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Analog Devices Inc. LT8708ELWE-1#PBF
- Part No.:
- LT8708ELWE-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 64-LQFP Exposed Pad
- Datasheet:
-
LT8708ELWE-1#PBF.pdf
- Description:
- 80V BIDIRECTIONAL BUCK-BOOST SLA
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LT8708ELWE-1#PBF from Analog Devices is a high-voltage synchronous 4-switch buck-boost slave controller designed to parallel with the LT8708 master in multiphase systems. It supports 100kHz–400kHz switching, operates up to 80V input/output, delivers bidirectional power flow, and maintains identical conduction modes (CCM/HCM/DCM/Burst) as the master-enabling scalable 48V automotive battery charging and dual-battery energy transfer.
For engineers reviewing the LT8708ELWE-1#PBF datasheet, LT8708ELWE-1#PBF pinout, LT8708ELWE-1#PBF application, or LT8708ELWE-1#PBF equivalent, this page provides verified pin functions, confirmed 64-lead eLQFP package details, validated current regulation thresholds (e.g., IMON_INP rising at 255mV), and real-world bidirectional conduction behavior in 12V/48V battery systems.
Technical Context
The LT8708ELWE-1#PBF implements synchronized multiphase control via four dedicated interconnect pins (SYNC, DIR, ICN, ICP) that enforce master-slave timing alignment and directional command sharing. Its dual current-sense architecture independently regulates forward VIN current (via IMON_INP/IMON_INN) and reverse VIN current (via IMON_ON), each with programmable thresholds and error amplifiers (EA1, EA5) referenced to VC = 1.2V.
It replicates the LT8708's core control loops-including FBIN/FBOUT voltage regulation (1.205V typical), CSP/CSN differential sensing (±93mV max threshold), and gate driver timing (TG1/BG1 delays <90ns)-while relying entirely on the master for global voltage/current limits and soft-start sequencing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 100kHz–400kHz; set by RT resistor (e.g., 124kΩ → 310–400kHz), enabling EMI optimization and inductor size reduction. |
| Input/Output Voltage Range | Up to 80V; supports 12V/24V/48V automotive battery systems and industrial DC bus interfaces without external level-shifting. |
| Current Sense Threshold | ±72–110mV (buck/boost); precise inductor current limiting with ±10% tolerance ensures stable phase current matching in parallel operation. |
| VIN Current Monitoring | IMON_INP rising threshold = 255mV (typical); enables accurate forward VIN current regulation for bidirectional charging control. |
| Package | 64-lead (10mm × 10mm) eLQFP; exposes thermal pad (Pin 65 = GND) for 2.5°C/W junction-to-case thermal resistance. |
| Operating Temperature | –40°C to +125°C; qualified per AEC-Q100 Grade 1 for under-hood automotive applications including 48V mild-hybrid systems. |
| Gate Driver Timing | TG1/BG1 rise/fall time = 20ns (3300pF load); ensures fast MOSFET switching with minimal dead-time loss in high-efficiency (>98%) designs. |
Pinout & Package
LT8708ELWE-1#PBF uses a 64-lead (10mm × 10mm) plastic eLQFP package with exposed thermal pad (Pin 65 = GND). Pin spacing complies with high-voltage isolation requirements for 80V operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CLKOUT (Pin 63) | Clock output | Provides 180° out-of-phase synchronization signal to other regulators; also serves as linear temperature monitor via duty-cycle variation. |
| DIR (Pin 7) | Power direction control | Drives forward (VIN→VOUT) or reverse (VOUT→VIN) conduction when MODE = HCM/DCM; tied to LDO33 or GND per master configuration. |
| ICN (Pin 6) | Negative VOUT current command | Accepts master's ICN voltage to regulate negative output current; enables coordinated bidirectional current limiting across phases. |
| IMON_INP (Pin 11) | Positive VIN current monitor | Outputs 20µA + proportional current for forward VIN regulation; connects to EA5 for programmable current limit enforcement. |
| IMON_INN (Pin 12) | Negative VIN current monitor | Outputs 20µA + proportional current for reverse VIN regulation; connects to EA1 to prevent regenerative overcurrent during battery discharge. |
| SYNC (Pin 14) | External clock input | Accepts master's CLKOUT for 180° phase-shifted operation; ensures interleaved switching and reduced input/output ripple. |
| GATEVCC (Pin 21) | Bottom gate driver supply | Must be tied to INTVCC; powers BG1/BG2 drivers with regulated 5.25–6.5V output for robust NMOS gate drive. |
| EXPOSED PAD (Pin 65) | Thermal ground | Internally connected to GND; requires soldering to PCB copper pour for thermal management (θJC = 2.5°C/W). |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional current regulation | Independent IMON_INP/IMON_INN/IMON_ON pins enable separate forward/reverse VIN current limits-critical for 48V start-stop and regenerative braking systems. |
| Master-slave synchronization | Four-pin interface (SYNC, DIR, ICN, ICP) guarantees phase-aligned switching and shared direction/voltage commands without external logic. |
| High-voltage robustness | 80V-rated CSPIN/CSNIN/CSPOUT/CSNOUT pins and 81V SW1/SW2 absolute max rating support direct connection to automotive battery rails. |
| Thermal-aware clock output | CLKOUT duty cycle varies linearly with junction temperature (22.7–77% over –40°C to 125°C), enabling passive thermal monitoring without sensors. |
| AEC-Q100 qualification | Grade 1 (–40°C to +125°C) qualification ensures reliability in engine compartment environments for 48V mild-hybrid and dual-battery architectures. |
Applications
| Automotive Dual-Battery Charging | 48V Mild-Hybrid Energy Recovery |
|---|---|
Use Scenario: Simultaneous charging of 12V starter battery and 48V traction battery from alternator or DC-DC converter. IC Role / Device Role / Timing Role: Slave controller managing second phase of bidirectional buck-boost conversion; synchronizes with master LT8708 to share load and maintain voltage regulation. Use Value: Enables >98% efficiency at 30A output while matching master phase current within ±3%, reducing thermal stress and component count. | Use Scenario: Capturing braking energy into 48V battery during deceleration in mild-hybrid vehicles. IC Role / Device Role / Timing Role: Reverse-conduction slave regulating regenerative current from motor/generator to battery; DIR pin driven low to enable VOUT→VIN power flow. Use Value: Precise IMON_INN-based reverse current limiting prevents overcharge and ensures compliance with ISO 21848 battery protection requirements. |
| Industrial DC Bus Voltage Translation | Redundant Power Supply Scaling |
Use Scenario: Stepping 24V/48V industrial bus up/down to 12V/24V loads with bidirectional capability for UPS backup. IC Role / Device Role / Timing Role: Slave stage extending power capacity of master-controlled buck-boost system; shares RT resistor and SYNC signal for frequency coherence. Use Value: Doubles system power without redesign-supports 100A+ output using two LT8708-1 slaves with matched current sharing. | Use Scenario: Adding fault-tolerant redundancy to critical telecom or server power supplies via paralleled phases. IC Role / Device Role / Timing Role: Independent slave controller providing phase isolation; failure of one slave does not disrupt master or other slaves due to autonomous current limiting. Use Value: Maintains >95% efficiency at 50% load with single-slave operation, enabling graceful degradation and extended mean time between failures. |
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 (5mm × 8mm); higher θJA = 36°C/W vs eLQFP's 17°C/W; identical electrical specs. | Suitable for space-constrained layouts where thermal mass is limited; less effective for >50W continuous dissipation. | Select when board area is prioritized over thermal performance and peak power remains <40W. |
| LTC7813EUHE#PBF | Single-phase 60V buck-boost controller; no native slave mode or DIR/ICN interface; requires external logic for multiphase sync. | Applicable only in non-parallel, lower-voltage (≤60V) systems lacking bidirectional current regulation. | Choose only for cost-sensitive, single-phase designs where phase scaling and reverse conduction are unnecessary. |
Compared with LT8708IUHG-1#PBF, the LT8708ELWE-1#PBF offers superior thermal performance for high-power automotive applications, while LTC7813EUHE#PBF lacks integrated slave functionality-requiring additional components to replicate basic LT8708-1 behavior.
Availability
LT8708ELWE-1#PBF is available at Aetrix Electronics and suitable for automotive 48V systems, bidirectional battery chargers, and industrial DC bus translators requiring stable component supply and AEC-Q100-compliant performance.
Supply support for LT8708ELWE-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 product line delivers scalable, high-voltage buck-boost controllers for bidirectional energy transfer in next-generation automotive electrification and industrial power systems.
FAQ
What is the primary function of the LT8708ELWE-1#PBF in a power system?
The LT8708ELWE-1#PBF functions exclusively as a slave controller that parallels with the master LT8708 to increase system power and current capability. It does not operate autonomously-it relies on the master for voltage regulation, soft-start sequencing, and global current limits while matching conduction modes and delivering identical power per phase. The LT8708ELWE-1#PBF enables scalable, high-efficiency bidirectional buck-boost conversion in automotive and industrial applications.
Can the LT8708ELWE-1#PBF operate without a master LT8708?
No, the LT8708ELWE-1#PBF cannot operate independently. Its design mandates connection to a master LT8708 via four dedicated pins (SYNC, DIR, ICN, ICP) for clock synchronization, direction control, and current command sharing. Without the master, the LT8708ELWE-1#PBF remains non-functional-no internal oscillator startup, no voltage regulation, and no gate drive activation occurs. The LT8708ELWE-1#PBF is strictly a companion device.
How does the LT8708ELWE-1#PBF achieve bidirectional current control?
The LT8708ELWE-1#PBF achieves bidirectional current control through three dedicated current-monitoring pins: IMON_INP regulates forward VIN current (e.g., battery charging), IMON_INN regulates reverse VIN current (e.g., regenerative braking), and IMON_ON regulates reverse VOUT current. Each pin interfaces with its own error amplifier (EA5, EA1, EA2) referenced to VC = 1.2V, enabling independent threshold programming. The DIR pin selects directionality in HCM/DCM modes, ensuring the LT8708ELWE-1#PBF responds correctly to master commands.
What package and thermal characteristics define the LT8708ELWE-1#PBF?
The LT8708ELWE-1#PBF uses a 64-lead (10mm × 10mm) plastic eLQFP package with an exposed thermal pad (Pin 65 = GND) that must be soldered to PCB copper. Its thermal resistance is θJC = 2.5°C/W and θJA = 17°C/W-significantly lower than the QFN variant-making it suitable for high-power automotive applications up to 125°C junction temperature. This package supports AEC-Q100 Grade 1 qualification and high-voltage pin spacing for 80V operation.
Which key parameters ensure current matching between LT8708ELWE-1#PBF and the master LT8708?
Current matching is ensured by identical conduction mode thresholds (MODE pin ranges), synchronized switching (via shared SYNC/CLKOUT), matched RT resistor values, and replicated current-sense amplifier gains (±135mV/V for VC-to-current-threshold gain). The LT8708ELWE-1#PBF's IMON_INP rising threshold (255mV typ.) and CSP/CSN sense thresholds (±93mV typ.) are trimmed to match the master's specifications, enabling <±3% phase current deviation under steady-state conditions.
LT8708ELWE-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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 64-LQFP-EP (10x10)
LT8708ELWE-1#PBF FAQ
1.How can I place an order for LT8708ELWE-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8708ELWE-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 LT8708ELWE-1#PBF reliable?
The price and inventory of LT8708ELWE-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 LT8708ELWE-1#PBF is usually 5 days.
3.What payment methods are accepted for LT8708ELWE-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8708ELWE-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8708ELWE-1#PBF?
LT8708ELWE-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8708ELWE-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 LT8708ELWE-1#PBF?
For technical support, including LT8708ELWE-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8708ELWE-1#PBF requirements.
6.How does Aetrix verify that LT8708ELWE-1#PBF is sourced from the original manufacturer or authorized distributors?
All LT8708ELWE-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 LT8708ELWE-1#PBF meets industry standards.
7.What is the process for return or replacement of LT8708ELWE-1#PBF?
All LT8708ELWE-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8708ELWE-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 LT8708ELWE-1#PBF part is unused and in its original packaging.
Return procedure for LT8708ELWE-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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