LTC3857 Datasheet, PDF (5/38 Pages) Linear Technology – Low IQ, Dual, 2-Phase Synchronous Step-Down Controller

Typical Performance Characteristics
LTC3857
Efficiency and Power Loss
vs Output Current
100
V_IN = 12V
90 _VOUT = 3.3V
80 ^{FIGURE 13 CIRCUIT}
10000
1000
70
60
100
50
40
10
30
20
1
10
0
0.1
0.00001 0.0001 0.001 0.01 0.1 1 10
OUTPUT CURRENT (A)
38 57 G01
BURST EFFICIENCY
PULSE-SKIPPING
EFFICIENCY
CCM EFFICIENCY
BURST LOSS
PULSE-SKIPPING
LOSS
CCM LOSS
Load Step (Burst Mode Operation)
Efficiency vs Output Current
100
90
V_IN = 5V
80
70
V_IN = 12V
60
50
40
30
20
10
0
0.00001 0.0001 0.001
V_OUT = 3.3V
FIGURE 13 CIRCUIT
0.01 0.1 1 10
OUTPUT CURRENT (A)
3857 G02
Efficiency vs Input Voltage
98
V_OUT = 3.3V
96
I_LOAD = 5A
94
92
90
88
86
84
82
80
1 5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
3857 G03
Load Step
(Forced Continuous Mode)
Load Step
(Pulse-Skipping Mode)
V_OUT
100mV/DIV
V_OUT
100mV/DIV
V_OUT
100mV/DIV
INDUCTOR
CURRENT
2A/DIV
INDUCTOR
CURRENT
2A/DIV
V_IN = 12V
20µs/DIV
V_OUT = 3.3V
FIGURE 13 CIRCUIT
3857 G04
Inductor Current at Light Load
V_IN = 12V
20µs/DIV
V_OUT = 3.3V
FIGURE 13 CIRCUIT
Soft Start-Up
INDUCTOR
CURRENT
2A/DIV
3857 G05
V_IN = 12V
20µs/DIV
V_OUT = 3.3V
FIGURE 13 CIRCUIT
Tracking Start-Up
3857 G06
FORCED
CONTINUOUS
MODE
Burst Mode
OPERATION
2A/DIV
PULSE-
SKIPPING MODE
V_IN = 12V
5µs/DIV
V_OUT = 3.3V
I_LOAD = 200µA
FIGURE 13 CIRCUIT
V_OUT2
2V/DIV
V_OUT1
2V/DIV
V_OUT2
2V/DIV
V_OUT1
2V/DIV
3857 G07
20ms/DIV
FIGURE 13 CIRCUIT
3857 G08
20ms/DIV
FIGURE 13 CIRCUIT
3857 G09
3857fa