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Analog Devices Inc. LT3505EMS8E#PBF
- Part No.:
- LT3505EMS8E#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3505EMS8E#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:6,812
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Product details
Overview
LT3505EMS8E#PBF from Analog Devices (formerly Linear Technology) is a current-mode PWM step-down DC/DC converter with 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 enhancement in an 8-lead MSOP package - used in automotive battery regulation and industrial control supplies.
For engineers reviewing the LT3505EMS8E#PBF datasheet, LT3505EMS8E#PBF pinout, LT3505EMS8E#PBF application, or LT3505EMS8E#PBF 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 thermal performance (θJA = 40°C/W).
Technical Context
The LT3505EMS8E#PBF 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 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. Soft-start is implemented via SHDN pin voltage ramping, while undervoltage lockout (3.1–3.6V) prevents operation below minimum input threshold.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V operating; supports unregulated wall transformers, 24V industrial rails, and automotive batteries (40V absolute max). |
| Output Current | Up to 1.2A continuous (at VIN > 8V); limited by thermal design and inductor saturation (max 2.2A peak). |
| Switching Frequency | Resistor-programmable 200kHz–3MHz; enables trade-off between component size (high-freq) and efficiency (low-freq). |
| Feedback Reference | 780mV ±15mV; sets output voltage via external resistor divider; enables precise regulation down to 780mV. |
| Shutdown Current | <2µA; disconnects output and minimizes quiescent drain in battery-powered systems. |
| Power Switch VCE(SAT) | 350mV at 1A; reduces conduction loss and improves efficiency at high load currents. |
| Package Thermal Resistance | θJA = 40°C/W (MSOP-8); requires exposed pad soldered to PCB ground plane with thermal vias for full 1.2A capability. |
Pinout & Package
LT3505EMS8E#PBF is housed in an 8-lead plastic MSOP package (MS8E) with exposed pad (Pin 9) electrically and thermally connected to GND. The exposed pad must be soldered to a PCB ground plane with multiple thermal vias for reliable 1.2A operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BOOST (1) | Bootstrap drive supply | Provides >VIN gate drive to internal bipolar NPN switch; requires external diode + capacitor network. |
| 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 near pin. |
| SHDN (4) | Enable/shutdown control | Logic-high (>2.3V) enables operation; tied to VIN if unused; also controls soft-start ramp. |
| GND (5) | Signal and power ground | Reference for FB, RT, VC; return path for internal regulator; exposed pad must connect here. |
| RT (6) | Frequency programming | Resistor-to-ground sets oscillator frequency; bias voltage ~0.5V; minimize stray capacitance. |
| FB (7) | Feedback input | Regulated to 780mV; connects to resistor divider tap; determines output voltage accuracy and stability. |
| VC (8) | Compensation node | Connects external RC network for loop compensation; clamped at 1.7V and to SHDN during soft-start. |
Key Features
| Feature | Design Value |
|---|---|
| Wide input voltage range | 3.6V–36V operation enables single part to serve automotive (cold crank), industrial (24V), and adapter-powered systems. |
| Integrated 1.4A bipolar switch | Eliminates external MOSFET; low 350mV VCE(SAT) at 1A reduces conduction loss without requiring gate driver. |
| Resistor-programmable frequency | 200kHz–3MHz tuning allows optimization of inductor size, EMI, and efficiency per application constraints. |
| Short-circuit robustness | Cycle-by-cycle current limit + frequency foldback prevent thermal runaway during output faults or start-up into heavy loads. |
| Low shutdown current | <2µA quiescent draw enables long battery life in portable and always-on monitoring equipment. |
Applications
| Automotive Battery Regulation | Industrial Control Supplies |
|---|---|
Use Scenario: Regulating 12V/24V vehicle battery (including load dump transients up to 36V) to 3.3V or 5V for infotainment microcontrollers and CAN transceivers. IC Role / Device Role / Timing Role: Primary buck converter providing isolated, stable, and fault-tolerant power domain for safety-critical ECUs. Use Value: Withstands 40V abs max input and includes frequency foldback to maintain safe die temperature during high-voltage transients. | Use Scenario: Powering PLC I/O modules, sensor signal conditioners, and fieldbus interface ICs from noisy 24V DC industrial rails. IC Role / Device Role / Timing Role: Point-of-load regulator delivering clean, regulated 3.3V/5V with high PSRR and transient response for analog front-ends. Use Value: 3.6V–36V input range accommodates brownouts and surges; soft-start prevents inrush into capacitive bus loads. |
| Wall Transformer Regulation | Battery-Powered Equipment |
Use Scenario: Converting unregulated 9–24V AC/DC wall adapter outputs to stable 3.3V for embedded gateways and Wi-Fi modules. IC Role / Device Role / Timing Role: Efficient, compact DC/DC stage replacing linear regulators to reduce heat and extend adapter lifetime. Use Value: Up to 90% efficiency at 1A load minimizes thermal stress in enclosed plastic enclosures; tiny DFN/MSOP footprint saves board space. | Use Scenario: Supplying 3.3V to portable medical monitors, handheld test instruments, or IoT edge nodes powered by Li-ion or alkaline batteries. IC Role / Device Role / Timing Role: Main system regulator managing battery discharge profile and enabling ultra-low-power sleep modes. Use Value: <2µA shutdown current preserves battery charge during extended standby; adjustable VOUT supports dynamic voltage scaling. |
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#PBF | Higher efficiency (MOSFET-based), lower quiescent current (25µA), but no BOOST pin; requires external high-side MOSFET driver. | Preferred for low-IQ battery apps where 2µA shutdown is not required; unsuitable for legacy bipolar-switch designs needing BOOST bootstrap. | Select LTC3605EMS8E#PBF only when redesigning for MOSFET architecture and higher light-load efficiency is critical. |
| LM5164QPWPRQ1 | Automotive-grade (AEC-Q100), wider temp range (–40°C to 150°C), integrated MOSFET, but fixed 400kHz/2.1MHz options (no resistor programming). | Required for ASIL-B automotive systems; lacks frequency flexibility for EMI-sensitive layouts; higher BOM cost. | Choose LM5164QPWPRQ1 only when AEC-Q100 qualification and extended junction temperature are mandatory. |
Compared with LTC3605EMS8E#PBF and LM5164QPWPRQ1, the LT3505EMS8E#PBF uniquely retains bipolar switch architecture with BOOST-driven saturation, enabling lower VCE(SAT) at high current without gate driver complexity - ideal for cost-sensitive, thermally constrained industrial and automotive non-AEC designs.
Availability
LT3505EMS8E#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial control supplies, and wall transformer regulation requiring stable component supply, long-lifecycle support, and consistent parametric performance across temperature.
Supply support for LT3505EMS8E#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 the LT® product family, including reliability testing, wafer fabrication, and package assembly.
The LT3505 belongs to Linear's high-voltage monolithic buck regulator product line, designed specifically for rugged, wide-input industrial and automotive power conversion where simplicity, fault tolerance, and thermal robustness outweigh ultra-low quiescent current requirements.
FAQ
What is the maximum input voltage rating for the LT3505EMS8E#PBF?
The LT3505EMS8E#PBF has an absolute maximum input voltage rating of 40V on the VIN pin. Its recommended operating range is 3.6V to 36V. Exceeding 36V continuously may trigger pulse-skipping mode above VIN(PS), though brief transients up to 40V are tolerated if output remains regulated and inductor does not saturate. Always observe the 40V absolute maximum to avoid permanent damage.
Does the LT3505EMS8E#PBF require an external catch diode?
Yes, the LT3505EMS8E#PBF requires an external Schottky catch diode (e.g., MBRM140) connected from SW to GND. Unlike synchronous buck controllers, it uses a bipolar NPN switch and cannot integrate a low-loss synchronous rectifier. The diode must withstand the full input voltage (≥40V reverse rating) and handle ≥1.2A average forward current.
What is the function of the BOOST pin on the LT3505EMS8E#PBF?
The BOOST pin on the LT3505EMS8E#PBF provides a bootstrapped voltage higher than VIN to fully saturate the internal bipolar NPN power switch. It must be connected to SW through a capacitor and to VIN through a diode. Without proper BOOST network implementation, the switch operates in linear region, causing excessive power dissipation and potential thermal failure.
Can the LT3505EMS8E#PBF operate in discontinuous conduction mode (DCM)?
Yes, the LT3505EMS8E#PBF naturally operates in DCM at light loads or with small inductors. Its current-mode architecture remains stable in DCM, and graphs in the datasheet show maximum load vs. input voltage for various inductor values (e.g., 2.2µH at 2.2MHz). DCM reduces light-load efficiency but does not compromise regulation or reliability.
How is soft-start implemented on the LT3505EMS8E#PBF?
Soft-start on the LT3505EMS8E#PBF is implemented by ramping the SHDN pin voltage using an external RC network (e.g., 100kΩ + 1nF). As SHDN rises from 0V to >2.3V, the internal VC clamp tracks SHDN, gradually increasing the error amplifier output and limiting inrush current. This eliminates input surge and ensures controlled output voltage rise without external circuitry.
LT3505EMS8E#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (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:
- 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#PBF FAQ
1.How can I place an order for LT3505EMS8E#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3505EMS8E#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 LT3505EMS8E#PBF reliable?
The price and inventory of LT3505EMS8E#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3505EMS8E#PBF is usually 5 days.
3.What payment methods are accepted for LT3505EMS8E#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3505EMS8E#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3505EMS8E#PBF?
LT3505EMS8E#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3505EMS8E#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 LT3505EMS8E#PBF?
For technical support, including LT3505EMS8E#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3505EMS8E#PBF requirements.
6.How does Aetrix verify that LT3505EMS8E#PBF is sourced from the original manufacturer or authorized distributors?
All LT3505EMS8E#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 LT3505EMS8E#PBF meets industry standards.
7.What is the process for return or replacement of LT3505EMS8E#PBF?
All LT3505EMS8E#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3505EMS8E#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 LT3505EMS8E#PBF part is unused and in its original packaging.
Return procedure for LT3505EMS8E#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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