Datasheet

4
LT1082
sn1082 1082fas
CCHARA TERIST
ICS
UW
AT
Y
P
I
CA
LPER
F
O
R
C
E
Suggested Core Size and
Inductance for Telecom
5V Supply
Telecom 5V Supply Short-Circuit
Frequency Shift-Down
Minimum Input Voltage
TEMPERATURE (°C)
–75
MINIMUM INPUT VOLTAGE (V)
2.9
2.8
2.7
2.6
2.5
2.4
2.3
–50
50
100
1082 G07
25
150
–25
0
75 125
I
SW
= 1A
I
SW
= 0A
Switch Saturation Voltage
SWITCH CURRENT (A)
0
SWITCH SATURATION VOLTAGE (V)
2.00
1082 G08
0.25
0.50
1.50
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
0.75
1.00 1.25 1.75
T
J
= 150°C
T
J
= 100°C
T
J
= 25°C
T
J
= –50°C
JUNCTION TEMPERATURE (°C)
–75
TIME (µs)
2.2
2.0
1.8
1.6
1.4
1.2
1.0
–50
50
100
1082 G06
25
150
–25
0
75 125
Flyback Blanking Time
Switch Current Limit
TEMPERATURE (°C)
–75
DUTY CYCLE (%)
97
96
95
94
93
92
91
90
–50
50
100
1082 G05
25
150
175
–25
0
75 125
Maximum Duty Cycle
DUTY CYCLE (%)
0
SWITCH CURRENT (A)
3
4
40
1082 G04
2
1
0
10
20
30
50 60 70 80 90 100
T
J
= –55°C
T
J
= 150°C
T
J
= 25°C
Short-Circuit Frequency
Shift-Down vs Feedback Current
FEEDBACK CURRENT (µA)
0 300
1082 G03
100 200 800
70
60
50
40
30
20
10
0
400 500 600 700
FREQUENCY (kHz)
T
A
= 150°C
T
A
= 0°C
T
A
= –55°C
LOAD
CURRENT
100mA
200mA
400mA
600mA
800mA
TYPE 52
POWDERED
IRON
T38 250µH
T50 250µH
T60 250µH
T60 250µH
T80 350µH
KOOL Mµ
OR MOLY-
PERMALLOY
T38 200µH
T38 150µH
T50 150µH
T50 200µH
T80 350µH
1082 GA
POWER OUTPUT (W)
0
EFFICIENCY (%)
4
1082 G01
1
2
3
79
76
73
70
67
64
61
58
55
V
IN
= –20V
V
IN
= –40V
V
IN
= –60V
V
IN
= –70V
NOTE: THIS GRAPH IS BASED ON LOW CORE LOSS
PERMALLOY INDUCTOR. IF POWDERED IRON CORE
INDUCTOR IS USED, THE CORE LOSS IS TYPICALLY
100mW HIGHER.
L = 250µH
R = 0.08Ω
Telecom 5V Supply Efficiency
OUTPUT VOLTAGE (V)
6
FREQUENCY (kHz)
54 32
1082 G02
80
70
60
50
40
30
20
10
0
10
T
A
= 25°C