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Analog Devices Inc. LT3509EMSE#PBF
- Part No.:
- LT3509EMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3509EMSE#PBF.pdf
- Description:
- IC REG BUCK ADJ 700MA DL 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,410
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Product details
Overview
LT3509EMSE#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, current-mode, 36V-input synchronous step-down DC/DC regulator with integrated 700mA power switches per channel, internal boost diodes, and on-chip loop compensation. It delivers independent 3.3V/5V outputs in automotive and industrial power rails, supports 300kHz–2.2MHz adjustable switching frequency, and features overvoltage lockout up to 60V transients.
For engineers reviewing the LT3509EMSE#PBF datasheet, LT3509EMSE#PBF pinout, LT3509EMSE#PBF application, or LT3509EMSE#PBF equivalent, key selection considerations include its 16-lead MSOP package with exposed pad, independent RUN/SS soft-start control per channel, cycle-by-cycle current limiting, thermal shutdown, and AM-band–free constant-frequency operation for noise-sensitive environments.
Technical Context
The LT3509EMSE#PBF implements two independent current-mode buck regulators sharing a common 0.8V reference and oscillator, operating in-phase with adjustable frequency set by a single RT resistor. Each channel uses internal NPN power switches with integrated boost diodes and external bootstrap capacitors to achieve low dropout (95% max duty cycle) and high efficiency across wide input ranges.
Protection architecture includes VIN undervoltage lockout (~3.6V), overvoltage shutdown (~38.5V), thermal shutdown, cycle-by-cycle current limit (1.4A typ), and DA-pin–based short-circuit robustness. Soft-start is controlled via voltage-ramped RUN/SS pins (0.8V–2V range), with internal 1µA pull-up and 250µA fault discharge capability.
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 24V/36V industrial or automotive batteries without pre-regulation. |
| Output Current per Channel | 700mA - sufficient for powering microcontrollers, FPGAs, and analog circuitry in multi-rail embedded systems. |
| Switching Frequency | 300kHz to 2.2MHz (adjustable via RT resistor; synchronizable) - allows optimization of size (high-freq → small inductors/ceramics) and EMI (AM-band avoidance). |
| Feedback Reference Voltage | 0.800V ±2% (–40°C to 125°C) - enables precise output regulation with standard resistor dividers; minimizes error due to FB bias current (≤500nA). |
| Current Limit Threshold | 1.4A typical per switch - provides robust cycle-by-cycle protection during overload or short-circuit events without latch-off. |
| Thermal Shutdown Threshold | Junction temperature >150°C (H-grade) or >125°C (E/I-grade) - ensures safe operation under sustained high-load or poor PCB thermal conditions. |
| Quiescent Current | 2.2mA (not switching, VFB > 0.8V) - supports low-power standby modes while maintaining regulation readiness. |
Pinout & Package
LT3509EMSE#PBF is housed in a thermally enhanced 16-lead plastic MSOP package with exposed pad (Pin 17 = GND), offering θJA = 43°C/W and θJC = 4.3°C/W. The exposed pad must be soldered to a PCB ground plane with thermal vias for reliable operation at full load.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| DA1, DA2 (Pins 1, 8) | Catch diode anode sense inputs | Internally connected to GND via current-sense resistors; used for valley-current monitoring and short-circuit protection. |
| BOOST1, BOOST2 (Pins 2, 7) | Bootstrap capacitor connection points | Drive internal NPN base above VIN via external capacitors; require ≥2V headroom above SW for full saturation. |
| SW1, SW2 (Pins 3, 6) | Internal power switch outputs | Connect to inductors and catch diode cathodes; switch saturation voltage ≤0.32V at 0.9A ensures low conduction loss. |
| VIN (Pins 4, 5) | Main input supply | Dual pins must be tied together; accepts 3.6V–36V input; supports 60V transient tolerance with OVP activation. |
| FB1, FB2 (Pins 16, 9) | Feedback voltage sensing inputs | Set output voltage via resistor divider; regulated to 0.8V reference; bias current ≤500nA minimizes divider error. |
| RUN/SS1, RUN/SS2 (Pins 15, 10) | Enable & soft-start control inputs | 0.4–0.8V = shutdown; 0.8–2.0V = current-limited soft-start; >2.0V = full 700mA output; internal 1µA pull-up enables float-to-enable. |
| RT (Pin 11) | Oscillator timing resistor input | Single external resistor sets switching frequency (e.g., 40.2kΩ = 1MHz); supports synchronization when free-run freq is ≥12% below external clock. |
| SYNC (Pin 12) | External clock synchronization input | 1.0V threshold; accepts logic-level clocks; must be tied low via ≤10kΩ if unused to prevent noise-induced frequency jitter. |
| BD (Pin 13) | Common anode for internal Schottky boost diodes | Supplies charge current to BOOST capacitors; requires local 1µF ceramic bypass; max 20V rating limits BD supply source selection. |
| AGND (Pin 14) | Analog ground reference | Separate low-current return for control circuitry; must connect to main GND but not serve as sole ground path for power components. |
| Exposed Pad (Pin 17) | Power ground and thermal interface | Electrically GND; mandatory solder connection to PCB ground plane with thermal vias for thermal performance and current return path. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost diodes and compensation | Eliminates 4 external diodes and 3–4 compensation components per channel, reducing BOM count and layout area. |
| Independent RUN/SS control per channel | Enables staggered startup, power sequencing, and individual fault recovery without affecting the other regulator. |
| Overvoltage lockout up to 60V | Protects downstream circuitry during load-dump events in 12V/24V automotive systems without external TVS clamping. |
| Adjustable 300kHz–2.2MHz switching | Permits trade-off between component size (high-freq) and efficiency/EMI (mid-freq), including AM-band–free operation (>1.8MHz). |
| 95% maximum duty cycle | Supports ultra-low dropout operation (e.g., 5V out from 5.3V in), critical for post-regulation in battery-powered or tightly constrained rails. |
Applications
| Automotive Infotainment Power | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering display controller, audio codec, and CAN transceiver from a 12V vehicle battery subject to load dump and cold-crank transients. IC Role / Device Role / Timing Role: Dual-output buck regulator providing isolated 3.3V (digital core) and 5V (interface/peripheral) rails with independent enable sequencing. Use Value: 60V transient tolerance and thermal shutdown ensure uninterrupted operation during ISO 7637-2 pulse 5a/b events; constant-frequency mode avoids AM radio interference. | Use Scenario: Generating 3.3V and 5V supplies for microcontroller, ADC, and digital isolators in a DIN-rail mounted programmable logic controller. IC Role / Device Role / Timing Role: Compact, rugged DC/DC solution replacing discrete buck controllers and external MOSFETs in space-constrained industrial enclosures. Use Value: Wide 3.6V–36V input range accommodates 24V DC field wiring with brownout margin; exposed-pad MSOP package enables reliable thermal management without heatsinks. |
| Networking Equipment PoE Midspan | FPGA Core & Auxiliary Power |
Use Scenario: Providing auxiliary 3.3V and 5V rails in IEEE 802.3af/at midspan PSE equipment powered from 48V DC input. IC Role / Device Role / Timing Role: Secondary regulator converting intermediate 12V or 24V bus to clean, sequenced low-voltage rails for PHY, MCU, and EEPROM. Use Value: Synchronizable switching frequency prevents beat frequencies with primary DC/DC converters; low quiescent current extends standby time during link idle. | Use Scenario: Supplying 1.8V (core) and 3.3V (I/O) to Xilinx Spartan or Intel Cyclone FPGA in test instrumentation with strict ripple and sequencing requirements. IC Role / Device Role / Timing Role: Dual-channel buck converter delivering tightly regulated, independently controlled power domains with soft-start ramp control. Use Value: Independent RUN/SS pins allow FPGA configuration logic to sequence core before I/O; 0.8V FB reference enables accurate low-voltage regulation with minimal divider error. |
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 integrated boost diodes; requires external bootstrap diodes; 200kHz–2MHz range. | Lacks dual-output capability and independent soft-start; better suited for single-rail, higher-current applications where board space permits external components. | Select when only one regulated rail is needed and higher peak current (1A) is required; avoid when dual independent outputs or reduced BOM count are priorities. |
| TPS54202DRCT | Single-channel, 2.9V–60V, 2A buck; integrated high-side MOSFET only; requires external bootstrap capacitor and diode; 200kHz–2.2MHz. | No second channel; lacks DA-based short-circuit protection and overvoltage lockout above 36V; lower thermal performance in MSOP. | Choose for cost-sensitive, single-output designs needing 2A output; not suitable as drop-in replacement due to missing second channel and different protection architecture. |
Compared with LTC3631EMSE#PBF and TPS54202DRCT, the LT3509EMSE#PBF uniquely delivers two fully independent, protected 700mA buck channels in one MSOP package with integrated boost diodes and OVP-making it optimal for compact, dual-rail systems where reliability under transients and minimal external components are critical.
Availability
LT3509EMSE#PBF is available at Aetrix Electronics and suitable for automotive infotainment, industrial PLC I/O modules, and networking equipment requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance across –40°C to +125°C.
Supply support for LT3509EMSE#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 its high-performance power management portfolio with rigorous qualification and long-term support.
The LT3509EMSE#PBF belongs to Linear's industrial-grade monolithic buck regulator family, designed specifically for harsh-environment DC/DC conversion in automotive, factory automation, and telecom infrastructure where input transients, thermal stress, and reliability are primary constraints.
FAQ
What is the maximum input voltage transient the LT3509EMSE#PBF can withstand?
The LT3509EMSE#PBF supports non-repetitive 60V transients on the VIN pin for up to 1 second, with overvoltage lockout activating at ~38.5V during continuous operation. This makes the LT3509EMSE#PBF suitable for automotive load-dump conditions per ISO 7637-2 without external clamping. The device resumes regulation after VIN falls below the OVP threshold, initiating a controlled soft-start sequence.
Does the LT3509EMSE#PBF require external boost diodes?
No, the LT3509EMSE#PBF integrates Schottky boost diodes connected to the BD pin, eliminating the need for external diodes in standard configurations. These internal diodes supply charge current to the BOOST1/BOOST2 capacitors. External diodes may be added in parallel only for extreme-duty-cycle operation (<3V output with high input) to reduce BD pin current stress, but are not required for typical 3.3V/5V applications.
How is output voltage programmed on the LT3509EMSE#PBF?
Each output voltage is set using a resistor divider from VOUT to the corresponding FB1 or FB2 pin, configured to develop exactly 0.8V at the FB pin when regulation is achieved. For example, for a 5V output: R1 = R2 × ((5V / 0.8V) − 1). R2 should be ≤20kΩ to minimize error from FB bias current (≤500nA). The LT3509EMSE#PBF's precision 0.8V reference ensures tight output tolerance across temperature and line variations.
Can both channels of the LT3509EMSE#PBF be synchronized to the same external clock?
Yes, the LT3509EMSE#PBF's single SYNC pin synchronizes both channels to the same external clock signal. To ensure reliable locking, the free-running frequency (set by the RT resistor) must be at least 12% lower than the minimum expected external clock frequency. The SYNC pin has a 1.0V threshold and accepts standard logic-level signals; if unused, it must be tied low with ≤10kΩ to prevent noise coupling and erratic frequency behavior.
What thermal design guidance applies to the LT3509EMSE#PBF in MSOP package?
The LT3509EMSE#PBF in 16-lead MSOP requires soldering the exposed pad (Pin 17) to a PCB ground plane with ≥4 thermal vias (0.3mm diameter) to achieve its rated θJA = 43°C/W. Without this, junction temperature rise exceeds specifications under 700mA load. AGND (Pin 14) must connect to the same ground net but should not carry high-current return paths. Layout must minimize VIN and SW node copper area to reduce EMI and improve thermal dissipation.
LT3509EMSE#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
LT3509EMSE#PBF FAQ
1.How can I place an order for LT3509EMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3509EMSE#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 LT3509EMSE#PBF reliable?
The price and inventory of LT3509EMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3509EMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3509EMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3509EMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3509EMSE#PBF?
LT3509EMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3509EMSE#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 LT3509EMSE#PBF?
For technical support, including LT3509EMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3509EMSE#PBF requirements.
6.How does Aetrix verify that LT3509EMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3509EMSE#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 LT3509EMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3509EMSE#PBF?
All LT3509EMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3509EMSE#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 LT3509EMSE#PBF part is unused and in its original packaging.
Return procedure for LT3509EMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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