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Analog Devices Inc. LTC3805IMSE#TRPBF
- Part No.:
- LTC3805IMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3805IMSE#TRPBF.pdf
- Description:
- IC REG CTRLR FLYBACK 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:6,905
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Product details
Overview
LTC3805IMSE#TRPBF from Analog Devices (formerly Linear Technology) is a current-mode DC/DC controller IC designed specifically for flyback, boost, and SEPIC converters, driving external N-channel MOSFETs in high-input-voltage applications up to 72V. It delivers ±1.5% output voltage accuracy, programmable 70–700kHz switching frequency via a single resistor, and operates with only 360µA quiescent current. Used in telecom power supplies and 42V automotive systems, it supports nonisolated flyback topologies such as 36V–72V input to 5V/2A outputs.
For engineers reviewing the LTC3805IMSE#TRPBF datasheet, LTC3805IMSE#TRPBF pinout, LTC3805IMSE#TRPBF application, or LTC3805IMSE#TRPBF equivalent, key selection considerations include its adjustable slope compensation, micropower startup (40µA), RUN pin with precision hysteresis, soft-start programmability via SSFLT capacitor, and compatibility with high-VIN bias schemes using the internal 9.5V shunt regulator.
Technical Context
The LTC3805IMSE#TRPBF implements peak current-mode control with an integrated error amplifier, programmable oscillator, and dual-function ISENSE pin that provides both current sensing and slope compensation ramp injection (10µA). Its control loop uses the ITH pin as the compensation node, where external RC networks shape transient response for line and load regulation.
It features two independent shutdown mechanisms: VCC undervoltage lockout (turn-on at 8.4V, turn-off at 4.0V) and a precision RUN pin (1.207V turn-on, 1.170V turn-off with 5µA hysteresis current). Fault protection includes overcurrent detection on the OC pin (100mV threshold, adjustable), automatic restart after fault timeout, and duty-cycle limiting (6–95%) to prevent subharmonic oscillation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology Support | Flyback, boost, SEPIC - enables flexible nonisolated/isolated converter design without topology-specific IC replacement. |
| Output Voltage Accuracy | ±1.5% - ensures stable regulation across temperature and line/load variations in telecom and automotive power rails. |
| Quiescent Current | 360µA normal / 40µA micropower startup - minimizes standby loss and enables reliable cold-start from high-impedance bias sources. |
| Switching Frequency Range | 70kHz to 700kHz, set by single RFS - allows EMI optimization and magnetics size trade-offs without changing controller IC. |
| VCC Shunt Regulator | 9.5V clamp, 25mA max sink - permits direct high-VIN biasing (e.g., 36–72V) without external LDO, simplifying supply design. |
| Operating Temperature | –40°C to +125°C - qualified for under-hood automotive and industrial telecom environments requiring extended thermal range. |
| Peak Current Sense Threshold | 100mV typical - sets primary-side current limit; adjustable via external resistor on OC pin for precise overload protection. |
| Soft-Start Time | Programmable via SSFLT capacitor - controls output voltage ramp rate and enables automatic restart after overcurrent faults. |
Pinout & Package
Package: 10-lead plastic MSOP (MSE), 3mm × 3mm footprint, exposed pad (Pin 11) connected to GND for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (1) | Soft-Start/Fault Timeout | Capacitor-to-GND sets soft-start ramp time and post-fault restart delay; internal 6µA charge / 2µA discharge currents. |
| ITH (2) | Error Amplifier Output | Compensation node; voltage (0.7–1.9V) sets current comparator threshold and defines closed-loop dynamics. |
| FB (3) | Feedback Input | Monitors output via resistor divider; regulates to 0.800V reference (±1.5%) for precise output voltage setting. |
| RUN (4) | Enable Control | Resistor-divider input with 1.207V turn-on / 1.170V turn-off thresholds and 5µA hysteresis current for clean start/stop sequencing. |
| FS (5) | Frequency Set | Resistor-to-GND programs oscillator frequency from 70kHz to 700kHz per fOSC = 24×10⁹/(RFS − 1500). |
| SYNC (6) | External Clock Input | Accepts rising-edge-triggered external clock (70–700kHz) for synchronization to system timing or noise reduction. |
| ISENSE (7) | Current Sense & Slope Ramp | Senses MOSFET current via external resistor; injects 10µA linear ramp for slope compensation in continuous conduction mode. |
| OC (8) | Overcurrent Detection | Monitors same current sense resistor as ISENSE; trips at 100mV (adjustable) to initiate fault shutdown and auto-restart. |
| VCC (9) | Supply Input | Powered via internal 9.5V shunt regulator; accepts 9V or less low-impedance DC or high-VIN through series resistor. |
| GATE (10) | MOSFET Driver Output | Drives external N-channel MOSFET gate with 30ns rise/fall times into 3000pF load; swing from GND to VCC. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable slope compensation | 10µA programmable ramp on ISENSE pin enables stable operation at >50% duty cycle in continuous conduction mode. |
| Programmable overcurrent protection | OC pin threshold adjustable with external resistor; supports precise short-circuit response without sacrificing normal load margin. |
| Synchronizable oscillator | SYNC pin accepts external clock (70–700kHz) to eliminate beat frequencies and align switching with system clocks or noise-sensitive bands. |
| Low-quiescent-current micropower startup | 40µA operating current during startup enables reliable initiation from weak bias sources like trickle chargers or high-resistance dividers. |
| Two-stage enable control | Independent VCC UVLO (8.4V/4.0V) and RUN pin (1.207V/1.170V) ensure robust power sequencing and brownout immunity. |
| Integrated soft-start and fault timeout | Single SSFLT capacitor configures both startup ramp and post-fault holdoff - eliminates need for separate timers or logic. |
Applications
| Telecom Power Supply | Automotive 42V System |
|---|---|
|
Use Scenario: 36V–72V input telecom rectifier supplying isolated 5V/2A for base station control circuitry. IC Role / Device Role / Timing Role: Primary-side flyback controller regulating output via optocoupler feedback; manages MOSFET gate drive, slope compensation, and fault recovery. Use Value: ±1.5% reference accuracy and current-mode control ensure tight regulation across wide input range and load transients typical in telecom infrastructure. |
Use Scenario: Nonisolated 42V-to-5V DC/DC converter powering infotainment ECUs in 42V mild-hybrid vehicles. IC Role / Device Role / Timing Role: Boost-mode controller driving N-MOSFET; handles cold-crank (4.5V) to load-dump (60V) transients with robust RUN/VCC enable sequencing. Use Value: Micropower startup (40µA) and wide VCC UVLO hysteresis (4.0V–8.4V) guarantee reliable operation during battery voltage sags and surges. |
| Industrial Isolated Equipment | High-VIN Industrial Sensor Power |
|
Use Scenario: Isolated 24V-to-12V flyback supply for PLC I/O modules requiring reinforced insulation and low EMI. IC Role / Device Role / Timing Role: Flyback controller implementing primary-side regulation with synchronous rectification support; manages transformer reset and leakage spike handling. Use Value: Adjustable frequency (70–700kHz) and SYNC capability allow EMI filtering optimization and deterministic noise placement in dense industrial layouts. |
Use Scenario: 60V input-to-3.3V/500mA point-of-load supply for industrial vision sensors mounted near high-voltage motor drives. IC Role / Device Role / Timing Role: Nonisolated flyback controller using high-VIN bias scheme; leverages internal 9.5V shunt regulator to eliminate external LDO. Use Value: Direct high-VIN biasing reduces component count and improves efficiency vs. cascaded regulators, critical in space-constrained sensor nodes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28C43DR | Fixed 100kHz frequency, no SYNC input, no programmable slope compensation; 1.5% reference accuracy, 2.5mA quiescent current. | Lower integration for cost-sensitive designs; lacks micropower startup and high-VIN bias flexibility of LTC3805IMSE#TRPBF. | Choose UCC28C43DR when fixed frequency and lower BOM cost outweigh need for programmability and ultra-low IQ. |
| MAX17595ATP+T | Wide 4.5V–60V input, integrated 0.5Ω high-side switch, no external MOSFET required; 1.2% reference accuracy, 1.2mA IQ. | Monolithic solution for lower-power flyback (<15W); not suitable for high-VIN (>60V) or high-current discrete MOSFET designs. | Choose MAX17595ATP+T for compact, integrated flyback where input ≤60V and output power <15W; LTC3805IMSE#TRPBF remains preferred for >60V or >2A applications. |
Compared with UCC28C43DR and MAX17595ATP+T, the LTC3805IMSE#TRPBF offers superior programmability (frequency, slope, OC threshold), lowest quiescent current (40µA startup), and unique high-VIN bias capability - making it optimal for demanding telecom, automotive, and industrial flyback designs above 60V or requiring precise fault management.
Availability
LTC3805IMSE#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, 42V automotive systems, and industrial isolated equipment requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3805IMSE#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LTC3805IMSE#TRPBF belongs to Linear's high-voltage DC/DC controller product line, engineered for robust flyback, boost, and SEPIC conversion in harsh environments where input voltage exceeds standard IC ratings - emphasizing programmability, fault resilience, and thermal reliability.
FAQ
What is the maximum input voltage supported by the LTC3805IMSE#TRPBF?
The LTC3805IMSE#TRPBF itself has no intrinsic VIN limit - its pins are isolated from input/output voltages. The practical maximum input is determined by external components: the MOSFET's BVDSS rating, transformer insulation, and output capacitor voltage rating. In published applications, the LTC3805IMSE#TRPBF controls converters with 36V–72V inputs, and can support higher voltages with appropriately rated external parts.
How does the LTC3805IMSE#TRPBF achieve micropower startup at 40µA?
The LTC3805IMSE#TRPBF achieves 40µA micropower startup by entering a low-power state when VRUN < VRUNON or VCC < VTURNON – 100mV. In this mode, internal circuitry is minimized while retaining RUN and VCC monitoring. Once thresholds are met, full operation resumes. This behavior is confirmed in the Electrical Characteristics table (ICC = 40µA under micropower conditions) and enables reliable startup from high-impedance bias sources.
Can the LTC3805IMSE#TRPBF be synchronized to an external clock, and what are the requirements?
Yes, the LTC3805IMSE#TRPBF supports synchronization via its SYNC pin. The external clock must have a frequency between 70kHz and 700kHz - matching the device's programmable oscillator range. A rising edge on SYNC triggers the start of each switching cycle (GATE high), and pulse width is flexible. This feature is documented in the Electrical Characteristics table (fSYNC specification) and Block Diagram, enabling EMI reduction and deterministic timing alignment.
What is the function of the ISENSE pin on the LTC3805IMSE#TRPBF beyond current sensing?
In addition to monitoring MOSFET current via an external sense resistor, the ISENSE pin on the LTC3805IMSE#TRPBF injects a 10µA linear current ramp used for slope compensation. This ramp begins at 6% duty cycle and peaks at 80%, counteracting subharmonic oscillation in continuous conduction mode. This dual functionality is explicitly described in the Pin Functions section and Applications Information, and is critical for stable operation at high duty cycles.
Does the LTC3805IMSE#TRPBF require an external VCC supply, or can it be powered directly from high input voltage?
The LTC3805IMSE#TRPBF can be powered directly from high input voltage (e.g., 36–72V) using its internal 9.5V shunt regulator - no external VCC supply is required. A series resistor from VIN to VCC limits current into the shunt, which sinks up to 25mA. This architecture is detailed in the Absolute Maximum Ratings, Applications Information (Figure 2), and Powering section, enabling simplified biasing in high-VIN applications.
LTC3805IMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LTC3805IMSE#TRPBF FAQ
1.How can I place an order for LTC3805IMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805IMSE#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 LTC3805IMSE#TRPBF reliable?
The price and inventory of LTC3805IMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3805IMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3805IMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805IMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805IMSE#TRPBF?
LTC3805IMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805IMSE#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 LTC3805IMSE#TRPBF?
For technical support, including LTC3805IMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805IMSE#TRPBF requirements.
6.How does Aetrix verify that LTC3805IMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3805IMSE#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 LTC3805IMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3805IMSE#TRPBF?
All LTC3805IMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805IMSE#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 LTC3805IMSE#TRPBF part is unused and in its original packaging.
Return procedure for LTC3805IMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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