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Analog Devices Inc. LT8708ILWE#PBF
- Part No.:
- LT8708ILWE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 64-LQFP Exposed Pad
- Datasheet:
-
LT8708ILWE#PBF.pdf
- Description:
- 80V BIDIRECTIONAL BUCK-BOOST CON
- Quantity:
- Payment:
- Shipping:
Inventory:4,761
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Product details
Overview
LT8708ILWE#PBF from Analog Devices is a high-performance 80V synchronous 4-switch buck-boost DC/DC controller with bidirectional power capability. It regulates input/output voltage (1.3V–80V) and current in both forward and reverse directions, supports six independent regulation modes (VIN/VOUT voltage, IIN/IOUT forward/reverse), and operates across 2.8V–80V VINCHIP range. Used in automotive 48V systems and dual-battery energy transfer.
For engineers reviewing the LT8708ILWE#PBF datasheet, LT8708ILWE#PBF pinout, LT8708ILWE#PBF application, or LT8708ILWE#PBF equivalent, key selection considerations include bidirectional conduction mode control (HCM/CCM/DCM/Burst), independent four-quadrant current limiting via external resistors, high-voltage pin spacing in LQFP package, AEC-Q100 qualification, and compatibility with solar, telecom, and battery backup architectures.
Technical Context
The LT8708ILWE#PBF implements a synchronous 4-switch topology with independent gate drivers for TG1/BG1/SW1 and TG2/BG2/SW2, enabling seamless transition between buck, boost, and buck-boost regions. Its MODE and DIR pins configure conduction mode (CCM/HCM/DCM/Burst) and unidirectional/bidirectional power flow without interrupting switching operation.
It integrates six error amplifiers for simultaneous regulation of VIN, VOUT, IIN (forward/reverse), and IOUT (forward/reverse), with dedicated IMON_INP/IMON_INN/IMON_OP/IMON_ON pins for current-sense signal conditioning. Internal oscillator supports 100–400 kHz switching, adjustable via RT resistor or external SYNC clock.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VINCHIP Range | 2.8V to 80V - powers internal circuitry directly from high-voltage rail; EXTVCC switchover at 6.4V enables auxiliary supply redundancy. |
| VOUT Range | 1.3V to 80V - single-inductor architecture supports output above, below, or equal to input voltage without topology change. |
| Switching Frequency | 100–400 kHz - programmable via RT resistor or external SYNC; CLKOUT provides buffered clock output with phase delay ≤200°. |
| Current Sensing | Four independent current limits (IIN_FWD/REV, IOUT_FWD/REV) set by external resistors - enables precise bidirectional protection in battery charging/discharging systems. |
| Operating Temp | –40°C to +125°C - industrial-grade rating (I-grade) ensures reliability in under-hood automotive and industrial power systems. |
| Package | 64-lead eLQFP (10mm × 10mm) with high-voltage pin spacing - meets creepage/clearance requirements for 80V applications; exposed pad is GND. |
| AEC-Q100 | Qualified - certified for automotive use per Grade 1 (–40°C to +125°C), supporting functional safety–aware designs in 48V mild-hybrid systems. |
Pinout & Package
LT8708ILWE#PBF is housed in a 64-lead plastic eLQFP (10mm × 10mm) with exposed thermal pad (Pin 65 = GND). High-voltage pin spacing complies with IPC-2221B for ≥80V working voltage. Pin 65 must be soldered to PCB for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW1, SW2 | Power switch node connections | Connect to external NMOS source terminals; rated for 81V max; body diode conduction tolerated during dead-time. |
| TG1, TG2 | Top-gate drivers | Drive gate of high-side NMOS (M1/M4); 20ns rise/fall time into 3300pF load; off-to-on delay ≤90ns. |
| BG1, BG2 | Bottom-gate drivers | Drive gate of low-side NMOS (M2/M3); 20ns rise/fall time; on-to-off delay ≤80ns; complements TG timing. |
| CSPIN/CSNIN | Input-side current sense inputs | Differential pair for IIN monitoring; common-mode range 0–80V; supports bidirectional sensing with ±100mV differential range. |
| CSPOUT/CSNOUT | Output-side current sense inputs | Differential pair for IOUT monitoring; identical 0–80V CMR and ±100mV DM range as CSPIN/CSNIN. |
| DIR | Direction control input | Logic-level pin (1.6V threshold for forward, 1.2V for reverse) configures unidirectional or bidirectional power flow. |
| MODE | Conduction mode select | Four-state analog input (0.4V CCM, 0.8–1.2V HCM, 1.6–2.0V DCM, ≥2.4V Burst Mode) sets regulation behavior. |
| FBIN/FBOUT | VIN and VOUT feedback inputs | High-impedance (≤15nA bias) inputs referenced to 1.205V internal bandgap; support resistive divider-based voltage regulation. |
| IMON_INP/IMON_INN | IIN regulation outputs | Current-source outputs (max 120μA) proportional to sensed IIN; used to drive external current-limit resistors. |
| IMON_OP/IMON_ON | IOUT regulation outputs | Current-source outputs (max 120μA) proportional to sensed IOUT; enable independent forward/reverse output current limiting. |
| RT | Oscillator frequency set | Resistor from RT to GND sets free-running frequency (e.g., 124kΩ → 310–400kHz); supports SYNC override. |
| SYNC | External clock input | Accepts 100–400kHz clock (1.3V high, 0.5V low); enables multi-phase synchronization and EMI reduction. |
| CLKOUT | Internal clock output | Buffered oscillator output with duty cycle varying from 22.7% to 77% over temperature; phase delay ≤200° vs SYNC. |
| VINHIMON/VOUTLOMON | VIN high / VOUT low monitors | Comparator inputs with 1.207V thresholds (±24mV hysteresis); detect overvoltage (VIN) and undervoltage (VOUT) faults. |
| RVSOFF | Reverse voltage shutdown | Open-drain output active low when reverse voltage detected; pulls down to ≤0.5V at 200μA load. |
| LDO33 | Integrated 3.3V regulator | Supplies 5mA max at 3.295V (±0.055V); includes UVLO (2.96–3.12V) and 17.25mA current limit. |
| INTVCC/GATEVCC | Internal supply rails | Regulated 6.3V outputs (±0.2V) sourced from VINCHIP or EXTVCC; UVLO at 4.65V with 170mV hysteresis. |
| SHDN/SWEN | Enable and soft-start control | SHDN (1.221V threshold) enables full chip; SWEN (1.208V threshold) controls gate driver startup sequence and soft-start initiation. |
Key Features
| Feature | Design Value |
|---|---|
| Six independent regulation loops | Simultaneous closed-loop control of VIN, VOUT, IIN_FWD/REV, and IOUT_FWD/REV eliminates need for external controllers in bidirectional battery systems. |
| Four-quadrant current limiting | Separate IMON_INP/IMON_INN/IMON_OP/IMON_ON pins allow independent resistor-based setting of all four current limits - critical for safe charge/discharge cycling. |
| HCM (Hybrid Conduction Mode) | Combines CCM efficiency at heavy loads with DCM light-load performance; reduces switching losses while maintaining regulation accuracy across wide load range. |
| Real-time DIR/MODE reconfiguration | Conduction mode and direction can be changed dynamically during operation - enables adaptive power routing in vehicle start-stop or regenerative braking scenarios. |
| High-voltage eLQFP package | 64-lead LQFP with reinforced creepage distances supports 80V operation without external isolation; exposed pad improves thermal resistance (θJC = 2.5°C/W). |
| AEC-Q100 Grade 1 qualification | Validated for automotive under-hood environments (–40°C to +125°C); includes HTOL, TC, UHAST, and ESD testing per stress test plan. |
Applications
| Automotive 48V Mild-Hybrid System | Industrial Dual-Battery Backup |
|---|---|
Use Scenario: Regulates power flow between 48V starter-generator and 12V battery during engine start, coasting, and regenerative braking. IC Role / Device Role / Timing Role: Primary buck-boost controller managing bidirectional energy transfer; synchronizes switching with vehicle CAN bus timing via SYNC pin. Use Value: Enables >97% peak efficiency at 15A output (VBAT2=13.5V), reducing thermal load and extending battery life in compact under-hood space. | Use Scenario: Maintains uninterrupted power to critical PLC I/O modules during AC mains failure using two 24V lead-acid banks. IC Role / Device Role / Timing Role: Bidirectional voltage/current regulator that switches direction automatically upon mains loss detection via VINHIMON comparator. Use Value: Eliminates need for mechanical contactors or separate charge/discharge ICs - reduces BOM count and system latency to <100μs. |
| Solar Microinverter DC Link | Telecom 48V/54V Battery Switchover |
Use Scenario: Interfaces PV panel (30–60V) with DC link capacitor (400V) in transformerless microinverter, requiring high-efficiency MPPT tracking. IC Role / Device Role / Timing Role: High-voltage buck-boost controller operating in CCM; uses FBIN/FBOUT for dual-loop MPPT + DC-link regulation. Use Value: Supports 80V input withstand and 1.3V–80V output flexibility - accommodates wide PV IV curve without topology change or external boost stage. | Use Scenario: Seamless switchover between primary 48V telecom rectifier and backup 54V lithium battery bank during grid outage. IC Role / Device Role / Timing Role: Bidirectional controller enforcing strict voltage windows (48V ±1V, 54V ±0.5V) using FBIN/FBOUT and VOUTLOMON/VINHIMON comparators. Use Value: Prevents brownouts during transition by maintaining <50μs response to voltage deviation - meets GR-1089-CORE immunity requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8714IUFD#PBF | Single-inductor 4-switch controller with integrated 5V/200mA LDO; no LDO33; 40-pin QFN only; supports up to 80V but lacks RVSOFF pin. | Targeted at space-constrained industrial SMPS where auxiliary 3.3V rail is provided externally; not AEC-Q100 qualified. | Select when board area is critical and automotive qualification is unnecessary; verify external 3.3V supply meets IMON/VC bias requirements. |
| MPQ4420AGU-A-P | 36V max input; integrated MOSFETs; fixed 3.3V LDO; no bidirectional capability; no independent IIN/IOUT limiting; 12–36V output range only. | Suitable for unidirectional DC/DC conversion in consumer electronics or non-automotive industrial equipment with lower voltage requirements. | Choose only for cost-sensitive, low-complexity 36V systems lacking bidirectional or multi-loop regulation needs. |
Compared with LT8714IUFD#PBF and MPQ4420AGU-A-P, the LT8708ILWE#PBF uniquely delivers AEC-Q100 qualification, independent four-quadrant current limiting, 80V operation, and integrated 3.3V LDO - making it the sole option for automotive 48V bidirectional energy management where safety, precision, and voltage headroom are mandatory.
Availability
LT8708ILWE#PBF is available at Aetrix Electronics and suitable for automotive 48V systems, industrial dual-battery backup, solar microinverter DC links, and telecom battery switchover applications requiring stable component supply and long-term lifecycle support.
Supply support for LT8708ILWE#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. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT8708 product line was designed specifically for high-voltage, bidirectional power conversion in automotive and industrial energy storage systems - emphasizing robustness, regulation precision, and seamless direction switching under dynamic load conditions.
FAQ
What is the maximum input voltage supported by the LT8708ILWE#PBF?
The LT8708ILWE#PBF supports a VINCHIP input voltage range of 2.8V to 80V. Its SW1 and SW2 pins tolerate up to 81V, and CSPIN/CSNIN/CSPOUT/CSNOUT pins operate with 0–80V common-mode voltage. This enables direct interface with 48V automotive systems, 60V solar arrays, and telecom 54V battery banks without external level-shifting.
Does the LT8708ILWE#PBF support true bidirectional power flow with independent current limiting?
Yes, the LT8708ILWE#PBF supports full bidirectional power flow with four independently configurable current limits: forward/reverse input current (IIN_FWD/REV) and forward/reverse output current (IOUT_FWD/REV). Each is set using dedicated external resistors connected to IMON_INP/IMON_INN/IMON_OP/IMON_ON pins - enabling precise protection during battery charging and discharging cycles.
How does the MODE pin affect operation of the LT8708ILWE#PBF?
The MODE pin on the LT8708ILWE#PBF selects conduction mode: 0.4V enables CCM for high-efficiency heavy loads; 0.8–1.2V enables HCM for optimal light-to-heavy load efficiency; 1.6–2.0V enables DCM for ultra-low quiescent current; ≥2.4V activates Burst Mode® for minimal standby power. All transitions occur dynamically without disrupting regulation.
Is the LT8708ILWE#PBF pin-compatible with other variants in the LT8708 family?
No - the LT8708ILWE#PBF uses a 64-lead eLQFP package, while QFN variants (e.g., LT8708IUHG#PBF) use a 40-lead QFN. Pin functions differ significantly between packages (e.g., NC pins in LQFP vs. active signals in QFN), and thermal pad connections are not interchangeable. Board redesign is required when migrating between packages.
What is the purpose of the RVSOFF pin on the LT8708ILWE#PBF?
RVSOFF is an open-drain fault indicator pin on the LT8708ILWE#PBF that asserts low (<0.5V at 200μA) when reverse voltage is detected at the input or output. It interfaces directly with system supervisors or microcontrollers to trigger protective shutdown, preventing damage during incorrect battery polarity connection or backfeed events in bidirectional systems.
LT8708ILWE#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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 64-LQFP-EP (10x10)
LT8708ILWE#PBF FAQ
1.How can I place an order for LT8708ILWE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8708ILWE#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 LT8708ILWE#PBF reliable?
The price and inventory of LT8708ILWE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8708ILWE#PBF is usually 5 days.
3.What payment methods are accepted for LT8708ILWE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8708ILWE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8708ILWE#PBF?
LT8708ILWE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8708ILWE#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 LT8708ILWE#PBF?
For technical support, including LT8708ILWE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8708ILWE#PBF requirements.
6.How does Aetrix verify that LT8708ILWE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8708ILWE#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 LT8708ILWE#PBF meets industry standards.
7.What is the process for return or replacement of LT8708ILWE#PBF?
All LT8708ILWE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8708ILWE#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 LT8708ILWE#PBF part is unused and in its original packaging.
Return procedure for LT8708ILWE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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