Datasheet LT3431 (Analog Devices) - 4

LT3431
W U TYPICAL PERFOR A CE CHARACTERISTICS Switch Peak Current Limit FB Pin Voltage and Current SHDN Pin Bias Current
6 1.234 2.0 250 Tj = 25°C CURRENT REQUIRED TO FORCE SHUTDOWN 1.229 200 (FLOWS OUT OF PIN). AFTER SHUTDOWN, CURRENT DROPS TO A FEW µA 5 1.5 TYPICAL CURRENT ( 1.224 150 µA) VOLTAGE 4 1.219 1.0 100 µA) CURRENT CURRENT ( 1.214 12 GUARANTEED MINIMUM FEEDBACK VOLTAGE (V) AT 2.38V STANDBY THRESHOLD 0.5 SWITCH PEAK CURRENT (A) 3 (CURRENT FLOWS OUT OF PIN) 1.209 6 2 1.204 0 0 0 20 40 60 80 100 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 DUTY CYCLE (%) JUNCTION TEMPERATURE (°C) JUNCTION TEMPERATURE (°C) 3431 G01 3431 G02 3431 G03
Lockout and Shutdown Thresholds Shutdown Supply Current Shutdown Supply Current
2.4 40 300 VSHDN = 0V LOCKOUT 35 2.0 250 µA) µA) V 30 IN = 60V 1.6 200 25 VIN = 15V 1.2 20 150 15 0.8 100 SHDN PIN VOLTAGE (V) 10 START-UP INPUT SUPPLY CURRENT ( INPUT SUPPLY CURRENT ( 0.4 50 5 SHUTDOWN 0 0 0 –50 –25 0 25 50 75 100 125 0 10 20 30 40 50 60 0 0.1 0.2 0.3 0.4 0.5 JUNCTION TEMPERATURE (°C) INPUT VOLTAGE (V) SHUTDOWN VOLTAGE (V) 3431 G04 3431 G05 3431 G06
Error Amplifier Transconductance Error Amplifier Transconductance Frequency Foldback
2500 3000 200 625 SWITCHING PHASE FREQUENCY 2000 2500 150 500 µmho) GAIN PHASE (DEG) µA) 1500 2000 100 375 µMho) VC R C 1000 1500 OUT OUT GAIN ( 50 V ( 250 FB 2 • 10–3 ) 200k 12pF OR FB CURRENT ( TRANSCONDUCTANCE ( 500 1000 ERROR AMPLIFIER EQUIVALENT CIRCUIT 0 SWITICHING FREQUENCY (kHz) 125 FB PIN RLOAD = 50Ω CURRENT 0 500 –50 0 –50 –25 0 25 50 75 100 125 100 1k 10k 100k 1M 10M 0 0.2 0.4 0.6 0.8 1.0 1.2 JUNCTION TEMPERATURE (°C) FREQUENCY (Hz) VFB (V) 3431 G08 3431 G07 3431 G09 sn3431 3431fs 4