LTC3876_15 Datasheet, PDF (7/48 Pages) Linear Technology – Dual DC/DC Controller for DDR Power with Differential VDDQ Sensing and 50mA VTT Reference

TYPICAL PERFORMANCE CHARACTERISTICS
LTC3876
Regular Soft Start-Up
(Forced Continuous Mode)
Soft Start-Up Into
Prebiased Output
Output Tracking
(Forced Continuous Mode)
V_IN
5V/DIV
VDDQ
500mV/DIV
VTT
500mV/DIV
TRACK/SS
200mV/DIV
2ms/DIV
C_SS = 10nF
V_IN = 12V
VDDQ = 1.5V, VTT = 0.75V
FIGURE 10 CIRCUIT
RUN
5V/DIV
VDDQ
500mV/DIV
TRACK/SS
200mV/DIV
VTT
500mV/DIV
3876 G10
1ms/DIV
CSS = 10nF
V_IN = 12V
VDDQ = 1.5V, VTT = 0.75V
VDDQ PREBIASED TO 0.75V
VTT PREBIASED TO 0.6V
FIGURE 10 CIRCUIT
3876 G11
TRACK/SS
200mV/DIV
VDDQ
500mV/DIV
VTT
500mV/DIV
10ms/DIV
V_IN = 12V
VDDQ = 1.5V, VTT - 0.75V
FIGURE 10 CIRCUIT
3876 G12
Overcurrent Protection
(Forced Continuous Mode)
24A
LOAD
CURRENT
10A
20A/DIV
I_L
10A/DIV
V_OUT
50mV/DIV
FULL CURRENT LIMIT V_OUT GREATER
THAN HALF REGULATED SETTING
5ms/DIV
V_IN = 12V
VDDQ = 1.5V
CURRENT LIMIT = 23A
OVERLOAD = 10A TO 17.5A
FICURE 10 CIRCUIT, VDDQ CHANNEL 1
3876 G13
Short-Circuit Protection
(Forced Continuous Mode)
Overvoltage Protection
(Forced Continuous Mode)
SHORT-
CIRCUIT
TRIGGER
1V/DIV
V_OUT
1V/DIV
I_L
20A/DIV
50A
0A
C_OUT
DISCHARGE
C_OUT
RECHARGE
500μs/DIV
3876 G14
V_IN = 12V
VDDQ = 1.5V
I_LOAD = 0A, SHORT = 50A
FIGURE 10 CIRCUIT,
CURRENT LIMIT
FOLDBACK V_OUT
DROPS BELOW
HALF REGULATED
VDDQ CHANNEL 1
SET POINT
I_L
20A/DIV
V_OUT
200mV/DIV
BG1
5V/DIV
BG STAYS
ON UNTIL V_OUT
PULLED BELOW V_IN = 12V
OVERVOLTAGE VDDQ = 1.5V
20μs/DIV
THRESHOLD I_LOAD = 0A
FIGURE 10 CIRCUIT,
VDDQ CHANNEL 1
3876 G15
OVERVOLTAGE
CREATED BY
APPLYING A
CHARGED
CAPACITOR
TO V_OUT
Phase Relationship:
PHASMD = Ground
(Forced Continuous Mode)
Phase Relationship:
PHASMD = Float
(Forced Continuous Mode)
PLLIN
5V/DIV
SW1
5V/DIV
0°
SW2
5V/DIV
180°
CLKOUT
5V/DIV
60°
500ns/DIV
PHASMD = GND
V_IN = 6V
VDDQ = 1.5V, VTT = 0.75V
LOAD = 0A
FIGURE 10 CIRCUIT
PLLIN
5V/DIV
SW1
5V/DIV
0°
SW2
5V/DIV
180°
3876 G16
CLKOUT
5V/DIV
90°
500ns/DIV
PHASMD = FLOAT
V_IN = 6V
VDDQ = 1.5V, VTT = 0.75V
LOAD = 0A
FIGURE 10 CIRCUIT
3876 G17
Phase Relationship:
PHASMD = INTV_CC
(Forced Continuous Mode)
PLLIN
5V/DIV
SW1
5V/DIV
0°
SW2
5V/DIV
240°
CLKOUT
5V/DIV
120°
500ns/DIV
PHASMD = INTV_CC
V_IN = 6V
VDDQ = 1.5V, VTT = 0.75V
LOAD = 0A
FIGURE 10 CIRCUIT
3876 G18
3876f
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