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