Datasheet LT8304, LT8304-1 (Analog Devices) - 8

LT8304/LT8304-1
BLOCK DIAGRAM
D T1 OUT V + IN N:1 VOUT CIN • L1A L1B COUT R • FB V – OUT 3 6 5 VIN RFB SW INTVCC 2 V LDO IN C 1:4 INTVCC M3 M2 START-UP, BOUNDARY REFERENCE, DETECTOR CONTROL 25µA REN1 OSCILLATOR EN/UVLO 1.214V – INTVCC 1 – REN2 – + g S + m 1V A3 R Q DRIVER M1 A1 + 2.5µA PTAT + VOLTAGE M4 A2 RSENSE – GND RREF TC 4, EXPOSED PAD PIN 9 7 8 RTC 8304 BD RREF
OPERATION
The LT8304 is a current mode switching regulator IC extra transformer windings also exhibit deficiencies, as designed specially for the isolated flyback topology. The using an extra winding adds to the transformer’s physical key problem in isolated topologies is how to communicate size and cost, and dynamic response is often mediocre. the output voltage information from the isolated secondary The LT8304 samples the isolated output voltage through side of the transformer to the primary side for regulation. the primary-side flyback pulse waveform. In this manner, Historically, opto-isolators or extra transformer windings neither opto-isolator nor extra transformer winding is re- communicate this information across the isolation bound- quired for regulation. Since the LT8304 operates in either ary. Opto-isolator circuits waste output power, and the boundary conduction mode or discontinuous conduction extra components increase the cost and physical size of mode, the output voltage is always sampled on the SW the power supply. Opto-isolators can also cause system pin when the secondary current is zero. This method im- issues due to limited dynamic response, nonlinearity, unit- proves load regulation without the need of external load to-unit variation and aging over lifetime. Circuits employing compensation components. 8304fa 8 For more information www.linear.com/LT8304 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Typical Application Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Revision History Typical Application Related Parts