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Analog Devices Inc. LTC3708EUH#PBF
- Part No.:
- LTC3708EUH#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3708EUH#PBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,106
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Product details
Overview
LTC3708EUH#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, 2-phase synchronous step-down controller with output voltage tracking capability, designed for high-efficiency power conversion in multi-rail systems. It supports no-RSENSE operation using MOSFET RDS(ON), delivers ≤85 ns minimum on-time, features 0.6 V ±1% reference, and operates across 3.3 V to 28 V input with up to 36 V absolute max VIN.
For engineers reviewing the LTC3708EUH#PBF datasheet, LTC3708EUH#PBF pinout, LTC3708EUH#PBF application, or LTC3708EUH#PBF equivalent, key selection criteria include its constant on-time valley current mode control, programmable output tracking (coincident/ratiometric), external clock synchronization, and integrated high-current MOSFET drivers for dual-phase interleaved buck topologies.
Technical Context
The LTC3708EUH#PBF implements a constant on-time, valley current mode architecture enabling stable low-duty-cycle operation without sense resistors. Its two channels operate 180° out of phase, synchronized via internal PLL (INTLPF) or external clock (FCB/EXTLPF), reducing input RMS current and EMI.
Fault protection includes instant output overvoltage detection (±10% window), monotonic soft-start via RUN/SS capacitor, adjustable cycle-by-cycle current limit (via ITH pins), and optional short-circuit shutdown timer using the RUN/SS node. Power good (PGOOD) provides 100 µs blanking and open-drain logic output.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 3.3 V to 28 V typical; supports up to 36 V absolute max - enables direct step-down from industrial or automotive supplies. |
| Output Reference | 0.6 V ±1% over –40°C to +85°C - ensures tight regulation for low-voltage DSP, FPGA, and ASIC core rails. |
| tON(MIN) | < 85 ns - allows stable operation at high input-to-output ratios (e.g., 20 V → 1.8 V @ ~200 kHz). |
| Tracking Modes | Coincident or ratiometric output voltage sequencing - supports controlled power-up/down for multi-rail processors and memory subsystems. |
| Phase Synchronization | Internal 180° phase shift (INTLPF) or external clock sync (FCB/EXTLPF) - reduces input capacitor stress and EMI by interleaving switch currents. |
| Current Limit Control | Adjustable via ITH voltage (0–2.4 V); VRNG pin sets nominal sense threshold (50–200 mV) - enables precise, temperature-stable overcurrent protection. |
| PGOOD Delay | 100 µs masking - prevents false fault triggering during transient load steps or startup overshoot. |
Pinout & Package
The LTC3708EUH#PBF is housed in a 32-lead, 5 mm × 5 mm plastic QFN package with exposed thermal pad (Pin 33 = SGND). The package supports high-power density layouts and requires soldering the exposed pad to PCB for thermal and signal integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS (1) | Run enable & soft-start timing input | Charging current (–1.2 µA typ.) sets ramp rate (~0.5 s/µF); latch-off threshold (2.2–2.8 V falling) enables short-circuit timeout. |
| ITH1, ITH2 (2, 8) | Error amplifier output / current limit threshold | 0–2.4 V control range sets comparator trip point; directly programs cycle-by-cycle current limit level. |
| VFB1, VFB2 (3, 7) | Feedback input for channel 1 & 2 | Connects to resistor divider from VOUT; 0.6 V reference enables accurate regulation of dual independent outputs. |
| TRACK1, TRACK2 (4, 6) | Output tracking reference inputs | Tie TRACK2 to VOUT1 divider for ratiometric tracking; TRACK1 links multiple LTC3708s for >2-rail sequencing. |
| SGND (5, 33) | Signal ground reference | Reference for all small-signal pins; exposed pad must be soldered to PCB ground plane for noise immunity and thermal performance. |
| EXTLPF (9) | External PLL loop filter | Compensates phase detector when synchronizing to external clock; required for deterministic frequency alignment. |
| INTLPF (10) | Internal PLL loop filter | Stabilizes 180° phase lock between channels; enables true 2-phase interleaving without external timing components. |
| VCC (17) | Main IC supply input | 3.6–7 V operating range; decoupled with RC filter (e.g., 10 Ω + 1 µF) to suppress switching noise coupling. |
| DRVCC (21) | Driver supply input | Powers bottom gate drivers and charges bootstrap capacitors; must be ≥3 V for reliable MOSFET turn-on. |
| BG1, BG2 (22, 20) | Bottom N-MOSFET gate drivers | Low-side drivers sourcing/sinking >2 A peak; optimized for fast turn-on/turn-off of synchronous rectifiers. |
| TG1, TG2 (27, 14) | Top N-MOSFET gate drivers | High-side drivers with floating bootstrap supply (BOOSTx); support >1 MHz switching with low dead-time loss. |
| PGOOD (30) | Power-good status output | Open-drain output pulled low if either VFB deviates >±10% for ≥100 µs - used for system enable/disable sequencing. |
| FCB (31) | Forced continuous / external clock input | Ground = forced continuous mode; AC signal = external sync; VCC = discontinuous mode at light load. |
| VRNG1, VRNG2 (32, 11) | Sense voltage range programming | 0.5–2 V input sets nominal current sense threshold (≈VRNG/7); enables optimal RDS(ON) or RSENSE selection. |
Key Features
| Feature | Design Value |
|---|---|
| No-RSENSE operation | Uses MOSFET RDS(ON) for current sensing - eliminates sense resistor losses and board space, improving efficiency in high-current rails. |
| 2-phase interleaved control | Reduces input RMS current by ~39% vs. single-phase (e.g., 2.53 A → 1.55 A), lowering input capacitor size, EMI filtering cost, and conduction losses. |
| Programmable output tracking | Supports both coincident (simultaneous ramp) and ratiometric (proportional ramp) sequencing - meets strict power-up order requirements for FPGAs and SoCs. |
| Constant on-time valley current mode | Delivers inherent line regulation and fast transient response without compensation network redesign - simplifies loop stability across wide VIN/VOUT ranges. |
| Integrated high-current gate drivers | On-chip TG/BG drivers deliver >2 A peak current - eliminates need for external driver stages, reducing BOM count and layout complexity. |
| Instant overvoltage protection | Detects >±10% VOUT excursion within nanoseconds and forces bottom-FET-on clamping - protects downstream logic from destructive transients. |
Applications
| Processor Core Supply | Network Server PSU |
|---|---|
|
Use Scenario: Powering dual-core DSPs or multi-core ARM processors requiring tightly sequenced 1.8 V and 2.5 V rails with fast load-step response. IC Role / Device Role / Timing Role: Dual-channel 2-phase buck controller providing independent, tracked outputs with <85 ns minimum on-time for high VIN/VOUT ratios. Use Value: Enables single-chip solution for complex rail sequencing while reducing input capacitance by 50% versus discrete controllers. |
Use Scenario: Generating primary 5 V and 3.3 V rails in 1U rack-mounted servers where thermal density and EMI compliance are critical. IC Role / Device Role / Timing Role: Interleaved 2-phase controller minimizing input ripple current and conducted EMI without adding magnetics or filters. Use Value: Lowers total RMS input current from 2.53 A to 1.55 A, reducing input capacitor count and shielding requirements. |
| FPGA I/O Bank Supply | Industrial PLC Power Module |
|
Use Scenario: Delivering matched 2.5 V and 1.8 V supplies to FPGA I/O banks with simultaneous power-up to prevent configuration glitches. IC Role / Device Role / Timing Role: Tracking controller supporting coincident ramp mode with monotonic soft-start and 100 µs PGOOD blanking. Use Value: Guarantees glitch-free configuration by enforcing strict voltage sequencing and eliminating false PGOOD asserts during transients. |
Use Scenario: High-reliability 24 V input to 5 V/3.3 V conversion in programmable logic controllers operating in harsh industrial environments. IC Role / Device Role / Timing Role: Robust controller with –40°C to +85°C rating, overvoltage/undervoltage protection, and latch-off shutdown for fault containment. Use Value: Ensures uninterrupted operation under brownout or short-circuit conditions via RUN/SS-based timeout and restart recovery. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-phase synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3855IUHF#PBF | Single-channel, 2-phase controller with integrated MOSFET drivers; lacks dual independent feedback loops and tracking capability. | Best suited for single-output, high-current rails (e.g., 12 V → 1.2 V @ 60 A); cannot independently regulate or track two outputs. | Select LTC3708EUH#PBF when dual independent regulated outputs with sequencing are required; LTC3855 for higher-current single-rail designs. |
| MP2918GL-Z | Monolithic dual-channel buck with integrated power stages; fixed 0.6 V reference; no external clock sync or VRNG-programmable current sense. | Targeted at cost-sensitive consumer applications; limited to ≤17 V VIN and lacks no-RSENSE flexibility or precision tracking. | Choose LTC3708EUH#PBF for industrial-grade reliability, wide VIN (≤36 V), and design flexibility in sensing method and sequencing. |
Compared with LTC3855IUHF#PBF and MP2918GL-Z, the LTC3708EUH#PBF uniquely combines dual independent regulation, programmable output tracking, no-RSENSE operation, and external clock synchronization - making it the only option among the three capable of managing complex multi-rail sequencing in high-performance embedded systems.
Availability
LTC3708EUH#PBF is available at Aetrix Electronics and suitable for processor core supplies, network server PSUs, FPGA I/O bank power, industrial PLC modules, and telecom baseband power requiring stable component supply and long-term lifecycle support.
Supply support for LTC3708EUH#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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for legacy Linear parts including the LTC3708 series.
The LTC3708 belongs to Linear's high-performance power controller family, engineered specifically for demanding multi-rail DC/DC conversion in computing, networking, and industrial systems where efficiency, sequencing accuracy, and thermal robustness are critical.
FAQ
What is the minimum on-time specification for the LTC3708EUH#PBF, and why does it matter?
The LTC3708EUH#PBF has a guaranteed minimum on-time of 85 ns (typical 50 ns). This enables stable operation at very high input-to-output voltage ratios - for example, stepping 20 V down to 1.8 V at ~200 kHz without pulse-skipping or regulation loss. It directly supports modern low-voltage, high-current processor rails where traditional controllers fail due to insufficient minimum pulse width.
How does the LTC3708EUH#PBF implement output voltage tracking without external circuitry?
The LTC3708EUH#PBF uses dedicated TRACK1 and TRACK2 pins to accept analog tracking references. When TRACK2 is tied to a resistor divider from VOUT1, the controller adjusts VOUT2 to follow VOUT1 either coincidentally (same ramp rate) or ratiometrically (proportional ramp). No external op-amps or comparators are needed - the function is fully integrated and calibrated across temperature.
Can the LTC3708EUH#PBF operate in forced continuous conduction mode (FCCM), and how is it enabled?
Yes, the LTC3708EUH#PBF supports forced continuous conduction mode. It is enabled by pulling the FCB pin below 1.9 V (typically grounded), which disables discontinuous mode operation and ensures both channels switch continuously even at light loads - critical for noise-sensitive applications and consistent EMI profiles.
What is the role of the VRNG1 and VRNG2 pins on the LTC3708EUH#PBF?
The VRNG1 and VRNG2 pins set the nominal current sense threshold for each channel: VRNG/7 ≈ maximum sense voltage (e.g., 1.4 V at VRNG = 1.0 V yields ~140 mV). This allows precise matching of the current limit to the chosen MOSFET RDS(ON) or sense resistor value, ensuring accurate, temperature-stable overcurrent protection across the full load range.
Does the LTC3708EUH#PBF require external MOSFET drivers, or are they integrated?
The LTC3708EUH#PBF integrates high-current gate drivers for both top (TG1/TG2) and bottom (BG1/BG2) N-channel MOSFETs - each capable of >2 A peak source/sink current. No external drivers are needed, reducing component count, PCB area, and layout complexity while maintaining fast switching transitions and low dead-time loss.
LTC3708EUH#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 32-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 3.2V ~ 36V
- Frequency - Switching:
- -
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Enable, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-QFN (5x5)
LTC3708EUH#PBF FAQ
1.How can I place an order for LTC3708EUH#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3708EUH#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 LTC3708EUH#PBF reliable?
The price and inventory of LTC3708EUH#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3708EUH#PBF is usually 5 days.
3.What payment methods are accepted for LTC3708EUH#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3708EUH#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3708EUH#PBF?
LTC3708EUH#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3708EUH#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 LTC3708EUH#PBF?
For technical support, including LTC3708EUH#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3708EUH#PBF requirements.
6.How does Aetrix verify that LTC3708EUH#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3708EUH#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 LTC3708EUH#PBF meets industry standards.
7.What is the process for return or replacement of LTC3708EUH#PBF?
All LTC3708EUH#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3708EUH#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 LTC3708EUH#PBF part is unused and in its original packaging.
Return procedure for LTC3708EUH#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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