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Analog Devices Inc. LTC3805EMSE#PBF
- Part No.:
- LTC3805EMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3805EMSE#PBF.pdf
- Description:
- IC REG CTRLR FLYBACK 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:204
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Product details
Overview
LTC3805EMSE#PBF from Analog Devices (formerly Linear Technology) is a current-mode DC/DC controller IC designed specifically for flyback, boost, and SEPIC converters, driving an external N-channel MOSFET. It delivers ±1.5% output voltage accuracy, programmable 70–700 kHz switching frequency via a single resistor, and operates with 360 µA quiescent current. It enables high-input-voltage telecom power supplies (e.g., 36–72 VIN to 5 V/2 A nonisolated flyback).
For engineers reviewing the LTC3805EMSE#PBF datasheet, LTC3805EMSE#PBF pinout, LTC3805EMSE#PBF application, or LTC3805EMSE#PBF equivalent, key selection considerations include its adjustable slope compensation, micropower startup (40 µA), RUN pin with precision threshold (1.207 V turn-on), soft-start timing control via SSFLT capacitor, and dual overcurrent protection with automatic restart.
Technical Context
The LTC3805EMSE#PBF implements peak-current-mode control using an internal error amplifier (333 µA/V transconductance), programmable oscillator, and dual-comparator architecture - one for current sensing (ITH-controlled trip), another for overcurrent fault detection (OC pin). Its ITH pin serves as both loop compensation node and PWM duty-cycle command point, enabling fast line/load transient response.
It features two independent undervoltage lockout mechanisms: VCC UVLO (8.4 V turn-on / 4.0 V turn-off) and RUN pin UVLO (1.207 V turn-on / 1.170 V turn-off with 5 µA hysteresis current), allowing flexible input enable sequencing. The internal 9.5 V shunt regulator permits direct high-VIN biasing through a resistor, decoupling controller operation from input voltage limits.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology Support | Flyback, boost, SEPIC - no inherent VIN/VOUT limits; constrained only by external components. |
| Switching Frequency | 70 kHz to 700 kHz, set by single RFS resistor; synchronizable to external clock. |
| Output Voltage Accuracy | ±1.5% over –40°C to +85°C (E-grade), referenced to 0.800 V internal bandgap. |
| Quiescent Current | 360 µA in normal operation; drops to 40 µA during micropower startup mode. |
| VCC Shunt Regulator | 9.5 V clamp (8.9–9.9 V range at 25 mA), enabling direct high-VIN biasing without external LDO. |
| Overcurrent Protection | Dual-stage: ISENSE-based peak current limit (100 mV typical) + OC pin fault detection (100 mV threshold, adjustable). |
| Soft-Start & Fault Timeout | Programmable via SSFLT capacitor; internal defaults: 1.8 ms soft-start, 4.5 ms fault timeout. |
Pinout & Package
The LTC3805EMSE#PBF is housed in a 10-lead plastic MSOP package (3 mm × 3 mm footprint, exposed pad) with θJA = 45°C/W and rated for –40°C to +85°C operation. The exposed pad (Pin 11) is GND and must be soldered to PCB ground for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (1) | Soft-Start/Fault Timeout Control | Capacitor to GND sets ramp time for output voltage rise and post-fault restart delay; also stores timeout state. |
| ITH (2) | Error Amplifier Output / Compensation Node | Voltage-controlled PWM comparator threshold; clamped 0.7–1.9 V; connects to RC network for loop stability. |
| FB (3) | Feedback Input | Monitors resistive divider output; regulates VOUT by servoing to 0.800 V reference. |
| RUN (4) | Enable/Disable Control | Precision UVLO input (1.207 V ON / 1.170 V OFF); hysteresis set by external divider's Thevenin resistance. |
| FS (5) | Frequency Set | Resistor to GND programs oscillator frequency per fOSC = 24×10⁹/(RFS − 1500). |
| SYNC (6) | External Clock Input | Rising-edge-triggered synchronization; supports external clock frequencies matching fOSC range. |
| ISENSE (7) | Current Sense & Slope Compensation | Measures MOSFET source current; injects 10 µA linear ramp for slope compensation (adjustable via external resistor). |
| OC (8) | Overcurrent Fault Detection | Second current sense path; trips shutdown if voltage exceeds programmed threshold (e.g., 100 mV default). |
| VCC (9) | Supply Input | Powered via internal 9.5 V shunt regulator; accepts up to 25 mA sink; requires local 1 µF bypass. |
| GATE (10) | MOSFET Gate Driver Output | Push-pull driver (30 ns rise/fall into 3 nF); swings GND to VCC to drive N-channel MOSFET gate. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable operating frequency | 70–700 kHz via single resistor (RFS), enabling EMI optimization and magnetics sizing flexibility. |
| Programmable slope compensation | 10 µA linear current ramp on ISENSE pin, usable with external resistor to stabilize current-mode control at >50% duty cycle. |
| Dual overcurrent protection | Primary ISENSE-based current limiting + secondary OC pin fault detection with automatic restart after timeout. |
| Low-power startup mode | 40 µA supply current during micropower start-up, reducing bias loss in high-VIN applications before regulation begins. |
| Precision RUN pin control | 1.207 V turn-on threshold with 5 µA hysteresis current, enabling accurate input voltage sequencing and brownout recovery. |
Applications
| Telecom Power Supplies | Automotive 42V Systems |
|---|---|
|
Use Scenario: 36–72 V input telecom rectified bus powering 5 V/2 A isolated or nonisolated flyback converter. IC Role / Device Role: Primary-side current-mode controller managing MOSFET switching, feedback regulation, and fault protection. Use Value: Enables compact, efficient conversion without optocoupler feedback; leverages high-VIN biasing via VCC shunt regulator. |
Use Scenario: 42 V nominal automotive battery system supplying 5 V logic rails in engine control units. IC Role / Device Role: Flyback controller delivering regulated output despite wide input transients (e.g., load dump, cold crank). Use Value: Dual UVLO (VCC + RUN) ensures reliable startup and shutdown across automotive temperature and voltage extremes. |
| Industrial Isolated Equipment | Nonisolated High-Voltage DC/DC |
|
Use Scenario: Medical or test equipment requiring reinforced isolation between primary and secondary sides. IC Role / Device Role: Primary-side controller implementing secondary-side regulation via auxiliary winding feedback. Use Value: Eliminates need for isolated feedback components; maintains ±1.5% output accuracy without optocoupler drift. |
Use Scenario: Point-of-load converter stepping down 48 V intermediate bus to 5 V for FPGA or ASIC core supplies. IC Role / Device Role: Nonisolated flyback controller operating with minimal component count and no transformer isolation barrier. Use Value: Simplifies layout and reduces BOM cost while retaining current-mode stability and fast transient response. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar current-mode flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3748IMSE#PBF | Integrated 10 V gate driver; no external VCC shunt required; supports higher VIN (100 V max); fixed 100 kHz–1 MHz freq range. | Designed for isolated flyback with transformer-coupled feedback; lacks RUN pin hysteresis and micropower startup. | Choose LT3748IMSE#PBF when higher input voltage rating and integrated gate drive simplify design, accepting trade-offs in startup current and enable flexibility. |
| UCC28740DR | Fixed-frequency quasi-resonant controller; lower IQ (250 µA); no programmable slope compensation; TI-specific bias architecture. | Optimized for low-noise AC/DC adapters; lacks SYNC input and dual UVLO; not suited for wide-VIN industrial bias schemes. | Choose UCC28740DR for cost-sensitive consumer adapters where QR operation reduces EMI, but avoid in telecom or automotive due to missing robust enable and bias features. |
Compared with LT3748IMSE#PBF and UCC28740DR, the LTC3805EMSE#PBF uniquely combines micropower startup (40 µA), dual UVLO control (VCC + RUN), and fully programmable slope compensation - making it optimal for ruggedized, wide-input industrial and telecom flyback designs requiring precise sequencing and stability.
Availability
LTC3805EMSE#PBF is available at Aetrix Electronics and suitable for telecom power supplies, 42V automotive systems, and industrial isolated equipment requiring stable component supply, long-term lifecycle support, and guaranteed E-grade temperature performance (–40°C to +85°C).
Supply support for LTC3805EMSE#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 product support, documentation, and manufacturing continuity for all Linear-branded parts including the LTC3805 series.
The LTC3805 belongs to Linear's high-voltage DC/DC controller family, engineered for flyback, boost, and SEPIC topologies in demanding environments where input voltage exceeds standard IC ratings and reliability under thermal stress is critical.
FAQ
What is the operating temperature range for the LTC3805EMSE#PBF?
The LTC3805EMSE#PBF is specified for operation from –40°C to +85°C (E-grade). This range is guaranteed per datasheet testing and applies to all electrical characteristics unless otherwise noted. The MSOP package's exposed pad must be thermally connected to PCB ground to maintain junction temperature within limits under full load.
How does the RUN pin function on the LTC3805EMSE#PBF?
The RUN pin on the LTC3805EMSE#PBF provides precision enable/disable control with a 1.207 V turn-on threshold and 1.170 V turn-off threshold. A 5 µA hysteresis current flows through the external voltage divider, creating programmable hysteresis. This allows clean startup/shutdown sequencing in systems with variable input voltage, such as automotive or telecom rectified buses.
Can the LTC3805EMSE#PBF be powered directly from a high input voltage like 48 V?
Yes - the LTC3805EMSE#PBF integrates a 9.5 V shunt regulator on the VCC pin, allowing direct connection to high-VIN sources (e.g., 48 V) via a current-limiting resistor. The internal regulator sinks up to 25 mA, protecting the IC while enabling simple, low-component-count biasing without external regulators or transformers.
What is the purpose of the SSFLT pin on the LTC3805EMSE#PBF?
The SSFLT pin on the LTC3805EMSE#PBF controls both soft-start timing and fault timeout duration. Connecting a capacitor from SSFLT to GND sets the ramp rate for output voltage rise during startup and determines the delay before automatic restart after an overcurrent fault. Internal defaults are 1.8 ms soft-start and 4.5 ms timeout, both extendable with external capacitance.
Does the LTC3805EMSE#PBF support synchronization to an external clock?
Yes - the LTC3805EMSE#PBF includes a dedicated SYNC pin (Pin 6) that accepts an external clock signal. A rising edge on SYNC triggers the start of each switching cycle (GATE high), enabling precise frequency alignment across multiple converters to reduce beat frequencies and EMI peaks. Supported SYNC frequency matches the internal oscillator range: 70 kHz to 700 kHz.
LTC3805EMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Flyback
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 3.95V ~ 9.5V
- Frequency - Switching:
- 70kHz ~ 700kHz
- Duty Cycle (Max):
- 80%
- Synchronous Rectifier:
- No
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Enable, Soft Start
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LTC3805EMSE#PBF FAQ
1.How can I place an order for LTC3805EMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805EMSE#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 LTC3805EMSE#PBF reliable?
The price and inventory of LTC3805EMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3805EMSE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3805EMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805EMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805EMSE#PBF?
LTC3805EMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805EMSE#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 LTC3805EMSE#PBF?
For technical support, including LTC3805EMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805EMSE#PBF requirements.
6.How does Aetrix verify that LTC3805EMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3805EMSE#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 LTC3805EMSE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3805EMSE#PBF?
All LTC3805EMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805EMSE#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 LTC3805EMSE#PBF part is unused and in its original packaging.
Return procedure for LTC3805EMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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