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Analog Devices Inc. LT3508IUF#PBF
- Part No.:
- LT3508IUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LT3508IUF#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.4A DL 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,645
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Product details
Overview
LT3508IUF#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 frequency, independent tracking/soft-start, and power-good signals for microcontroller sequencing in automotive and industrial power systems.
For engineers reviewing the LT3508IUF#PBF datasheet, LT3508IUF#PBF pinout, LT3508IUF#PBF application, or LT3508IUF#PBF equivalent, key selection considerations include its dual 1.4A output capability, 4mm × 4mm 24-pin QFN package with exposed thermal pad, –40°C to 125°C operating junction temperature, internal current limiting (2.6A typ), and 0.800V ±1.4% feedback reference voltage.
Technical Context
The LT3508IUF#PBF implements dual constant-frequency current-mode control with master/slave oscillator architecture, enabling precise 180° anti-phase switching to minimize input ripple. Each channel uses independent error amplifiers (VC1/VC2), cycle-by-cycle current limiting, and frequency foldback during overload (down to 120kHz at VFB = 0V).
It supports flexible configuration via RT/SYNC pin for resistor-set (250kHz–2.5MHz) or external clock synchronization, while TRACK/SS pins enable output voltage tracking or soft-start ramp generation via external capacitor. The device integrates undervoltage lockout (UVLO) with 2.63V SHDN threshold and operates with internal 0.800V reference referenced to FB1/FB2 pins.
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 - enables dual-rail power delivery without external MOSFETs or controllers. |
| Switching Frequency | 250kHz to 2.5MHz - adjustable via RT resistor or SYNC signal; high frequency allows compact 2.2μH–10μH inductors and ceramic output caps. |
| Feedback Reference Voltage | 0.800V ±1.4% - accurate reference enables stable output regulation down to 800mV with minimal resistor divider error. |
| Operating Temperature | –40°C to +125°C junction - qualified for automotive and industrial environments with guaranteed performance across full range. |
| Shutdown Current | <2μA - enables ultra-low-power battery management when disabled via SHDN pin. |
| Power Good Threshold | ±75mV offset from regulation - provides reliable sequencing signal for microcontrollers and DSPs during startup and fault conditions. |
Pinout & Package
LT3508IUF#PBF is housed in a thermally enhanced 24-lead 4mm × 4mm plastic QFN package with exposed GND pad (Pin 25), requiring soldering to PCB for electrical and thermal integrity. θJA = 40°C/W, θJC = 10°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 / FB2 | Feedback Input | Regulates each output to 0.800V; connects to resistor divider tap for precise output voltage setting. |
| TRACK/SS1 / TRACK/SS2 | Tracking/Soft-Start Control | Enables output voltage tracking between channels or linear soft-start ramp via external capacitor (1.2μA internal current source). |
| PG1 / PG2 | Open-Collector Power-Good Output | Signals regulation status (low = out-of-regulation); used for supply sequencing with microcontrollers and DSPs. |
| VC1 / VC2 | Error Amplifier Output | Controls peak switch current; used for loop compensation or individual channel shutdown by pulling to GND. |
| RT/SYNC | Oscillator Programming / Sync Input | Sets switching frequency via resistor-to-GND or accepts external logic-level sync signal (0.25–2.5MHz). |
| SHDN | Enable/Shutdown Control | Active-high enable with 2.63V threshold; doubles as accurate UVLO for input voltage monitoring. |
| VIN1 / VIN2 | Input Supply Pins | VIN1 powers internal circuitry and Channel 1; VIN2 powers Channel 2 only; VIN1 must exceed 3.7V for either channel to operate. |
| SW1 / SW2 | Switch Node Outputs | Connect to external inductor, catch diode, and boost capacitor; drive internal NPN power switches. |
| BOOST1 / BOOST2 | Bootstrap Drive Supply | Provides >VIN gate drive for internal NPN switches via external diode/capacitor; enables efficient saturation at high duty cycles. |
| GND (Pins 3–7, 9–14, 18–24) | Ground Terminals | Multiple low-inductance GND connections tied to exposed thermal pad; essential for noise immunity and thermal dissipation. |
Key Features
| Feature | Design Value |
|---|---|
| Anti-phase switching | Reduces RMS input ripple current by up to 70% compared to in-phase operation, lowering input capacitor stress and EMI. |
| Independent tracking & soft-start | Allows controlled power-up sequencing of dual outputs or synchronized ramp-up with external supplies, preventing inrush and bus droop. |
| Programmable frequency with sync capability | Enables EMI optimization and noise avoidance in dense layouts; full-range synchronization supports multi-converter systems. |
| Integrated current limit & thermal protection | 2.6A typical switch current limit plus thermal shutdown prevents damage during short-circuit or overload without external components. |
| Accurate 0.800V reference with line regulation | 0.01%/V line regulation ensures stable output under varying input conditions; ±1.4% tolerance over temperature simplifies precision design. |
Applications
| Automotive Infotainment Power | DSP Core & I/O Supply |
|---|---|
Use Scenario: Dual-rail power for head unit SoC requiring 3.3V I/O and 5V USB peripheral interface under wide-input 9–16V battery conditions. IC Role / Device Role / Timing Role: Primary dual-output buck regulator providing sequenced, low-noise, high-efficiency DC/DC conversion with PG signaling for safe boot. Use Value: Eliminates need for discrete controllers and external FETs; anti-phase operation reduces input cap count and size by 40% vs. single-phase solutions. | Use Scenario: Powering TI C6000 or Analog Devices SHARC DSPs with separate core (1.2V) and I/O (3.3V) rails using tracking configuration. IC Role / Device Role / Timing Role: Dual-channel synchronous buck controller with TRACK/SS pins configured for I/O rail to track core rail during dynamic load transitions. Use Value: Ensures monotonic startup and prevents reverse bias on I/O interfaces; independent soft-start avoids supply contention during reset. |
| PCI Express Slot Regulation | DSL/Cable Modem Power |
Use Scenario: Generating +3.3V and +12V auxiliary rails (via secondary stage) for PCIe add-in cards in industrial servers with 12V or 24V backplane input. IC Role / Device Role / Timing Role: High-voltage capable primary regulator delivering [email protected] and enabling downstream 12V generation via second-stage boost or flyback. Use Value: Wide 3.7–36V input accommodates legacy 12V and modern 24V server platforms; 2.5MHz max frequency enables <3mm² solution footprint. | Use Scenario: Compact dual-output power for residential DSL modems requiring isolated 3.3V logic and 5V PHY rails from unregulated 12V wall adapter. IC Role / Device Role / Timing Role: Monolithic dual buck converter replacing discrete IC + MOSFET solutions; PG outputs coordinate FPGA and PHY initialization. Use Value: Reduces BOM count by 6+ components; small QFN package fits tight 25mm × 25mm modem PCB area constraints. |
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 |
|---|---|---|---|
| LM5143AQPWPRQ1 | 42V dual-channel synchronous buck controller (external FETs); 50ns min on-time; no integrated switches. | Requires external high-side/low-side MOSFETs and gate drivers; suited for >2A per channel or higher efficiency demands. | Select when >1.4A output or >95% efficiency at light loads is required; not drop-in due to external power stage. |
| TPS54290PWPR | 36V dual-channel synchronous buck converter; 2A per channel; 100μA quiescent current; no TRACK/SS or PG pins. | Lacks independent tracking, soft-start, and power-good outputs - limits use in sequenced or safety-critical systems. | Choose for cost-sensitive, non-sequencing applications where 2A output and lower IQ outweigh missing PG/track functionality. |
Compared with LM5143AQPWPRQ1 and TPS54290PWPR, the LT3508IUF#PBF delivers integrated 1.4A switches, precise 0.800V reference, and full sequencing support in a smaller footprint - making it optimal for space-constrained, dual-rail embedded systems needing guaranteed startup behavior and robust fault protection.
Availability
LT3508IUF#PBF is available at Aetrix Electronics and suitable for automotive infotainment, industrial DSP power supplies, and broadband communications equipment requiring stable component supply, long-term lifecycle assurance, and AEC-Q200-aligned reliability.
Supply support for LT3508IUF#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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.
The LT3508IUF#PBF belongs to ADI's Power by Linear™ family of monolithic DC/DC converters, designed specifically for high-reliability, wide-input industrial and automotive power systems demanding integrated protection, sequencing, and thermal robustness.
FAQ
What is the maximum allowable input voltage for LT3508IUF#PBF?
The LT3508IUF#PBF has an absolute maximum VIN pin voltage rating of 40V, but its functional maximum input voltage is limited to 36V under normal operation. This 36V limit arises from minimum duty cycle constraints at high switching frequencies - exceeding it may cause pulse-skipping mode, increased ripple, and higher peak inductor current. Operation above 36V risks permanent damage and violates Absolute Maximum Ratings.
Does LT3508IUF#PBF support independent output voltage adjustment?
Yes, LT3508IUF#PBF supports fully independent output voltage adjustment via separate FB1 and FB2 pins, each regulated to 0.800V. Users set VOUT1 and VOUT2 using independent resistor dividers. The device also supports tracking mode: connecting TRACK/SS2 to a resistor divider from VOUT1 configures Channel 2 to follow Channel 1's ramp during startup or transient events.
How does the anti-phase switching in LT3508IUF#PBF reduce input ripple?
The LT3508IUF#PBF synchronizes its two channels to a single oscillator and forces them to switch 180° out-of-phase. This causes their input current pulses to partially cancel at the VIN node, reducing RMS input ripple current by up to 70% compared to in-phase operation. As a result, fewer or smaller input capacitors are needed - critical for EMI reduction and board space savings in compact designs.
Can LT3508IUF#PBF be synchronized to an external clock?
Yes, LT3508IUF#PBF can be synchronized to an external clock via the RT/SYNC pin. When driven with a logic-level signal having ≥80ns positive and negative pulse widths, the internal oscillator locks to the external frequency across its full 0.25MHz–2.5MHz range. This feature enables noise-sensitive systems to avoid interference bands and allows multiple LT3508IUF#PBF devices to operate coherently without beat frequencies.
What thermal management requirements apply to LT3508IUF#PBF?
The LT3508IUF#PBF requires soldering of its exposed thermal pad (Pin 25) directly to a large PCB copper pour for effective heat dissipation. With θJA = 40°C/W, maintaining junction temperature ≤125°C demands ≥2 cm² of 2-oz copper connected to the pad. Thermal vias (≥6×0.3mm) beneath the pad are strongly recommended. Derating is required above 85°C ambient - full 1.4A output per channel is only guaranteed up to 85°C ambient with proper layout.
LT3508IUF#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)
LT3508IUF#PBF FAQ
1.How can I place an order for LT3508IUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3508IUF#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 LT3508IUF#PBF reliable?
The price and inventory of LT3508IUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3508IUF#PBF is usually 5 days.
3.What payment methods are accepted for LT3508IUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3508IUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3508IUF#PBF?
LT3508IUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3508IUF#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 LT3508IUF#PBF?
For technical support, including LT3508IUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3508IUF#PBF requirements.
6.How does Aetrix verify that LT3508IUF#PBF is sourced from the original manufacturer or authorized distributors?
All LT3508IUF#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 LT3508IUF#PBF meets industry standards.
7.What is the process for return or replacement of LT3508IUF#PBF?
All LT3508IUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3508IUF#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 LT3508IUF#PBF part is unused and in its original packaging.
Return procedure for LT3508IUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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