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| LTC3879_15 Datasheet, PDF (5/28 Pages) Linear Technology – Fast, Wide Operating Range No RSENSE Step-Down Controller | |||
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TYPICAL PERFORMANCE CHARACTERISTICS
LTC3879
Transient Response FCM
(Forced Continuous Mode)
VOUT (AC)
50mV/DIV
IL
10A/DIV
ILOAD
10A/DIV
50μs/DIV
LOAD STEP 0A TO 10A TO 0A
VIN = 12V
VOUT = 1.2V
MODE = 0V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
3879 G01
Transient Response FCM
Positive Load Step
VSW
20V/DIV
VOUT (AC)
50mV/DIV
IL
10A/DIV
ILOAD
10A/DIV
5μs/DIV
LOAD STEP 0A TO 10A
VIN = 12V
VOUT = 1.2V
MODE = 0V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
3879 G02
Transient Response FCM
Negative Load Step
VSW
20V/DIV
VOUT (AC)
50mV/DIV
IL
10A/DIV
ILOAD
10A/DIV
5μs/DIV
LOAD STEP 10A TO 0A
VIN = 12V
VOUT = 1.2V
MODE = 0V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
3879 G03
Transient Response DCM
(Discontinuous Mode)
VOUT (AC)
50mV/DIV
IL
10A/DIV
ILOAD
10A/DIV
50μs/DIV
LOAD STEP 1A TO 11A TO 1A
VIN = 12V
VOUT = 1.2V
MODE = INTVCC
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
3879 G04
Normal Start-Up, RUN Pin
Released from GND
RUN
5V/DIV
VOUT
0.5V/DIV
TRACK/SS
0.5V/DIV
20ms/DIV
VIN = 12V
VOUT = 1.2V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
3879 G05
Start-Up Into a Pre-Biased Output
RUN Pin Released from GND
IL
5A/DIV
VOUT
0.5V/DIV
TRACK/SS
0.5V/DIV
20ms/DIV
VIN = 12V
VOUT = 1.2V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
3879 G06
Start-Up After Input Undervoltage
VIN Cycled Low to High
VIN
10V/DIV
TRACK/SS
5V/DIV
VOUT
1V/DIV
100ms/DIV
VIN = 12V
VOUT = 1.2V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
3879 G07
Coincident Rail Tracking 1.2V
VOUT Tracks External 1.8V Supply
VMASTER
0.5V/DIV
VOUT
0.5V/DIV
5ms/DIV
VIN = 12V
VOUT = 1.2V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
3879 G08
Efï¬ciency vs Load Current
100
90 DISCONTINUOUS
MODE
80
70
60
CONTINUOUS
MODE
50
40
30
20
10
0
0.01
VIN = 12V
VOUT = 1.2V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
0.1
1
10
100
LOAD CURRENT (A)
3879 G09
3879f
5
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