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Analog Devices Inc. LT3504IUFD#PBF
- Part No.:
- LT3504IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT3504IUFD#PBF.pdf
- Description:
- IC REG BUCK ADJ 1A QUAD 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:982
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Product details
Overview
LT3504IUFD#PBF from Analog Devices (formerly Linear Technology) is a quad 40V/1A synchronous step-down DC/DC regulator with integrated boost circuit enabling 100% duty cycle operation. It features four independent 1A buck channels, resistor-programmable switching frequency (350kHz–2.2MHz), 800mV feedback reference, and thermal shutdown. Used in automotive battery regulation and distributed supply systems requiring high input voltage tolerance and output sequencing.
For engineers reviewing the LT3504IUFD#PBF datasheet, LT3504IUFD#PBF pinout, LT3504IUFD#PBF application, or LT3504IUFD#PBF equivalent, key selection criteria include input voltage range (3.2V–40V), per-channel current limit (1.75A typ), SKY pin drive capability (4.85V above VIN), anti-phase switching for ripple reduction, and independent RUN/SS pins for soft-start and tracking.
Technical Context
The LT3504IUFD#PBF integrates four current-mode buck regulators sharing a single on-chip boost regulator (SW5/SKY) that generates a 4.85V-over-VIN gate drive voltage to enable full saturation of internal bipolar switches. Each channel operates with cycle-by-cycle peak current limiting and catch diode current limiting, supported by independent soft-start and tracking via RUN/SS pins.
Its oscillator supports antiphase clocking (CH1/CH3/CH5 vs CH2/CH4) to reduce input ripple, and the RT/SYNC pin accepts either a programming resistor (200kHz–2.5MHz) or external sync signal (350kHz–2.2MHz). Power Good (PG) asserts only when all four FB pins exceed 710mV, ensuring coordinated regulation across outputs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.2V to 40V - supports wide-range industrial and automotive inputs without external pre-regulation |
| Output Current per Channel | 1A continuous - sufficient for powering FPGAs, DSPs, and multi-rail ASICs |
| Feedback Reference Voltage | 800mV ±16mV - enables precise output programming with standard resistor dividers |
| Switching Frequency Range | 350kHz to 2.2MHz - allows optimization of size (high-f) vs efficiency (low-f) and EMI compliance |
| Thermal Shutdown Threshold | 125°C junction - protects device during sustained overload or poor PCB thermal design |
| Quiescent Current (VIN) | 2.7mA typical at 1.5V EN/UVLO - low bias current preserves efficiency in always-on subsystems |
| SKY Pin Voltage Offset | +4.85V above VIN - ensures robust gate drive for internal bipolar switches across full input range |
Pinout & Package
Tiny 28-lead (4mm × 5mm) thermally enhanced QFN package with exposed pad (Pin 29) soldered to PCB ground for optimal thermal performance and EMI control.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| DA1–DA4 (Pins 1,3,6,8) | Catch diode anode sense | Monitors Schottky diode current to prevent inductor current runaway during transients |
| SW1–SW4 (Pins 2,4,5,7) | Buck switch node | Connects to inductor and diode cathode; drives each channel's power stage |
| VIN (Pins 9,11,26,28) | Main input supply | Distributes input current to internal regulators and power switches; requires local bypassing |
| GND (Pins 10,18,27,29) | Ground reference | Exposes pad must be soldered to PCB ground plane with thermal vias for thermal management |
| RUN/SS1–SS4 (Pins 12–15) | Soft-start & tracking control | Internal 1.3µA current source ramps voltage; enables per-channel startup sequencing |
| EN/UVLO (Pin 16) | Enable & undervoltage lockout | 1.44V rising threshold enables startup; 110mV hysteresis prevents chatter near UVLO point |
| RT/SYNC (Pin 17) | Oscillator programming | Accepts resistor for frequency setting or external clock for synchronization up to 2.2MHz |
| FB1–FB4 (Pins 19–22) | Output voltage feedback | Regulated to 800mV; determines output via R1/R2 divider; 15nA max bias current |
| PG (Pin 23) | Power good indicator | Open-collector output active-low when all outputs are within regulation (FB > 710mV) |
| SW5 (Pin 24) | Boost regulator switch | Drives external inductor to generate SKY voltage; 320mA current limit |
| SKY (Pin 25) | Boost output & gate drive rail | Supplies 4.85V above VIN to internal buck switches; requires 1µF capacitor to VIN |
Key Features
| Feature | Design Value |
|---|---|
| 100% duty cycle operation | Enables output voltages approaching VIN-critical for automotive cold-crank (e.g., 5V out from 5.5V min input) |
| Anti-phase switching | Reduces input ripple amplitude by interleaving CH1/CH3/CH5 and CH2/CH4 clock phases |
| Independent RUN/SS pins | Allows per-channel soft-start timing and output voltage tracking without external circuitry |
| Integrated boost regulator (SW5/SKY) | Eliminates four external charge pumps-reduces BOM count and layout complexity |
| Short-circuit robust architecture | Dual current limiting (switch + catch diode) prevents damage during output faults or startup into short |
Applications
| Automotive Battery Regulation | Industrial Control Supplies |
|---|---|
Use Scenario: Regulating 12V/24V automotive battery to multiple rails (5V, 3.3V, 2.5V, 1.8V) under cold-crank (5.5V) and load-dump (40V) conditions. IC Role / Device Role / Timing Role: Quad buck controller providing isolated, sequenced, and tracked outputs with 100% duty cycle support for lowest VIN operation. Use Value: Eliminates need for pre-regulator stages; reduces system component count and improves reliability in harsh environments. | Use Scenario: Powering PLC I/O modules, motor drivers, and sensor interfaces requiring stable 3.3V, 5V, and analog rails from unregulated 24V industrial bus. IC Role / Device Role / Timing Role: Centralized multi-output regulator with independent soft-start and thermal protection for fault-tolerant operation. Use Value: Enables clean power-up sequencing across subsystems; simplifies board-level power architecture versus discrete solutions. |
| Wall Transformer Regulation | Distributed Supply Regulation |
Use Scenario: Converting 9–36V wall adapter output to tightly regulated 5V/3.3V/2.5V/1.8V for embedded computing and networking equipment. IC Role / Device Role / Timing Role: High-efficiency quad buck converter with programmable frequency to meet EMI requirements across varying line conditions. Use Value: Achieves >90% efficiency at full load across wide input range; reduces heatsink requirements and improves energy certification scores. | Use Scenario: Providing localized power to remote sensors, actuators, or communication nodes in building automation or IoT edge devices. IC Role / Device Role / Timing Role: Compact, thermally efficient multi-rail regulator supporting dynamic voltage scaling and independent enable control. Use Value: Minimizes PCB area and interconnect losses; enables flexible power domain partitioning without sacrificing regulation accuracy. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar quad buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3375EFE#PBF | 8-channel configurable buck (1–4×1A, 1–2×2A); lower max VIN (20V); no integrated boost; uses external VDRV | Better suited for low-input-voltage, high-channel-count systems where 40V tolerance is unnecessary | Select LTC3375EFE#PBF when needing more than four outputs or tighter integration of channel configuration logic |
| MPQ4436GL-AEC1-P | Quad 3A buck; 3.3–36V input; AEC-Q100 qualified; no boost circuit; requires external bootstrap caps | Designed for automotive ADAS with higher per-channel current and functional safety support | Select MPQ4436GL-AEC1-P when AEC-Q100 qualification and >1A per channel are mandatory |
Compared with LTC3375EFE#PBF and MPQ4436GL-AEC1-P, the LT3504IUFD#PBF uniquely combines 40V input capability, integrated boost for 100% duty cycle, and independent RUN/SS control-making it optimal for high-VIN industrial and legacy automotive designs where external charge pumps are undesirable.
Availability
LT3504IUFD#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial control supplies, and distributed supply regulation requiring stable component supply across extended temperature ranges.
Supply support for LT3504IUFD#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 its high-performance power management portfolio with rigorous characterization and long-term product support.
The LT3504IUFD#PBF belongs to Linear's high-voltage monolithic buck regulator family, designed specifically for demanding industrial and automotive applications where wide input range, fault robustness, and minimal external components are critical.
FAQ
What is the maximum input voltage rating for the LT3504IUFD#PBF?
The LT3504IUFD#PBF has an absolute maximum VIN rating of 40V. It operates continuously across 3.2V to 40V input, but constant-frequency operation without pulse-skipping is limited by minimum on-time (110ns at 125°C) and programmed switching frequency. For example, at 2MHz and 3.3V output, VIN(PS) ≈ 26.5V - above which pulse-skipping occurs but regulation is maintained.
How does the LT3504IUFD#PBF achieve 100% duty cycle operation?
The LT3504IUFD#PBF achieves 100% duty cycle using an integrated boost regulator (SW5/SKY) that generates a drive voltage 4.85V above VIN. This SKY voltage fully saturates the internal bipolar power switches, allowing the buck regulators to maintain regulation even when VOUT approaches VIN - unlike conventional buck controllers requiring a minimum dropout voltage.
Can the LT3504IUFD#PBF synchronize to an external clock?
Yes, the LT3504IUFD#PBF supports external synchronization via the RT/SYNC pin. It accepts TTL/CMOS-compatible signals from 350kHz to 2.2MHz with minimum pulse width of 50ns. The internal sync detect circuit automatically distinguishes between resistor programming and external clock modes, enabling seamless transition between standalone and synchronized operation.
What is the function of the DA pins on the LT3504IUFD#PBF?
The DA1–DA4 pins on the LT3504IUFD#PBF serve as catch diode anode sense inputs. Each DA pin connects to the anode of its corresponding external Schottky diode and enables cycle-by-cycle monitoring of diode current. When diode current exceeds the internal limit, the controller halts switching to prevent inductor current runaway during transient overloads or short-circuit events.
Does the LT3504IUFD#PBF require external compensation components?
No, the LT3504IUFD#PBF features internal compensation for its error amplifiers, eliminating the need for external compensation networks. This simplifies design, reduces component count, and ensures stable loop response across all four channels without manual tuning - provided external components (inductors, capacitors, feedback resistors) meet recommended values and layout guidelines.
LT3504IUFD#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:
- 4
- Voltage - Input (Min):
- 3.2V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 40V
- Current - Output:
- 1A
- Frequency - Switching:
- 250kHz ~ 2.1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LT3504IUFD#PBF FAQ
1.How can I place an order for LT3504IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3504IUFD#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 LT3504IUFD#PBF reliable?
The price and inventory of LT3504IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3504IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LT3504IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3504IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3504IUFD#PBF?
LT3504IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3504IUFD#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 LT3504IUFD#PBF?
For technical support, including LT3504IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3504IUFD#PBF requirements.
6.How does Aetrix verify that LT3504IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3504IUFD#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 LT3504IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LT3504IUFD#PBF?
All LT3504IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3504IUFD#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 LT3504IUFD#PBF part is unused and in its original packaging.
Return procedure for LT3504IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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