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Analog Devices Inc. LT3508HUF#PBF
- Part No.:
- LT3508HUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LT3508HUF#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.4A DL 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:369
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Product details
Overview
LT3508HUF#PBF from Analog Devices (formerly Linear Technology) is a dual monolithic 1.4A step-down DC/DC converter IC with internal NPN power switches, designed for automotive and industrial power rails requiring high input voltage tolerance (3.7V–36V), anti-phase switching, and independent output sequencing. It delivers two regulated outputs-e.g., 3.3V and 5V-at up to 1.4A each, with programmable 250kHz–2.5MHz switching frequency and integrated power-good signaling.
For engineers reviewing the LT3508HUF#PBF datasheet, LT3508HUF#PBF pinout, LT3508HUF#PBF application, or LT3508HUF#PBF equivalent, this page provides verified technical context on dual-channel current-mode control, thermal-rated QFN packaging (–40°C to 150°C), tracking/soft-start implementation, and real-world efficiency vs. load curves at 12V/24V/32V inputs.
Technical Context
The LT3508HUF#PBF implements dual constant-frequency current-mode PWM regulation using separate error amplifiers (VC1/VC2), independent TRACK/SS pins for soft-start or output tracking, and master-slave oscillator architecture enabling 180° anti-phase switching. Its internal bipolar NPN switches are driven via BOOST1/BOOST2 pins, supporting duty cycles up to 98% with external bootstrap capacitors.
It features cycle-by-cycle current limiting (2.0A–3.2A, temperature-dependent), frequency foldback under overload (down to 120kHz), and undervoltage lockout with accurate 2.63V SHDN threshold. The device operates with 0.800V ±14mV FB reference, 300μS error amp transconductance, and supports synchronization across its full 250kHz–2.5MHz range via RT/SYNC pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.7V to 36V - supports direct connection to automotive batteries, 24V industrial rails, and unregulated wall adapters without pre-regulation. |
| Output Current per Channel | 1.4A continuous - enables dual-rail DSP, FPGA, or microcontroller core/I/O supply generation from single IC. |
| Switching Frequency Range | 250kHz to 2.5MHz - allows optimization of inductor size (e.g., 6.8μH at 700kHz) and EMI profile via RT resistor or external SYNC signal. |
| FB Reference Voltage | 0.800V ±14mV - sets output voltage accuracy; enables down to 0.8V output using standard resistor dividers (R2 ≤20kΩ). |
| Junction Temperature Range | –40°C to +150°C - H-grade qualification ensures reliable operation in under-hood automotive or high-ambient industrial environments. |
| Shutdown Current | <2μA - enables ultra-low-power battery backup modes and clean system-level power management. |
| Power Good Threshold | ±75mV offset from regulation - provides precise sequencing signal for microcontrollers or FPGAs during multi-rail startup. |
Pinout & Package
LT3508HUF#PBF uses a 24-pin 4mm × 4mm plastic QFN package with exposed thermal pad (Pin 25 = GND). The package supports high-power dissipation (θJA = 40°C/W) and requires soldering of the exposed pad to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 / FB2 | Feedback Input | Regulates respective output to 0.800V; connects to resistor divider tap - determines output voltage with ±1.75% total error over temp. |
| TRACK/SS1 / TRACK/SS2 | Soft-Start / Tracking Control | Internal 1.2μA current source charges external capacitor for linear soft-start ramp; or accepts external voltage for output tracking. |
| PG1 / PG2 | Open-Collector Power-Good Output | Active-low signal asserted when corresponding output reaches ±10% of target - used for supply sequencing and fault indication. |
| RT/SYNC | Oscillator Timing / Sync Input | Resistor-to-GND sets frequency (e.g., 33.2kΩ = 1MHz); logic-level AC signal synchronizes both channels across full 250kHz–2.5MHz range. |
| BOOST1 / BOOST2 | Bootstrap Drive Supply | Accepts diode-connected VOUT or VIN to generate >VIN gate drive - enables high-side NPN saturation and low VCE(SAT) (~300mV @ 1.5A). |
| VIN1 / VIN2 | Input Power Supplies | VIN1 powers internal bias circuitry and Channel 1 switch; VIN2 powers Channel 2 switch - allows independent sourcing or shared rail. |
| SW1 / SW2 | Switch Node Outputs | Connect to inductors and catch diodes; internally driven by NPN switches - require low-inductance layout to minimize EMI and ringing. |
| VC1 / VC2 | Error Amplifier Output | Controls peak switch current; usable for loop compensation or external override shutdown (pull to GND disables channel). |
Key Features
| Feature | Design Value |
|---|---|
| Anti-phase switching | 180° phase shift between channels reduces RMS input ripple current by up to 70%, lowering required input capacitance. |
| Independent tracking & soft-start | Separate TRACK/SS pins allow one output to follow another (e.g., I/O before core) or implement staggered startup - eliminates external timers. |
| Programmable UVLO | SHDN pin doubles as precision 2.63V undervoltage lockout - prevents regulator operation until input stabilizes above minimum operating voltage. |
| Thermal grade H | Guaranteed operation from –40°C to +150°C junction - validated for under-hood automotive modules and high-temperature industrial enclosures. |
| Small ceramic-capacitor compatible | High 2.5MHz max frequency enables use of compact 4.7μF X7R ceramics (≥500kHz) - eliminates bulk electrolytics and simplifies layout. |
Applications
| Automotive Infotainment Power | DSP Core + I/O Supply |
|---|---|
|
Use Scenario: Dual-rail power for automotive head unit MCU (1.2V core) and interface peripherals (3.3V I/O), operating directly from 12V battery with cold-crank tolerance. IC Role / Device Role / Timing Role: LT3508HUF#PBF acts as primary dual-output buck controller, providing sequenced 1.2V/3.3V rails with PG signals for safe boot order. Use Value: Anti-phase operation minimizes input ripple under dynamic load changes; H-grade thermal rating ensures reliability during extended engine-off cabin heat exposure. |
Use Scenario: Powering TI C6000 or Analog Devices SHARC DSPs requiring tightly regulated, low-noise 1.1V core and 3.3V I/O supplies. IC Role / Device Role / Timing Role: LT3508HUF#PBF generates both rails with independent TRACK/SS pins enabling core voltage to ramp after I/O is stable - preventing latch-up. Use Value: 0.800V FB reference and <1% line/load regulation enable sub-50mV output deviation; soft-start eliminates inrush into large output caps. |
| PCI Express Slot Power | DSL/Cable Modem Power |
|
Use Scenario: Generating +3.3V AUX and +12V main rails for PCIe add-in cards in industrial servers, where space and thermal constraints limit discrete solutions. IC Role / Device Role / Timing Role: LT3508HUF#PBF serves as compact dual-buck controller; PG1/PG2 coordinate with host BIOS for hot-plug detection and power sequencing compliance. Use Value: 36V max input withstands transient surges on backplane rails; 24-pin QFN fits tight board areas while exposed pad dissipates >2W at 150°C ambient. |
Use Scenario: Regulating 5V and 3.3V from 12V wall adapter in broadband gateway devices, requiring low standby power and EMI-compliant layout. IC Role / Device Role / Timing Role: LT3508HUF#PBF functions as primary DC/DC stage with programmable 700kHz switching - balancing efficiency and filter size. Use Value: <2μA shutdown current extends battery backup time; ceramic-capacitor compatibility eliminates electrolytic aging concerns in sealed modems. |
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 |
|---|---|---|---|
| LT3508EUF#PBF | Same architecture and pinout, but rated for –40°C to +125°C junction temperature - lacks H-grade thermal margin. | Suitable for commercial/industrial environments without sustained high-ambient exposure. | Select when ambient temperature remains below 105°C and cost sensitivity outweighs extended thermal safety margin. |
| MP2491DS-LF-Z | Single-channel 2A buck with external sync capability; no integrated dual-channel anti-phase control or TRACK/SS functionality. | Requires two separate ICs to replicate dual-rail sequencing - increases BOM count and layout area. | Consider only if design already uses Monolithic Power Systems ecosystem and can accept discrete sequencing implementation. |
Compared with LT3508EUF#PBF, the LT3508HUF#PBF adds guaranteed 150°C operation for harsh environments; compared with MP2491DS-LF-Z, it integrates dual-channel coordination, tracking, and power-good logic - reducing component count and improving startup reliability.
Availability
LT3508HUF#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial DSP power supplies, and broadband communications equipment requiring stable component supply, long-term lifecycle support, and guaranteed high-temperature performance.
Supply support for LT3508HUF#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving aerospace, automotive, industrial, and communications markets.
The LT3508HUF#PBF belongs to Linear's high-voltage monolithic buck regulator product line, engineered specifically for robust, compact dual-rail power conversion in automotive and industrial applications demanding wide VIN, sequencing, and thermal resilience.
FAQ
What is the maximum junction temperature specification for LT3508HUF#PBF?
The LT3508HUF#PBF is guaranteed to operate continuously from –40°C to +150°C junction temperature. This H-grade rating is validated per manufacturer test conditions and exceeds the –40°C to +125°C spec of E/I-grade variants. Derating applies above 125°C per datasheet Note 2; sustained operation at 150°C requires proper PCB thermal design including full soldering of the exposed pad.
How does LT3508HUF#PBF achieve anti-phase switching between its two channels?
The LT3508HUF#PBF uses an internal master-slave oscillator architecture where the slave channel's clock is inherently inverted relative to the master - resulting in fixed 180° phase separation. This is implemented in silicon and requires no external configuration; it reduces input capacitor RMS current and eases EMI filtering compared to in-phase operation.
Can LT3508HUF#PBF regulate outputs below 0.8V?
No - the LT3508HUF#PBF has a fixed 0.800V feedback reference voltage. Output voltage is set by the resistor divider ratio: VOUT = 0.800V × (1 + R1/R2). The minimum achievable output is therefore constrained by the 0.800V reference and practical resistor values; outputs down to 0.8V are supported, but not lower.
What is the purpose of the BOOST1 and BOOST2 pins on LT3508HUF#PBF?
The BOOST1 and BOOST2 pins provide elevated gate drive voltage (>VIN) to the internal NPN power switches, enabling full saturation and minimizing VCE(SAT). Each BOOST pin must be connected via a Schottky diode and capacitor to a voltage source ≥2.8V (e.g., VOUT or VIN) - critical for achieving specified 1.4A output current and high efficiency.
Does LT3508HUF#PBF support external synchronization, and what are the timing requirements?
Yes - the RT/SYNC pin accepts external logic-level SYNC signals across the full 250kHz–2.5MHz range. Positive and negative pulse widths must each be ≥80ns. The device automatically detects SYNC presence and switches from internal RT-resistor mode to external sync mode without glitching or reinitialization.
LT3508HUF#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 ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LT3508HUF#PBF FAQ
1.How can I place an order for LT3508HUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3508HUF#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 LT3508HUF#PBF reliable?
The price and inventory of LT3508HUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3508HUF#PBF is usually 5 days.
3.What payment methods are accepted for LT3508HUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3508HUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3508HUF#PBF?
LT3508HUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3508HUF#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 LT3508HUF#PBF?
For technical support, including LT3508HUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3508HUF#PBF requirements.
6.How does Aetrix verify that LT3508HUF#PBF is sourced from the original manufacturer or authorized distributors?
All LT3508HUF#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 LT3508HUF#PBF meets industry standards.
7.What is the process for return or replacement of LT3508HUF#PBF?
All LT3508HUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3508HUF#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 LT3508HUF#PBF part is unused and in its original packaging.
Return procedure for LT3508HUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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