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Analog Devices Inc. LT8708HLWE-1#PBF
- Part No.:
- LT8708HLWE-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 64-LQFP Exposed Pad
- Datasheet:
-
LT8708HLWE-1#PBF.pdf
- Description:
- 80V SYNCHRONOUS 4-SWITCH BUCK-BO
- Quantity:
- Payment:
- Shipping:
Inventory:160
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Product details
Overview
LT8708HLWE-1#PBF from Analog Devices is a high-voltage synchronous 4-switch buck-boost DC/DC slave controller designed to parallel with the LT8708 master in multiphase systems. It operates as a current-matched slave up to 80V input, supports bidirectional conduction (forward/reverse VIN current limiting), delivers up to 98% efficiency in synchronous rectification mode, and targets automotive 48V systems and dual-battery charging applications.
For engineers reviewing the LT8708HLWE-1#PBF datasheet, LT8708HLWE-1#PBF pinout, LT8708HLWE-1#PBF application, or LT8708HLWE-1#PBF equivalent, key selection considerations include its −40°C to +150°C junction temperature rating, 64-lead eLQFP package with high-voltage pin spacing, AEC-Q100 qualification, and precise current regulation via IMON_INP/IMON_INN pins for slave-phase current matching.
Technical Context
The LT8708HLWE-1#PBF implements identical conduction modes (CCM/HCM/DCM/Burst) as the LT8708 master and synchronizes via CLKOUT/SYNC signals to maintain phase alignment. Its error amplifiers (EA1, EA3–EA5) regulate forward/reverse VIN current, VOUT voltage, and slave output current using dedicated feedback paths including FBIN, FBOUT, IMON_INP, IMON_INN, and IMON_ON.
It features independent forward and reverse VIN current limits set by IMON_INP and IMON_INN pins, respectively, with programmable thresholds (e.g., 235mV rising for FDCM), and integrates gate drivers (TG1/TG2/BG1/BG2) with 20ns rise/fall times and controlled dead-time sequencing (e.g., 90ns TG1-off-to-BG1-on delay) for robust 4-switch operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Voltage Range | VINCHIP: 5.5V to 80V; CSPIN/CSNIN/CSPOUT/CSNOUT: 0V to 80V - enables direct interface with high-voltage battery rails without level-shifting. |
| Switching Frequency | 100kHz to 400kHz - adjustable via RT resistor; supports noise-sensitive automotive EMI requirements and thermal optimization. |
| Current Sense Threshold | ±72mV to ±110mV (buck/boost modes) - defines precise inductor current trip points for overcurrent protection and regulation. |
| Junction Temperature Range | −40°C to +150°C - qualified for under-hood automotive environments and high-power industrial converters. |
| Package | 64-lead (10mm × 10mm) eLQFP with exposed pad - provides low thermal resistance (θJC = 2.5°C/W) and high-voltage creepage for 80V systems. |
| AEC-Q100 Grade | Grade H - certified for automotive applications requiring extended temperature and reliability validation. |
| Efficiency | Up to 98% - achieved via synchronous rectification and optimized gate drive timing, reducing conduction and switching losses. |
Pinout & Package
LT8708HLWE-1#PBF is housed in a 64-lead (10mm × 10mm) plastic eLQFP package with exposed thermal pad (Pin 65 = GND). The package meets MSL Level 3 and supports reflow soldering per JEDEC J-STD-020.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CLKOUT (Pin 63) | Clock output | Provides synchronized 180° out-of-phase clock signal for multi-phase coordination; also serves as linear junction temperature monitor via duty cycle variation. |
| IMON_INP (Pin 11) | Forward VIN current monitor | Outputs 20µA + proportional current for positive average VIN current sensing; used to regulate or limit forward power flow (VIN → VOUT). |
| IMON_INN (Pin 12) | Reverse VIN current monitor | Outputs 20µA + proportional current for negative average VIN current sensing; enables reverse power flow control (VOUT → VIN) in bidirectional systems. |
| DIR (Pin 7) | Power direction control | Configures conduction direction in DCM/HCM modes: logic high (LDO33) enables forward mode; logic low (GND) enables reverse mode. |
| SYNC (Pin 14) | External clock input | Accepts external clock (≥1.3V high, ≤0.5V low) to synchronize switching frequency; connected to master's CLKOUT for 180° interleaving. |
| TG1/TG2 (Pins 23/29) | Top gate drivers | Drive gates of high-side NMOS switches (M1/M4); rail-to-rail output with 20ns rise/fall times and controlled dead-time sequencing. |
| BG1/BG2 (Pins 20/22) | Bottom gate drivers | Drive gates of low-side NMOS switches (M2/M3); referenced to GATEVCC (tied to INTVCC) with 20ns rise/fall times and 80–90ns inter-driver delays. |
| FBIN/FBOUT (Pins 8/9) | VIN/VOUT feedback inputs | Connect to error amplifiers EA3/EA4; typically tied to LDO33/GND to disable respective loops when slave relies on master regulation. |
| VC (Pin 10) | Error amplifier output | Summing node for all regulation loops; external compensation network connects here to stabilize voltage/current control loops. |
| CSNIN/CSPIN (Pins 16/15) | Slave current sense inputs | Differential inputs for measuring current through slave-phase sense resistor; common-mode range extends to 80V for high-side sensing. |
| CSNOUT/CSPOUT (Pins 19/18) | Slave current sense outputs | Provide differential current-sense signals referenced to VC; used for precision current monitoring and limiting in slave phase. |
| SHDN (Pin 3) | Shutdown control | Active-high enable: ≥1.221V enables operation; ≤0.3V disables chip and reduces quiescent current to ≤1µA. |
| RT (Pin 13) | Oscillator timing | Resistor-to-ground sets switching frequency (e.g., 365kΩ → ~120kHz); matched to master for phase coherence. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional current regulation | Independent IMON_INP and IMON_INN pins enable precise forward/reverse VIN current limiting-critical for regenerative braking and dual-battery charge/discharge. |
| Multiphase synchronization | CLKOUT and SYNC pins support deterministic 180° phase interleaving across master/slave pairs, reducing input/output ripple and improving thermal distribution. |
| High-voltage robustness | 80V-rated CSPIN/CSNIN/CSPOUT/CSNOUT pins and 81V SW1/SW2 absolute max ratings allow direct integration into 48V automotive and industrial battery systems. |
| Automotive-grade reliability | AEC-Q100 Grade H qualification and −40°C to +150°C operation ensure compliance with stringent automotive under-hood thermal and lifetime requirements. |
| Flexible conduction mode control | MODE and DIR pins configure CCM, HCM, DCM, or Burst Mode operation-enabling optimization for efficiency (light load) or regulation accuracy (heavy load). |
Applications
| Automotive Dual-Battery Charging | 48V Mild Hybrid Power Transfer |
|---|---|
Use Scenario: Bidirectional energy transfer between 12V starter battery and 48V traction battery during engine start-stop and regenerative braking. IC Role / Device Role / Timing Role: LT8708HLWE-1#PBF acts as slave-phase controller in a two-phase LT8708 + LT8708HLWE-1#PBF system, matching master current and enforcing reverse VIN current limits during regeneration. Use Value: Enables >95% efficiency at 30A bidirectional transfer (VBAT2 = 13.5V), meeting ISO 16750-2 pulse load and thermal derating requirements. | Use Scenario: Power conversion between 48V bus and auxiliary 12V systems in mild hybrid electric vehicles (MHEVs), supporting active suspension and ADAS ECUs. IC Role / Device Role / Timing Role: LT8708HLWE-1#PBF operates as synchronized slave in a multiphase buck-boost topology, sharing load with LT8708 master to deliver >1.5kW continuous power. Use Value: Achieves <20mV output ripple at full load via 180° phase interleaving, reducing bulk capacitor size and meeting CISPR 25 Class 5 EMI limits. |
| Industrial High-Voltage UPS | Renewable Energy Storage Interface |
Use Scenario: DC-DC stage in 48–80V battery-backed uninterruptible power supplies for telecom and data center infrastructure. IC Role / Device Role / Timing Role: LT8708HLWE-1#PBF serves as redundant slave phase, enhancing system power capacity and fault tolerance while maintaining tight voltage regulation during line transients. Use Value: Supports seamless transition between grid and battery with <100µs response to 10A load steps, validated per IEC 62040-3 dynamic performance criteria. | Use Scenario: Interfacing lithium-ion battery banks (24–60V) with variable PV array outputs in off-grid solar microinverters and storage systems. IC Role / Device Role / Timing Role: LT8708HLWE-1#PBF functions as slave controller in a scalable multiphase architecture, enabling modular power expansion without redesigning control loop compensation. Use Value: Delivers >97% peak efficiency across 10–100% load range using HCM mode, extending battery runtime and reducing thermal management complexity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost slave controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8708IUHG-1#PBF | 40-lead QFN package; −40°C to +125°C rating; same electrical functionality but lower thermal capability (θJC = 38°C/W vs. 2.5°C/W). | Suitable for non-automotive industrial applications where board space is constrained and ambient temperature remains below 105°C. | Select when PCB real estate is limited and junction temperature stays within 125°C; avoid in under-hood automotive use. |
| LT8708ELWE-1#PBF | Same 64-lead eLQFP package and pinout; −40°C to +125°C rating; identical feature set except reduced temperature grade. | Applicable in commercial/industrial systems requiring AEC-Q100 exemption but retaining mechanical compatibility and layout reuse. | Choose for cost-sensitive designs where full Grade H qualification is unnecessary and thermal margin is sufficient. |
Compared with LT8708IUHG-1#PBF and LT8708ELWE-1#PBF, the LT8708HLWE-1#PBF uniquely supports sustained 150°C junction operation and automotive qualification-making it the only option for high-reliability, thermally demanding vehicle platforms.
Availability
LT8708HLWE-1#PBF is available at Aetrix Electronics and suitable for automotive 48V systems, bidirectional battery charging, and high-voltage industrial UPS requiring stable component supply, long-term lifecycle assurance, and AEC-Q100-compliant traceability.
Supply support for LT8708HLWE-1#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 automotive, industrial, communications, and healthcare markets.
The LT8708 family-including LT8708HLWE-1#PBF-is engineered for high-efficiency, high-voltage, bidirectional DC/DC conversion in automotive and industrial power systems, emphasizing multiphase scalability, thermal robustness, and functional safety readiness.
FAQ
What is the primary function of the LT8708HLWE-1#PBF in a power system?
The LT8708HLWE-1#PBF is a slave controller that parallels with the LT8708 master to increase total system power and current capability in synchronous 4-switch buck-boost topologies. It does not operate independently-it relies on the master for voltage regulation, clocking, and overall system coordination while precisely matching output current and enforcing independent forward/reverse input current limits. The LT8708HLWE-1#PBF enables scalable, high-efficiency bidirectional power transfer in applications such as automotive dual-battery systems.
How does the LT8708HLWE-1#PBF achieve bidirectional operation?
The LT8708HLWE-1#PBF achieves bidirectional operation through dedicated current-monitoring pins (IMON_INP for forward VIN current and IMON_INN for reverse VIN current) and the DIR pin, which configures conduction direction in DCM or HCM modes. When DIR is pulled high (to LDO33), power flows from VIN to VOUT; when pulled low (to GND), power flows from VOUT to VIN. The LT8708HLWE-1#PBF regulates both directions using separate error amplifiers and maintains precise current matching to the master phase. This behavior is intrinsic to the LT8708HLWE-1#PBF architecture and requires no external logic.
Can the LT8708HLWE-1#PBF be used without an LT8708 master?
No-the LT8708HLWE-1#PBF is explicitly designed as a slave-only device and cannot operate autonomously. It lacks internal voltage reference generation for FBIN/FBOUT regulation, depends on the master's CLKOUT for synchronization, and requires the master to set system-level voltage and current limits. All startup sequencing, soft-start control, and primary regulation loops are managed by the LT8708 master. Attempting standalone use of the LT8708HLWE-1#PBF will result in undefined behavior or failure to switch. The LT8708HLWE-1#PBF must always be paired with an LT8708 master in hardware and firmware design.
What is the significance of the "H" grade in LT8708HLWE-1#PBF?
The "H" grade in LT8708HLWE-1#PBF denotes AEC-Q100 Grade H qualification and guaranteed operation from −40°C to +150°C junction temperature. This exceeds standard automotive Grade 1 (−40°C to +125°C) and ensures reliability in extreme under-hood environments, such as near turbochargers or exhaust manifolds. The LT8708HLWE-1#PBF undergoes additional stress testing-including extended temperature cycling, high-temperature operating life, and package reliability validation-to meet automotive safety and longevity requirements. This grade is mandatory for safety-critical 48V mild hybrid systems.
How does the LT8708HLWE-1#PBF handle thermal management in high-power applications?
The LT8708HLWE-1#PBF uses a 64-lead eLQFP package with an exposed thermal pad (Pin 65 = GND) and ultra-low junction-to-case thermal resistance (θJC = 2.5°C/W), enabling efficient heat transfer to the PCB ground plane. Its integrated overtemperature protection activates only during momentary overload conditions and is complemented by the high-temperature-rated silicon (150°C max junction). For sustained high-power operation, the LT8708HLWE-1#PBF requires proper copper pour, thermal vias under the exposed pad, and airflow or heatsinking per Analog Devices' layout guidelines. Thermal performance is validated in dual-phase 48V systems delivering >1.5kW continuously.
LT8708HLWE-1#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 ~ 80V
- 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-1#PBF FAQ
1.How can I place an order for LT8708HLWE-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8708HLWE-1#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-1#PBF reliable?
The price and inventory of LT8708HLWE-1#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-1#PBF is usually 5 days.
3.What payment methods are accepted for LT8708HLWE-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8708HLWE-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8708HLWE-1#PBF?
LT8708HLWE-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8708HLWE-1#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-1#PBF?
For technical support, including LT8708HLWE-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8708HLWE-1#PBF requirements.
6.How does Aetrix verify that LT8708HLWE-1#PBF is sourced from the original manufacturer or authorized distributors?
All LT8708HLWE-1#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-1#PBF meets industry standards.
7.What is the process for return or replacement of LT8708HLWE-1#PBF?
All LT8708HLWE-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8708HLWE-1#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-1#PBF part is unused and in its original packaging.
Return procedure for LT8708HLWE-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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