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Analog Devices Inc. LT3514IUFD#PBF
- Part No.:
- LT3514IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT3514IUFD#PBF.pdf
- Description:
- IC REG BCK ADJ 2A/1A TRPL 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:978
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Product details
Overview
LT3514IUFD#PBF from Analog Devices (formerly Linear Technology) is a triple-output synchronous buck switching regulator IC with 2A/1A/1A channel capability, wide 3.2V–36V input range, and integrated boost regulator enabling true 100% duty cycle operation. It integrates independent soft-start, output voltage tracking, programmable frequency (350kHz–2.2MHz), and power-good monitoring - designed for compact, high-reliability industrial power supplies.
For engineers reviewing the LT3514IUFD#PBF datasheet, LT3514IUFD#PBF pinout, LT3514IUFD#PBF application, or LT3514IUFD#PBF equivalent, key selection considerations include its QFN-28 thermally enhanced package, channel-specific current limits (SW1/SW4: 1.75A typ, SW3: 3.5A typ), 800mV feedback reference, and robust fault protection including cycle-by-cycle current limiting and thermal shutdown.
Technical Context
The LT3514IUFD#PBF implements three independent buck regulators (CH1: 1A, CH3: 2A, CH4: 1A) driven by a shared antiphase oscillator and powered via an internal boost regulator (CH5) that generates SKY = VIN + 4.85V to fully saturate bipolar switches. Each channel features dedicated RUN/SS pins for sequencing and independent shutdown.
It uses internal compensation, resistor-programmed constant-frequency operation (via RT/SYNC), and dual current-sense paths: switch current limit (for overcurrent) and catch diode current limit (for transient inductor current runaway). The PG pin asserts open-drain low only when all three FB voltages exceed 710mV.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.2V to 36V (40V transient rating); enables direct connection to automotive battery, wall adapters, and industrial DC rails without pre-regulation. |
| Output Current Capability | CH1: 1A, CH3: 2A, CH4: 1A - supports mixed-voltage rail generation (e.g., 1.8V/3.3V/5V) from single input with asymmetric load demands. |
| Switching Frequency Range | 350kHz to 2.2MHz (programmable via RT resistor or external SYNC signal); allows optimization of size (higher fSW → smaller inductors) vs. efficiency (lower fSW → lower switching loss). |
| Feedback Reference Voltage | 790–816mV (±1.5% over temp); precise 0.8V nominal reference enables accurate output regulation with standard resistor dividers (e.g., R2 = 10.2kΩ). |
| Thermal Protection | Internal thermal shutdown activates at ~175°C junction temperature; protects against sustained overload or poor PCB thermal design without external circuitry. |
| Power Good Threshold | PG asserts high when all FB pins >710mV (65mV offset above reference); provides reliable system-level power sequencing and fault detection. |
| Quiescent Current (Shutdown) | ≤2µA (VEN/UVLO < 0.7V); enables ultra-low-power standby in battery-backed or energy-sensitive systems. |
Pinout & Package
Tiny 28-lead (4mm × 5mm) thermally enhanced QFN package with exposed pad (Pin 29) soldered to PCB ground for optimal thermal performance (θJA = 43°C/W). Pin count and layout match LT3504EUFD for partial footprint compatibility.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pins 9,11,26,28) | Main input supply connection | Supplies internal LDOs and power switches; must be locally bypassed and tied together - not isolated per channel. |
| SW1/SW3/SW4 (Pins 4,5,7) | Power switch outputs | Drive external inductors/diodes; SW3 rated for 3.5A peak (supports 2A continuous), SW1/SW4 rated for 1.75A peak (support 1A continuous). |
| FB1/FB3/FB4 (Pins 19,20,21) | Output voltage feedback inputs | Each regulated to 800mV; enables independent output programming (e.g., 1.8V, 3.3V, 5V) using resistor dividers. |
| RUN/SS1/RUN/SS3/RUN/SS4 (Pins 12,13,15) | Channel enable & soft-start control | Internal 1.3µA current source ramps voltage; capacitor-to-ground sets startup time; pulling below 0.1V shuts down individual channel. |
| EN/UVLO (Pin 16) | Global enable & input undervoltage lockout | 1.44V rising threshold with 110mV hysteresis; doubles as precision UVLO (2.9V typical) to prevent erratic startup at low VIN. |
| RT/SYNC (Pin 17) | Oscillator programming & synchronization | Accepts resistor-to-GND (350kHz–2.2MHz) or external clock (350kHz–2.2MHz, ≥50ns pulse width); no level-shifting required. |
| PG (Pin 23) | Open-drain power-good indicator | Asserts low until all three outputs reach regulation; requires external pull-up; disabled during shutdown. |
| SW5 (Pin 24) | Boost regulator switch output | Drives external inductor to generate SKY voltage; internal 320mA switch limit ensures stable SKY rail under all loads. |
| SKY (Pin 25) | Boost regulator output (VIN + 4.85V) | Provides gate drive for all buck switches; requires 1µF ceramic cap to VIN; must not be externally loaded or driven. |
| GND (Pins 10,18,27,29) | Ground reference & thermal path | Exposed pad (Pin 29) is GND and mandatory for thermal reliability; multiple GND pins reduce ground impedance and EMI. |
Key Features
| Feature | Design Value |
|---|---|
| Triple independent buck regulation | Enables single-chip generation of three distinct, sequenced DC rails (e.g., 1.8V core, 3.3V I/O, 5V peripheral) without external controllers or discrete FETs. |
| 100% duty cycle support via integrated boost | SKY = VIN + 4.85V ensures full saturation of internal bipolar switches even at VOUT ≈ VIN - critical for low-dropout industrial and automotive applications. |
| Programmable anti-phase switching | Reduces input ripple current by staggering channel switching (CH5 antiphase to CH3/CH4), lowering required input capacitance and EMI filtering complexity. |
| Independent RUN/SS pins with tracking capability | Allows precise power-up/down sequencing (e.g., core before I/O) and output voltage tracking via simple resistor networks - eliminates need for external supervisors. |
| Short-circuit and overload robustness | Dual current limiting (switch + catch diode) plus thermal shutdown protect against sustained shorts, start-up surges, and PCB layout faults without latch-off or external components. |
Applications
| Industrial Control Supply | Automotive Battery Regulation |
|---|---|
|
Use Scenario: Powering PLC I/O modules, sensor transmitters, and fieldbus interfaces from unregulated 24VDC industrial rails with ±10% tolerance and 40V transients. IC Role / Device Role / Timing Role: Primary triple-output DC-DC converter providing isolated 3.3V logic, 5V analog, and 12V auxiliary rails with coordinated soft-start and fault isolation. Use Value: Eliminates need for three separate regulators; 36V max input and 40V transient rating ensure operation during load-dump events without external TVS. |
Use Scenario: Regulating power for infotainment head units, ADAS camera modules, and body control modules directly from 12V vehicle battery with cold-crank (4.5V) and load-dump (40V) conditions. IC Role / Device Role / Timing Role: System PMIC delivering 1.2V processor core, 3.3V CAN interface, and 5V USB host from battery with UVLO set to 5.5V to prevent brownout resets. Use Value: 100% duty cycle operation maintains 3.3V output down to 3.7V input during cold-crank; PG pin enables safe MCU reset sequencing. |
| Wall Transformer Regulation | Distributed Supply Regulation |
|
Use Scenario: Converting 9–24V AC/DC adapter output into clean, low-noise 1.8V, 3.3V, and 5V rails for networking equipment (routers, switches) with strict ripple and efficiency requirements. IC Role / Device Role / Timing Role: High-efficiency triple buck controller operating at 1MHz to minimize inductor size while maintaining >85% efficiency across 10%–100% load range. Use Value: Programmable frequency avoids noise coupling into sensitive RF sections; anti-phase switching cuts input capacitor RMS current by 30% vs. in-phase. |
Use Scenario: Local point-of-load regulation on dense PCBs (e.g., server backplanes, FPGA carrier cards) where space is constrained and thermal management is critical. IC Role / Device Role / Timing Role: Compact, thermally optimized power solution replacing discrete buck ICs + MOSFETs; QFN-28 package with exposed pad enables direct copper pour attachment. Use Value: Integrated boost eliminates external charge pump; 43°C/W θJA allows 2A output at 70°C ambient without forced air - reducing system cooling cost. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-output buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3504IUFD#PBF | Four 1A channels (no 2A channel); identical pinout and package; lacks CH3 2A capability but adds CH2 1A output. | Suitable for symmetric 1A-rail designs (e.g., quad-core SoC with four 1V rails); not drop-in for LT3514IUFD#PBF's 2A/1A/1A configuration. | Select LT3504IUFD#PBF only if four equal-current rails are needed and board layout allows re-routing CH2 connections. |
| MPQ4436AGL-AEC1-P | Triple 3A/3A/2A buck with 3.8–32V input; AEC-Q100 Grade 1; no integrated boost - requires external gate driver for 100% duty cycle. | Automotive-qualified alternative with higher current per channel; lacks native 100% duty cycle and tracking/sequencing features. | Choose MPQ4436AGL-AEC1-P for AEC-Q100 compliance and higher current, but expect added complexity for cold-crank support and sequencing. |
Compared with LT3504IUFD#PBF and MPQ4436AGL-AEC1-P, the LT3514IUFD#PBF uniquely combines asymmetric current capability (2A+1A+1A), integrated boost for true 100% duty cycle, and hardware-based output tracking - making it optimal for space-constrained industrial and non-automotive embedded systems requiring mixed-rail flexibility and cold-input resilience.
Availability
LT3514IUFD#PBF is available at Aetrix Electronics and suitable for industrial control supplies, automotive battery regulation, and distributed supply regulation requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to +125°C operation.
Supply support for LT3514IUFD#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3514IUFD#PBF belongs to Linear's high-voltage monolithic buck regulator product line, engineered for rugged, high-density DC-DC conversion in harsh environments where input transients, wide temperature ranges, and minimal external components are critical design constraints.
FAQ
What is the maximum input voltage rating for the LT3514IUFD#PBF?
The LT3514IUFD#PBF has an absolute maximum input voltage rating of 40V on the VIN pin, with guaranteed operation from 3.2V to 36V. Transient spikes up to 40V are tolerated, but continuous operation above 36V risks exceeding the 125°C maximum junction temperature due to instantaneous power dissipation during startup.
Does the LT3514IUFD#PBF support 100% duty cycle operation, and how is it implemented?
Yes, the LT3514IUFD#PBF supports true 100% duty cycle operation via its integrated boost regulator (CH5), which generates SKY = VIN + 4.85V to fully saturate the internal bipolar power switches. This eliminates dropout voltage limitations, enabling stable output regulation even when VOUT approaches VIN - critical for automotive cold-crank and industrial low-input scenarios.
How does the LT3514IUFD#PBF handle output voltage sequencing and tracking?
The LT3514IUFD#PBF implements sequencing and tracking through dedicated RUN/SS pins (RUN/SS1, RUN/SS3, RUN/SS4). Connecting a resistor divider from a master output to a RUN/SS pin forces the slave channel to track that voltage during startup. Independent capacitor-to-ground connections program individual soft-start times, enabling precise power-up order without external supervisors.
What are the current limit specifications for each switch in the LT3514IUFD#PBF?
The LT3514IUFD#PBF specifies switch current limits of 1.75A (typ) for SW1 and SW4 (1A channels) and 3.5A (typ) for SW3 (2A channel), with corresponding catch diode current limits of 1.45A (SW1/SW4) and 2.5A (SW3) at FB = 0.7V. These limits are enforced cycle-by-cycle and include thermal derating over temperature.
Can the LT3514IUFD#PBF be synchronized to an external clock, and what are the requirements?
Yes, the LT3514IUFD#PBF can be synchronized to an external clock applied to the RT/SYNC pin. The sync signal must have a frequency between 350kHz and 2.2MHz, minimum pulse width of 50ns, and logic-compatible amplitude (0V to ≥1.5V). No level-shifting is required, and the internal sync detect circuit automatically distinguishes sync mode from resistor-programmed mode.
LT3514IUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 3
- Voltage - Input (Min):
- 3.2V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 36V
- Current - Output:
- 2A, 1A
- Frequency - Switching:
- 270kHz ~ 2.1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LT3514IUFD#PBF FAQ
1.How can I place an order for LT3514IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3514IUFD#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 LT3514IUFD#PBF reliable?
The price and inventory of LT3514IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3514IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LT3514IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3514IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3514IUFD#PBF?
LT3514IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3514IUFD#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 LT3514IUFD#PBF?
For technical support, including LT3514IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3514IUFD#PBF requirements.
6.How does Aetrix verify that LT3514IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3514IUFD#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 LT3514IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LT3514IUFD#PBF?
All LT3514IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3514IUFD#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 LT3514IUFD#PBF part is unused and in its original packaging.
Return procedure for LT3514IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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