LT3975
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Thermal Derating
Switch Current Limit
Switch Current Limit
7.0
3.0
2.5
2.0
1.5
1.0
0.5
0
7
6
V
V
= 12V
OUT
30% DUTY CYCLE
IN
= 5V
6.5
6.0
I-GRADE
H-GRADE
5
4
3
2
1
0
5.5
5.0
4.5
4.0
3.5
LIMITED BY MAXIMUM
JUNCTION TEMPERATURE
θ
= 40°C/W
JA
3.0
75 100
–50 –25
0
25 50
125 150
–55 –25
5
35
65
95 125 155
0.2
0.4
0.6
1
0
0.8
TEMPERATURE (°C)
TEMPERATURE (°C)
DUTY CYCLE
3975 G10
3975 G12
3975 G11
Current Limit Foldback
Soft-Start
Switch VCESAT
250
200
150
100
6
5
4
3
2
1
0
6
5
30% DUTY CYCLE
30% DUTY CYCLE
V
= 1V
FB
V
SS
= 3V
V
= 0V
FB
4
3
2
1
0
50
0
0
1
1.5
2.0
2.5
3.0
0.5
0
0.4
0.6
0.8
1.0
1.2
0
0.5
1
1.5
2
2.5
0.2
SWITCH CURRENT (A)
FB PIN VOLTAGE (V)
SS PIN VOLTAGE (V)
3975 G15
3975 G13
3975 G14
BOOST Pin Current
Minimum On-Time
Minimum Off-Time
180
170
160
150
140
130
120
110
100
90
200
190
180
170
160
150
140
130
120
110
100
50
45
40
35
30
25
20
15
10
5
V
SW
= 0V
V
SW
= 0V
SYNC
SYNC
f
= 2MHz
f
= 2MHz
LOAD = 1A
LOAD = 2.5A
LOAD = 1A
LOAD = 2.5A
80
70
60
0
65
95 125 155
–55
5
35
65
95 125 155
–55
5
35
0
0.5
1.5
2
2.5
3
–25
–25
1
TEMPERATURE (°C)
TEMPERATURE (°C)
SWITCH CURRENT (A)
3975 G17
3975 G18
3975 G16
3975f
5
Linear [ Linear ]
