Datasheet

LTC3557/LTC3557-1
8
35571fc
Oscillator Frequency
vs Temperature
Step-Down Switching Regulator 1
3.3V Output Effi ciency vs I
OUT1
Step-Down Switching Regulator
Output Transient (MODE = 1)
Step-Down Switching Regulator
Output Transient (MODE = 0)
Step-Down Switching Regulator
Switch Impedance vs Temperature
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C unless otherwise specifi ed
Step-Down Switching Regulator
Pulse Skip Supply Current vs V
INX
Step-Down Switching
Regulator Short-Circuit Current
vs Temperature
TEMPERATURE (°C)
–50
1.5
f
OSC
(MHz)
1.6
1.8
1.9
2.0
2.5
2.2
0
50
75
35571 G13
1.7
2.3
2.4
2.1
–25
25
100
125
V
IN
= 5V
V
IN
= 3.8V
V
IN
= 2.7V
V
IN
= 2.9V
I
OUT1
(mA)
0.01
40
EFFICIENCY (%)
50
60
70
80
0.1 1 10 100 100
0
35571 G14
30
20
10
0
90
100
V
IN1
= 3.8V
V
IN1
= 5V
Burst Mode
OPERATION
PULSE SKIP
V
OUT1
= 3.3V
I
OUT2
(mA)
0.01
40
EFFICIENCY (%)
50
60
70
80
0.1 1 10 100 100
0
35571 G15
30
20
10
0
90
100
V
IN2
= 3.8V
V
IN2
= 5V
Burst Mode
OPERATION
PULSE SKIP
V
OUT2
= 1.2V
I
OUT3
(mA)
0.01
40
EFFICIENCY (%)
50
60
70
80
0.1 1 10 100 100
0
35571 G16
30
20
10
0
90
100
V
IN3
= 3.8V
V
IN3
= 5V
Burst Mode
OPERATION
PULSE SKIP
V
OUT3
= 1.8V
V
INX
(V)
2.5
100
I
IN
(µA)
150
200
250
300
350
110°C
75°C
25°C
–45°C
400
3.0 3.5 4.0 4.5
35571 G17
5.0
V
OUTX
= 1.2V
I
OUTX
= 0mA
TEMPERATURE (°C)
–50
SHORT-CIRCUIT CURRENT (mA)
1100
25
35571 G18
800
600
–25 0 50
500
400
1200
1000
900
700
75 100 125
600mA BUCK
400mA BUCK
V
OUT2
50mV/DIV
(AC)
V
OUT3
50mV/DIV
(AC)
I
OUT2
300mA
5mA
35571 G1
50µs/DIVV
OUT2
= 1.2V
V
OUT3
= 1.8V
I
OUT3
= 16mA
V
OUT2
50mV/DIV
(AC)
V
OUT3
50mV/DIV
(AC)
I
OUT2
300mA
5mA
35571 G2
50µs/DIVV
OUT2
= 1.2V
V
OUT3
= 1.8V
I
OUT3
= 100mA
TEMPERATURE (°C)
–50
0
SWITCH IMPEDANCE ()
0.1
0.3
0.4
0.5
50
0.9
35571 G21
0.2
0
–25
75 100
25 12
0.6
0.7
0.8
600mA NMOS
600mA PMOS
400mA
PMOS
400mA
NMOS
V
INX
= 3.2V
Step-Down Switching Regulator 2
1.2V Output Effi ciency vs I
OUT2
Step-Down Switching Regulator 3
1.8V Output Effi ciency vs I
OUT3