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Analog Devices Inc. LT3508EFE#PBF
- Part No.:
- LT3508EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3508EFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.4A DL 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,569
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Product details
Overview
LT3508EFE#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, delivering independently regulated 3.3V and 5V outputs with anti-phase switching, 1MHz typical switching frequency, and independent power-good signals - used in automotive infotainment power rails and DSP supply sequencing.
For engineers reviewing the LT3508EFE#PBF datasheet, LT3508EFE#PBF pinout, LT3508EFE#PBF application, or LT3508EFE#PBF equivalent, key selection considerations include its dual-channel tracking/soft-start capability, 0.8V feedback reference, thermal shutdown protection, 16-pin TSSOP package with exposed pad, and compatibility with ceramic output capacitors for low-ripple industrial power supplies.
Technical Context
The LT3508EFE#PBF 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 up to 2.5MHz, reducing input ripple by interleaving channel currents.
Each channel features dedicated TRACK/SS pins for soft-start ramp generation or output voltage tracking, programmable UVLO via SHDN pin (2.63V threshold), and open-collector PG outputs valid only when VIN1 > 3.7V and SHDN is high - enabling precise power-up sequencing with microcontrollers and FPGAs.
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 - sufficient to power dual-core DSPs, PCI Express auxiliary rails, or dual-sensor modules without external boost stages. |
| Switching Frequency | 250kHz to 2.5MHz (adjustable via RT/SYNC resistor or external clock) - enables use of sub-3mm height inductors and compact ceramic capacitor arrays. |
| Feedback Reference Voltage | 0.800V ±14mV (–40°C to 125°C) - allows precise output setting down to 800mV using standard 1% resistors with minimal bias current error. |
| Power Good Threshold | ±75mV offset from regulation - ensures reliable sequencing signal assertion only when output is within 9.4% of target, preventing false wake-up in noisy environments. |
| Shutdown Current | <2μA - enables multi-week battery runtime in always-on telematics modules with controlled wake-up via SHDN pin. |
| Junction Temperature Range | –40°C to 125°C - qualified for under-hood automotive applications and industrial control cabinets without derating. |
Pinout & Package
LT3508EFE#PBF uses a 16-lead plastic TSSOP package with exposed thermal pad (pin 17), requiring soldering to PCB ground plane for thermal and electrical integrity. Pin count, layout, and thermal metrics match Linear Technology's FE package specification.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TRACK/SS1, TRACK/SS2 | Soft-start & tracking input | Internal 1.2μA current source charges external capacitor to generate linear voltage ramp; tied to another regulator's output to enforce voltage sequencing. |
| FB1, FB2 | Feedback input | Regulates output to 0.800V reference; connects to resistor divider tap - determines final output voltage with <0.3% line regulation error. |
| PG1, PG2 | Open-collector power-good output | Pulled low until respective output reaches 90.6% of target; used to enable downstream logic or trigger reset controllers in multi-rail systems. |
| RT/SYNC | Oscillator programming & sync input | Resistor-to-GND sets frequency (e.g., 33.2kΩ = 1MHz); accepts external 0.25–2.5MHz logic-level clock for system-wide timing alignment. |
| SHDN | Enable/disable control | Logic-high (>2.63V) enables both channels; <0.3V forces shutdown with <2μA quiescent draw - serves as accurate UVLO or remote ON/OFF control. |
| VIN1, VIN2 | Channel input supplies | VIN1 powers internal bias circuitry and Channel 1 switch; VIN2 powers Channel 2 switch - allows independent sourcing (e.g., VIN1 = battery, VIN2 = backup rail). |
| SW1, SW2 | Switch node outputs | Drive external inductors and catch diodes; bipolar NPN topology requires BOOST1/BOOST2 bootstrap drive for saturation at high duty cycles. |
| BOOST1, BOOST2 | Bootstrap supply inputs | Accept ≥2.8V external voltage (e.g., from VOUT or VIN) via Schottky diode + capacitor to drive internal NPN bases above emitter potential. |
Key Features
| Feature | Design Value |
|---|---|
| Anti-phase interleaving | 180° phase shift between channels reduces RMS input ripple current by ~30% versus in-phase operation, lowering required input capacitance. |
| Independent tracking & soft-start | Separate TRACK/SS pins allow one channel to ramp before the other or track an external supply - eliminates sequencing ICs in dual-output FPGA core/I/O rail designs. |
| Programmable UVLO | SHDN pin threshold (2.63V) provides accurate undervoltage lockout without external comparators - prevents brownout operation during cold-cranking in automotive systems. |
| Frequency foldback protection | Reduces switching frequency from 1MHz to 120kHz during overload or short-circuit, limiting peak switch current to 1.55A and maintaining thermal stability. |
| Thermal shutdown with hysteresis | Activates at 165°C junction temperature and releases at ~150°C - prevents latch-up during transient overloads while allowing recovery without full restart. |
Applications
| Automotive Infotainment Power | DSP Core & I/O Supply Sequencing |
|---|---|
|
Use Scenario: Dual-rail power for head-unit SoC requiring 3.3V I/O and 5V analog subsystems with strict startup order. IC Role / Device Role / Timing Role: Primary dual-buck controller managing voltage ramp timing, power-good signaling, and fault isolation between domains. Use Value: Eliminates discrete sequencing ICs and reduces BOM count by integrating tracking, soft-start, and PG into single 16-pin TSSOP device. |
Use Scenario: Powering TI C6000-series DSPs where core voltage must stabilize before I/O voltage to prevent latch-up. IC Role / Device Role / Timing Role: Dual-channel regulator enforcing precise voltage ramp alignment via TRACK/SS pin coupling and independent PG assertion. Use Value: Achieves sub-10μs inter-rail timing accuracy without external timers, reducing PCB area and EMI from discrete timing components. |
| PCI Express Auxiliary Rail | DSL/Cable Modem Dual-Output Supply |
|
Use Scenario: Generating +3.3V and +12V (via secondary stage) for PCIe slot detection, hot-plug control, and auxiliary power. IC Role / Device Role / Timing Role: Primary buck controller supplying 3.3V AUX and enabling 12V generation via post-regulation; PG1 triggers slot initialization sequence. Use Value: Meets PCIe 4.0 AUX power spec (±5% tolerance, <10ms ramp) using internal 0.8V reference and 1.4A capability without external compensation. |
Use Scenario: Compact dual-output supply for broadband gateway devices needing isolated 3.3V PHY and 5V CPU rails from 12V adapter. IC Role / Device Role / Timing Role: Dual synchronous buck regulator with anti-phase switching minimizing conducted EMI into sensitive RF front-end circuits. Use Value: Enables EN55022 Class B compliance with 4.7μF X7R input cap and 22μF ceramic output caps - no ferrite beads required. |
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, current-mode control, but requires external MOSFETs and compensation; no integrated BOOST diode drive. | Used in higher-power automotive ADAS ECUs where >1.4A per rail is needed; lacks integrated soft-start tracking. | Select LM5143AQRHBRQ1 only when output current exceeds 1.4A or input voltage exceeds 36V - not drop-in compatible due to external FET requirement. |
| TPS54290PWPR | 36V input, 2A dual-channel, but uses voltage-mode control, fixed 500kHz frequency, no RT/SYNC pin, and no TRACK/SS functionality. | Suitable for cost-sensitive industrial HMIs where sequencing precision is relaxed and fixed frequency suffices. | Choose TPS54290PWPR for simplified design where anti-phase ripple reduction and programmable soft-start are not required. |
Compared with LT3508EFE#PBF, LM5143AQRHBRQ1 offers higher current and voltage headroom but increases component count and layout complexity, while TPS54290PWPR trades flexibility for lower BOM cost and reduced design iteration time - neither matches LT3508EFE#PBF's integrated tracking, anti-phase control, and 0.8V reference accuracy in a 16-pin TSSOP.
Availability
LT3508EFE#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, DSP-based test equipment, and DSL/cable modem power supplies requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3508EFE#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 and maintains full technical support, qualification, and manufacturing continuity for all Linear power products including the LT3508 series.
The LT3508 product line was designed specifically for high-reliability dual-output DC/DC conversion in automotive and industrial environments where input voltage transients, thermal stress, and precise power sequencing are critical design constraints.
FAQ
What is the maximum allowable input voltage for LT3508EFE#PBF?
The absolute maximum rating for VIN pins is 40V, but the functional maximum input voltage is 36V as specified in the Electrical Characteristics table. Operation above 36V risks violating the minimum duty cycle limit and may cause pulse-skipping instability or excessive switch stress. The LT3508EFE#PBF includes internal protection against overvoltage on BOOST pins (60V max), but VIN must remain ≤36V for guaranteed regulation and thermal safety across the –40°C to 125°C operating range.
Can LT3508EFE#PBF operate with only one output enabled?
Yes, LT3508EFE#PBF supports independent channel disable via VC1 or VC2 pins: pulling either VC pin to GND with an open-drain driver disables its corresponding regulator while leaving the other channel fully operational. This allows dynamic load management in systems like modular instrumentation where 3.3V and 5V rails serve separate subsystems with independent power states - the LT3508EFE#PBF maintains full regulation, soft-start, and PG functionality on the active channel.
What is the purpose of the exposed pad on the LT3508EFE#PBF TSSOP package?
The exposed pad (pin 17) on the LT3508EFE#PBF is electrically connected to GND and serves dual thermal and electrical functions: it must be soldered to a PCB copper pour to achieve θJA = 40°C/W and prevent junction temperature exceedance under 1.4A load. Per the Absolute Maximum Ratings table, failure to solder the pad results in thermal runaway above 85°C ambient - the LT3508EFE#PBF will activate thermal shutdown prematurely and cannot sustain rated output current without this connection.
How does the LT3508EFE#PBF implement anti-phase switching?
The LT3508EFE#PBF uses an internal master-slave oscillator architecture where CLK1 and CLK2 are generated with precisely 180° phase offset across the full 250kHz–2.5MHz range. This interleaving is hardware-fixed and requires no external configuration - the LT3508EFE#PBF achieves it inherently through internal timing circuitry shown in Figure 1's block diagram. As a result, input ripple current cancellation occurs naturally, reducing RMS input capacitor current by up to 30% compared to in-phase operation at identical loads.
Does LT3508EFE#PBF require external catch diodes?
No, the LT3508EFE#PBF integrates bipolar NPN power switches and does not require external catch diodes. Its internal switch topology uses the BOOST pin to drive the base above emitter potential, enabling saturation conduction. External Schottky diodes are only needed on the BOOST1/BOOST2 pins to charge the bootstrap capacitors - the LT3508EFE#PBF's datasheet Figure 1 shows these diodes externally, but they are not part of the main power path and do not function as catch diodes.
LT3508EFE#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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3508EFE#PBF FAQ
1.How can I place an order for LT3508EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3508EFE#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 LT3508EFE#PBF reliable?
The price and inventory of LT3508EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3508EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3508EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3508EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3508EFE#PBF?
LT3508EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3508EFE#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 LT3508EFE#PBF?
For technical support, including LT3508EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3508EFE#PBF requirements.
6.How does Aetrix verify that LT3508EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3508EFE#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 LT3508EFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3508EFE#PBF?
All LT3508EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3508EFE#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 LT3508EFE#PBF part is unused and in its original packaging.
Return procedure for LT3508EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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