Datasheet LT8645S-2 (Analog Devices) - 7

LT8645S-2
TYPICAL PERFORMANCE CHARACTERISTICS Minimum On-Time Switching Frequency Burst Frequency
50 740 1200 BURST MODE OPERATION RT = 60.4k PULSE–SKIPPING MODE 730 1000 45 720 800 40 710 700 600 35 690 400 MINIMUM ON-TIME (ns) 680 30 I SWITCHING FREQUENCY (kHz) SWITCHING FREQUENCY (kHz) FRONT PAGE APPLICATION LOAD = 3A 200 V 670 V OUT = 0.97V IN = 12V f V SW = 2.2MHz OUT = 5V 25 660 0 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 150 0 100 200 300 400 500 600 TEMPERATURE (°C) TEMPERATURE (°C) LOAD CURRENT (mA) 8645S-2 G19 8645S-2 G20 8645S-2 G21
Minimum Load to Full Frequency (Pulse-Skipping Mode) Soft-Start Tracking Soft-Start Current
400 1.2 2.2 FRONT PAGE APPLICATION VSS = 0.5V 350 VOUT = 5V 2.1 fSW = 1MHz 1.0 300 VSYNC = Float 2.0 0.8 250 1.9 200 0.6 1.8 150 FB VOLTAGE (V) 1.7 0.4 LOAD CURRENT (mA) SS PIN CURRENT (µA) 100 1.6 0.2 50 1.5 0 0 1.4 5 15 25 35 45 55 65 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 –50 –25 0 25 50 75 100 125 150 INPUT VOLTAGE (V) TR/SS VOLTAGE (V) TEMPERATURE (°C) 8645S-2 G22 8645S-2 G24 8645S-2 G23
RT Programmed Switching PG High Thresholds PG High Thresholds PG Low Thresholds Frequency
10.0 –6.0 250 9.5 225 (%) –6.5 (%) REF REF 200 9.0 –7.0 175 8.5 –7.5 FB RISING 150 FB RISING 8.0 –8.0 125 7.5 –8.5 FB FALLING 100 FB FALLING 75 7.0 –9.0 RT PIN RESISTOR (kΩ) 50 6.5 –9.5 PG THRESHOLD OFFSET FROM V PG THRESHOLD OFFSET FROM V 25 6.0 –10.0 0 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 0.2 0.6 1 1.4 1.8 2.2 TEMPERATURE (°C) TEMPERATURE (°C) SWITCHING FREQUENCY (MHz) 8645S-2 G25 8645S-2 G26 8645S-2 G27 Rev. A For more information www.analog.com 7 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Applications Related Parts