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Analog Devices Inc. LT3508HFE#PBF
- Part No.:
- LT3508HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3508HFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.4A DL 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:200
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Product details
Overview
LT3508HFE#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/5V outputs with anti-phase switching. It features programmable 250kHz–2.5MHz frequency, independent soft-start and tracking, and power-good signals for sequencing in automotive and industrial power systems.
For engineers reviewing the LT3508HFE#PBF datasheet, LT3508HFE#PBF pinout, LT3508HFE#PBF application, or LT3508HFE#PBF equivalent, key selection considerations include its –40°C to 150°C junction-rated TSSOP-16 package, dual-channel phase interleaving for reduced input ripple, 0.800V ±14mV feedback reference, cycle-by-cycle current limiting up to 3.2A, and thermal shutdown protection.
Technical Context
The LT3508HFE#PBF implements dual constant-frequency current-mode control with master-slave oscillator architecture, generating 180° out-of-phase clock signals to minimize input capacitor RMS current. Each channel uses an internal error amplifier (600 V/V gain, 300 µS transconductance) driving VC pins to regulate peak switch current against a 0.800V FB reference.
It supports programmable switching frequency via RT/SYNC pin (250kHz–2.5MHz), frequency foldback under overload (down to 120kHz), and flexible startup control via TRACK/SS pins-enabling output voltage tracking, soft-start ramp generation (1.2µA internal current source), and independent channel enable/disable via VC pin grounding.
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 - sustained delivery with internal NPN switches rated for 3.2A peak current limit (min @ low duty cycle). |
| Feedback Reference Voltage | 0.800V ±14mV - precise regulation threshold enabling accurate output setting down to 800mV with resistor divider. |
| Switching Frequency Range | 250kHz to 2.5MHz - adjustable via RT resistor or external SYNC signal; enables compact magnetics and ceramic capacitor use. |
| Operating Junction Temp | –40°C to +150°C - H-grade qualification ensures reliability in under-hood automotive and high-temp industrial environments. |
| Shutdown Current | <2µA - ultra-low quiescent draw enables long battery life in always-on systems. |
| Power Good Threshold | FB rising edge offset of 56–110mV - provides robust sequencing signal with built-in hysteresis for noise immunity. |
Pinout & Package
LT3508HFE#PBF is housed in a thermally enhanced 16-lead plastic TSSOP package (FE) with exposed pad (Pin 17) soldered to PCB ground for optimal thermal dissipation (θJA = 40°C/W, θJC = 10°C/W). The package is RoHS-compliant and lead-free.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TRACK/SS1, TRACK/SS2 | Soft-start / tracking input | Accepts linear ramp (via capacitor) or external voltage divider to coordinate startup sequencing or output tracking between channels. |
| FB1, FB2 | Feedback input | Senses output voltage divider; regulates to 0.800V reference for precise output control. |
| VC1, VC2 | Error amplifier output | Drives internal switch current limit; grounding disables respective channel independently. |
| PG1, PG2 | Open-collector power-good | Asserts low until FB reaches regulation ±10%; used for system-level power sequencing with external pull-up. |
| RT/SYNC | Oscillator control | Configures switching frequency via resistor-to-GND or accepts external logic-level SYNC signal (0.25–2.5MHz). |
| SHDN | Enable/disable control | Active-high shutdown with 2.63V threshold; doubles as accurate undervoltage lockout (UVLO) for input rail monitoring. |
| VIN1, VIN2 | Input power supply | VIN1 powers internal bias circuitry and Channel 1; VIN2 supplies Channel 2 only - allows split-input configurations. |
| SW1, SW2 | Switch node output | Drives external inductor/catch diode; requires local boost capacitor + Schottky diode for NPN gate drive above VIN. |
| BOOST1, BOOST2 | Bootstrap supply | Provides >VIN drive voltage to internal NPN switches; must be tied via diode to ≥2.8V source (e.g., VOUT or VIN). |
| GND | Ground reference | Multiple GND pins plus exposed pad - all must connect directly to PCB ground plane for stable operation and thermal management. |
Key Features
| Feature | Design Value |
|---|---|
| Anti-phase switching | Reduces input ripple current by ~70% vs. in-phase operation, allowing smaller input capacitors and lower EMI. |
| Independent tracking & soft-start | Enables precise power-up sequencing across dual rails without external controllers - critical for FPGA, DSP, and multi-core SoC supplies. |
| Programmable UVLO | SHDN pin functions as accurate 2.63V ±100mV undervoltage lockout, preventing erratic startup during brownout conditions. |
| Frequency foldback | Automatically reduces switching frequency to 120kHz under overload or short-circuit, limiting peak switch current and thermal stress. |
| Thermal shutdown | Protects device at junction temperatures exceeding 150°C; recovery occurs after cooldown - no latch-up behavior. |
Applications
| Automotive Infotainment Power | DSP Core & I/O Supply |
|---|---|
|
Use Scenario: Dual-rail power for head-unit processors requiring 3.3V core and 5V I/O with strict sequencing and thermal resilience in engine bay environments. IC Role / Device Role: Primary dual-output buck regulator managing both voltage domains with anti-phase switching to meet CISPR-25 conducted EMI limits. Use Value: Eliminates need for discrete sequencing ICs; H-grade rating ensures operation at 150°C junction temperature under hood. |
Use Scenario: Powering TI C6000 or Analog Devices SHARC DSPs where core (1.2V) and I/O (3.3V) rails require controlled ramp rates and fault isolation. IC Role / Device Role: Configured with TRACK/SS pins to force 3.3V rail to track 1.2V rail during startup, preventing back-powering of I/O buffers. Use Value: Independent soft-start and PG signals simplify compliance with JEDEC JESD8-12B power sequencing requirements. |
| Industrial PLC Backplane | PCIe Slot Power Management |
|
Use Scenario: Regulating 24V field bus input to generate isolated 5V and 3.3V rails for microcontroller, CAN transceiver, and analog sensor interfaces. IC Role / Device Role: High-input-voltage capable buck converter delivering clean, sequenced power with <2µA shutdown current for low-power sleep modes. Use Value: Wide 3.7–36V range accommodates 24V nominal with ±20% tolerance; PG outputs interface directly with PLC watchdog timers. |
Use Scenario: Providing auxiliary 3.3V and 5V power to PCIe add-in cards in servers and telecom equipment with hot-plug capability. IC Role / Device Role: Dual-channel regulator with independent SHDN control via VC pins, enabling dynamic rail disable during card insertion/removal. Use Value: Anti-phase operation minimizes input ripple on shared backplane rails; 150°C rating supports dense board layouts near CPUs/FPGAs. |
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 |
|---|---|---|---|
| LTC3892EFE#PBF | Two-phase synchronous buck controller (external MOSFETs); 4–60V input; supports higher current (>10A/channel) and higher efficiency. | Requires external power stage; better suited for high-current, high-efficiency designs where layout control and thermal optimization are critical. | Select when >1.4A per rail is required or when synchronous rectification is needed for >95% efficiency at light loads. |
| TPS54290PWPR | Dual 2A synchronous buck converter (integrated FETs); 4.5–28V input; fixed 500kHz/700kHz frequencies; no phase interleaving. | Lacks anti-phase switching and independent tracking; simpler design but higher input ripple and less sequencing flexibility. | Choose for cost-sensitive industrial applications where 28V max input suffices and sequencing complexity is low. |
Compared with LTC3892EFE#PBF and TPS54290PWPR, the LT3508HFE#PBF uniquely combines integrated 1.4A NPN switches, 36V input capability, anti-phase operation, and H-grade 150°C operation in a single 16-pin TSSOP - making it optimal for space-constrained, high-temp dual-rail systems where external FETs are undesirable.
Availability
LT3508HFE#PBF is available at Aetrix Electronics and suitable for automotive infotainment, industrial PLC backplanes, and PCIe slot power management requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3508HFE#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 precision instrumentation, automotive, industrial, and communications markets.
The LT3508HFE#PBF belongs to Linear's high-voltage monolithic DC/DC converter product line, designed specifically for rugged, wide-input industrial and automotive power conversion where integration, thermal resilience, and sequencing control are critical.
FAQ
What is the maximum junction temperature rating for the LT3508HFE#PBF?
The LT3508HFE#PBF is specified for operation from –40°C to +150°C junction temperature, confirmed by full characterization and guaranteed over this range. This H-grade rating distinguishes it from E-grade (–40°C to 125°C) and I-grade (–40°C to 125°C) variants, enabling deployment in under-hood automotive and high-ambient industrial environments where thermal margins are tight. The LT3508HFE#PBF incorporates overtemperature protection that activates above 150°C.
Can the LT3508HFE#PBF operate with separate input supplies on VIN1 and VIN2?
Yes, the LT3508HFE#PBF supports independent input sources: VIN1 powers internal bias circuitry and Channel 1, while VIN2 supplies only Channel 2. However, VIN1 must exceed 3.7V for either channel to operate, and VIN2 must be ≥3.0V when VIN1 is valid. This configuration enables split-rail inputs - for example, using a 12V supply for VIN1 and a 5V auxiliary rail for VIN2 - but requires careful attention to sequencing and ground referencing. The LT3508HFE#PBF datasheet confirms this capability in the Absolute Maximum Ratings and Applications Information sections.
How does the LT3508HFE#PBF achieve anti-phase switching, and what is its benefit?
The LT3508HFE#PBF uses an internal master-slave oscillator architecture that generates two clock signals precisely 180° out of phase, driving SW1 and SW2 with opposite timing. This anti-phase operation reduces RMS input capacitor current by canceling harmonic components, lowering input ripple voltage and EMI emissions. In practice, this allows use of smaller, lower-cost ceramic input capacitors and eases compliance with stringent EMC standards like CISPR-25. The LT3508HFE#PBF achieves this without external synchronization components.
What is the role of the BOOST pins on the LT3508HFE#PBF, and how must they be connected?
The BOOST1 and BOOST2 pins on the LT3508HFE#PBF provide elevated gate drive voltage to the internal NPN power switches, enabling saturation and low conduction loss. Each BOOST pin must be connected through a Schottky diode (e.g., 1N5819) to a ≥2.8V source - typically the corresponding output (VOUT1 or VOUT2) or VIN - and bypassed with a 10nF ceramic capacitor to SW. Failure to properly configure BOOST results in incomplete switch turn-on, increased VCE(SAT), and thermal derating. The LT3508HFE#PBF datasheet specifies minimum boost voltage as 1.7V and typical boost current as 50mA at 1.5A load.
Does the LT3508HFE#PBF support output voltage tracking, and how is it implemented?
Yes, the LT3508HFE#PBF supports precise output voltage tracking via its TRACK/SS1 and TRACK/SS2 pins. To make one output track another, connect a resistor divider from the master output to the TRACK/SS pin of the slave channel. The internal error amplifier compares the TRACK/SS voltage against its 0.800V reference, forcing the slave output to follow the master. This eliminates need for external op-amps or dedicated tracking ICs and is commonly used for FPGA core/I/O sequencing. The LT3508HFE#PBF supports bidirectional tracking and independent soft-start ramp generation using the same pins.
LT3508HFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) 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:
- 16-TSSOP-EP
LT3508HFE#PBF FAQ
1.How can I place an order for LT3508HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3508HFE#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 LT3508HFE#PBF reliable?
The price and inventory of LT3508HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3508HFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3508HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3508HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3508HFE#PBF?
LT3508HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3508HFE#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 LT3508HFE#PBF?
For technical support, including LT3508HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3508HFE#PBF requirements.
6.How does Aetrix verify that LT3508HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3508HFE#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 LT3508HFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3508HFE#PBF?
All LT3508HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3508HFE#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 LT3508HFE#PBF part is unused and in its original packaging.
Return procedure for LT3508HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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