LTC3805-5

PRODUCTION

Adjustable Frequency Current Mode Flyback/Boost/SEPIC DC/DC Controller

Data Sheet Product Selection Table
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Overview

  • VIN and VOUT Limited Only by External Components
  • 4.5V Undervoltage Lockout Threshold
  • Adjustable Slope Compensation
  • Adjustable Overcurrent Protection with Automatic Restart
  • Adjustable Operating Frequency (70kHz to 700kHz) With One External Resistor
  • Synchronizable to an External Clock
  • ±1.5% Reference Accuracy
  • Only 100mV Current Sense Voltage Drop
  • RUN Pin with Precision Threshold and Adjustable Hysteresis
  • Programmable Soft-Start with One External Capacitor
  • Low Quiescent Current: 360μA
  • Small 10-Lead MSOP and 3mm × 3mm DFN

The LTC3805-5 is a current mode DC/DC controller designed to drive an N-channel MOSFET in flyback, boost and SEPIC converter applications. Operating frequency and slope compensation can be programmed by external resistors. Programmable overcurrent sensing protects the converter from overload and short-circuit conditions. Soft-start can be programmed using an external capacitor and the soft-start capacitor also programs an automatic restart feature.

The LTC3805-5 provides ±1.5% output voltage accuracy and consumes only 360μA of quiescent current during normal operation and only 40μA during micropower startup. Using a 9.5V internal shunt regulator, the LTC3805-5 can be powered from a high VIN through a resistor or it can be powered directly from a low impedance DC voltage from 4.7V to 8.8V.

The LTC3805-5 is available in the 10-lead MSOP package and the 3mm × 3mm DFN package.


 Turn On Voltage
LTC3805 8.4V
LTC3805-5 4.5V

Applications

  • Automotive Power Supplies
  • Telecom Power Supplies
  • Isolated Electronic Equipment
  • Auxiliary/Housekeeping Power Supplies
  • Power over Ethernet
LTC3805-5
Adjustable Frequency Current Mode Flyback/Boost/SEPIC DC/DC Controller
5V to 12V/1A Boost Converter Efficiency and Power Loss vs Load Current Product Package 1 Product Package 2
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 2

Design Note 2

Technical Articles 1

Data Sheet

This is the most up-to-date revision of the Data Sheet.

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Software Resources

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Hardware Ecosystem

Parts Product Life Cycle Description
Oscillators 2
LTC6908
Resistor Set SOT-23 Oscillator with Spread Spectrum Modulation
LTC6909
PRODUCTION 1 to 8 Output, Multiphase Silicon Oscillator with Spread Spectrum Modulation
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Tools & Simulations

LTspice 2

Models for the following parts are available in LTspice:

  • LTC3805
  • LTC3805-5
LTspice

LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.

Evaluation Kits

eval board
schematic 1
DC1576A

LTC3805IMSE-5 Demo Board | SEPIC, 5V ≤ VIN ≤ 30V, VOUT = 12V @ 3A

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Product Details

Demonstration circuit 1576 is high efficiency non-isolated SEPIC (Single Ended Primary Inductor Converter) converter featuring the LTC3805-5 switching controller. The DC1576 converts a 5V to 30V input to 12V at 3A of output current. The DC1576 can be easily modified to generate output voltages in the range from 0.8V to 48V.

eval board
schematic 2
DC1311A-B

LTC3805-5 Isolated Demo Board | Flyback Controller, 18V ≤ VIN ≤ 72V, VOUT = 3.3V @ 3A

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Product Details

Demonstration circuit 1311 is a Telecom isolated DC/DC converter featuring the LTC3805/-5 constant frequency current mode flyback controller. The DC1311 converts an 18V to 72V input voltage to an isolated 3A of output current at 3.3V. The 300kHz constant frequency operation is maintained down to very light load to reduce low frequency noise generated over a wide range of load current. The converter provides high output voltage accuracy (typically ±2%) over wide load range with no minimum load requirement.

The DC1311 also provides non-isolated design by removing opto coupler and LTC4430 circuit. The demonstration circuit can be easily modified to generate different output voltages up to 15V.

DC1576A
LTC3805IMSE-5 Demo Board | SEPIC, 5V ≤ VIN ≤ 30V, VOUT = 12V @ 3A
DC1576A - Schematic
DC1311A-B
LTC3805-5 Isolated Demo Board | Flyback Controller, 18V ≤ VIN ≤ 72V, VOUT = 3.3V @ 3A
DC1311A-A - Schematic

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