LT1977
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Peak Current Limit
3.5
50
45
PEAK SWITCH CURRENT (A)
3.0
CURRENT (µA)
40
35
30
25
20
15
10
5
1.5
–50 –25
75
–0
25
50
TEMPERATURE (°C)
100
125
0
0
0.2
0.6
0.8
0.4
FB VOLTAGE (V)
1.0
1.2
1977 G11
FOLDBACK PERCENTAGE (%)
2.5
2.0
Switch On Voltage (V
CESAT
)
500
450
400
SUPPLY CURRENT (µA)
350
VOLTAGE (mV)
100
75
50
25
0
INPUT VOLTAGE (V)
300
250
200
150
100
50
0
–0.1 0.1
0.3
T
J
= –50°C
T
J
= 125°C
T
J
= 25°C
0.5 0.7 0.9 1.1
LOAD CURRENT (A)
Burst Mode Threshold
vs Input Voltage
500
V
OUT
= 3.3V
450 L = 10µH
= 100µF
C
400
OUT
LOAD CURRENT (mA)
350
ON TIME (ns)
350
Burst Mode EXIT
(INCREASING LOAD)
LOAD CURRENT = 0.5A
BOOST CURRENT (mA)
300
250
200
150
100
50
0
Burst Mode ENTER
(DECREASING LOAD)
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
INPUT VOLTAGE (V)
1977 G20
U W
1977 G10
Soft-Start Current Threshold
vs FB Voltage
100
Frequency Foldback Percentage
90
80
70
60
50
40
30
20
10
0
0
0.25
0.75
0.5
FB PIN VOLTAGE (V)
1
1.25
1977 G12
T
J
= 25°C
SOFT-START
DEFEATED
Supply Current vs Input Voltage
150
125
8.0
Minimum Input Voltage
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
V
OUT
= 3.3V
START-UP
RUNNING
V
OUT
= 5V
START-UP
RUNNING
V
OUT
= 3.3V
T
A
= 25°C
1.3
1.5
0
10
30
40
20
INPUT VOLTAGE (V)
50
60
1977 F05
0
0.25
0.75
0.5
LOAD CURRENT (A)
1
1.25
1977 G19
1977 G13
Minimum On Time
500
450
400
45
40
35
30
25
20
15
10
5
Boost Current vs Load Current
300
250
200
150
100
50
0
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
LOAD CURRENT = 1A
0
0
0.25
0.5
0.75
1
LOAD CURRENT (A)
1.25
1.5
1977 G21
1977 G22
1977f
5
LINER [ LINEAR TECHNOLOGY ]
