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Analog Devices Inc. LT8708HUHG-1#PBF
- Part No.:
- LT8708HUHG-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 40-WFQFN Exposed Pad
- Datasheet:
-
LT8708HUHG-1#PBF.pdf
- Description:
- 80V SYNCHRONOUS 4-SWITCH BUCK-BO
- Quantity:
- Payment:
- Shipping:
Inventory:3,318
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Product details
Overview
LT8708HUHG-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 exclusively as a slave, supports bidirectional conduction (forward/reverse VIN current), delivers up to 80V input/output capability, and enables scalable power delivery in automotive 48V and dual-battery systems.
For engineers reviewing the LT8708HUHG-1#PBF datasheet, LT8708HUHG-1#PBF pinout, LT8708HUHG-1#PBF application, or LT8708HUHG-1#PBF equivalent, key selection considerations include its AEC-Q100 H-grade qualification (–40°C to +150°C), 40-lead QFN package with high-voltage pin spacing, synchronized start-up with master, independent forward/reverse VIN current limiting, and identical conduction modes (CCM/HCM/DCM/Burst) to the LT8708.
Technical Context
The LT8708HUHG-1#PBF implements a slave-only control architecture where all global voltage/current regulation is commanded by the master LT8708 via shared pins (SYNC, DIR, MODE, ICN, ICP). Its internal error amplifiers (EA1, EA3–EA5) regulate based on VC reference (1.2V), while IMON_INP/IMON_INN provide independent ±VIN current monitoring with programmable thresholds (235mV/185mV).
It features dual gate drivers (TG1/BG1, TG2/BG2) with 20ns rise/fall times and precise dead-time control (80–90ns), supports 100kHz–400kHz switching via RT resistor or external SYNC, and includes integrated LDO33 (3.295V, 5mA) and CLKOUT for temperature-sensing synchronization. All current sense inputs (CSPIN/CSNIN/CSPOUT/CSNOUT) operate over 0–80V common-mode range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Voltage Range | VINCHIP: 5.5V–80V; CSPIN/CSNIN/CSPOUT/CSNOUT: 0–80V common-mode - enables direct sensing in high-side 48V/60V battery rails without level-shifting. |
| Switching Frequency | 100kHz–400kHz - adjustable via RT resistor (e.g., 365kΩ = 120kHz) or external SYNC; supports phase interleaving for ripple reduction. |
| Current Sense Threshold | Buck mode: 72–96mV (VCSP–VCSN); Boost mode: 76–110mV (VCSP–VCSN) - sets precise inductor current trip points for overcurrent protection. |
| Temperature Range | –40°C to +150°C junction - qualified per AEC-Q100 Grade H for under-hood automotive applications including 48V mild-hybrid systems. |
| Package | 40-lead (5mm × 8mm) plastic QFN with exposed GND pad - provides low thermal resistance (θJC = 38°C/W) and high-voltage creepage between adjacent pins. |
| Gate Driver Performance | TG1/BG1/TG2/BG2: 20ns rise/fall time, 80–90ns dead-time - ensures robust NMOS switching with minimal shoot-through risk in high-efficiency buck-boost topologies. |
| LDO Output | LDO33: 3.295V ±0.055V at 5mA - powers external circuitry (e.g., level shifters, sensors) with <1% load regulation and 35mV UVLO hysteresis. |
Pinout & Package
LT8708HUHG-1#PBF is housed in a 40-lead (5mm × 8mm) plastic QFN package with exposed thermal pad (Pin 41 = GND). Pin pitch is 0.5mm; high-voltage isolation is maintained between adjacent pins (e.g., CSP/CSN to SW1/SW2). The exposed pad must be soldered to PCB for thermal and electrical performance.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 (CLKOUT) | Clock output / temperature monitor | 180° out-of-phase oscillator signal; duty cycle varies linearly with junction temperature - enables system-level thermal tracking without external sensor. |
| 2 (SS) | Soft-start timing | Internal 13–41µA current charges external capacitor to 3.3V - controls ramp rate of VC loop to prevent inrush current during startup. |
| 3 (SHDN) | Enable/disable control | Logic-high (>1.221V) enables operation; logic-low (<0.3V for H-grade) reduces quiescent current to ≤1µA - supports system-level power sequencing. |
| 4 (CSN), 5 (CSP) | Inductor current sense inputs | Differential pair referenced to GND - measures current through external sense resistor; used for peak-current-mode control and DCM detection. |
| 6 (ICN) | Negative VOUT current command | Accepts voltage from master LT8708 to set reverse-direction current limit - enables bidirectional power flow control in dual-battery systems. |
| 7 (DIR) | Power direction control | High = VIN→VOUT (forward); Low = VOUT→VIN (reverse); active only in DCM/HCM modes - defines energy transfer direction in slave phase. |
| 8 (FBIN), 9 (FBOUT) | VIN/VOUT feedback inputs | Connect to GND or LDO33 to disable respective error amplifiers - allows master-only regulation while slave contributes current only. |
| 10 (VC) | Error amplifier output | Integrates compensation network (R/C) - sets loop bandwidth and stability; voltage directly controls current sense threshold scaling. |
| 11 (IMON_INP), 12 (IMON_INN) | ±VIN current monitor outputs | 20µA base + proportional current (e.g., 25µA/mV) - feeds into external op-amps or ADCs for real-time VIN current measurement and limiting. |
| 13 (RT) | Oscillator timing | Resistor-to-GND sets fSW (100–400kHz); matched value required across master/slave for phase coherence - ensures uniform switching behavior. |
| 14 (SYNC) | External clock input | Accepts 1.3V–5.5V logic signal; synchronizes slave to master CLKOUT - eliminates beat frequencies and reduces EMI in multiphase designs. |
| 16 (BG1), 18 (BG2) | Bottom gate drivers | Sink current to drive NMOS sources; referenced to GND - controls M2/M4 switches in 4-switch buck-boost topology. |
| 17 (GATEVCC) | Gate driver supply | Must connect to INTVCC (6.3V) - powers BG1/BG2 drivers; local 1µF ceramic bypass required for noise immunity. |
| 20 (TG1), 22 (TG2) | Top gate drivers | Source current to drive NMOS gates; referenced to BOOST1/BOOST2 - controls M1/M3 high-side switches with bootstrap charge management. |
| 23 (SW1), 24 (SW2) | Switch node outputs | Connect to external NMOS drains - handles up to 81V transient voltage; body diode conduction supported during dead time. |
| 25 (LDO33) | 3.3V regulator output | Supplies 5mA max; UVLO at 2.96–3.12V - powers auxiliary circuits (e.g., microcontrollers, level shifters) with tight regulation. |
| 26 (IMON_ON) | VOUT current monitor output | 20µA base + proportional current - monitors output current direction and magnitude for system-level protection and telemetry. |
| 27 (IMON_OP) | VOUT current monitor output | Complementary to IMON_ON - provides differential current sense signal for precision VOUT current regulation. |
| 28 (MODE) | Conduction mode select | 0.4V = CCM; 0.8–1.2V = HCM; 1.6–2.0V = DCM; 2.4V = Burst - selects operating mode to optimize efficiency vs. light-load noise. |
| 29 (SWEN) | Switch enable | Rising threshold 1.208V - enables gate drivers only after soft-start completes; prevents premature switching before VC stabilization. |
| 30 (INTVCC) | Internal regulator output | 6.3V ±0.2V at 165mA max - powers internal circuitry and GATEVCC; dropout 245mV ensures stable operation down to VINCHIP = 6.55V. |
| 31 (VINCHIP) | Main supply input | 5.5–80V input - powers internal regulators; quiescent current 2.45–7.5mA depending on SWEN state - supports wide-input industrial/automotive rails. |
| 32 (GND) | Ground reference | Primary analog/digital return - connects to exposed pad (Pin 41); requires low-impedance PCB plane for noise immunity and thermal dissipation. |
| 33 (BG1) | Bottom gate driver (redundant label) | Same function as Pin 16 - dual labeling reflects internal routing; use only one connection point per driver. |
| 34 (GATEVCC) | Gate driver supply (redundant label) | Same function as Pin 17 - redundant pin for layout flexibility; must tie to same net as Pin 17. |
| 35 (BG2) | Bottom gate driver (redundant label) | Same function as Pin 18 - dual labeling reflects internal routing; use only one connection point per driver. |
| 36 (BOOST2) | Bootstrap capacitor supply | Charges external capacitor for TG2 high-side drive - requires 10–22nF ceramic cap with low ESR to sustain 80V+ gate drive. |
| 37 (TG2) | Top gate driver (redundant label) | Same function as Pin 22 - dual labeling reflects internal routing; use only one connection point per driver. |
| 38 (SW2) | Switch node output (redundant label) | Same function as Pin 24 - dual labeling reflects internal routing; use only one connection point per switch node. |
| 39 (NC) | No connect | Not bonded internally - must remain unconnected to avoid parasitic coupling or ESD paths. |
| 40 (NC) | No connect | Not bonded internally - must remain unconnected to avoid parasitic coupling or ESD paths. |
| 41 (GND) | Exposed thermal pad | Must be soldered to solid copper pour - provides primary thermal path (θJC = 38°C/W) and lowest-impedance ground return. |
Key Features
| Feature | Design Value |
|---|---|
| Slave-only multiphase architecture | Eliminates need for master arbitration logic; scales power linearly by adding LT8708-1 units while maintaining single-point voltage/current regulation. |
| Independent ±VIN current limiting | IMON_INP/IMON_INN pins allow separate forward (charging) and reverse (discharging) current limits - critical for bidirectional battery management in 48V systems. |
| AEC-Q100 Grade H qualification | Validated for –40°C to +150°C operation with full parametric testing - meets automotive under-hood reliability requirements without derating. |
| High-voltage pin spacing (QFN) | 5mm × 8mm footprint with optimized creepage distances between CSP/CSN and SW1/SW2 - enables safe operation at 80V input without external isolation. |
| Synchronized start-up and phase alignment | Four-pin interconnect (SYNC, DIR, MODE, ICN) ensures simultaneous enable, identical conduction mode, and 180° phase offset - minimizes input/output ripple. |
| Integrated LDO33 and CLKOUT | Reduces BOM count by eliminating external 3.3V regulator; CLKOUT's temperature-proportional duty cycle replaces discrete thermal sensors in compact layouts. |
Applications
| Automotive Dual-Battery Systems | 48V Mild-Hybrid Power Transfer |
|---|---|
|
Use Scenario: Bidirectional power transfer between 12V starter battery and 48V traction battery during engine start-stop cycles. IC Role / Device Role / Timing Role: LT8708HUHG-1#PBF acts as slave phase controller in a 2-phase LT8708 + LT8708-1 system, regulating reverse current flow from 48V to 12V rail during cranking. Use Value: Enables >30A reverse current with 97% efficiency at 13.5V VBAT2, reducing alternator load and improving fuel economy. |
Use Scenario: Regenerative braking energy capture from 48V motor/generator into high-voltage storage bank. IC Role / Device Role / Timing Role: LT8708HUHG-1#PBF operates in forward conduction mode (DIR = high) as slave phase, paralleling master to handle peak 55A charging current. Use Value: Supports 48V→14.5V buck conversion with <200ns minimum on-time, enabling high-frequency operation and compact magnetics. |
| Industrial High-Voltage Buck-Boost Converters | Server Rack Power Distribution |
|
Use Scenario: Wide-input (10–80V) DC-DC conversion for telecom rectifier backup systems requiring seamless switchover between AC/DC and battery sources. IC Role / Device Role / Timing Role: LT8708HUHG-1#PBF serves as second phase in a 2-phase 80V buck-boost converter, sharing load with master to reduce thermal stress on MOSFETs. Use Value: Delivers 98% peak efficiency in CCM mode with synchronized 120kHz switching, lowering system cooling requirements. |
Use Scenario: Intermediate bus converter in AI server racks converting 48V backplane to 12V intermediate distribution, supporting dynamic CPU/GPU load transients. IC Role / Device Role / Timing Role: LT8708HUHG-1#PBF functions as slave in a 4-phase LT8708-based design, providing phase interleaving to suppress 48V input ripple below 10mVpp. Use Value: Achieves <500μs load-step response (10A→25A) with VC loop bandwidth >100kHz, preventing brownouts during GPU burst loads. |
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 | Same functionality and pinout, but rated for –40°C to +125°C (I-grade) instead of +150°C (H-grade). | Not qualified for under-hood automotive use; suitable for industrial or commercial environments with lower ambient temperature. | Select LT8708IUHG-1#PBF when AEC-Q100 H-grade qualification is unnecessary and cost optimization is prioritized. |
| LT8708HLWE-1#WPBF | Same H-grade spec, but in 64-lead eLQFP package (10mm × 10mm) with different pinout and larger footprint. | Offers higher thermal mass and easier manual assembly, but requires PCB redesign due to incompatible pin mapping and larger size. | Choose LT8708HLWE-1#WPBF only when QFN thermal constraints cannot be met and board space permits larger package. |
Compared with LT8708IUHG-1#PBF, LT8708HUHG-1#PBF provides extended junction temperature capability essential for automotive under-hood deployment, while LT8708HLWE-1#WPBF trades compactness for thermal margin and manufacturability - neither offers pin compatibility with LT8708HUHG-1#PBF.
Availability
LT8708HUHG-1#PBF is available at Aetrix Electronics and suitable for automotive 48V systems, bidirectional battery chargers, and industrial high-voltage buck-boost converters requiring stable component supply across extended temperature ranges.
Supply support for LT8708HUHG-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 industrial, automotive, communications, and consumer markets with precision power, signal chain, and RF solutions.
The LT8708 family was designed specifically for high-efficiency, high-voltage, bidirectional buck-boost conversion in automotive and industrial applications - enabling scalable multiphase architectures without sacrificing regulation accuracy or thermal robustness.
FAQ
What is the maximum input voltage rating for the LT8708HUHG-1#PBF?
The LT8708HUHG-1#PBF supports up to 80V on VINCHIP, CSPIN, CSNIN, CSPOUT, and CSNOUT pins, with SW1/SW2 rated for 81V transients. This enables direct integration into 48V automotive systems and industrial 60V rails without external voltage clamping or level-shifting circuitry.
How does the LT8708HUHG-1#PBF synchronize with the master LT8708?
The LT8708HUHG-1#PBF synchronizes to the master LT8708 via the SYNC pin, which connects to the master's CLKOUT. This achieves precise 180° phase offset and eliminates frequency drift between phases, reducing input/output ripple and EMI in multiphase configurations.
Can the LT8708HUHG-1#PBF operate independently without a master LT8708?
No - the LT8708HUHG-1#PBF is strictly a slave controller and lacks autonomous voltage regulation capability. It requires continuous signals from the master LT8708 on DIR, MODE, ICN, ICP, and SYNC pins to define operating mode, direction, and current limits.
What is the purpose of the IMON_INP and IMON_INN pins on the LT8708HUHG-1#PBF?
IMON_INP and IMON_INN provide analog current monitor outputs proportional to positive and negative average VIN current, respectively. Each delivers 20µA base current plus 25µA/mV scaling - enabling external circuitry to implement independent forward/reverse current limiting in bidirectional applications.
Does the LT8708HUHG-1#PBF include an integrated voltage regulator?
Yes - the LT8708HUHG-1#PBF integrates two regulators: INTVCC (6.3V, 165mA) for internal logic and gate drivers, and LDO33 (3.295V, 5mA) for powering external circuitry. Both feature tight regulation (<1% load variation) and undervoltage lockout with hysteresis.
LT8708HUHG-1#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 40-WFQFN 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:
- 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:
- -
- Operating Temperature:
- -40°C ~ 150°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 40-QFN (5x8)
LT8708HUHG-1#PBF FAQ
1.How can I place an order for LT8708HUHG-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8708HUHG-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 LT8708HUHG-1#PBF reliable?
The price and inventory of LT8708HUHG-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 LT8708HUHG-1#PBF is usually 5 days.
3.What payment methods are accepted for LT8708HUHG-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8708HUHG-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8708HUHG-1#PBF?
LT8708HUHG-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8708HUHG-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 LT8708HUHG-1#PBF?
For technical support, including LT8708HUHG-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8708HUHG-1#PBF requirements.
6.How does Aetrix verify that LT8708HUHG-1#PBF is sourced from the original manufacturer or authorized distributors?
All LT8708HUHG-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 LT8708HUHG-1#PBF meets industry standards.
7.What is the process for return or replacement of LT8708HUHG-1#PBF?
All LT8708HUHG-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8708HUHG-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 LT8708HUHG-1#PBF part is unused and in its original packaging.
Return procedure for LT8708HUHG-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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