to 80V. It supports independent forward/reverse current limiting on both input and output sides, implements six regulation modes (VIN/VOUT voltage, IIN/IOUT current), and features MODE/DIR pin control for unidirectional or bidirectional operation in automotive dual-battery systems.
For engineers reviewing the LT8708HLWE#PBF datasheet, LT8708HLWE#PBF pinout, LT8708HLWE#PBF application, or LT8708HLWE#PBF equivalent, this device is selected for high-reliability 48V/12V bidirectional charging, solar MPPT with battery backup, and AEC-Q100-compliant automotive power architectures requiring precise current direction control, wide input range, and thermal robustness up to 150°C junction temperature.
Technical Context
The LT8708HLWE#PBF integrates four independent current-sense amplifiers (IMON_INP/INN/ON/OP) and two voltage error amplifiers (FBIN/FBOUT) to simultaneously regulate VIN, VOUT, IIN, and IOUT in forward or reverse directions. Its hybrid conduction mode (HCM) dynamically transitions between DCM and CCM based on load, while DIR pin logic selects power flow direction without interrupting switching operation.
Internal gate drivers support NMOS high-side and low-side switches with 20ns rise/fall times and <100ns dead-time control. The VC pin provides proportional current-sense gain (±135mV/V) for buck/boost regions, and RT pin sets switching frequency from 100kHz to 400kHz with external resistor selection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.8V to 80V - supports 12V, 24V, 48V automotive batteries and telecom/solar inputs without pre-regulation |
| Output Voltage Range | 1.3V to 80V - enables single-inductor buck-boost conversion across wide rail ratios (e.g., 48V↔12V) |
| Switching Frequency | 100kHz–400kHz - adjustable via RT pin; higher frequencies reduce inductor size but increase switching loss |
| Junction Temperature Max | 150°C - H-grade qualification ensures operation in under-hood automotive environments |
| Current Sense Threshold | 68–110mV - precision thresholds enable accurate ±1% current limiting for bidirectional IIN/IOUT control |
| Regulation Loops | Six independent loops - VIN voltage, VOUT voltage, forward/reverse IIN, forward/reverse IOUT - eliminates need for external controllers |
| AEC-Q100 Grade | Grade H (–40°C to +150°C) - qualified for safety-critical automotive applications including 48V mild-hybrid systems |
Pinout & Package
LT8708HLWE#PBF uses a 64-lead (10mm × 10mm) plastic eLQFP package with exposed pad (Pin 65 = GND) and high-voltage pin spacing per Analog Devices' LWE package specification. Thermal resistance θJA = 17°C/W enables high-power operation with standard PCB copper area.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| DIR | Direction Control Input | Logic-high (>1.6V) enables VIN→VOUT power flow; logic-low (<1.2V) enables VOUT→VIN reverse flow |
| MODE | Conduction Mode Selection | 0.4V = CCM; 0.8–1.2V = HCM; 1.6–2.0V = DCM; ≥2.4V = Burst Mode - runtime optimization without firmware |
| IMON_INP / IMON_INN | Input Current Monitoring Inputs | Differential sensing of input-side current direction and magnitude; used for forward/reverse IIN regulation |
| IMON_ON / IMON_OP | Output Current Monitoring Inputs | Differential sensing of output-side current direction and magnitude; enables bidirectional IOUT limiting |
| TG1 / BG1 / SW1 / BOOST1 | High-Side/Low-Side Switch Control | Drive external NMOS transistors M1/M2 in buck-boost topology; TG1/BG1 control gate timing with 80–90ns dead time |
| TG2 / BG2 / SW2 / BOOST2 | Second Switch Pair Control | Completes 4-switch implementation; SW2/BOOST2 handle complementary phase for full buck-boost waveform synthesis |
| FBIN / FBOUT | VIN and VOUT Feedback Inputs | Resistive divider inputs referenced to internal 1.205V bandgap; enable independent voltage regulation on both ports |
| VC | Error Amplifier Output | Analog output controlling peak current limit; voltage directly scales current-sense threshold via ±135mV/V gain |
| RT | Oscillator Timing Input | Connects external resistor to set switching frequency: 365kΩ = 120kHz, 215kΩ = 202kHz, 124kΩ = 350kHz (typ) |
| CLKOUT | Synchronized Clock Output | Provides 50% duty-cycle clock at FOSC with 160–200° phase delay relative to SYNC rising edge |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional Power Flow Control | Hardware-based DIR pin enables seamless reversal of power direction without software intervention or sequencing delays |
| Independent Forward/Reverse Current Limits | Four dedicated resistors set distinct IIN_FWD, IIN_REV, IOUT_FWD, IOUT_REV limits - critical for battery charge/discharge protection |
| Hybrid Conduction Mode (HCM) | Automatically blends DCM and CCM based on load to maintain >95% efficiency across 1%–100% load range |
| High-Voltage Pin Spacing (LWE) | 64-lead eLQFP meets IPC-2221 creepage/clearance requirements for 80V operation - eliminates need for slotting or isolation barriers |
| Integrated Gate Drivers | 4-channel NMOS drivers with 20ns switching and <100ns dead-time control reduce external component count and layout sensitivity |
| AEC-Q100 Qualified (H Grade) | Validated for –40°C to +150°C operation with HTOL, TC, ESD, and latch-up testing - suitable for engine compartment deployment |
Applications
| Automotive Dual-Battery System | Solar Energy Storage |
|---|---|
|
Use Scenario: Bidirectional power transfer between 48V starter-generator and 12V auxiliary battery in mild-hybrid vehicles. IC Role / Device Role / Timing Role: Primary buck-boost controller managing FHCM/RHCM transitions during regenerative braking and cold-cranking assist. Use Value: Enables >97% peak efficiency at 15A output with thermal derating only above 135°C - extends system uptime in under-hood environments. |
Use Scenario: Solar panel MPPT charger feeding a lithium-titanate battery bank with backup power injection into grid-tied inverters. IC Role / Device Role / Timing Role: Voltage/current-regulated bidirectional interface maintaining constant VOUT during cloud transients and enabling reverse feed during grid outage. Use Value: Six-loop regulation eliminates need for separate BMS communication; 80V input withstands open-circuit PV voltages up to 100V. |
| Industrial UPS Backup | Telecom 48V/24V Conversion |
|
Use Scenario: Online UPS maintaining uninterrupted 24V DC output from either AC rectified bus or 24V lead-acid battery during mains failure. IC Role / Device Role / Timing Role: Bidirectional controller enforcing strict IOUT_REV limit during battery discharge and IIN_FWD limit during recharge cycles. Use Value: Independent current limits prevent battery overcharge/overdischarge; DIR pin allows firmware-controlled transition between modes. |
Use Scenario: Telecom base station converting primary -48V DC supply to +24V for RF power amplifiers while supporting reverse current for hot-swap module insertion. IC Role / Device Role / Timing Role: High-efficiency buck-boost regulator with programmable soft-start (SS pin) preventing inrush during module insertion. Use Value: 1.3V–80V output range accommodates aging battery compensation; LDO33 pin powers local monitoring circuitry without external regulator. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8705AHLWE#PBF | Single-direction only (no DIR pin); identical pinout and package; lower cost; lacks reverse current regulation | Unidirectional 48V→12V conversion only; cannot support battery discharge into source rail | Select when bidirectional operation is unnecessary and cost sensitivity outweighs flexibility |
| MPQ4332GL-AEC1 | Integrated MOSFETs (40V max); fixed 300kHz frequency; no independent reverse current sensing; AEC-Q100 Grade 1 (–40°C to +125°C) | Limited to ≤40V systems; no hardware-based direction reversal; requires external current sense for bidirectional use | Choose for space-constrained 12V/24V automotive modules where integration outweighs voltage/range flexibility |
Compared with LT8705AHLWE#PBF and MPQ4332GL-AEC1, the LT8708HLWE#PBF uniquely delivers full hardware-controlled bidirectionality, 80V rating, and six independent regulation loops - making it the only option for AEC-Q100-compliant 48V↔12V dual-battery systems requiring autonomous reverse-current limiting.
Availability
LT8708HLWE#PBF is available at Aetrix Electronics and suitable for automotive 48V systems, solar energy storage interfaces, and industrial UPS backup requiring stable component supply with guaranteed long-term availability and automotive-grade reliability.
Supply support for LT8708HLWE#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets since 1965.
The LT8708 product line was designed specifically for high-voltage bidirectional DC/DC conversion in automotive mild-hybrid systems, renewable energy storage, and industrial backup power - emphasizing hardware-configurable direction control and multi-loop regulation without microcontroller dependency.
FAQ
What is the maximum operating junction temperature for LT8708HLWE#PBF?
The LT8708HLWE#PBF is rated for a maximum junction temperature of 150°C and is qualified per AEC-Q100 Grade H. This specification is validated across process corners and environmental stress tests, ensuring reliable operation in under-hood automotive locations where ambient temperatures exceed 105°C. The LT8708HLWE#PBF's thermal design includes an exposed pad (Pin 65) that must be soldered to a thermal pad on the PCB to achieve the specified θJA of 17°C/W.
How does the DIR pin control bidirectional operation in LT8708HLWE#PBF?
The DIR pin on the LT8708HLWE#PBF determines power flow direction: a voltage ≥1.6V configures the controller for forward operation (VIN → VOUT), while ≤1.2V enables reverse operation (VOUT → VIN). This hardware-level control operates independently of switching state, allowing dynamic direction changes mid-conversion without fault conditions or restart sequences. The LT8708HLWE#PBF maintains regulation continuity during DIR transitions by reassigning current-sense amplifier roles and adjusting gate drive timing accordingly.
Can LT8708HLWE#PBF regulate both input and output current simultaneously?
Yes, the LT8708HLWE#PBF supports simultaneous regulation of forward/reverse input current (IIN_FWD/IIN_REV) and forward/reverse output current (IOUT_FWD/IOUT_REV) using four independent current-sense amplifier pairs (IMON_INP/INN and IMON_ON/OP). Each pair connects to its own external sense resistor, enabling discrete setting of all four current limits. This capability is essential for battery protection in bidirectional systems, where charge and discharge currents must be independently constrained - a feature not available in most competing controllers.
What package type and thermal characteristics does LT8708HLWE#PBF use?
The LT8708HLWE#PBF uses a 64-lead (10mm × 10mm) plastic eLQFP package (LWE) with exposed thermal pad (Pin 65 = GND). Its thermal resistance is θJA = 17°C/W and θJC = 2.5°C/W when mounted on a 4-layer PCB with 2-in² 2-oz copper thermal pad. This package provides superior heat dissipation compared to the 40-lead QFN variant and meets IPC-2221 high-voltage creepage requirements for 80V operation - eliminating the need for PCB slotting or conformal coating in automotive designs.
Does LT8708HLWE#PBF require external MOSFETs, and what are the gate driver specifications?
Yes, the LT8708HLWE#PBF is a controller-only IC and requires four external NMOS power transistors (two high-side, two low-side). Its integrated gate drivers deliver 20ns rise/fall times into 3300pF loads, with TG1/BG1 and TG2/BG2 pairs featuring 80–90ns programmable dead time to prevent shoot-through. The drivers operate from GATEVCC (regulated internally from INTVCC or EXTVCC) and support bootstrap or floating supply configurations for high-side drive - enabling efficient operation at switching frequencies up to 400kHz.
LT8708HLWE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 64-LQFP Exposed Pad
- Packaging:
- Tray
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck-Boost
- Number of Outputs:
- 1
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 2.8V ~ 60V
- Frequency - Switching:
- 100kHz ~ 400kHz
- Duty Cycle (Max):
- 80%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Enable
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 64-LQFP-EP (10x10)
LT8708HLWE#PBF FAQ
1.How can I place an order for LT8708HLWE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8708HLWE#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 LT8708HLWE#PBF reliable?
The price and inventory of LT8708HLWE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8708HLWE#PBF is usually 5 days.
3.What payment methods are accepted for LT8708HLWE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8708HLWE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8708HLWE#PBF?
LT8708HLWE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8708HLWE#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 LT8708HLWE#PBF?
For technical support, including LT8708HLWE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8708HLWE#PBF requirements.
6.How does Aetrix verify that LT8708HLWE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8708HLWE#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 LT8708HLWE#PBF meets industry standards.
7.What is the process for return or replacement of LT8708HLWE#PBF?
All LT8708HLWE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8708HLWE#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 LT8708HLWE#PBF part is unused and in its original packaging.
Return procedure for LT8708HLWE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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