Datasheet LT1956, LT1956-5 (Analog Devices) - 4

LT1956/LT1956-5
W U TYPICAL PERFOR A CE CHARACTERISTICS Switch Peak Current Limit FB Pin Voltage and Current SHDN Pin Bias Current
2.5 1.234 2.0 250 CURRENT REQUIRED TO FORCE SHUTDOWN 1.229 200 (FLOWS OUT OF PIN). AFTER SHUTDOWN, 1.5 CURRENT DROPS TO A FEW µA TYPICAL 2.0 CURRENT ( 1.224 150 µA) VOLTAGE 1.219 1.0 100 µA) GUARANTEED MINIMUM CURRENT 1.5 CURRENT ( 1.214 12 FEEDBACK VOLTAGE (V) AT 2.38V STANDBY THRESHOLD 0.5 SWITCH PEAK CURRENT (A) (CURRENT FLOWS OUT OF PIN) 1.209 6 1.0 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) 1956 G01 1956 G02 1956 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) 1956 G04 1956 G05 1956 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 COUT 1000 1500 OUT GAIN ( 50 V ( FB 2 • 10–3 ) 250 200k 12pF OR FB CURRENT ( 1000 TRANSCONDUCTANCE ( 500 ERROR AMPLIFIER EQUIVALENT CIRCUIT 0 SWITICHING FREQUENCY (kHz) 125 FB PIN RLOAD = 50Ω CURRENT 500 0 –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 FREQUENCY (Hz) VFB (V) 1956 G08 1956 G07 1956 G09 1956f 4