LTC3557 Datasheet, PDF (8/28 Pages) Linear Technology – USB Power Manager with Li-Ion Charger and Three Step-Down Regulators

LTC3557/LTC3557-1
TYPICAL PERFORMANCE CHARACTERISTICS T_A = 25°C unless otherwise specified
Oscillator Frequency
vs Temperature
2.5
2.4
2.3
V_IN = 3.8V
2.2
V_IN = 5V
2.1
2.0
1.9
V_IN = 2.9V
1.8
V_IN = 2.7V
1.7
1.6
1.5
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
35571 G13
Step-Down Switching Regulator 1
3.3V Output Efficiency vs I_OUT1
100
Burst Mode
90 _OPERATION
80
70
60
50
PULSE SKIP
40
30
20
10
0
0.01 0.1
1
10
I_OUT1 (mA)
V_OUT1 = 3.3V
V_IN1 = 3.8V
V_IN1 = 5V
100 1000
35571 G14
Step-Down Switching Regulator 3
1.8V Output Efficiency vs I_OUT3
100
90
80 ^{Burst Mode}
OPERATION
70
60
PULSE SKIP
50
40
30
20
10
0
0.01 0.1
1
10
I_OUT3 (mA)
V_OUT3 = 1.8V
V_IN3 = 3.8V
V_IN3 = 5V
100 1000
35571 G16
Step-Down Switching Regulator
Output Transient (MODE = 1)
V_OUT2
50mV/DIV
(AC)
Step-Down Switching Regulator
Pulse Skip Supply Current vs V_INX
400
V_OUTX = 1.2V
I_OUTX = 0mA
350
110°C
300
75°C
250
25°C
200
–45°C
150
100
2.5 3.0
3.5 4.0
V_INX (V)
4.5
5.0
35571 G17
Step-Down Switching Regulator
Output Transient (MODE = 0)
V_OUT2
50mV/DIV
(AC)
V_OUT3
50mV/DIV
(AC)
300mA
I_{OUT2 5mA}
V_OUT2 = 1.2V
V_OUT3 = 1.8V
I_OUT3 = 16mA
50μs/DIV
V_OUT3
50mV/DIV
(AC)
35571 G1
300mA
I_{OUT2 5mA}
V_OUT2 = 1.2V
V_OUT3 = 1.8V
I_OUT3 = 100mA
50μs/DIV
35571 G2
8
Step-Down Switching Regulator 2
1.2V Output Efficiency vs I_OUT2
100
90
80 ^{Burst Mode}
OPERATION
70
60
50
PULSE SKIP
40
30
20
10
0
0.01 0.1
1
10
I_OUT2 (mA)
V_OUT2 = 1.2V
V_IN2 = 3.8V
V_IN2 = 5V
100 1000
35571 G15
Step-Down Switching
Regulator Short-Circuit Current
vs Temperature
1200
1100
1000
900
600mA BUCK
800
700
400mA BUCK
600
500
400
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
35571 G18
Step-Down Switching Regulator
Switch Impedance vs Temperature
0.9
V_INX = 3.2V
0.8
0.7
400mA
0.6 _NMOS
400mA
PMOS
0.5
0.4
600mA PMOS
0.3
600mA NMOS
0.2
0.1
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
35571 G21
35571fc