rt9202 ETC-unknow, rt9202 Datasheet - Page 11

• Manufacturer Part Number: rt9202
• Description: Single Synchronous Buck Dc-dc Controller
• Manufacturer: ETC-unknow

Applications Information
Inductor Selection
The RT9202 was designed for V
application mainly. Fig.5 shows the typical topology
and waveforms of step-down converter.
The ripple current of inductor can be calculated as
follows:
Because operation frequency is fixed at 300kHz,
The V
ESR is output capacitor equivalent series resistor
Table 1 shows the ripple voltage of V
DS9202-02 August 2002
IL
T
V
ON
OUT RIPPLE
RIPPLE
OUT
= 3.33 × V
ripple is
= (5V - V
Table 1
*Refer to Sanyo low ESR series (CE, DX, PX…)
The suggested L and C are as follows:
2µH with ≥ 1500µF C
5µH with ≥ 1000µF C
1000µF (ESR=53mΩ)
1500µF (ESR=33mΩ)
3000µF (ESR=21mΩ)
= IL
OUT
RIPPLE
OUT
/5V
Inductor
V
)/L × T
OUT
× ESR
ON
IN
OUT
OUT
= 5V, step-down
OUT
: VIN = 5V
100mV
62mV
40mV
2µH
3.3V
40mV
25mV
16mV
5µH
110mV
68mV
43mV
2µH
2.5V
V
I
V
i
i
i
D
L
Q
L
44mV
28mV
18mV
C.C.M.
5µH
Q
T
ON
T
S
V
93mV
58mV
37mV
I
2µH
T
-
µI
D
OFF
V
Fig.5
L
O
V
L
L
1.5V
-
V
O
C
37mV
23mV
15mV
5µH
µQ
RT9202
www.richtek.com
R
I
I
I
V
D
L
Q
O
= I
O
11