LT3975
TYPICAL PERFORMANCE CHARACTERISTICS
Switching Frequency
780
720
660
600
540
480
420
–55 –25
R
T
RESISTOR (k )
350
SWITCHING FREQUENCY (kHz)
300
250
200
150
100
50
65
35
95
5
TEMPERATURE (°C)
125
155
0
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2
SWITCHING FREQUENCY (MHz)
3975 G20
T
A
= 25°C, unless otherwise noted.
R
T
Programmed Switching
Frequency
700
600
500
400
300
200
100
0
Frequency Foldback
SWITCHING FREQUENCY (kHz)
0
0.2
0.8
0.6
0.4
FB PIN VOLTAGE (V)
1
1.2
3975 G21
3975 G19
Internal Undervoltage Lockout
(UVLO)
6
5
INPUT VOLTAGE (V)
EN THRESHOLD (V)
4
3
2
1
0
–55 –25
1.09
1.08
1.07
EN Thresholds
1.12
EN RISING
1.11
1.10
PG THRESHOLD (V)
1.09
1.08
1.07
1.06
EN FALLING
1.05
125
155
PG Thresholds
1.06
1.05
1.04
1.03
1.02
FB RISING
FB FALLING
65
35
95
5
TEMPERATURE (°C)
125
155
1.01
–55 –25
5
95
65
35
TEMPERATURE (°C)
1.04
–55 –25
5
95
65
35
TEMPERATURE (°C)
125
155
3975 G22
3975 G23
3975 G24
Minimum Input Voltage,
V
OUT
= 5V
6.5
V
OUT
= 5V
f
SW
= 800kHz
TO RUN/TO START
5.5
5.0
Minimum Input Voltage,
V
OUT
= 3.3V
V
OUT
= 3.3V
FRONT PAGE APPLICATION
SWITCHING FREQUENCY (kHz)
900
800
700
600
500
400
300
200
100
Burst Frequency
V
OUT
= 5V
f
SW
= 800kHz
6.0
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
4.5
TO RUN/TO START
4.0
5.0
4.5
3.5
3.0
V
OUT
= 3.3V
f
SW
= 600kHz
4.0
0
0.5
1.5
1
LOAD CURRENT (A)
2
2.5
3975 G25
2.5
0
0.5
1.5
1
LOAD CURRENT (A)
2
2.5
3975 G26
0
0
20
40 60 80 100 120 140 160
LOAD CURRENT (mA)
3975 G27
3975f
6
LINER [ LINEAR TECHNOLOGY ]
