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Analog Devices Inc. LT3509IMSE#PBF
- Part No.:
- LT3509IMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3509IMSE#PBF.pdf
- Description:
- IC REG BUCK ADJ 700MA DL 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:102
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Product details
Overview
LT3509IMSE#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, current-mode, synchronous step-down DC/DC regulator 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 LT3509IMSE#PBF datasheet, LT3509IMSE#PBF pinout, LT3509IMSE#PBF application, or LT3509IMSE#PBF equivalent, key selection considerations include its 16-lead MSOP package with exposed pad, adjustable 300kHz–2.2MHz switching frequency via RT resistor, integrated boost diodes and compensation, and dual independent soft-start/shutdown functionality for CPU/FPGA core and I/O rail sequencing.
Technical Context
The LT3509IMSE#PBF implements two independent current-mode buck regulators sharing a common 0.8V reference and oscillator, operating in-phase with cycle-by-cycle current limiting and thermal shutdown. Each channel features dedicated RUN/SS pins enabling staged startup and fault-initiated soft-restart via internal 250µA pull-down.
Its boost architecture uses internal Schottky diodes (BD pin) and external BOOST capacitors to drive the switch base above VIN-enabling >95% duty cycle and low dropout operation-while overvoltage lockout (38.5V typ.) and undervoltage lockout (3.6V typ.) protect against 60V transients and brownouts.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous; withstands 60V non-repetitive transients-supports 12V/24V automotive and industrial bus inputs with surge immunity. |
| Output Current per Channel | 700mA max-sufficient for powering FPGA I/O banks, microcontroller peripherals, or dual-core DSP subsystems. |
| Switching Frequency | Adjustable 300kHz–2.2MHz via RT resistor; synchronizable externally-enables EMI optimization and ceramic capacitor use. |
| Feedback Reference Voltage | 0.800V ±2% over –40°C to 125°C-ensures stable output regulation across temperature with minimal resistor-divider error. |
| Current Limit Threshold | 1.4A typical per switch-provides cycle-by-cycle protection during short-circuit or overload without latch-off. |
| Thermal Shutdown | Activates at ~160°C junction-prevents permanent damage during sustained overload or poor PCB thermal design. |
| Package | 16-Lead MSOP with exposed thermal pad-offers θJA = 43°C/W and requires soldered GND pad for reliable 125°C operation. |
Pinout & Package
LT3509IMSE#PBF is housed in a thermally enhanced 16-lead plastic MSOP package with exposed pad (Pin 17 = GND), requiring PCB soldering of the pad for thermal and electrical integrity. Pin count and layout match the MSE footprint defined in Linear Technology's official package drawing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| DA1, DA2 (Pins 1, 8) | Catch diode anode sense | Internally connected to GND via current-sense resistors-monitors valley inductor current for short-circuit protection. |
| BOOST1, BOOST2 (Pins 2, 7) | Bootstrap capacitor connection | Drives switch base above VIN via external capacitors-enables high duty cycle (>95%) and low dropout operation. |
| SW1, SW2 (Pins 3, 6) | Power switch output | Connects to inductor, catch diode cathode, and BOOST capacitor-carries full switched current with 0.32V saturation voltage. |
| VIN (Pins 4, 5) | Main input supply | Dual pins must be tied together-supplies both control circuitry and power switches; requires local 22µF ceramic input capacitance. |
| FB1, FB2 (Pins 16, 9) | Output voltage feedback | Sets regulated output via resistor divider to 0.8V reference-supports 3.3V, 5V, or custom outputs with <±1% accuracy. |
| RUN/SS1, RUN/SS2 (Pins 15, 10) | Enable & soft-start control | 0.8V–2V range enables current-limited soft-start; <0.4V shuts down channel; internal 1µA pull-up allows floating enable. |
| RT (Pin 11) | Oscillator timing | Resistor-to-GND sets switching frequency (e.g., 40.2kΩ = 1MHz); supports precise EMI control and synchronization margin. |
| SYNC (Pin 12) | External clock input | Accepts logic-level clock ≥1.0V threshold-requires free-run frequency ≥12% below sync source for reliable locking. |
| BD (Pin 13) | Boost diode common anode | Supplies charge current to BOOST capacitors-must be bypassed locally with 0.1µF ceramic for stable bootstrap operation. |
| AGND (Pin 14) | Analog ground reference | Separate low-noise return for feedback and control circuitry-must connect to main GND plane but not carry high-current return paths. |
| Exposed Pad (Pin 17) | Power ground / thermal path | Electrically and thermally connected to GND-requires multiple thermal vias to inner ground planes for 125°C continuous operation. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent soft-start | Each channel uses separate RUN/SS pin with programmable ramp time-enables controlled power-up sequencing for 3.3V/5V rails or core/I/O domains. |
| Integrated boost diodes | Internal Schottky BD pin eliminates external diodes-reduces BOM count and PCB area while maintaining >95% duty cycle capability. |
| Overvoltage lockout (OVL) | Shuts down at 38.5V typical-protects downstream circuitry during load-dump events in automotive 12V/24V systems. |
| Internal loop compensation | No external compensation components required-simplifies design, improves stability margin, and reduces board space vs. traditional buck controllers. |
| Thermally enhanced MSOP | Exposed pad with θJC = 4.3°C/W-enables 700mA/channel operation at 125°C ambient when properly mounted on 2oz copper with thermal vias. |
Applications
| Automotive Infotainment Power | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering dual-rail processors (e.g., ARM Cortex-A series) and display interfaces in vehicle head units exposed to 60V load-dump transients. IC Role / Device Role / Timing Role: Dual buck regulator providing isolated 3.3V (core) and 5V (USB/HDMI PHY) rails with independent soft-start and OVL protection. Use Value: Eliminates need for external TVS and discrete boost diodes-reducing solution size by >30% while meeting ISO 7637-2 Pulse 5a requirements. | Use Scenario: Generating stable 3.3V and 5V supplies for digital I/O expansion cards in programmable logic controllers operating in factory environments. IC Role / Device Role / Timing Role: Primary DC/DC converter delivering regulated power to isolated RS-485 transceivers, optocouplers, and microcontroller peripherals. Use Value: Withstands 36V nominal input with 60V surge tolerance-ensuring uninterrupted operation during 24V DC bus fluctuations and motor-switching noise. |
| Networking Equipment Midspan PSE | FPGA-Based Test Instrumentation |
Use Scenario: Providing auxiliary 3.3V and 5V rails in PoE midspan injectors where space and thermal management are constrained. IC Role / Device Role / Timing Role: Secondary regulator sourcing power for MCU, EEPROM, and LED drivers-operating from primary 48V PoE-derived supply. Use Value: Adjustable switching frequency avoids interference with Ethernet signaling bands-maintaining Class A EMI compliance without shielding. | Use Scenario: Powering Xilinx Artix-7 FPGA banks (VCCINT = 1.0V, VCCAUX = 1.8V, VCCO = 3.3V) and analog front-end ADCs in portable test equipment. IC Role / Device Role / Timing Role: Pre-regulator supplying clean, sequenced 3.3V and 5V to LDOs that generate sub-1V FPGA core voltages. Use Value: Independent RUN/SS control enables precise power-on reset timing-meeting FPGA configuration voltage ramp requirements per Xilinx DS182. |
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, 36V, 1A buck; no dual output or independent soft-start-requires two devices for dual-rail use. | Lacks integrated dual-channel sequencing; higher BOM cost and board area for equivalent functionality. | Choose only if single-rail 1A output suffices and dual-channel integration is unnecessary. |
| TPS54290PWPR | 36V, dual 2A buck with integrated FETs; wider 0.8V–15V output adjust range but no BD pin or internal boost diodes. | Requires external bootstrap diodes and larger external compensation-less suitable for compact automotive modules. | Select when higher output current (>700mA) is mandatory and board space permits added components. |
Compared with LTC3631EMSE#PBF and TPS54290PWPR, the LT3509IMSE#PBF uniquely integrates dual 700mA regulators with internal boost diodes, independent RUN/SS control, and 60V transient tolerance in a single 4mm × 3mm MSOP-making it optimal for space-constrained, multi-rail automotive and industrial power designs where reliability under harsh conditions is critical.
Availability
LT3509IMSE#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLC I/O modules, and networking midspan power supplies requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3509IMSE#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 and manufacturing continuity for all Linear power products-including the LT3509 family.
The LT3509 product line was designed specifically for ruggedized dual-output DC/DC conversion in automotive and industrial environments-emphasizing transient robustness, thermal resilience, and minimal external component count.
FAQ
What is the maximum input voltage rating for LT3509IMSE#PBF, and how does it handle transients?
The LT3509IMSE#PBF has an absolute maximum VIN rating of 60V for non-repetitive 1-second transients and a continuous operating limit of 36V. Its overvoltage lockout triggers at 38.5V typical, halting switching to protect internal circuitry and downstream loads. After the transient subsides and VIN drops below the OVL threshold, the LT3509IMSE#PBF automatically initiates a soft-start sequence before resuming regulation-ensuring safe recovery without manual reset.
Can LT3509IMSE#PBF operate with input voltages below 3.6V, and what limits its minimum input?
No-the LT3509IMSE#PBF incorporates an undervoltage lockout that prevents operation below ~3.6V (typical). Below this threshold, the internal bias circuitry cannot sustain stable reference and oscillator operation. Even with external boosting, the LT3509IMSE#PBF will not switch until VIN exceeds the UVLO threshold. For true low-input applications (<3.6V), a different regulator such as the LT8609S is recommended.
How does the LT3509IMSE#PBF achieve >95% duty cycle, and what design considerations apply?
The LT3509IMSE#PBF achieves >95% duty cycle using its internal boost diodes (BD pin) and external BOOST capacitors to drive the power switch base above VIN-reducing saturation voltage and enabling near-dropout operation. To maintain boost capacitor charge at high duty cycles, the LT3509IMSE#PBF forces occasional minimum off-times. Designers must ensure the BD supply is ≥3V (e.g., tie BD to a regulated 3.3V rail) and use ≥0.1µF ceramic BOOST capacitors placed close to the BOOST/SW pins.
What is the purpose of the AGND pin on LT3509IMSE#PBF, and how should it be connected?
The AGND pin (Pin 14) on the LT3509IMSE#PBF provides a dedicated low-noise analog ground return for the feedback amplifier, error comparator, and reference circuitry. It must be connected to the main system GND plane-but should not carry high-current return paths (e.g., from SW or DA pins). Best practice is to route AGND separately to the exposed pad or a quiet GND node, then tie it to the power ground plane at a single point near the IC to avoid noise coupling into the regulation loop.
Does LT3509IMSE#PBF require external compensation components, and why?
No-the LT3509IMSE#PBF integrates all loop compensation components internally, including the error amplifier compensation network and slope compensation for current-mode stability. This eliminates the need for external capacitors or resistors in the feedback path, simplifying layout, reducing BOM count, and improving consistency across production units. The internal compensation is optimized for standard ceramic output capacitors (e.g., 10µF–22µF X5R/X7R) and typical inductor values (e.g., 4.7µH–10µH).
LT3509IMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm 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):
- 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:
- 16-MSOP-EP
LT3509IMSE#PBF FAQ
1.How can I place an order for LT3509IMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3509IMSE#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 LT3509IMSE#PBF reliable?
The price and inventory of LT3509IMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3509IMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3509IMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3509IMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3509IMSE#PBF?
LT3509IMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3509IMSE#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 LT3509IMSE#PBF?
For technical support, including LT3509IMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3509IMSE#PBF requirements.
6.How does Aetrix verify that LT3509IMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3509IMSE#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 LT3509IMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3509IMSE#PBF?
All LT3509IMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3509IMSE#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 LT3509IMSE#PBF part is unused and in its original packaging.
Return procedure for LT3509IMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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