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LTC3838-2_15 Datasheet, PDF (7/56 Pages) Linear Technology – Dual, Fast, Accurate Step-Down DC/DC Controller with xternal Reference Voltage and Dual Differential Output Sensing
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TYPICAL PERFORMANCE CHARACTERISTICS
LTC3838-2
Soft Start-Up with Internal
Reference
Soft Start-Up Into
Prebiased Output
RUN1
5V/DIV
TRACK/SS1
200mV/DIV
VOUT
500mV/DIV
CSS = 10nF
1ms/DIV
VIN = 12V
VOUT = 1.2V
FORCED CONTINUOUS MODE
FIGURE 17 CIRCUIT, CHANNEL 1
RUN1
5V/DIV
VOUT
500mV/DIV
TRACK/SS1
200mV/DIV
38382 G09
CSS = 10nF
1ms/DIV
VIN = 12V
VOUT = 1.2V
VOUT PRE-BIASED TO 0.75V
FIGURE 17 CIRCUIT, CHANNEL 1
Soft Start-Up with External
Reference
RUN2
5V/DIV
EXTVREF2
500mV/DIV
38382 G10
TRACK/SS2
500mV/DIV
VOUT
500mV/DIV
CSS = 10nF
2ms/DIV
VIN = 12V
EXTVREF2 = 1.2V
VOUT = 1.2V
FORCED CONTINUOUS MODE
FIGURE 17 CIRCUIT, CHANNEL 2
38382 G11
Overcurrent Protection
IL
5A/DIV
FULL CURRENT LIMIT
WHEN VOUT HIGHER
THAN HALF OF REGULATED
VOUT
100mV/DIV
AC-COUPLED
VIN = 12V
5ms/DIV
VOUT = 1.2V
FORCED CONTINUOUS MODE
CURRENT LIMIT = 17A
OVERLOAD = 7.5A TO 17.5A
FIGURE 17 CIRCUIT, CHANNEL 1
38382 G12
Short-Circuit Protection
Overvoltage Protection
SHORT-
CIRCUIT
TRIGGER
IL
10A/DIV
VOUT
1V/DIV
IL
10A/DIV
CURRENT LIMIT STARTS TO FOLD BACK AS
VOUT DROPS BELOW HALF OF REGULATED
COUT
RECHARGE
VOUT
100mV/DIV
AC-COUPLED
BG1
5V/DIV
OVERVOLTAGE CREATED BY APPLYING
A CHARGED CAPACITOR TO VOUT
VIN = 12V
500µs/DIV
VOUT = 1.2V
ILOAD = 0A
FIGURE 17 CIRCUIT, CHANNEL 1
38382 G13
VIN = 12V
20µs/DIV
38382 G14
VOUT = 1.2V
BG STAYS ON UNTIL
FORCED
VOUT IS PULLED
CONTINUOUS MODE BELOW OVERVOLTAGE
ILOAD = 0A
THRESHOLD
FIGURE 17 CIRCUIT, CHANNEL 1
Phase Relationship:
PHASMD = Ground
PLLIN
5V/DIV
SW1
10V/DIV
0°
SW2
10V/DIV
180°
CLKOUT
5V/DIV
60°
500ns/DIV
38382 G15
FIGURE 21 CIRCUIT
VIN = 12V
VOUT1 = 5V, VOUT2 = 3.3V
LOAD = 0A
MODE/PLLIN = 333kHz EXTERNAL CLOCK
Phase Relationship:
PHASMD = Float
PLLIN
5V/DIV
SW1
10V/DIV
0°
SW2
10V/DIV
180°
CLKOUT
5V/DIV
90°
500ns/DIV
38382 G16
FIGURE 21 CIRCUIT
VIN = 12V
VOUT1 = 5V, VOUT2 = 3.3V
LOAD = 0A
MODE/PLLIN = 333kHz EXTERNAL CLOCK
Phase Relationship:
PHASMD = INTVCC
PLLIN
5V/DIV
SW1
10V/DIV
0°
SW2
10V/DIV
240°
CLKOUT
5V/DIV
120°
500ns/DIV
38382 G17
FIGURE 21 CIRCUIT
VIN = 12V
VOUT1 = 5V, VOUT2 = 3.3V
LOAD = 0A
MODE/PLLIN = 333kHz EXTERNAL CLOCK
For more information www.linear.com/3838-2
38382f
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