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Analog Devices Inc. LTC3805EDD#TRPBF
- Part No.:
- LTC3805EDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LTC3805EDD#TRPBF.pdf
- Description:
- IC REG CTRLR FLYBACK 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,500
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Product details
Overview
LTC3805EDD#TRPBF from Analog Devices (formerly Linear Technology) is a current-mode DC/DC controller IC designed to drive an external N-channel MOSFET in nonisolated flyback, boost, and SEPIC converters. It supports input/output voltage ranges limited only by external components, offers adjustable switching frequency from 70kHz to 700kHz via a single resistor, provides ±1.5% reference accuracy, and delivers 360µA quiescent current in normal operation - enabling high-efficiency telecom and automotive power supplies.
For engineers reviewing the LTC3805EDD#TRPBF datasheet, LTC3805EDD#TRPBF pinout, LTC3805EDD#TRPBF application, or LTC3805EDD#TRPBF equivalent, key selection considerations include programmable slope compensation, adjustable overcurrent protection with automatic restart, RUN pin with precision threshold and hysteresis, soft-start timing control via external capacitor, and compatibility with high-voltage bias schemes using the internal 9.5V shunt regulator.
Technical Context
The LTC3805EDD#TRPBF implements peak current-mode control with an integrated error amplifier, programmable oscillator, slope compensation current ramp (10µA), and dual-threshold RUN pin with 5µA hysteresis current. Its ITH pin serves as both compensation node and current comparator threshold setter, enabling stable closed-loop regulation against line and load transients.
It features dual shutdown mechanisms - VCC undervoltage lockout (turn-on at 8.4V, turn-off at 4.0V) and precision RUN pin control (1.207V turn-on, 1.170V turn-off) - plus fault handling via SSFLT pin with internal 1.8ms soft-start and 4.5ms timeout, extendable with external capacitor. The GATE driver delivers fast 30ns rise/fall times into 3000pF loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology Support | Flyback, boost, SEPIC - no internal limits on VIN/VOUT; determined solely by external component ratings. |
| Switching Frequency | 70kHz to 700kHz, set by single resistor on FS pin; synchronizable to external clock via SYNC pin. |
| Reference Accuracy | ±1.5% over –40°C to 85°C; enables tight output voltage regulation in telecom and automotive supplies. |
| Quiescent Current | 360µA during normal operation; drops to 40µA in micropower startup mode for low-power biasing. |
| VCC Shunt Regulator | 9.5V clamp (8.9–9.9V range at 25mA); allows direct high-VIN biasing without external LDO or transformer winding. |
| Overcurrent Protection | Adjustable trip threshold (85–115mV) via OC pin resistor; includes automatic restart after fault timeout. |
| Soft-Start Control | Programmable via capacitor on SSFLT pin; internal default is 1.8ms; also defines fault recovery timing. |
Pinout & Package
Package: 10-lead (3mm × 3mm) plastic DFN with exposed pad (Pin 11 = GND). Thermal resistance θJA = 45°C/W; exposed pad must be soldered to PCB ground for electrical and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (1) | Soft-Start / Fault Timeout | Capacitor-to-GND sets soft-start ramp rate and fault recovery delay; internal timers are minimums only. |
| ITH (2) | Error Amplifier Output / Compensation Node | Voltage (0.7–1.9V clamped) sets current comparator threshold; RC network here stabilizes loop dynamics. |
| FB (3) | Feedback Input | Receives resistor-divider voltage from output; regulates to 0.800V nominal reference (±1.5%). |
| RUN (4) | Enable Control with Hysteresis | External divider sets precise start/stop thresholds (1.207V/1.170V); 5µA hysteresis current adds stability. |
| FS (5) | Frequency Set | Resistor-to-GND programs oscillator frequency per fOSC = 24×10⁹/(RFS − 1500). |
| SYNC (6) | External Clock Input | Rising edge triggers GATE high; supports synchronization across multiple controllers or noise-sensitive systems. |
| ISENSE (7) | Current Sense + Slope Compensation | Monitors MOSFET source current; injects 10µA linear ramp for duty-cycle-dependent slope compensation. |
| OC (8) | Overcurrent Detection | Second current sense path; trips if voltage exceeds programmed threshold (e.g., 100mV), initiating fault shutdown. |
| VCC (9) | Supply Input | Internally clamped to ~9.5V; accepts high-VIN via resistor or low-impedance 9V-or-less source. |
| GATE (10) | MOSFET Driver Output | Drives N-channel MOSFET gate from GND to VCC; 30ns rise/fall into 3000pF load ensures fast switching. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable Frequency Range | 70kHz–700kHz via single resistor - enables EMI optimization and magnetics size reduction without changing IC. |
| Programmable Slope Compensation | 10µA linear current ramp on ISENSE pin - prevents subharmonic oscillation in >50% duty-cycle flyback designs. |
| Two-Stage Enable Control | VCC UVLO (8.4V/4.0V) + RUN pin (1.207V/1.170V) - supports robust power sequencing and brownout immunity. |
| Integrated Fault Management | SSFLT pin controls both soft-start ramp and fault timeout - eliminates need for separate timing ICs or discrete logic. |
| High-VIN Bias Flexibility | Internal 9.5V shunt regulator accepts input up to 72V+ via resistor - simplifies auxiliary supply design in telecom rectifiers. |
Applications
| Telecom Power Supplies | Automotive 42V Systems |
|---|---|
|
Use Scenario: 36V–72V input telecom rectifier powering 5V/2A base station subsystems. IC Role / Device Role / Timing Role: Flyback controller managing primary-side switching, feedback regulation, and fault recovery. Use Value: Adjustable frequency avoids AM band interference; ±1.5% reference ensures stable 5V rail under wide line/load variation. |
Use Scenario: Nonisolated flyback converter in 42V automotive ECU supplying 5V microcontroller rail. IC Role / Device Role / Timing Role: Primary-side controller with RUN pin enabling ignition-synchronized enable/disable and cold-crank tolerance. Use Value: Micropower 40µA startup allows reliable boot from weak battery; VCC shunt regulator tolerates 60V load-dump transients. |
| Industrial Isolated Equipment | High-Voltage DC Distribution |
|
Use Scenario: 24V–48V input isolated flyback powering analog sensor front-ends in factory automation. IC Role / Device Role / Timing Role: Current-mode controller providing fast transient response to step-load changes on isolated secondary. Use Value: ITH-based loop compensation enables <100µs load-step recovery; programmable OC threshold protects against shorted secondary windings. |
Use Scenario: 72V DC distribution bus converter delivering 12V/3A to downstream POL modules. IC Role / Device Role / Timing Role: High-efficiency flyback controller operating at 300kHz to minimize transformer size and EMI filter footprint. Use Value: Synchronizable SYNC input allows phase alignment with other converters to reduce input ripple current and bulk capacitor stress. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3748EMSE#TRPBF | Integrated 100V MOSFET driver; no external gate driver needed; higher VCC max rating (100V). | Designed for isolated flyback with transformer feedback; lacks SSFLT-based fault timeout. | Choose LT3748EMSE#TRPBF when transformer-coupled feedback is preferred and higher integration reduces BOM count. |
| UCC28740DR | Fixed 65kHz frequency; no FS/SYNC pins; lower quiescent current (250µA); no programmable slope compensation. | Optimized for cost-sensitive AC/DC adapters; lacks RUN pin hysteresis and VCC shunt regulator. | Choose UCC28740DR for low-cost, fixed-frequency offline flyback where bias flexibility and precision enable control are not required. |
Compared with LT3748EMSE#TRPBF and UCC28740DR, the LTC3805EDD#TRPBF uniquely combines programmable frequency, dual-stage enable control, and SSFLT-based unified soft-start/fault-timing - making it optimal for high-reliability, high-input-voltage flyback designs requiring field-serviceable fault recovery and EMI tuning.
Availability
LTC3805EDD#TRPBF is available at Aetrix Electronics and suitable for telecom rectifiers, 42V automotive power modules, industrial isolated sensors, and high-voltage DC distribution systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LTC3805EDD#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-performance analog and power management product lines with rigorous reliability testing and automotive-grade qualification.
The LTC3805EDD#TRPBF belongs to Linear's legacy high-voltage DC/DC controller family, engineered specifically for nonisolated and isolated flyback, boost, and SEPIC topologies in harsh environments like telecom infrastructure and automotive electronics.
FAQ
What is the operating temperature range for the LTC3805EDD#TRPBF?
The LTC3805EDD#TRPBF is rated for –40°C to +85°C junction temperature. This E-grade version uses the 10-lead 3mm × 3mm DFN package with exposed pad thermally connected to PCB ground. Its absolute maximum junction temperature is 125°C, and thermal derating applies above 125°C per manufacturer guidelines. The part marking "EDD" explicitly denotes this temperature grade.
How does the LTC3805EDD#TRPBF achieve programmable slope compensation?
The LTC3805EDD#TRPBF achieves programmable slope compensation by injecting a 10µA linear current ramp from the ISENSE pin during each switching cycle. When routed through an external resistor to ground, this current develops a voltage ramp that counteracts duty-cycle-dependent instability in flyback converters. The ramp starts at zero at 6% duty cycle and peaks at 80%, ensuring stable operation even at high duty cycles without requiring additional op-amps or timing circuits.
Can the LTC3805EDD#TRPBF be powered directly from a 48V input rail?
Yes, the LTC3805EDD#TRPBF can be powered directly from a 48V input rail using a series resistor into the VCC pin. Its internal 9.5V shunt regulator safely clamps VCC and sinks up to 25mA, allowing robust biasing without external regulators. For example, a 1.5kΩ resistor from 48V yields ~26mA - within spec - and drops ~38.5V, dissipating ~1W. Layout must ensure low-inductance VCC bypassing with ≥1µF ceramic capacitor adjacent to the pin.
What is the function of the SSFLT pin on the LTC3805EDD#TRPBF?
The SSFLT pin on the LTC3805EDD#TRPBF serves a dual function: it controls both soft-start timing and fault timeout recovery. During startup, an external capacitor charges at 6µA, delaying full regulation until SSFLT reaches ~2.25V. After an overcurrent fault, the same capacitor discharges at 2µA from ~4.75V to ~0.7V, initiating automatic restart. Leaving SSFLT open defaults to internal 1.8ms soft-start and 4.5ms timeout - eliminating need for external timing circuitry.
Does the LTC3805EDD#TRPBF support synchronization with other controllers?
Yes, the LTC3805EDD#TRPBF supports synchronization via its dedicated SYNC pin (Pin 6). A rising edge on this pin forces the oscillator to begin a new switching cycle - i.e., drives GATE high - allowing precise phase alignment across multiple converters. It accepts external clock frequencies from 70kHz to 700kHz, matching its own programmable range, and requires minimum 2.9V amplitude. This capability reduces input ripple current and EMI in multi-rail power systems.
LTC3805EDD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN 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 ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LTC3805EDD#TRPBF FAQ
1.How can I place an order for LTC3805EDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805EDD#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 LTC3805EDD#TRPBF reliable?
The price and inventory of LTC3805EDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3805EDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3805EDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805EDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805EDD#TRPBF?
LTC3805EDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805EDD#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 LTC3805EDD#TRPBF?
For technical support, including LTC3805EDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805EDD#TRPBF requirements.
6.How does Aetrix verify that LTC3805EDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3805EDD#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 LTC3805EDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3805EDD#TRPBF?
All LTC3805EDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805EDD#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 LTC3805EDD#TRPBF part is unused and in its original packaging.
Return procedure for LTC3805EDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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