LT3975
TYPICAL PERFORMANCE CHARACTERISTICS
SS Pin Current
2.6
2.4
OUT PIN CURRENT (mA)
SS PIN CURRENT (µA)
2.2
2.0
1.8
1.6
1.4
1.2
1.0
–55 –25
5
95
65
35
TEMPERATURE (°C)
125
155
V
SS
= 0.5V
160
140
BOOST DIODE VOLTAGE (V)
120
100
80
60
40
20
0
0
2
4
8
10 12
6
OUT PIN VOLTAGE (V)
14
16
T
A
= 25°C, unless otherwise noted.
Boost Diode Forward Voltage
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
1
0.5
1.5
BOOST DIODE CURRENT (A)
2
3975 G30
Boost Capacitor Charger
V
BST
= V
IN
3975 G28
3975 G29
Dropout Comparator Thresholds
600
580
DROPOUT THRESHOLD (mV)
560
540
520
500
480
460
440
420
400
–55
–25
65
35
5
95
TEMPERATURE (°C)
125
155
V
OUT
FALLING
V
OUT
RISING
V
IN
1V/DIV
Start-Up/Dropout Performance
V
IN
V
OUT
V
IN
1V/DIV
Start-Up/Dropout Performance
V
IN
V
OUT
V
OUT
1V/DIV
V
OUT
1V/DIV
2.5 LOAD
100ms/DIV
(2A IN REGULATION)
3975 G32
1k LOAD
100ms/DIV
(5mA IN REGULATION)
3975 G33
3975 G31
Burst Mode Switching Waveforms
V
SW
5V/DIV
I
L
0.5A/DIV
V
OUT
10mV/DIV
V
IN
= 12V
V
OUT
= 3.3V
I
LOAD
= 20mA
C
OUT
= 47µF
5µs/DIV
3975 G34
Full Frequency Switching
Waveforms
V
SW
5V/DIV
I
L
1A/DIV
V
OUT
20mV/DIV
V
IN
= 12V
V
OUT
= 3.3V
I
LOAD
= 1A
C
OUT
= 47µF
1µs/DIV
3975 G35
Dropout Switching Waveforms
V
SW
2V/DIV
I
L
1A/DIV
V
OUT
50mV/DIV
V
IN
= 5V
5µs/DIV
V
OUT
SET FOR 5V
I
LOAD
= 0.5A
C
OUT
= 47µF
3975 G36
3975f
7
LINER [ LINEAR TECHNOLOGY ]
