LTC1709-8_15 Datasheet, PDF (25/28 Pages) Linear Technology – 2-Phase, 5-Bit VID, Current Mode, High Efficiency, Synchronous Step-Down Switching Regulators

APPLICATIO S I FOR ATIO
SW1
D1
LTC1709-8/LTC1709-9
L1
R_SENSE1
V_IN
R_IN
+
C_IN
V_OUT
+ ^COUT
R_L
BOLD LINES INDICATE
HIGH, SWITCHING
CURRENT LINES.
KEEP LINES TO A
MINIMUM LENGTH.
SW2
D2
L2
R_SENSE2
170989 F10
Figure 10. Instantaneous Current Path Flow in a Multiple Phase Switching Regulator
Simplified Visual Explanation of How a 2-Phase
Controller Reduces Both Input and Output RMS Ripple
Current
A multiphase power supply significantly reduces the
amount of ripple current in both the input and output
capacitors. The RMS input ripple current is divided by, and
the effective ripple frequency is multiplied up by the
number of phases used (assuming that the input voltage
is greater than the number of phases used times the output
voltage). The output ripple amplitude is also reduced by,
and the effective ripple frequency is increased by the
number of phases used. Figure 11 graphically illustrates
the principle.
SW V
SINGLE PHASE
SW1 V
DUAL PHASE
I_CIN
I_COUT
SW2 V
I_L1
I_L2
I_CIN
I_COUT
RIPPLE
1709 F11
Figure 11. Single and 2-Phase Current Waveforms
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