Datasheet LTC3806 (Analog Devices)

LTC3806 Synchronous Flyback DC/DC Controller
U FEATURES DESCRIPTIO
■
High Efficiency at Full Load
The LTC®3806 is a current mode synchronous flyback ■
Better Cross Regulation Than Nonsynchronous
controller that drives N-channel power MOSFETs and
Converters (Multiple Outputs)
requires very few external components. It is intended for ■
Soft-Start Minimizes Inrush Current
medium power applications where multiple outputs are ■ Current Mode Control Provides Excellent required. Synchronous rectification provides higher effi- Transient Response ciency and improved output cross regulation than ■ High Maximum Duty Cycle: 89% Typical nonsynchronous converters. ■ ±2% Programmable Undervoltage Lockout Threshold The IC contains all the necessary control circuitry includ- ■ ±1% Internal Voltage Reference ing a 250kHz oscillator, precision undervoltage lockout ■ Micropower Start-Up circuit with hysteresis, gate drivers for primary and syn- ■ Constant Frequency Operation (Never Audible) chronous switches, current mode control circuitry and ■ 3mm × 4mm 12-Pin DFN Package soft-start circuitry.
U
Programmable soft-start reduces inrush currents. This
APPLICATIO S
makes it easier to design compliant Power Over Ethernet ■ 48V Telecom Supplies supplies. ■ 12V/42V Automotive Low start-up current reduces power dissipation in the ■ 24V Industrial start-up resistor and reduces the size of the external start- ■ VoIP Phone up capacitor. ■ Power Over Ethernet The LTC3806 is available in a 12-pin, exposed pad DFN package. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
U TYPICAL APPLICATIO
VOUT1 VIN 3.3V 36V TO 72V V C7 OUT2 3A D1 T1 2.5V 4.7μF • 3A R1 R2 51k 604k LTC3806 RUN SENSE • • I SS R8 TH 100Ω FB G2 V G1 IN M1 M2 M3 C1 C2 INTV GND CC 100μF 1nF R3 R4 C3 C4 R5 C5 C6 26.7k 3.4k 4.7μF 0.47μF 0.056Ω 470μF 470μF 3806 F01 R7 R6 12.4k 21k
Figure 1. Multiple Output Flyback Converter for Telecom
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