LT1072_1 Datasheet, PDF (5/16 Pages) Linear Technology – 1.25A High Efficiency Switching Regulator

LT1072
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Current* vs Switch Current
80
70
60
50
40
30
20
10
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
SWITCH CURRENT (A)
*AVERAGE LT1072 POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT
LT1072 • TPC10
Normal/Flyback Mode Threshold
on Feedback Pin
500
– 24
490
– 22
480
– 20
470
–18
460 ^{FEEDBACK PIN VOLTAGE}
–16
(AT THRESHOLD)
450
–14
440
–12
430
–10
420
FEEDBACK PIN CURRENT
(AT THRESHOLD)
–8
410
–6
400
–4
–50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
LT1072 • TPC13
Shutdown Thresholds
400
–400
350 _{CURRENT (OUT OF VC PIN)}
300
–350
–300
250
–250
200
VOLTAGE
150
–200
–150
100
–100
V_C VOLTAGE IS REDUCED UNTIL
50
REGULATOR CURRENT DROPS
–50
BELOW 300µA
0
0
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
LT1072 • TPC16
Supply Current vs Input Voltage*
15
T_J = 25°C
14
NOTE THAT THIS CURRENT DOES NOT
13 INCLUDE DRIVER CURRENT, WHICH IS
12
A FUNCTION OF LOAD CURRENT AND
DUTY CYCLE.
90% DUTY CYCLE
11
10
9
50% DUTY CYCLE
8
10% DUTY CYCLE
7
6
0% DUTY CYCLE
5
0 10 20 30 40 50 60
INPUT VOLTAGE (V)
*UNDER VERY LOW OUTPUT CURRENT CONDITIONS,
DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH
10% OR LESS
LT1072 • TPC11
Supply Current vs Supply Voltage
(Shutdown Mode)
160
T_J = 25°C
140
120
100
V_C = 50mV
80
60
40
20
V_C = 0V
0
0 10 20 30 40 50 60
SUPPLY VOLTAGE (V)
LT1072 • TPC12
Shutdown Mode Supply Current
200
180
160
140
120
T_J = 150°C
100
80
60
– 55°C ≤ T_J ≤ 125°C
40
20
0
0 10 20 30 40 50 60 70 80 90 100
V_C PIN VOLTAGE (mV)
LT1072 • TPC14
Idle Supply Current vs
Temperature
11
10 ^{VC = 0.6V}
9
8
7
V_SUPPLY = 60V
6
V_SUPPLY = 3V
5
4
3
2
1
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
LT1072 • TPC17
Error Amplifier Transconductance
5000
4500
4000
G_m =
∆I
∆V
(V_C PIN)
(FB PIN)
3500
3000
2500
2000
1500
1000
500
0
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (C°)
LT1072 • TPC15
Feedback Pin Clamp Voltage
500
450
400
–55°C
350
300
25°C
250
150°C
200
150
100
50
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
FEEDBACK CURRENT (mA)
LT1072 • TPC18
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5