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Analog Devices Inc. LT3509IDE#PBF
- Part No.:
- LT3509IDE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 14-WFDFN Exposed Pad
- Datasheet:
-
LT3509IDE#PBF.pdf
- Description:
- IC REG BUCK ADJ 700MA DL 14DFN
- Quantity:
- Payment:
- Shipping:
Inventory:941
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Product details
Overview
LT3509IDE#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, current-mode, synchronous step-down DC/DC converter IC with integrated 700mA power switches, 3.6V–36V input range, and independent RUN/SS control per channel-designed for automotive multi-rail power systems requiring robust transient protection up to 60V and constant-frequency operation above the AM band.
For engineers reviewing the LT3509IDE#PBF datasheet, LT3509IDE#PBF pinout, LT3509IDE#PBF application, or LT3509IDE#PBF equivalent, key selection considerations include its dual 700mA output capability, adjustable 300kHz–2.2MHz switching frequency via RT resistor, integrated boost diodes and compensation, thermal shutdown, overvoltage lockout (38.5V typ), and 14-lead 4mm × 3mm DFN package with exposed GND pad.
Technical Context
The LT3509IDE#PBF implements a dual, phase-aligned, current-mode control architecture with shared oscillator and reference but independent error amplifiers, soft-start, and shutdown logic per channel. Each regulator uses cycle-by-cycle peak current limiting and valley current monitoring via DA pins to enforce short-circuit robustness.
Its BOOST circuit employs internal Schottky diodes (BD pin) and external capacitors to drive the switch base above VIN, enabling >95% duty cycle and low dropout operation; switching frequency is set by RT (264kHz–2.2MHz) or synchronized externally via SYNC pin with ≥12% margin below external clock.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous; withstands 60V non-repetitive transients-enables direct connection to automotive battery rails with load dump immunity. |
| Output Current per Channel | 700mA maximum-supports dual-core microcontrollers, FPGAs, or sensor subsystems without external pass devices. |
| Switching Frequency | Adjustable 300kHz–2.2MHz via RT resistor; synchronizable externally-avoids AM band interference and enables compact magnetics. |
| Feedback Reference Voltage | 0.800V ±2% over temperature-allows precise output setting (e.g., 3.3V or 5V) using standard resistor dividers with minimal bias error. |
| Overvoltage Lockout Threshold | 38.5V typical-halts switching during ISO 7637-2 pulse 5a/b transients, protecting downstream circuitry. |
| Thermal Shutdown | Activates at TJ ≈ 165°C; device resumes operation after cooldown-provides fail-safe protection in sealed enclosures or high ambient conditions. |
| Duty Cycle Range | Up to 95% maximum-enables regulation down to VIN ≈ VOUT + VF, supporting low-dropout operation in wide-input applications. |
Pinout & Package
LT3509IDE#PBF is housed in a thermally enhanced 14-lead (4mm × 3mm) plastic DFN package with exposed GND pad (Pin 15), requiring PCB soldering for thermal and electrical integrity. θJA = 43°C/W, θJC = 4.3°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1, FB2 (Pins 14, 8) | Feedback input | Connects to resistor divider to regulate output voltage; referenced to 0.8V internal bandgap-sets VOUT = 0.8V × (1 + R1/R2). |
| RUN/SS1, RUN/SS2 (Pins 13, 9) | Enable & soft-start control | Pull <0.4V to shut down channel; 0.8–2.0V enables current-limited soft-start; >2.0V enables full 700mA-supports sequenced power-up and fault recovery. |
| SW1, SW2 (Pins 3, 5) | Switch node | Drives external inductor and catch diode cathode; internal NPN switch with 0.32V saturation at 0.9A-defines power stage topology and loss budget. |
| BOOST1, BOOST2 (Pins 2, 6) | Bootstrap supply node | Tied to SW via capacitor; charged by BD pin-raises switch base above VIN to minimize conduction loss and enable high duty cycle. |
| DA1, DA2 (Pins 1, 7) | Catch diode anode | Internally connected to GND pad via current-sense resistors-monitors valley inductor current for short-circuit protection (0.95A threshold). |
| BD (Pin 12) | Boost diode common anode | Supplies charging current to both BOOST capacitors; must be locally bypassed-determines boost efficiency and maximum duty cycle capability. |
| RT (Pin 10) | Oscillator timing | Resistor-to-GND sets free-run frequency (e.g., 40.2kΩ = 1MHz); tolerance directly impacts regulation accuracy and EMI profile. |
| SYNC (Pin 11) | External clock input | Accepts logic-level signal ≥1.0V threshold; forces synchronization only if free-run frequency is ≥12% lower-prevents beat frequencies in multi-converter systems. |
| VIN (Pin 4) | Main power input | Supplies control circuitry and power switches; requires low-ESR input capacitor placed adjacent to pin-critical for stability under 60V transients. |
| GND / Exposed Pad (Pin 15) | Power and signal ground | Reference for all analog circuits and return path for catch diode current-must be soldered with thermal vias to maintain TJ ≤ 125°C in continuous operation. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent regulators | Enables simultaneous 3.3V/5V or 3.3V/1.8V generation from single input-reduces BOM count and board area vs. discrete solutions. |
| Integrated boost diodes and compensation | Eliminates 4 external diodes and 2 compensation networks-simplifies layout, improves reliability, and reduces startup time variability. |
| Overvoltage lockout (38.5V typ) and 60V transient tolerance | Meets automotive ISO 7637-2 Pulse 5a/b requirements without external TVS-lowers system-level protection cost. |
| Constant-frequency operation above AM band | Supports 300kHz–2.2MHz tuning-ensures clean RF environment in infotainment and telematics modules. |
| Thermally enhanced DFN with exposed pad | Delivers 4.3°C/W junction-to-case thermal resistance-enables 700mA/channel operation at 85°C ambient without heatsink. |
Applications
| Automotive Infotainment Power | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering DSP, display controller, and audio codec in head-unit with 12V battery input subject to load dump and cold-crank transients. IC Role / Device Role / Timing Role: Dual-output DC/DC regulator providing isolated 3.3V (DSP core) and 5V (USB interface) rails with independent sequencing and fault recovery. Use Value: Withstands 60V transients and maintains regulation during 3.6V cold-crank events-eliminates need for upstream pre-regulator or backup LDO. | Use Scenario: Generating 5V and 3.3V for microcontroller, CAN transceiver, and analog front-end in DIN-rail mounted programmable logic controller. IC Role / Device Role / Timing Role: Primary point-of-load regulator with overtemperature and overvoltage protection-ensures safe shutdown during field wiring faults or ambient overheating. Use Value: Integrated DA current monitoring detects output shorts before fuse blow, enabling graceful degradation instead of catastrophic failure. |
| Networking Edge Router | FPGA Development Board |
Use Scenario: Supplying 3.3V and 1.8V to Ethernet PHY, switch fabric, and management MCU in fanless enterprise switch operating at 45°C ambient. IC Role / Device Role / Timing Role: Compact dual buck converter with adjustable frequency-minimizes EMI coupling into Gigabit Ethernet signals while meeting thermal limits. Use Value: 2.2MHz operation allows use of 1.0µH inductors and 10µF ceramic output caps-reducing solution size by >40% vs. 500kHz designs. | Use Scenario: Providing configurable 1.2V, 1.8V, and 3.3V rails for Xilinx Artix-7 FPGA I/O banks and core logic during lab validation. IC Role / Device Role / Timing Role: Flexible evaluation power source with independent RUN/SS pins-enables dynamic rail sequencing and current-limited hot-plug testing. Use Value: Soft-start ramp rate controlled by external capacitor on RUN/SS pins-prevents inrush current tripping bench supplies during FPGA configuration. |
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 |
|---|---|---|---|
| LTC3631EMSE#PBF | Single-channel, 1A, 4V–15V input; no integrated boost diodes; requires external bootstrap components. | Lower input voltage range; lacks 60V transient tolerance and dual-channel integration. | Choose when only one rail is needed and input is tightly regulated (e.g., intermediate 5V bus). |
| TPS65270RGET | Dual 1.5A/1.5A, 4.5V–18V input; integrated MOSFETs; no BD/DA pins; fixed 500kHz/2.1MHz options. | Higher current, narrower input range; lacks overvoltage lockout >36V and independent soft-start per channel. | Prefer for higher-current, lower-voltage industrial applications where 60V transient immunity is not required. |
Compared with LTC3631EMSE#PBF and TPS65270RGET, the LT3509IDE#PBF uniquely combines dual 700mA outputs, 3.6V–36V operation with 60V transient survival, integrated boost diodes, and per-channel RUN/SS control-making it optimal for automotive and harsh-environment multi-rail systems where space, reliability, and input ruggedness are critical.
Availability
LT3509IDE#PBF is available at Aetrix Electronics and suitable for automotive infotainment, industrial PLCs, and networking edge equipment requiring stable component supply across extended temperature and transient-prone environments.
Supply support for LT3509IDE#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. (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 LT3509IDE#PBF belongs to Linear's legacy high-voltage monolithic buck regulator product line, engineered specifically for automotive and industrial applications demanding wide input range, transient robustness, and integrated protection-without compromising efficiency or solution size.
FAQ
What is the maximum input voltage rating for LT3509IDE#PBF, and how does it handle transients?
The LT3509IDE#PBF has an absolute maximum VIN rating of 60V for non-repetitive 1-second transients and is rated for continuous operation from 3.6V to 36V. Its overvoltage lockout activates at 38.5V (typical), halting switching to protect internal circuitry during ISO 7637-2 load-dump events. After the transient subsides, the part automatically initiates a soft-start sequence to resume regulation-ensuring robust operation in automotive battery systems without external clamping components.
Can LT3509IDE#PBF operate with input voltage below 3.6V, and what limits its minimum input?
The LT3509IDE#PBF incorporates an undervoltage lockout that disables switching below ~3.3V (typical), but functional operation can begin near 3.6V. Below this, the primary limitation becomes achievable duty cycle: with 95% maximum duty cycle and typical diode/switch drops, the practical minimum VIN for 3.3V output is ~4.0V at full load, rising to ~4.5V at light loads due to boost capacitor recharge requirements. Figure 5 in the datasheet shows measured VIN-to-start values across load conditions for the LT3509IDE#PBF.
How does the DA pin function in LT3509IDE#PBF, and what protection does it provide?
The DA1 and DA2 pins on the LT3509IDE#PBF serve as anode connections for the internal catch diodes and are tied to the exposed GND pad through precision current-sense resistors. They feed a dedicated comparator that monitors valley inductor current; if DA current exceeds 0.95A (typical), the comparator forces pulse skipping to limit average output current-providing inherent short-circuit protection without external sensing. This mechanism ensures the LT3509IDE#PBF survives sustained output shorts even at 36V input.
What is the role of the BD pin in LT3509IDE#PBF, and how should it be decoupled?
The BD pin on the LT3509IDE#PBF is the common anode connection for both internal Schottky boost diodes and supplies charging current to the BOOST1 and BOOST2 capacitors. It must be locally bypassed with a low-ESR ceramic capacitor (e.g., 1µF X7R) placed within 2mm of the pin and connected directly to the exposed GND pad. Insufficient BD decoupling causes premature switch turn-off, reduced efficiency, and instability-especially at high duty cycles or frequencies above 1MHz.
Does LT3509IDE#PBF require external compensation components, and how is loop stability ensured?
No, the LT3509IDE#PBF integrates all loop compensation components-including error amplifier compensation network and slope compensation-on-die. This eliminates external RC networks and simplifies design while ensuring stable operation across the full 300kHz–2.2MHz frequency range and 3.6V–36V input span. Stability is verified over temperature and load; users only need to select appropriate output capacitors (minimum 22µF ceramic recommended) and follow layout guidelines for the FB and RT nodes to maintain phase margin.
LT3509IDE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 14-WFDFN 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):
- 36V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 34.2V
- Current - Output:
- 700mA
- Frequency - Switching:
- 260kHz ~ 2.15MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-DFN (4x3)
LT3509IDE#PBF FAQ
1.How can I place an order for LT3509IDE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3509IDE#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 LT3509IDE#PBF reliable?
The price and inventory of LT3509IDE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3509IDE#PBF is usually 5 days.
3.What payment methods are accepted for LT3509IDE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3509IDE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3509IDE#PBF?
LT3509IDE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3509IDE#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 LT3509IDE#PBF?
For technical support, including LT3509IDE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3509IDE#PBF requirements.
6.How does Aetrix verify that LT3509IDE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3509IDE#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 LT3509IDE#PBF meets industry standards.
7.What is the process for return or replacement of LT3509IDE#PBF?
All LT3509IDE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3509IDE#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 LT3509IDE#PBF part is unused and in its original packaging.
Return procedure for LT3509IDE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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