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Analog Devices Inc. LT3505EMS8E#TRPBF
- Part No.:
- LT3505EMS8E#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3505EMS8E#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,102
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Product details
Overview
LT3505EMS8E#TRPBF from Analog Devices (formerly Linear Technology) is a current-mode PWM step-down DC/DC converter with an integrated 1.4A bipolar NPN power switch, operating from 3.6V to 36V input and delivering up to 1.2A output at adjustable voltages down to 780mV. It features resistor-programmable switching frequency (200kHz–3MHz), soft-start, <2µA shutdown current, and thermal protection - ideal for automotive battery regulation and industrial control supplies.
For engineers reviewing the LT3505EMS8E#TRPBF datasheet, LT3505EMS8E#TRPBF pinout, LT3505EMS8E#TRPBF application, or LT3505EMS8E#TRPBF equivalent, key selection criteria include input voltage range (3.6–36V), output current capability (1.2A), programmable frequency (200kHz–3MHz), feedback reference (780mV), and MSOP-8 package compatibility with thermal pad grounding.
Technical Context
The LT3505EMS8E#TRPBF implements constant-frequency, current-mode control using an RS flip-flop driven by a resistor-programmed oscillator. Its internal bipolar NPN switch requires BOOST pin bootstrapping for full saturation, enabling low VCE(SAT) (350mV at 1A) and high efficiency across wide input ranges.
Cycle-by-cycle current limiting, frequency foldback during overload, and active VC-node clamping provide robust short-circuit protection. The SHDN pin enables both shutdown (<2µA quiescent) and soft-start via external RC ramping, while RT pin biasing (0.5V typical) sets switching frequency with ±10% tolerance over temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V operating; supports unregulated 24V industrial rails and automotive batteries (40V abs max). |
| Output Current | Up to 1.2A continuous; validated at VIN > 8V, VOUT = 3.3V, fSW = 750kHz per datasheet Figure G05. |
| Switching Frequency | Resistor-programmable 200kHz–3MHz; RT = 75.0kΩ yields 750kHz typical (±75kHz) at TA = 25°C. |
| Feedback Reference | 780mV ±15mV; sets output voltage via external resistor divider (R2 = 10.0kΩ recommended). |
| Shutdown Current | <2µA; enables true output disconnect and ultra-low power management in battery systems. |
| VCE(SAT) | 350mV at 1A; minimizes conduction loss and improves efficiency at high load currents. |
| Operating Temp | –40°C to +85°C (E-grade); specified and guaranteed over full range per datasheet Note 2. |
Pinout & Package
LT3505EMS8E#TRPBF uses the 8-lead plastic MSOP package (MS8E) with exposed thermal pad (Pin 9, GND). The package measures 3mm × 3mm footprint with 0.65mm lead pitch and requires soldering of the exposed pad to PCB ground for thermal and electrical integrity (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BOOST (1) | Bootstrap drive supply | Provides >VIN gate drive to internal bipolar NPN switch; must be connected to SW via external capacitor/diode. |
| SW (2) | Switch node | Connects to inductor, catch diode cathode, and BOOST capacitor; carries high di/dt switching current. |
| VIN (3) | Main power input | Supplies internal regulator and power switch; requires local 1µF ceramic bypass (X7R/X5R) near pin. |
| SHDN (4) | Enable/soft-start control | Logic-high (>2.3V) enables operation; tied to VIN if unused; external RC on this pin implements soft-start ramp. |
| GND (5) | Power and signal reference | Return path for internal circuits and feedback divider; must connect to large PCB ground plane with thermal vias. |
| RT (6) | Frequency programming | Resistor to GND sets oscillator frequency; bias voltage ~0.5V; minimize stray capacitance. |
| FB (7) | Output voltage sense | Regulated to 780mV; connects to resistor divider tap; 55–150nA bias current affects high-R divider accuracy. |
| VC (8) | Compensation node | Connects external RC network to GND for loop stability; clamped to 1.7V max and SHDN voltage during soft-start. |
Key Features
| Feature | Design Value |
|---|---|
| Wide input range support | 3.6V–36V operation enables direct regulation from 24V industrial buses and automotive batteries without pre-regulation. |
| Programmable high-frequency switching | 200kHz–3MHz range allows trade-off between small magnetics (2.2MHz) and peak efficiency (750kHz). |
| Integrated soft-start and shutdown | Single SHDN pin provides <2µA shutdown current and controlled startup via external RC ramp - no extra IC needed. |
| Robust short-circuit protection | Cycle-by-cycle current limit (1.4–2.2A) plus frequency foldback prevents thermal runaway during output faults. |
| Thermally enhanced MSOP package | Exposed pad (Pin 9) soldered to GND delivers θJA = 40°C/W - critical for 1.2A continuous operation in compact layouts. |
Applications
| Automotive Battery Regulation | Industrial Control Supply |
|---|---|
Use Scenario: Regulating 12V/24V vehicle battery to 3.3V or 5V for infotainment microcontrollers and CAN transceivers under cold-crank (6V) and load-dump (36V) conditions. IC Role / Device Role / Timing Role: Primary buck converter providing stable, fault-tolerant power with undervoltage lockout (~3.35V) and 40V absolute max rating. Use Value: Eliminates need for external pre-regulator; withstands automotive transients without derating; soft-start prevents inrush into large capacitive loads. | Use Scenario: Powering PLC I/O modules and sensor interfaces from 24V factory bus where EMI and thermal density are constrained. IC Role / Device Role / Timing Role: High-efficiency, low-noise step-down regulator with programmable 750kHz switching to minimize conducted EMI in shared 24V rail environments. Use Value: Enables use of compact 10µH inductors and 10µF ceramic output caps; <2µA shutdown extends uptime in sleep-mode field devices. |
| Wall Transformer Regulation | Battery-Powered Equipment |
Use Scenario: Converting unregulated 9–24V AC/DC wall adapter outputs to clean 3.3V for embedded networking gear with variable load profiles. IC Role / Device Role / Timing Role: Input-flexible buck controller accepting wide-input, low-cost transformers while maintaining tight output regulation. Use Value: Resistor-programmable frequency avoids AM-band interference; 780mV reference enables precise 3.3V/5V outputs with 1% resistors. | Use Scenario: Powering portable test instruments with Li-ion (8.4V max) or 9V alkaline inputs requiring 3.3V for MCU and ADC subsystems. IC Role / Device Role / Timing Role: Low-quiescent buck regulator with <2µA shutdown and output disconnect for multi-week standby battery life. Use Value: Delivers 1.2A peak current for measurement bursts while drawing only nanoamps in deep sleep - no external load switch required. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3605EMS8E#TRPBF | MOSFET-based synchronous buck; 3.1V–35V input; 1.5A output; 3mm × 3mm DFN only; no BOOST pin required. | Better light-load efficiency (pulse-skipping mode); no external catch diode; higher cost; not pin-compatible. | Select when synchronous rectification and lower BOM count outweigh MSOP-8 layout reuse. |
| LM2678SD-3.3/NOPB | N-channel MOSFET controller; 8V–40V input; fixed 3.3V output; 5A capable; SO-8 package; external MOSFET required. | Higher current capacity but needs external FET and gate driver; larger solution size; no integrated soft-start. | Select for >1.2A loads or when thermal budget allows discrete FET placement away from IC. |
Compared with LTC3605EMS8E#TRPBF, LT3505EMS8E#TRPBF offers bipolar switch ruggedness and BOOST-based gate drive for higher voltage stress tolerance, while LM2678SD-3.3/NOPB provides scalable current handling at the cost of added components and board area - making LT3505EMS8E#TRPBF optimal for space-constrained 1.2A industrial and automotive designs.
Availability
LT3505EMS8E#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial control supplies, and wall transformer regulation requiring stable component supply across extended temperature and input voltage ranges.
Supply support for LT3505EMS8E#TRPBF 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-reliability analog and power management portfolio with rigorous qualification and long-term product support.
The LT3505 series is designed for rugged, wide-input DC/DC conversion in harsh environments - targeting automotive, industrial, and telecom infrastructure where input transients, thermal constraints, and long product lifecycles are critical.
FAQ
What is the maximum input voltage rating for LT3505EMS8E#TRPBF?
The LT3505EMS8E#TRPBF has an absolute maximum input voltage rating of 40V on the VIN pin, with continuous operation specified from 3.6V to 36V. Operation above 36V is limited to transient conditions (e.g., automotive load dump) and must remain below 40V to avoid permanent damage per Absolute Maximum Ratings table.
Does LT3505EMS8E#TRPBF require an external catch diode?
Yes, LT3505EMS8E#TRPBF requires an external Schottky catch diode (e.g., MBRM140) connected from SW to GND. Its internal bipolar NPN switch lacks synchronous rectification, so the diode provides the return path for inductor current during switch-off time.
What is the function of the BOOST pin on LT3505EMS8E#TRPBF?
The BOOST pin on LT3505EMS8E#TRPBF supplies a bootstrapped voltage (>VIN) to fully saturate the internal bipolar NPN power switch. It must be connected to the SW node via a capacitor and external diode to generate ~VIN + 2V, ensuring low VCE(SAT) (350mV at 1A) and high efficiency.
Can LT3505EMS8E#TRPBF operate in pulse-skipping mode?
Yes, LT3505EMS8E#TRPBF enters pulse-skipping mode when input voltage exceeds VIN(PS) - the point where required duty cycle falls below minimum on-time (130ns typical). This occurs above ~33V at 750kHz and causes increased output ripple but does not damage the device if peak inductor current stays ≤2.2A.
What is the thermal pad connection requirement for LT3505EMS8E#TRPBF?
The exposed pad (Pin 9) of LT3505EMS8E#TRPBF must be soldered directly to a PCB ground plane with ≥4 thermal vias (0.3mm diameter) to achieve θJA = 40°C/W. Failure to connect it results in thermal shutdown at ~1.0A load due to junction temperature exceeding 125°C.
LT3505EMS8E#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.6V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.78V
- Voltage - Output (Max):
- 33.84V
- Current - Output:
- 1.2A
- Frequency - Switching:
- 200kHz ~ 3.01MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP-EP
LT3505EMS8E#TRPBF FAQ
1.How can I place an order for LT3505EMS8E#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3505EMS8E#TRPBF 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 LT3505EMS8E#TRPBF reliable?
The price and inventory of LT3505EMS8E#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3505EMS8E#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3505EMS8E#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3505EMS8E#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3505EMS8E#TRPBF?
LT3505EMS8E#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3505EMS8E#TRPBF 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 LT3505EMS8E#TRPBF?
For technical support, including LT3505EMS8E#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3505EMS8E#TRPBF requirements.
6.How does Aetrix verify that LT3505EMS8E#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3505EMS8E#TRPBF 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 LT3505EMS8E#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3505EMS8E#TRPBF?
All LT3505EMS8E#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3505EMS8E#TRPBF, 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 LT3505EMS8E#TRPBF part is unused and in its original packaging.
Return procedure for LT3505EMS8E#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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