LT1977 Linear Technology, LT1977 Datasheet - Page 5

• Manufacturer Part Number: LT1977
• Description: Step-Down Switching Regulator
• Manufacturer: Linear Technology

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