Datasheet

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