LT1956/LT1956-5
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Peak Current Limit
2.5
1.234
1.229
SWITCH PEAK CURRENT (A)
TYPICAL
2.0
FEEDBACK VOLTAGE (V)
VOLTAGE
1.219
CURRENT
1.214
0.5
1.209
1.0
CURRENT (µA)
1.5
GUARANTEED MINIMUM
1.0
0
20
40
60
DUTY CYCLE (%)
80
100
1956 G01
Lockout and Shutdown
Thresholds
2.4
INPUT SUPPLY CURRENT (µA)
40
INPUT SUPPLY CURRENT (µA)
2.0
SHDN PIN VOLTAGE (V)
1.6
1.2
0.8
LOCKOUT
START-UP
0.4
SHUTDOWN
0
–50
–25
0
25
50
75
JUNCTION TEMPERATURE (°C)
1956
G04
Error Amplifier Transconductance
2500
TRANSCONDUCTANCE (µmho)
2000
GAIN (µMho)
2500
GAIN
150
PHASE (DEG)
SWITICHING FREQUENCY (kHz)
OR FB CURRENT (µA)
1500
1000
500
0
–50
–25
0
25
50
75
JUNCTION TEMPERATURE
1956
G07
4
U W
100
100
FB Pin Voltage and Current
2.0
250
200
1.5
1.224
150
100
12
6
0
125
SHDN Pin Bias Current
CURRENT REQUIRED TO FORCE SHUTDOWN
(FLOWS OUT OF PIN). AFTER SHUTDOWN,
CURRENT DROPS TO A FEW
µA
CURRENT (µA)
AT 2.38V STANDBY THRESHOLD
(CURRENT FLOWS OUT OF PIN)
1.204
50
100
25
75
–50 –25
0
JUNCTION TEMPERATURE (°C)
0
50
100
–50 –25
25
75
0
JUNCTION TEMPERATURE (°C)
125
1956 G02
1956 G03
Shutdown Supply Current
300
V
SHDN
= 0V
35
30
25
20
15
10
5
0
0
10
20
30
40
INPUT VOLTAGE (V)
50
60
1956
G05
Shutdown Supply Current
250
V
IN
= 60V
200
V
IN
= 15V
150
100
50
0
0
0.1
0.2
0.3
0.4
SHUTDOWN VOLTAGE (V)
0.5
1956
G06
125
Error Amplifier Transconductance
3000
PHASE
200
Frequency Foldback
625
SWITCHING
FREQUENCY
500
2000
100
375
1500
V
FB
2 • 10
–3
(
)
R
OUT
200k
V
C
C
OUT
12pF
50
250
1000
ERROR AMPLIFIER EQUIVALENT CIRCUIT
0
125
FB PIN
CURRENT
0
0
0.2
0.4
0.6
V
FB
(V)
0.8
1.0
1.2
1956
G09
R
LOAD
= 50Ω
125
500
100
1k
10k
100k
FREQUENCY (Hz)
1M
–50
10M
1956
G08
1956f
LINER [ LINEAR TECHNOLOGY ]
