RT9209 RICHTEK [Richtek Technology Corporation], RT9209 Datasheet - Page 11

• Manufacturer Part Number: RT9209
• Description: Synchronous Buck PWM DC-DC with Enable & PGOOD
• Manufacturer: RICHTEK [Richtek Technology Corporation]

Inductor Selection
The RT9209/A was designed for V
application mainly. Figure 4 shows the typical topology
and waveforms of step-down converter.
The ripple currents of inductor can be calculated as follows:
Because operation frequency is fixed at 260kHz/400kHz,
The V
ESR is output capacitor equivalent series resistor
DS9209/A-08 March 2007
IL
T
V
ON
OUT RIPPLE
RIPPLE
OUT
0 A
4 V
2 V
0 V
= 3.85
ripple is
=
COUNT = 1
(5V - V
×
= IL
V
5V
T0
OUT
L
RIPPLE
T1
OUT
, or 2.5
)
Figure 3
×
×
COUNT = 2
ESR
T
OVERLOAD
ON
×
APPLIED
T2
V
5V
TIME
OUT
IN
COUNT = 3
= 5V, step-down
T3
i
i
L
V
Q
i
V
D
I
L
C.C.M.
T
ON
T
Q
V
S
I
- V
T
OFF
uI
O
D
L
Figure 4
- V
O
L
C
RT9209/A
uQ
www.richtek.com
R
V
I
I
O
L
I
D
Q
= I
O
11