Datasheet LT1977 (Analog Devices) - 5

LT1977
W U TYPICAL PERFOR A CE CHARACTERISTICS Soft-Start Current Threshold Switch Peak Current Limit vs FB Voltage Frequency Foldback Percentage
3.5 50 100 TJ = 25°C 45 90 40 80 3.0 35 70 SOFT-START µA) 30 60 DEFEATED 2.5 25 50 20 40 CURRENT ( 15 30 2.0 PEAK SWITCH CURRENT (A) 10 FOLDBACK PERCENTAGE (%) 20 5 10 1.5 0 0 –50 –25 –0 25 50 75 100 125 0 0.2 0.4 0.6 0.8 1.0 1.2 0 0.25 0.5 0.75 1 1.25 TEMPERATURE (°C) FB VOLTAGE (V) FB PIN VOLTAGE (V) 1977 G10 1977 G11 1977 G12
Switch On Voltage (VCESAT) Supply Current vs Input Voltage Minimum Input Voltage
500 150 7.5 VOUT = 3.3V 450 TA = 25°C 7.0 125 400 6.5 350 µA) 100 6.0 5V START 300 5V RUNNING TJ = 125°C 5.5 250 75 5.0 200 TJ = 25°C VOLTAGE (mV) 50 4.5 150 INPUT VOLTAGE (V) 3.3V START SUPPLY CURRENT ( 100 4.0 T 25 J = –50°C 3.3V RUNNING 50 3.5 0 0 3.0 –0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 0 10 20 30 40 50 60 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 LOAD CURRENT (A) INPUT VOLTAGE (V) LOAD CURRENT (A) 1977 G13 1977 F05 1977 G19
Burst Mode Threshold vs Input Voltage Minimum On Time Boost Current vs Switch Current
500 500 45 VOUT = 3.3V 450 L = 10µH 450 40 C 400 OUT = 100µF 400 35 350 350 LOAD CURRENT = 0.5A 30 Burst Mode EXIT 300 300 (INCREASING LOAD) 25 250 250 LOAD CURRENT = 1A 20 200 200 ON TIME (ns) Burst Mode ENTER 15 LOAD CURRENT (mA) 150 (DECREASING LOAD) 150 BOOST CURRENT (mA) 10 100 100 50 50 5 0 0 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 –50 –25 0 25 50 75 100 125 0 0.25 0.5 0.75 1 1.25 1.5 INPUT VOLTAGE (V) TEMPERATURE (°C) SWITCH CURRENT (A) 1977 G20 1977 G21 1977 G22 1977fa 5