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Analog Devices Inc. LT3508EUF#PBF
- Part No.:
- LT3508EUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LT3508EUF#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.4A DL 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,801
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Product details
Overview
LT3508EUF#PBF from Analog Devices (formerly Linear Technology) is a dual monolithic current-mode PWM step-down DC/DC converter with two integrated 1.4A NPN power switches, operating from 3.7V to 36V input and delivering independently regulated 3.3V and 5V outputs in anti-phase switching mode. It features programmable 250kHz–2.5MHz switching frequency, independent tracking/soft-start, and power-good signals for microcontroller sequencing in automotive and industrial power systems.
For engineers reviewing the LT3508EUF#PBF datasheet, LT3508EUF#PBF pinout, LT3508EUF#PBF application, or LT3508EUF#PBF equivalent, this page delivers verified specifications including FB voltage (0.800V ±1.4%), switch current limit (2.6A typ), thermal shutdown at 150°C, 24-pin 4mm × 4mm QFN package with exposed GND pad, and anti-phase ripple reduction - all critical for high-density dual-rail power supply design.
Technical Context
The LT3508EUF#PBF implements dual constant-frequency current-mode control with master-slave oscillator architecture, enabling precise 180° phase offset between channels to minimize input ripple. Each channel uses an internal error amplifier (transconductance 300μS, gain 600V/V) and VC-pin-controlled peak-current limiting with slope compensation.
It supports synchronous external clocking via RT/SYNC pin (0.25–2.5MHz logic-level input), frequency foldback under overload (down to 120kHz), and undervoltage lockout with adjustable threshold (2.63V typ). The BOOST1/BOOST2 pins enable efficient NPN saturation via external bootstrap capacitors, while TRACK/SS pins allow output voltage tracking or soft-start ramp generation via external capacitor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.7V to 36V - supports direct regulation from automotive batteries, 24V industrial rails, and unregulated wall adapters without pre-regulation. |
| Output Current per Channel | 1.4A continuous - enables dual-rail power for DSPs, FPGAs, or PCI Express interfaces with single-chip integration. |
| Feedback Reference Voltage | 0.800V ±1.4% - sets output accuracy; allows down to 800mV adjustable output using resistor divider with ≤20kΩ R2. |
| Switching Frequency Range | 250kHz to 2.5MHz - permits small ceramic capacitors and low-profile inductors; anti-phase operation reduces input RMS ripple by up to 30%. |
| Thermal Shutdown Threshold | 150°C junction - protects against sustained overloads; LT3508E grade rated for –40°C to +125°C operation. |
| Shutdown Current | <2μA - enables ultra-low-power battery backup modes without significant drain on primary supply. |
| Power Good Accuracy | ±75mV threshold offset - ensures reliable sequencing of downstream logic with tight regulation monitoring. |
Pinout & Package
LT3508EUF#PBF is housed in a thermally enhanced 24-lead plastic QFN package (4mm × 4mm), with exposed pad (Pin 25) electrically and thermally connected to GND and requiring PCB soldering for proper thermal performance (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 / FB2 | Feedback Input | Regulates each output to 0.800V reference; connects to resistor divider tap for precise output voltage setting. |
| TRACK/SS1 / TRACK/SS2 | Tracking/Soft-Start Control | Enables output voltage tracking or linear soft-start ramp via external capacitor; overrides internal 0.8V reference when pulled lower. |
| PG1 / PG2 | Power Good Open-Collector Output | Signals regulation status (low = fault); used for supply sequencing with microcontrollers or DSPs. |
| VC1 / VC2 | Error Amplifier Output | Controls peak switch current; can be externally compensated or pulled to GND to disable individual channel. |
| SW1 / SW2 | Internal Switch Output | Drives external inductor and catch diode; requires low-inductance layout due to fast switching edges. |
| BOOST1 / BOOST2 | Bootstrap Drive Supply | Provides >VIN gate drive for internal NPN switches via external diode/capacitor; enables high-efficiency saturation. |
| VIN1 / VIN2 | Input Power Supplies | VIN1 powers internal bias and Channel 1; VIN2 powers Channel 2 only; VIN1 must exceed 3.7V for either channel to operate. |
| RT/SYNC | Oscillator Control | Sets switching frequency via resistor-to-GND (e.g., 33.2kΩ = 1MHz) or accepts external sync signal (0.25–2.5MHz). |
| SHDN | Enable/Shutdown Input | Active-high logic input; 2.63V threshold provides accurate UVLO; <0.3V disables both channels with <2μA quiescent draw. |
| GND (Pins 3–7, 9–12, 14–16) | Ground Return | Multiple dedicated GND pins plus exposed pad ensure low-impedance return path and thermal dissipation. |
Key Features
| Feature | Design Value |
|---|---|
| Anti-phase dual-channel switching | Reduces input ripple current magnitude and EMI by canceling fundamental harmonics between channels. |
| Independent tracking and soft-start | Allows controlled power-up sequencing of multiple rails (e.g., core before I/O) without external controllers. |
| Programmable undervoltage lockout | SHDN pin threshold (2.63V typ) enables system-level brown-out protection with no external components. |
| Integrated cycle-by-cycle current limit | Guarantees 2.6A typical switch current limit with automatic foldback during overload, eliminating need for external sensing. |
| Small-footprint QFN packaging | 24-pin 4mm × 4mm thermally enhanced QFN enables high-density layouts while maintaining θJC = 10°C/W. |
Applications
| Automotive Infotainment Systems | DSP Power Supplies |
|---|---|
Use Scenario: Dual-rail power for audio DSP and display controller in vehicle head units with wide battery voltage swing (9–16V). IC Role / Device Role / Timing Role: Primary DC/DC regulator generating 3.3V for digital logic and 5V for analog interface circuits with synchronized start-up. Use Value: Anti-phase operation minimizes conducted EMI into sensitive RF receivers; UVLO prevents erratic behavior during cold-crank events. |
Use Scenario: High-efficiency, low-noise power for TI C6000 or Analog Devices SHARC processors in real-time signal processing equipment. IC Role / Device Role / Timing Role: Dual-output buck converter providing core (1.2V derived via LDO) and I/O (3.3V) rails with precise sequencing via PG and TRACK/SS pins. Use Value: Independent soft-start prevents inrush current damage to FPGA configuration memory; 1.4A per rail supports burst-mode processing loads. |
| PCI Express Add-in Cards | DSL/Cable Modem Power |
Use Scenario: Compact power solution for PCIe x1/x4 cards requiring separate 3.3V and 12V-derived 5V rails in space-constrained enclosures. IC Role / Device Role / Timing Role: Main switching regulator delivering 3.3V directly and 5V via secondary winding or auxiliary converter, with PG signaling PCIe reset timing. Use Value: 2.5MHz max frequency enables sub-3mm inductor height; exposed pad ensures thermal stability under full load in passive-cooled modules. |
Use Scenario: Dual-output power for broadband gateway devices with Ethernet PHY (3.3V) and line driver (5V) sections sharing common 12V input. IC Role / Device Role / Timing Role: Integrated buck regulator replacing discrete solutions to reduce BOM count and improve reliability in consumer-grade modems. Use Value: 36V absolute max input withstands transient surges on PoE-powered DSLAM interfaces; low 2μA shutdown current extends standby battery life. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3573EFE#PBF | Single 2.25A output, 3.6–40V input, no anti-phase or dual-tracking capability; TSSOP-16 package. | Not suitable for dual-rail sequencing; better for higher-current single-output applications where footprint is less constrained. | Select LT3573EFE#PBF only if single-rail power suffices and higher peak current (2.25A) is required over dual 1.4A outputs. |
| TPS54290PWPR | Dual 2A/channel, 4.5–28V input, 300kHz–2MHz sync range, but requires external MOSFETs and compensation; HTSSOP-28 package. | Higher design complexity due to external FETs and loop compensation; lacks integrated BOOST circuitry and PG sequencing logic. | Choose TPS54290PWPR only when input voltage is limited to ≤28V and board area allows larger package with external components. |
Compared with LT3508EUF#PBF, LT3573EFE#PBF offers higher single-rail current but no dual-channel coordination, while TPS54290PWPR provides greater flexibility at the cost of increased component count and layout sensitivity - making LT3508EUF#PBF optimal for compact, self-contained dual-rail designs with strict sequencing requirements.
Availability
LT3508EUF#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, DSP power supplies, and DSL/cable modem designs requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.
Supply support for LT3508EUF#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. (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 LT3508EUF#PBF belongs to Linear's high-voltage dual buck regulator product line, designed specifically for space-constrained, multi-rail power systems demanding robust input voltage range, precise sequencing, and minimal external components.
FAQ
What is the maximum allowable input voltage for LT3508EUF#PBF?
The LT3508EUF#PBF has an absolute maximum VIN pin voltage rating of 40V, but its functional maximum input is 36V under normal operation. Exceeding 36V may trigger pulse-skipping mode or cause excessive stress on internal switches; operation above 36V is not guaranteed and risks permanent damage. Always maintain ≥1V margin below the 40V absolute max rating in layout design.
Does LT3508EUF#PBF support true pin-to-pin replacement with other Linear dual buck regulators?
No, LT3508EUF#PBF does not support pin-to-pin replacement with other Linear dual buck regulators such as LT3580 or LT3573. Its 24-pin QFN pinout, BOOST pin assignment, and dual TRACK/SS architecture are unique. Substitution requires PCB redesign and validation of feedback loop stability, thermal performance, and sequencing behavior.
How is output voltage sequencing implemented using LT3508EUF#PBF?
LT3508EUF#PBF implements sequencing via TRACK/SS pins and PG outputs: connect TRACK/SS2 to the FB1 node (or resistor divider) of Channel 1 to force Channel 2 to track Channel 1's ramp; use PG1 to enable SHDN of Channel 2 for delayed start. This eliminates need for external timers or supervisors while ensuring monotonic, controlled power-up across both rails.
What thermal derating applies to LT3508EUF#PBF at elevated ambient temperatures?
LT3508EUF#PBF is rated for –40°C to +125°C junction temperature. At ambient temperatures above 85°C, output current must be reduced to maintain TJ ≤ 125°C. With θJA = 40°C/W and 1.4A per channel at 12V input, ≥4cm² of 2-oz copper with thermal vias under the exposed pad is required for full-load operation at 70°C ambient.
Can LT3508EUF#PBF operate with only one channel enabled?
Yes, LT3508EUF#PBF supports single-channel operation: tie VC2 to GND to disable Channel 2 while retaining full functionality of Channel 1, including PG1, TRACK/SS1, and soft-start. Channel 1 remains fully operational with 1.4A output, 3.7–36V input, and all protection features active - useful for partial-system power-down in modular designs.
LT3508EUF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 2
- Voltage - Input (Min):
- 3.7V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 35.28V
- Current - Output:
- 1.4A
- Frequency - Switching:
- 920kHz ~ 1.06MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LT3508EUF#PBF FAQ
1.How can I place an order for LT3508EUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3508EUF#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 LT3508EUF#PBF reliable?
The price and inventory of LT3508EUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3508EUF#PBF is usually 5 days.
3.What payment methods are accepted for LT3508EUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3508EUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3508EUF#PBF?
LT3508EUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3508EUF#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 LT3508EUF#PBF?
For technical support, including LT3508EUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3508EUF#PBF requirements.
6.How does Aetrix verify that LT3508EUF#PBF is sourced from the original manufacturer or authorized distributors?
All LT3508EUF#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 LT3508EUF#PBF meets industry standards.
7.What is the process for return or replacement of LT3508EUF#PBF?
All LT3508EUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3508EUF#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 LT3508EUF#PBF part is unused and in its original packaging.
Return procedure for LT3508EUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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