LTC1709-9 Linear Technology, LTC1709-9 Datasheet - Page 25

• Manufacturer Part Number: LTC1709-9
• Description: 2-Phase/ 5-Bit VID/ Current Mode/ High Efficiency/ Synchronous Step-Down Switching Regulators
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
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.
R
IN
V
IN
C
IN
BOLD LINES INDICATE
HIGH, SWITCHING
CURRENT LINES.
KEEP LINES TO A
MINIMUM LENGTH.
+
U
Figure 10. Instantaneous Current Path Flow in a Multiple Phase Switching Regulator
U
W
SW1
SW2
D1
D2
U
L1
L2
SW V
I
COUT
I
CIN
Figure 11. Single and 2-Phase Current Waveforms
R
R
SENSE1
SENSE2
SINGLE PHASE
LTC1709-8/LTC1709-9
+
C
SW1 V
SW2 V
V
OUT
I
OUT
COUT
I
CIN
I
I
L1
L2
DUAL PHASE
170989 F10
R
25
L
RIPPLE
1709 F11