RT9204AGS RICHTEK [Richtek Technology Corporation], RT9204AGS Datasheet - Page 10

• Manufacturer Part Number: RT9204AGS
• Description: Dual Regulators - Standard Buck PWM DC-DC and Linear Controller
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9204/A
Inductor Selection
The RT9204/A was designed for V
application mainly. Figure 6 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 600kHz,
The V
ESR is COUT capacitor equivalent series resistor
Table 1 shows the ripple voltage of V
*Refer to Sanyo low ESR series (CE, DX, PX......)
The suggested L and C are as follows:
2 H with
5 H with
www.richtek.com
10
1000 F (ESR = 53m )
1500 F (ESR = 33m )
3000 F (ESR = 21m )
IL
T
V
ON
OUT RIPPLE
RIPPLE
OUT
= 3.33
Inductor
4V
2V
0V
ripple is
=
V
1500 F C
1000 F C
(5V - V
OUT
COUNT = 1
= IL
V
5V
OUT
L
RIPPLE
OUT
T0T1
OUT
OUT
)
Figure 5
COUNT = 2
T
ESR
OVERLOAD
ON
APPLIED
100mV
62mV
40mV
2 H
T2
TIME
3.3V
IN
OUT
COUNT = 3
= 5V, step-down
40mV
25mV
16mV
: VIN = 5V
5 H
T3
110mV
68mV
43mV
Preliminary
2 H
2.5V
28mV
18mV
44mV
5 H
Shutdown
Pulling high the SD pin by a small single transistor can
shutdown the RT9204/A PWM controller as shown in
typical application circuit. Normally SD pin can be floating
because an internal 40 A current source will pull low
the SD shutdown pin voltage.
i
i
L
V
Q
i
V
D
I
L
93mV
58mV
37mV
2 H
C.C.M.
Table 1
T
1.5V
ON
T
Q
V
S
I
37mV
23mV
15mV
- V
T
5 H
OFF
uI
O
D
L
Figure 6
- V
O
DS9204/A-08 March 2007
L
C
uQ
R
V
I
I
O
L
I
D
Q
= I
O