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Analog Devices Inc. LTC3815IUFE#PBF
- Part No.:
- LTC3815IUFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LTC3815IUFE#PBF.pdf
- Description:
- IC REG BUCK PROG 6A 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,161
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Product details
Overview
LTC3815IUFE#PBF from Analog Devices is a 6A monolithic synchronous step-down DC/DC converter with PMBus interface, operating from 2.25V to 5.5V input and delivering programmable output voltage from 0.4V to 72% of VIN. It features ±1% total output voltage accuracy over temperature, integrated 13-bit ADC for telemetry, and phase-lockable switching frequency up to 3MHz-designed for high-precision power delivery in FPGA and ASIC point-of-load applications.
For engineers reviewing the LTC3815IUFE#PBF datasheet, LTC3815IUFE#PBF pinout, LTC3815IUFE#PBF application, or LTC3815IUFE#PBF equivalent, key selection considerations include its 38-lead 4mm × 6mm QFN package, PMBus-compliant margining (±25% at 0.1% resolution), real-time readback of input/output voltage/current/temperature, and master shutdown mode drawing <1μA supply current.
Technical Context
The LTC3815IUFE#PBF employs a controlled-on-time, current-mode architecture with valley-current sensing via internal NMOS RDS(ON) (20mΩ typical) and PMOS RDS(ON) (35mΩ typical), enabling fast transient response and stable operation down to 75ns minimum on-time. Its error amplifier delivers 80dB open-loop gain and 20MHz gain-bandwidth product for tight regulation under dynamic load conditions.
System-level control is implemented through a fully compliant PMBus 1.2 interface supporting 25Hz telemetry refresh, fault status reporting, and programmable PGOOD thresholds via PGFD and PGLIM pins. The device integrates a 13-bit ADC for VOUT, VIN, IOUT, IIN, and die temperature measurement with ±0.75% total unadjusted error on output voltage and ±3% on current readings.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.25V to 5.5V - supports direct operation from 2.5V, 3.3V, 5V rails or single-cell Li-ion batteries. |
| Output Current | 6A continuous - delivered via integrated high-side PMOS and low-side NMOS switches with thermal enhancement via exposed PGND pad. |
| Output Voltage Range | 0.4V to 72% of VIN - set by single external resistor on REF pin or external reference; enables precise low-VDD scaling for modern processors. |
| Switching Frequency | 400kHz to 3MHz - programmable via RT resistor or synchronized to external clock; allows noise-sensitive system coexistence. |
| Output Accuracy | ±1% over temperature at VIN = 3.3V or 5V - includes offset, line regulation, and reference current drift contributions per datasheet Note 10. |
| PMBus Interface | Full SMBus 2.0 compliance - supports MFR_VOUT_COMMAND, READ_VOUT/READ_IOUT/READ_TEMPERATURE_1, peak capture, and fault logging without host MCU intervention. |
| Thermal Performance | θJA = 38°C/W - achieved with soldered exposed PGND pad (Pin 39); junction temperature rated to 125°C for industrial operation. |
Pinout & Package
Package: 38-lead (4mm × 6mm) plastic QFN with thermally enhanced exposed PGND pad (Pin 39), rated for –40°C to +125°C junction temperature. Exposed pad must be soldered to PCB for electrical continuity and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RT (1) | Oscillator frequency programming | Resistor-to-ground sets switching frequency from 400kHz to 3MHz; tie to VIN for fixed 1MHz internal oscillator. |
| REF (36) | Reference voltage input | 100µA internal current source times external resistor sets base VOUT; also accepts external voltage reference for precision tracking. |
| MODE/SYNC (9) | Mode selection & external clock input | Ground = forced continuous conduction; VIN = discontinuous mode; AC signal = synchronization to external clock across full 400kHz–3MHz range. |
| PGOOD (29) | Power-good flag output | Open-drain signal asserted only when VOUT remains within programmable window (±6% to ±17%) for delay set by PGFD pin (200μs × 2N, N = 0–5,7). |
| SCL/SDA (8,7) | PMBus serial interface | Standard SMBus 2.0 bidirectional data/clock lines; support 10–400kHz clock rate, automatic ACK/NACK, and stuck-bus timeout (30ms). |
| SW (10,11,13,14,18,19,21,22,23) | Switching node | Connects to drains of internal main PMOS and synchronous NMOS FETs; requires low-inductance layout to minimize EMI and switching losses. |
| PGND (39) | Power ground | Exposed thermal pad; must be soldered to PCB plane for thermal dissipation and low-impedance return path for high di/dt currents. |
Key Features
| Feature | Design Value |
|---|---|
| Differential remote voltage sensing | VCC_SENSE and VSS_SENSE pins enable Kelvin connection to load, eliminating IR drop errors in high-current PCB traces. |
| Integrated 13-bit ADC telemetry | Simultaneous time-averaged (~4ms) and peak readback of VIN, VOUT, IIN, IOUT, and die temperature at 25Hz refresh - no external sensors required. |
| Fast margining with slew control | MARGIN pin triggers immediate ramp to pre-stored ±25% offsets; CSLEW pin accepts capacitor to program 0.1%/ms/nF slew rate for controlled voltage transitions. |
| Master shutdown mode | RUN_MSTR pin below 0.4V disables all circuitry and reduces supply current to <1μA - critical for battery-backed systems requiring ultra-low standby power. |
| Two-phase clock-out capability | CLKOUT pin provides 180° phase-shifted clock signal for seamless 2-phase interleaving; enables 12A total output with reduced ripple and thermal stress. |
Applications
| FPGA Core Power Supply | ASIC Point-of-Load Regulation |
|---|---|
|
Use Scenario: Delivering tightly regulated 0.85V/4A to Xilinx Kintex-7 FPGA core rail with dynamic load steps up to 3A/μs. IC Role / Device Role / Timing Role: Primary synchronous buck regulator with differential sensing, PMBus telemetry, and programmable PGOOD for FPGA configuration sequencing. Use Value: ±1% output accuracy and 75ns minimum on-time ensure stable core voltage during high-speed transients; integrated ADC eliminates need for external monitoring ICs. |
Use Scenario: Powering 1.2V/5A ARM-based SoC in industrial gateway with remote firmware updates requiring real-time rail health monitoring. IC Role / Device Role / Timing Role: PMBus-configurable POL converter providing margining, peak current/voltage capture, and fault logging via SCL/SDA interface. Use Value: MFR_VOUT_PEAK and MFR_IOUT_PEAK registers enable post-event diagnostics; 0.1% margining resolution supports production test margin validation. |
| Distributed Telecom Power System | Intelligent Server VRM |
|
Use Scenario: 48V-to-3.3V intermediate bus conversion feeding multiple downstream POLs in compact 1RU telecom shelf. IC Role / Device Role / Timing Role: High-efficiency (94% at 6A) primary buck with 3MHz sync capability to avoid sensitive RF bands and reduce filter size. Use Value: Phase-lockable architecture allows synchronization across multiple LTC3815IUFE#PBF units to suppress beat frequencies; 4mm × 6mm QFN saves board space vs discrete solutions. |
Use Scenario: Dual-rail 1.8V/25A and 0.9V/40A CPU voltage regulation in enterprise server motherboard with dynamic thermal throttling. IC Role / Device Role / Timing Role: Master controller in multi-phase configuration using CLKOUT and TRACK/SS for voltage ramp coordination and current sharing. Use Value: TRACK/SS pin enables precise voltage sequencing between rails; RUN_STBY pin allows independent standby control of secondary rails while maintaining telemetry. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3880IUHF#PBF | Dual-output, 2-phase capable, higher integration (dual 30A channels), 16-bit ADC, wider VIN (4.5–24V), larger 52-lead QFN. | Targeted at multi-rail server VRMs; lacks single-rail simplicity and 2.25V low-VIN capability of LTC3815IUFE#PBF. | Select LTC3880IUHF#PBF when dual-output coordination, higher current, or wider input range is required; not drop-in compatible due to pin count, package, and VIN limits. |
| TPS546D24RQFT | Single-output, 6A, PMBus 1.3, 2.95–16V VIN, 0.5–5.5V VOUT, 3.5mm × 4.5mm QFN, no integrated REF current source. | Optimized for higher-input industrial systems; requires external reference circuitry and lacks differential sensing pins. | Choose TPS546D24RQFT for cost-sensitive 12V-input applications where REF resistor programming and Kelvin sensing are not needed. |
Compared with LTC3880IUHF#PBF and TPS546D24RQFT, the LTC3815IUFE#PBF uniquely combines ultra-low 2.25V input operation, integrated REF current source for single-resistor VOUT programming, and differential remote sensing in a compact 4mm × 6mm footprint-making it optimal for space-constrained, low-VIN, high-accuracy POL designs.
Availability
LTC3815IUFE#PBF is available at Aetrix Electronics and suitable for FPGA core power, ASIC point-of-load regulation, distributed telecom power systems, and intelligent server VRM applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LTC3815IUFE#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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets with precision power, signal chain, and RF solutions.
The LTC3815IUFE#PBF belongs to Analog Devices' Power by Linear™ monolithic DC/DC controller family, engineered specifically for high-efficiency, digitally monitored point-of-load power delivery in advanced computing and infrastructure systems.
FAQ
What is the minimum input voltage supported by the LTC3815IUFE#PBF?
The LTC3815IUFE#PBF supports an input voltage range from 2.25V to 5.5V. This low 2.25V minimum enables direct operation from single-cell Li-ion batteries or low-voltage logic rails such as 2.5V, making it suitable for portable and battery-powered applications where headroom is constrained. The device maintains regulation and telemetry functionality across this full range.
How does the LTC3815IUFE#PBF implement output voltage margining?
The LTC3815IUFE#PBF implements output voltage margining via its PMBus interface using the MFR_VOUT_COMMAND register, allowing ±25% adjustment around the base reference voltage at 0.1% resolution. Margining is executed through an internal 9-bit DAC, with slew rate controlled by the CSLEW pin capacitor. The MARGIN pin provides hardware-triggered fast margining to pre-stored high/low values.
Can the LTC3815IUFE#PBF operate in discontinuous conduction mode (DCM)?
Yes, the LTC3815IUFE#PBF automatically enters discontinuous conduction mode at light loads when the MODE/SYNC pin is tied to ground. In DCM, the bottom MOSFET is disabled when inductor current reaches zero, reducing switching losses and improving light-load efficiency. Forced continuous mode is enabled by tying MODE/SYNC to VIN, ensuring constant frequency under all load conditions.
What thermal management provisions does the LTC3815IUFE#PBF include?
The LTC3815IUFE#PBF features a thermally enhanced 38-lead QFN package with an exposed PGND pad (Pin 39) that must be soldered to the PCB for optimal thermal performance. Its specified θJA is 38°C/W, and it includes integrated overtemperature protection that activates above 125°C junction temperature. The device also supports real-time die temperature readback via READ_TEMPERATURE_1 command.
Is the LTC3815IUFE#PBF pin-compatible with other members of the LTC38xx family?
No, the LTC3815IUFE#PBF is not pin-compatible with other LTC38xx devices such as the LTC3880 or LTC3882. It uses a unique 38-lead 4mm × 6mm QFN footprint with dedicated pins for PMBus, margining control (MARGIN, CSLEW), and dual ground domains (SGND, PGND). Pin assignments-including SW, REF, and MODE/SYNC-differ significantly across the family, requiring custom PCB layout for each variant.
LTC3815IUFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Programmable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.25V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 0.4V
- Voltage - Output (Max):
- 3.96V
- Current - Output:
- 6A
- Frequency - Switching:
- 1MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-QFN (4x6)
LTC3815IUFE#PBF FAQ
1.How can I place an order for LTC3815IUFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3815IUFE#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 LTC3815IUFE#PBF reliable?
The price and inventory of LTC3815IUFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3815IUFE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3815IUFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3815IUFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3815IUFE#PBF?
LTC3815IUFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3815IUFE#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 LTC3815IUFE#PBF?
For technical support, including LTC3815IUFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3815IUFE#PBF requirements.
6.How does Aetrix verify that LTC3815IUFE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3815IUFE#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 LTC3815IUFE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3815IUFE#PBF?
All LTC3815IUFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3815IUFE#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 LTC3815IUFE#PBF part is unused and in its original packaging.
Return procedure for LTC3815IUFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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