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Analog Devices Inc. LT3506IFE#PBF
- Part No.:
- LT3506IFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3506IFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.6A DL 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,613
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Product details
Overview
LT3506IFE#PBF from Analog Devices (formerly Linear Technology) is a dual monolithic current-mode PWM step-down DC/DC converter with integrated 2A bipolar NPN power switches, operating at 575kHz switching frequency and supporting 3.6V–25V input to deliver two independent 1.6A outputs. It features anti-phase switching to reduce input ripple, independent RUN/SS and PGOOD pins per channel, and 0.8V ±1% feedback reference - used in DSP power supplies, DSL/cable modems, and distributed power regulation.
For engineers reviewing the LT3506IFE#PBF datasheet, LT3506IFE#PBF pinout, LT3506IFE#PBF application, or LT3506IFE#PBF equivalent, this page delivers verified technical context, exact pin functions, real-world application constraints (e.g., minimum inductor requirements for VOUT=3.3V, thermal derating in TSSOP), and validated alternative parts with documented functional trade-offs.
Technical Context
The LT3506IFE#PBF implements a constant-frequency current-mode control architecture with shared master oscillator and independent slave oscillators per channel, enabling precise anti-phase operation (180° phase shift) that cuts input RMS ripple by ~30% versus in-phase dual buck converters. Its bipolar NPN internal switches require external BOOST capacitors and Schottky catch diodes for saturation drive.
Each channel features independent error amplifiers (gm = 350 μMhos), soft-start via RUN/SS pins (2.1 μA charging current), and open-collector PGOOD comparators triggered at 90% of regulated FB voltage (720 mV threshold). Frequency foldback activates below 0.4V on FB to limit switch current during overload or short-circuit conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 575 kHz - enables use of ≤6.8 μH inductors and ceramic input/output caps for compact layout; fixed, not programmable. |
| Input Voltage Range | 3.6 V to 25 V - supports 4-cell Li-ion, 5 V logic rails, unregulated wall adapters, and lead-acid batteries without external pre-regulation. |
| Output Current per Channel | 1.6 A continuous - achievable with ≥4.7 μH inductor (e.g., Sumida CR43-4R7), 22 μF X5R/X7R output cap, and proper thermal management in I-grade TSSOP. |
| Feedback Reference Voltage | 0.800 V ±1% over –40°C to 125°C - sets output accuracy; requires R1/R2 divider with ≤10 kΩ parallel resistance to minimize bias current error. |
| Power Good Threshold | 720 mV rising on FB pin - asserts open-drain PGOOD when output reaches 90% of target, enabling safe sequencing with microcontrollers/DSPs. |
| Shutdown Quiescent Current | 30–45 μA - measured at VRUN/SS = 0 V; enables ultra-low-power system standby with both channels disabled. |
| Thermal Rating | –40°C to +125°C junction (I-grade) - validated across full range; θJA = 45°C/W in FE package requires ≥250 mm² 2-oz copper pad under exposed pad for 1.6A sustained operation. |
Pinout & Package
LT3506IFE#PBF is housed in a 16-lead plastic TSSOP narrow package (FE) with exposed thermal pad (Pin 17 = GND), measuring 5 mm × 4.4 mm × 1.1 mm. The exposed pad must be soldered to PCB ground for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BOOST1 (1), BOOST2 (8) | Bootstrap drive supply | Must be biased ≥1.5 V above respective SW pin via external diode+capacitor; enables full saturation of internal NPN switches. |
| SW1 (2), SW2 (7) | Switch node output | Connects directly to inductor, catch diode cathode, and BOOST capacitor; carries high di/dt; requires tight loop layout. |
| VIN1 (3,4), VIN2 (5,6) | Input power supply inputs | VIN1 powers internal bias regulator and Channel 1 switch; VIN2 powers Channel 2 switch only; both require local 4.7 μF ceramic bypass. |
| RUN/SS1 (13), RUN/SS2 (12) | Enable & soft-start control | Pull low to disable channel; capacitor to GND sets soft-start ramp time; 0.8 V threshold enables switching; 2.1 μA internal current source. |
| PG1 (14), PG2 (11) | Power-good status indicator | Open-collector output; pulled high externally; asserts low when FB < 720 mV; valid only if VIN > 3.4 V and corresponding RUN/SS is high. |
| VC1 (15), VC2 (10) | Error amplifier output | Controls peak switch current; clamped between 0.75 V and 1.9 V; can be overridden to force shutdown (pull to GND). |
| FB1 (16), FB2 (9) | Feedback input | Regulated to 0.800 V; connects to resistor divider tap; 40–100 nA bias current requires ≤10 kΩ Thevenin resistance. |
Key Features
| Feature | Design Value |
|---|---|
| Anti-phase switching | Reduces input capacitor RMS current by up to 30% vs. in-phase dual buck, allowing smaller 4.7 μF ceramic input caps instead of 22 μF. |
| Independent channel control | Separate RUN/SS, PGOOD, and VC pins enable staggered startup, fault isolation, and dynamic current limiting per output without cross-talk. |
| Current-mode PWM architecture | Provides inherent cycle-by-cycle current limiting, fast transient response (<10 μs to 1% regulation), and stable loop compensation with minimal external components. |
| Frequency foldback protection | Automatically reduces switching frequency to 170 kHz under overload or short-circuit, limiting peak switch current and thermal stress without external circuitry. |
| I-grade temperature rating | Guaranteed operation from –40°C to +125°C junction; validated across full range for industrial and automotive under-hood applications. |
Applications
| DSP Power Supply | DSL/Cable Modem Power |
|---|---|
Use Scenario: Dual-rail power for TI C6000 or Analog Devices SHARC DSPs requiring 1.2V core and 3.3V I/O with strict sequencing. IC Role / Device Role / Timing Role: Primary dual-output DC/DC regulator delivering 1.6A @ 1.2V and 1.6A @ 3.3V from 5V or 12V input; PGOOD signals coordinate FPGA configuration timing. Use Value: Anti-phase operation minimizes input ripple on shared 5V rail; independent soft-start prevents inrush current conflicts during boot. |
Use Scenario: Compact power solution for residential broadband gateways with space-constrained PCBs and thermal limits. IC Role / Device Role / Timing Role: Single-package replacement for two discrete buck ICs powering PHY, MAC, and memory subsystems (e.g., 1.8V + 3.3V). Use Value: 575kHz operation allows 4.7μH inductors and 22μF ceramic caps - reducing board area by >40% vs. 300kHz alternatives. |
| Distributed Power Regulation | Wall Transformer Regulation |
Use Scenario: Local point-of-load regulation from 12V/24V backplane in industrial PLCs or network switches. IC Role / Device Role / Timing Role: Dual 1.6A buck converter stepping down 24V to 5V and 3.3V for isolated MCU and interface ICs; thermal pad soldered to 2-oz copper plane. Use Value: Wide 3.6V–25V input handles brownout and surge transients; I-grade rating ensures reliability at 85°C ambient. |
Use Scenario: Regulating unregulated 9–24V AC/DC wall adapters into clean 3.3V/5V rails for consumer electronics. IC Role / Device Role / Timing Role: High-efficiency (>85% at 1A) dual-output regulator eliminating need for linear post-regulators and their heat dissipation. Use Value: Constant-frequency operation simplifies EMI filtering; ceramic caps eliminate electrolytic aging concerns in long-life products. |
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 |
|---|---|---|---|
| LTC3631EFE#PBF | Single-channel 3A buck; 3MHz switching; no integrated PGOOD or anti-phase capability. | Requires two separate ICs to match dual 1.6A output; higher frequency demands smaller inductors but increases EMI sensitivity. | Choose when higher efficiency at light load (pulse-skipping mode) or tighter output tolerance (±0.5%) is prioritized over integration and sequencing simplicity. |
| TPS54290PWPR | Dual 2A synchronous buck; 300–2000kHz adjustable frequency; integrated MOSFETs; no BOOST pin requirement. | Eliminates external diodes and BOOST components but lacks guaranteed anti-phase operation; max input 20V (vs. 25V). | Prefer for designs needing lower BOM count and simplified layout, accepting reduced input voltage headroom and no factory-guaranteed 180° phase shift. |
Compared with LT3506IFE#PBF, LTC3631EFE#PBF offers superior light-load efficiency but doubles component count and removes built-in sequencing; TPS54290PWPR reduces external parts and enables frequency tuning but sacrifices absolute input voltage range and deterministic anti-phase behavior critical for low-input-ripple systems.
Availability
LT3506IFE#PBF is available at Aetrix Electronics and suitable for industrial PLCs, broadband modems, DSP-based test equipment, and distributed power systems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3506IFE#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 product support, documentation, and manufacturing continuity for all Linear-branded power management ICs.
The LT3506 series was designed specifically for space-constrained, high-density dual-rail applications where anti-phase ripple cancellation, independent channel control, and robust industrial temperature operation are mandatory - targeting communications infrastructure and embedded computing.
FAQ
What is the maximum output current per channel for LT3506IFE#PBF at 125°C junction temperature?
The LT3506IFE#PBF delivers 1.6A per channel continuously when thermally managed per datasheet guidelines: exposed pad soldered to ≥250 mm² 2-oz copper, ambient ≤85°C, and input voltage ≤12V. At 125°C junction, derating begins at ~1.3A due to thermal shutdown activation and reduced current limit (ILIM drops from 2.0A to ~1.7A at 80% duty cycle). Full 1.6A is guaranteed only up to 105°C junction under typical PCB conditions.
Can LT3506IFE#PBF operate with ceramic output capacitors only, and what is the minimum recommended value?
Yes, LT3506IFE#PBF is optimized for ceramic output capacitors. For 3.3V or 5V outputs delivering ≥1A, a minimum of 22μF X5R/X7R ceramic (6.3V rating) is recommended to ensure <15mV peak-to-peak ripple and adequate transient response. Lower voltages (e.g., 1.2V) may use 22μF, but increasing to 47μF improves load-step recovery. Electrolytic caps are unnecessary and discouraged due to ESR-related instability risks.
Does LT3506IFE#PBF require external Schottky diodes, and why?
Yes, LT3506IFE#PBF requires external Schottky diodes (e.g., ON Semiconductor MBR5230LT3) because its internal bipolar NPN power switches lack body diodes. During the off-time, inductor current freewheels through the external diode. Using Schottky types (VF < 0.4V) minimizes conduction loss and maintains efficiency; standard silicon diodes increase losses and thermal stress significantly.
How does the anti-phase switching in LT3506IFE#PBF reduce input ripple current?
LT3506IFE#PBF synchronizes its two channels with 180° phase offset, causing their input current pulses to alternate in time. This cancels the fundamental 575kHz ripple component and reduces RMS input ripple current by up to 30% compared to in-phase operation. As a result, the required input capacitance drops from ≥22μF to just 4.7μF ceramic, lowering cost, size, and ESL-related EMI.
What is the purpose of the BOOST pins on LT3506IFE#PBF, and how must they be connected?
The BOOST1 and BOOST2 pins provide gate drive voltage >VIN to fully saturate the internal bipolar NPN switches. Each must be connected via a Schottky diode (anode to VOUTx) and 100nF ceramic capacitor (cathode to respective BOOST pin). This generates a boost voltage ≈VOUTx + 0.3V, ensuring low VCE(sat) (~210mV) and high efficiency. Leaving BOOST pins unconnected disables switching.
LT3506IFE#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):
- 3.6V
- Voltage - Input (Max):
- 25V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 23.25V
- Current - Output:
- 1.6A
- Frequency - Switching:
- 575kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3506IFE#PBF FAQ
1.How can I place an order for LT3506IFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3506IFE#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 LT3506IFE#PBF reliable?
The price and inventory of LT3506IFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3506IFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3506IFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3506IFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3506IFE#PBF?
LT3506IFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3506IFE#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 LT3506IFE#PBF?
For technical support, including LT3506IFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3506IFE#PBF requirements.
6.How does Aetrix verify that LT3506IFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3506IFE#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 LT3506IFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3506IFE#PBF?
All LT3506IFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3506IFE#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 LT3506IFE#PBF part is unused and in its original packaging.
Return procedure for LT3506IFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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