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Analog Devices Inc. LT3508EUF#TRPBF
- Part No.:
- LT3508EUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LT3508EUF#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.4A DL 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:7,072
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Product details
Overview
LT3508EUF#TRPBF from Analog Devices (formerly Linear Technology) is a dual monolithic current-mode PWM step-down DC/DC converter IC with two integrated 1.4A NPN power switches, 3.7V–36V input range, and independent tracking/soft-start circuits. It delivers regulated 3.3V and 5V outputs in automotive power supplies and DSP core logic rails.
For engineers reviewing the LT3508EUF#TRPBF datasheet, LT3508EUF#TRPBF pinout, LT3508EUF#TRPBF application, or LT3508EUF#TRPBF equivalent, key selection criteria include its anti-phase 250kHz–2.5MHz switching capability, 0.800V ±1.4% feedback reference, thermal shutdown protection, and 4mm × 4mm 24-pin QFN package with exposed GND pad.
Technical Context
The LT3508EUF#TRPBF implements dual constant-frequency current-mode control with independent error amplifiers (VC1/VC2), cycle-by-cycle current limiting, and frequency foldback under overload. Its master-slave oscillator architecture enables synchronized anti-phase operation, reducing input ripple by canceling harmonic components between channels.
Each channel features programmable undervoltage lockout (UVLO), open-collector power-good outputs (PG1/PG2), and TRACK/SS pins supporting output sequencing, soft-start via external capacitor, or voltage tracking from another rail. The BOOST1/BOOST2 pins supply gate drive above VIN to saturate internal NPN switches.
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. |
| Output Current per Channel | 1.4A continuous - sufficient for powering dual-core DSPs, PCI Express auxiliary rails, or DSL modem PHYs. |
| Switching Frequency | 250kHz to 2.5MHz - adjustable via RT/SYNC resistor or external clock; enables compact magnetics and low-profile ceramic capacitors. |
| Feedback Reference Voltage | 0.800V ±1.4% over –40°C to 125°C - ensures accurate output regulation across temperature for stable 3.3V/5V generation. |
| Shutdown Current | <2μA - enables ultra-low-power state management in battery-backed systems without compromising wake-up latency. |
| Thermal Shutdown Threshold | Junction temperature >125°C (E-grade) - protects against sustained overload or poor PCB thermal design. |
| Power Good Accuracy | ±75mV threshold offset - provides reliable sequencing signal for microcontrollers and FPGAs during power-up/down transitions. |
Pinout & Package
LT3508EUF#TRPBF uses a 24-lead (4mm × 4mm) plastic QFN package with exposed thermal pad (Pin 25 = GND). The package provides θJA = 40°C/W and requires soldering of the exposed pad to PCB ground for electrical integrity and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 / FB2 | Feedback input | Regulates each output to 0.800V; connects to resistor divider tap for precise VOUT programming. |
| TRACK/SS1 / TRACK/SS2 | Tracking/Soft-start control | Enables output sequencing (capacitor ramp) or cross-rail tracking (resistor divider from another output). |
| PG1 / PG2 | Open-collector power-good | Asserts high when respective output reaches ±10% regulation; used for system-level power sequencing. |
| RT/SYNC | Oscillator control | Sets switching frequency via resistor-to-GND or accepts external logic-level sync signal (0.25–2.5MHz). |
| BOOST1 / BOOST2 | Bootstrap drive supply | Provides gate drive voltage >VIN to internal NPN switches via external diode + capacitor; enables high duty-cycle operation. |
| VIN1 / VIN2 | Input power rails | VIN1 powers internal bias circuitry and Channel 1 switch; VIN2 powers Channel 2 switch only (requires VIN1 > 3.7V). |
| SW1 / SW2 | Switch node outputs | Connect to external inductor, catch diode, and boost capacitor; carry high di/dt switching currents. |
| VC1 / VC2 | Error amplifier output | Controls peak switch current; used for loop compensation or independent channel disable (pull to GND). |
| SHDN | Enable/disable control | Active-high shutdown with 2.63V threshold; doubles as accurate UVLO for input voltage monitoring. |
| GND (Pins 3–7, 9–12, 14–16) | Ground reference | Multiple dedicated GND pins plus exposed pad ensure low-impedance return path and minimize noise coupling. |
Key Features
| Feature | Design Value |
|---|---|
| Anti-phase switching | Reduces RMS input ripple current by up to 30% compared to in-phase operation, easing input capacitor sizing and EMI filtering. |
| Independent soft-start & tracking | Eliminates inrush current and enables controlled power-up sequence between 3.3V and 5V rails without external timers. |
| Programmable UVLO | Configurable input voltage turn-on point via SHDN pin, preventing regulator operation until source meets minimum stability threshold. |
| Frequency foldback | Automatically reduces switching frequency to 12% of nominal under short-circuit or overload, limiting peak switch current and thermal stress. |
| Integrated NPN power switches | Eliminates need for external MOSFETs or driver ICs, reducing BOM count and layout complexity in space-constrained applications. |
Applications
| Automotive Infotainment Power | DSP Core & I/O Supply |
|---|---|
|
Use Scenario: Dual-rail power for head-unit SoC requiring isolated 3.3V I/O and 1.2V core (via secondary LDO), with cold-crank tolerance down to 3.7V. IC Role / Device Role / Timing Role: Primary buck regulator generating clean, sequenced 3.3V and 5V rails directly from vehicle battery. Use Value: Wide input range and anti-phase operation maintain regulation during engine cranking transients while minimizing input capacitor size. |
Use Scenario: Powering TI C6000 or Analog Devices SHARC DSPs with separate core (1.2V) and I/O (3.3V) requirements. IC Role / Device Role / Timing Role: Dual-channel DC/DC converter delivering independent, tracked outputs for digital signal processing subsystems. Use Value: Independent TRACK/SS pins enable precise startup alignment between core and I/O voltages, preventing latch-up or initialization faults. |
| PCI Express Auxiliary Rail | DSL/Cable Modem PHY Power |
|
Use Scenario: Generating +3.3V AUX and +12V (via secondary boost) for PCIe slot detection, hot-plug control, and wake-on-LAN circuitry. IC Role / Device Role / Timing Role: High-efficiency dual buck providing standby and active-mode power with fast transient response. Use Value: 2.5MHz max switching frequency allows use of sub-2mm height inductors, meeting strict mechanical envelope requirements. |
Use Scenario: Regulating 3.3V and 5V rails for ADSL2+ line drivers, Ethernet PHYs, and analog front-end components. IC Role / Device Role / Timing Role: Compact dual-output regulator replacing discrete buck controllers and external MOSFETs. Use Value: Integrated power switches and small QFN package reduce solution footprint by >40% versus controller+FET solutions. |
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 |
|---|---|---|---|
| LM5143AQRHBRQ1 | 42V input, 3A/channel, synchronous FETs, spread-spectrum EMI reduction | Better suited for high-current automotive ADAS cameras where efficiency >92% at 2A load is critical | Choose LM5143AQRHBRQ1 when higher output current, lower quiescent current (<15μA), or AEC-Q100 Grade 1 qualification is required. |
| TPS54290PWPR | 36V input, 2A/channel, external FETs, adjustable current limit, no integrated BOOST | Preferred for designs needing flexible MOSFET selection or thermal separation of power stage and controller | Choose TPS54290PWPR when board-level thermal management demands separation of power switches from control IC. |
Compared with LT3508EUF#TRPBF, LM5143AQRHBRQ1 offers higher current and automotive qualification but requires more external components; TPS54290PWPR provides greater flexibility in FET selection and thermal layout but lacks integrated BOOST and anti-phase synchronization.
Availability
LT3508EUF#TRPBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial DSP power supplies, and broadband communications equipment requiring stable component supply with full production lifecycle support.
Supply support for LT3508EUF#TRPBF 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 the LT® family of high-performance power management ICs.
The LT3508 belongs to Linear's monolithic switching regulator product line, designed specifically for compact, high-reliability dual-rail power conversion in automotive, industrial, and communications infrastructure applications.
FAQ
What is the maximum junction temperature rating for the LT3508EUF#TRPBF?
The LT3508EUF#TRPBF is rated for operation from –40°C to +125°C junction temperature. This E-grade specification is guaranteed over the full range, with thermal shutdown engaging above 125°C to protect the device. The 24-pin QFN package's exposed pad must be soldered to PCB ground to achieve the specified θJA = 40°C/W and ensure reliable thermal performance at full 1.4A load per channel.
Can the LT3508EUF#TRPBF generate outputs below 3.3V, such as 1.8V or 1.2V?
Yes, the LT3508EUF#TRPBF supports output voltages down to 800mV using standard resistor divider networks on FB1/FB2 pins. Its 0.800V feedback reference enables precise regulation of 1.8V (R1/R2 = 1.25) or 1.2V (R1/R2 = 0.5) rails. However, achieving stable 1.2V operation requires careful inductor selection to avoid sub-harmonic oscillation at duty cycles >50%, and the minimum inductance must satisfy LMIN = (VOUT + 0.4V) × 0.8µH / fSW.
How does the anti-phase switching in the LT3508EUF#TRPBF reduce input ripple current?
The LT3508EUF#TRPBF configures its two channels to operate 180° out-of-phase using an internal master-slave oscillator. This causes input current pulses from each channel to partially cancel at the VIN pins, reducing RMS input ripple current by up to 30% compared to in-phase operation. As a result, the input capacitor RMS rating can be reduced, enabling smaller X7R/X5R ceramics and lowering overall EMI filter complexity without sacrificing stability.
Is the LT3508EUF#TRPBF pin-compatible with other variants like LT3508EFE#TRPBF?
No, the LT3508EUF#TRPBF (24-pin QFN) is not pin-compatible with LT3508EFE#TRPBF (16-pin TSSOP). They share identical electrical functionality and parameter specifications but differ fundamentally in package type, pin count, pin assignment, and thermal characteristics. The QFN version provides superior thermal performance (θJC = 10°C/W) and higher pin density, while the TSSOP offers easier prototyping and rework. PCB layout must be redesigned when substituting between these packages.
What is the role of the BOOST pins in the LT3508EUF#TRPBF, and what happens if they are left unconnected?
The BOOST1 and BOOST2 pins provide elevated gate drive voltage to the internal NPN power switches, enabling high duty-cycle operation (up to 98%) by maintaining saturation even when VIN approaches VOUT. Each BOOST pin must be connected through a Schottky diode to a voltage ≥2.8V (e.g., VOUT or VIN) and bypassed with a 10nF–100nF capacitor. Leaving BOOST pins unconnected disables high-duty-cycle capability, limits maximum duty cycle to ~84%, and may cause regulation failure or excessive switch dissipation at low input-to-output ratios.
LT3508EUF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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#TRPBF FAQ
1.How can I place an order for LT3508EUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3508EUF#TRPBF 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#TRPBF reliable?
The price and inventory of LT3508EUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3508EUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3508EUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3508EUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3508EUF#TRPBF?
LT3508EUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3508EUF#TRPBF 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#TRPBF?
For technical support, including LT3508EUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3508EUF#TRPBF requirements.
6.How does Aetrix verify that LT3508EUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3508EUF#TRPBF 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#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3508EUF#TRPBF?
All LT3508EUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3508EUF#TRPBF, 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#TRPBF part is unused and in its original packaging.
Return procedure for LT3508EUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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