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Analog Devices Inc. LTC3805IDD#TRPBF
- Part No.:
- LTC3805IDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LTC3805IDD#TRPBF.pdf
- Description:
- IC REG CTRLR FLYBACK 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,569
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Product details
Overview
LTC3805IDD#TRPBF from Analog Devices (formerly Linear Technology) is a current mode DC/DC controller IC 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 one resistor, and operates across –40°C to +125°C. Used in telecom power supplies converting 36–72 VIN to 5 V/2 A nonisolated flyback outputs.
For engineers reviewing the LTC3805IDD#TRPBF datasheet, LTC3805IDD#TRPBF pinout, LTC3805IDD#TRPBF application, or LTC3805IDD#TRPBF equivalent, key selection considerations include its adjustable slope compensation, micropower startup (40 µA), RUN pin with precision threshold and hysteresis, soft-start programmability, and dual overcurrent protection with automatic restart.
Technical Context
The LTC3805IDD#TRPBF 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 ISENSE pin injects a 10 µA linear ramp for slope compensation, synchronized to duty cycle (6–80%).
It features two independent undervoltage lockout mechanisms: VCC UVLO (turn-on at 8.4 V, turn-off at 4.0 V) and RUN pin UVLO (1.207 V on, 1.170 V off, with 5 µA hysteresis current). The SSFLT pin supports both soft-start timing and fault timeout via a single external capacitor, enabling controlled ramp-up and automatic recovery after OC-triggered shutdown.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology Support | Flyback, boost, SEPIC - no internal power switch; requires external N-MOSFET. |
| Switching Frequency | 70–700 kHz, set by single RFS resistor; synchronizable to external clock. |
| Output Voltage Accuracy | ±1.5% over –40°C to +125°C, referenced to 0.800 V FB threshold. |
| Quiescent Current | 360 µA normal operation; 40 µA micropower startup - enables high-efficiency light-load operation. |
| VCC Supply Range | Internally clamped to 9.5 V (±0.25 V) via shunt regulator; accepts up to 25 mA sink current. |
| Overcurrent Protection | Dual-stage: ISENSE-based peak current limit (100 mV typ) + OC pin fault detection (100 mV typ) with automatic restart. |
| Soft-Start & Fault Timeout | Programmable via SSFLT capacitor; internal times are 1.8 ms (soft-start) and 4.5 ms (fault timeout). |
Pinout & Package
Package: 10-lead (3 mm × 3 mm) 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 Control | Capacitor to GND sets soft-start ramp time and post-fault restart delay; internal 6 µA charge / 2 µA discharge currents. |
| ITH (2) | Error Amplifier Output / Compensation Node | Voltage (0.7–1.9 V range) sets peak current comparator threshold; connects to RC network for loop stability. |
| FB (3) | Feedback Input | Compares divided output voltage against 0.800 V reference; regulates output with ±1.5% accuracy. |
| RUN (4) | Enable/Shutdown Control | Resistor divider from VIN sets precise enable threshold (1.207 V) and hysteresis (5 µA current source). |
| FS (5) | Frequency Set | Resistor to GND programs oscillator frequency per fOSC = 24×10⁹/(RFS − 1500) Hz. |
| 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 via external resistor; injects 10 µA linear ramp for duty-cycle-dependent slope compensation. |
| OC (8) | Overcurrent Fault Detection | Second current sense input; trips shutdown if voltage exceeds 100 mV - independent of ITH control loop. |
| VCC (9) | Supply Input | Internally regulated to ~9.5 V; accepts high-VIN bias via resistor or direct low-impedance ≤9 V supply. |
| GATE (10) | MOSFET Gate Driver | 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 Slope Compensation | 10 µA linear current ramp from ISENSE pin enables stable operation at >50% duty cycle without external op-amp. |
| Programmable Overcurrent Protection | OC pin allows independent adjustment of fault threshold (via external resistor) without affecting main current limit. |
| Synchronizable Oscillator | SYNC pin accepts external clock (70–700 kHz) to eliminate beat frequencies in multi-rail or EMI-critical systems. |
| Precision RUN Pin Threshold | 1.207 V turn-on with 30 mV hysteresis (via 5 µA current) enables clean, jitter-free start-up sequencing in automotive/telecom rails. |
| Low-IQ Micropower Startup | 40 µA supply current during startup allows reliable operation from high-impedance bias sources like resistor-fed VIN. |
Applications
| Telecom Power Supplies | Automotive 42V Systems |
|---|---|
Use Scenario: 36–72 V input telecom rectifier powering 5 V/2 A base station subsystems with strict efficiency and reliability requirements. IC Role / Device Role: Primary-side flyback controller managing MOSFET switching, output regulation, and fault recovery without optocoupler feedback. Use Value: Adjustable frequency avoids AM band interference; ±1.5% accuracy ensures stable logic rail delivery under wide line/load variation. | Use Scenario: 42 V battery-powered infotainment module requiring isolated 5 V/1.5 A supply with cold-crank tolerance down to 6 VIN. IC Role / Device Role: Boost-mode controller operating from low VIN, delivering regulated output while maintaining UVLO hysteresis for robust start-stop cycling. Use Value: RUN pin hysteresis prevents chattering during battery sag; micropower startup enables reliable boot from weak auxiliary sources. |
| Industrial Isolated Equipment | Nonisolated Flyback Converters |
Use Scenario: DIN-rail mounted PLC I/O module needing reinforced isolation between 24 V field bus and 3.3 V logic domain. IC Role / Device Role: Secondary-side synchronous rectification controller (with external diode/FET) in isolated flyback topology. Use Value: Dual overcurrent protection (ISENSE + OC) prevents transformer saturation faults; SSFLT capacitor enables controlled restart after short-circuit events. | Use Scenario: Cost-sensitive embedded system using nonisolated flyback to generate 5 V from 24 V industrial bus with minimal BOM count. IC Role / Device Role: Controller for low-component-count, high-efficiency nonisolated flyback with shared primary-secondary winding. Use Value: VCC shunt regulator allows direct bias from 24 V input via single resistor; FS pin simplifies EMI tuning without changing magnetics. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3873EMSE#TRPBF | Fixed 300 kHz frequency; no SYNC or FS pin; lower quiescent current (25 µA startup). | Lacks programmable frequency and synchronization - suitable only for fixed-frequency, low-noise designs. | Select when frequency stability and minimal external components outweigh flexibility needs. |
| UCC28C43DR | BiCMOS process; 1 A gate drive; no integrated slope compensation ramp; different UVLO thresholds (16 V on/10 V off). | Requires external slope compensation network; higher gate drive supports larger MOSFETs but increases layout complexity. | Choose for cost-sensitive, high-volume applications where external compensation is acceptable and higher drive strength is needed. |
Compared with LTC3805IDD#TRPBF, LTC3873EMSE#TRPBF trades programmability for lower IQ and simpler layout, while UCC28C43DR offers stronger gate drive but demands more external circuitry for stability - making LTC3805IDD#TRPBF optimal for flexible, high-accuracy flyback designs requiring dual overcurrent protection and seamless synchronization.
Availability
LTC3805IDD#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, automotive 42V systems, and industrial isolated equipment requiring stable component supply across extended temperature ranges.
Supply support for LTC3805IDD#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, Inc. (including former Linear Technology products) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and power management ICs.
The LTC3805 product line was designed specifically for high-voltage, high-accuracy current mode DC/DC controllers in flyback, boost, and SEPIC topologies - targeting telecom, automotive, and industrial applications demanding robust fault handling and wide input range operation.
FAQ
What is the operating temperature range for the LTC3805IDD#TRPBF?
The LTC3805IDD#TRPBF is rated for –40°C to +125°C junction temperature. This "I-grade" specification is confirmed in the order information table and supported by guaranteed electrical characteristics across that full range, including ±1.5% FB reference accuracy and stable oscillator frequency performance.
How does the LTC3805IDD#TRPBF achieve slope compensation without external components?
The LTC3805IDD#TRPBF achieves slope compensation by injecting a 10 µA linear current ramp from the ISENSE pin during each switching cycle - starting at 6% duty cycle and peaking at 80%. When combined with an external resistor to ground, this current develops a voltage ramp that counteracts subharmonic oscillation, eliminating the need for an external op-amp or timing capacitor in most designs.
Can the LTC3805IDD#TRPBF be powered directly from a 48 V input?
Yes - the LTC3805IDD#TRPBF can be powered directly from a 48 V input using a series resistor to VCC, leveraging its internal 9.5 V shunt regulator (rated for up to 25 mA sink current). This allows safe biasing even when input voltage far exceeds the IC's absolute maximum ratings, as confirmed in the Applications Information section and Absolute Maximum Ratings table.
What is the function of the SSFLT pin on the LTC3805IDD#TRPBF?
The SSFLT pin on the LTC3805IDD#TRPBF serves dual functions: it controls soft-start timing (via 6 µA charging current) and fault timeout duration (via 2 µA discharging current) using a single external capacitor. During startup, it ramps GATE duty cycle until reaching ~2.25 V; after an OC fault, it discharges from ~4.75 V to ~0.7 V before enabling automatic restart.
Does the LTC3805IDD#TRPBF support synchronization to an external clock signal?
Yes - the LTC3805IDD#TRPBF supports synchronization via its SYNC pin (Pin 6), which accepts an external clock signal between 70 kHz and 700 kHz. A rising edge on SYNC forces the GATE pin high, aligning switching edges across multiple controllers or to external noise sources - a feature explicitly documented in the Electrical Characteristics and Applications sections.
LTC3805IDD#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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LTC3805IDD#TRPBF FAQ
1.How can I place an order for LTC3805IDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805IDD#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 LTC3805IDD#TRPBF reliable?
The price and inventory of LTC3805IDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3805IDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3805IDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805IDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805IDD#TRPBF?
LTC3805IDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805IDD#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 LTC3805IDD#TRPBF?
For technical support, including LTC3805IDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805IDD#TRPBF requirements.
6.How does Aetrix verify that LTC3805IDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3805IDD#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 LTC3805IDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3805IDD#TRPBF?
All LTC3805IDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805IDD#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 LTC3805IDD#TRPBF part is unused and in its original packaging.
Return procedure for LTC3805IDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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