LTC3878_15 Datasheet, PDF (4/26 Pages) Linear Technology – Fast, Wide Operating Range No RSENSE Step-Down DC/DC Controller

LTC3878
Typical Performance Characteristics
Transient Response FCM
(Forced Continuous Mode)
V_OUT (AC)
50mV/DIV
I_L
10A/DIV
I_LOAD
10A/DIV
50µs/DIV
LOAD STEP 0A TO 10A TO 0A
V_IN = 12V
V_OUT = 1.2V
FCB = 0V
SW FREQ = 400kHz
FIGURE 7 CIRCUIT
Transient Response FCM
Positive Load Step
V_SW
20V/DIV
V_OUT (AC)
50mV/DIV
I_L
10A/DIV
I_LOAD
10A/DIV
3878 G01
5µs/DIV
LOAD STEP 0A TO 10A
V_IN = 12V
V_OUT = 1.2V
FCB = 0V
SW FREQ = 400kHz
FIGURE 7 CIRCUIT
3878 G02
Transient Response FCM
Negative Load Step
V_SW
20V/DIV
V_OUT (AC)
50mV/DIV
I_L
10A/DIV
I_LOAD
10A/DIV
5µs/DIV
LOAD STEP 10A TO 0A
V_IN = 12V
V_OUT = 1.2V
FCB = 0V
SW FREQ = 400kHz
FIGURE 7 CIRCUIT
3878 G03
Transient Response DCM
(Discontinuous Mode)
V_OUT (AC)
50mV/DIV
I_L
10A/DIV
I_LOAD
10A/DIV
50µs/DIV
LOAD STEP 1A TO 11A TO 1A
V_IN = 12V
V_OUT = 1.2V
FCB = INTV_CC
SW FREQ = 400kHz
FIGURE 7 CIRCUIT
Normal Start-Up, RUN/SS
Release from Zero
RUN/SS
2V/DIV
I_L
10A/DIV
V_OUT
500mV/DIV
3878 G04
V_IN = 12V
V_OUT = 1.2V
FCB = 0V
50ms/DIV
SW FREQ = 400kHz
FIGURE 7 CIRCUIT
3878 G05
Start-Up V_IN Cycled Low and High
V_IN
10V/DIV
RUN/SS
5V/DIV
I_L
10A/DIV
V_OUT
1V/DIV
V_IN = 12V
V_OUT = 1.2V
FCB = 0V
100ms/DIV
SW FREQ = 400kHz
FIGURE 7 CIRCUIT
3878 G06
Efficiency vs Load Current
100
90 DISCONTINUOUS
MODE
80
70
60
CONTINUOUS
MODE
50
40
30
20
10
0
0.01
V_IN = 12V
V_OUT = 1.2V
SW FREQ = 400kHz
FIGURE 7 CIRCUIT
0.1
1
10
100
LOAD CURRENT (A)
3878 G07
Efficiency vs Input Voltage
100
95
90
15A CCM
85
80
1A DCM
75
70
1A CCM
65
60 _{VOUT = 1.2V}
55 ^{SW FREQ = 400kHz}
FIGURE 7 CIRCUIT
50
4
8
12 16 20 24 28
V_IN (V)
3878 G08
Frequency vs Input Voltage
420
410
15A
400
390
380
370
360
350
0A
340
330
320
310
V_OUT = 1.2V
FIGURE 7 CIRCUIT
300
4
8 12 16 20 24 28
V_IN (V)
3878 G09
3878fa