rt9204 ETC-unknow, rt9204 Datasheet - Page 9

• Manufacturer Part Number: rt9204
• Description: Dual Regulator - Standard Buck Pwm Dc-dc And Linear Power Controller
• Manufacturer: ETC-unknow

Applications Information
Inductor Selection
The RT9204 was designed for V
application mainly. Fig.4 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:
2µH with ≥ 1500µF C
5µH with ≥ 1000µF C
DS9204-00 February 2002
IL
T
V
ON
OUT RIPPLE
RIPPLE
4V
2V
0V
OUT
= 3.33 × V
COUNT = 1 COUNT = 2
ripple is
= (5V - V
T0T1
= IL
1000µF (ESR = 53mΩ)
1500µF (ESR = 33mΩ)
3000µF (ESR = 21mΩ)
OUT
RIPPLE
OUT
OVERLOAD
/5V
OUT
OUT
APPLIED
Inductor
Fig. 3
)/L × T
T2
TIME
V
OUT
× ESR
ON
COUNT = 3
IN
T3
= 5V, step-down
OUT
: VIN = 5V
100mV
62mV
40mV
2µH
3.3V
Preliminary
40mV
25mV
16mV
5µH
Shutdown
Pulling high the SD pin by a small single transistor
can shutdown the RT9204 PWM controller as shown
in typical application circuit. Normally SD pin can be
floating because an internal 40µA current source will
pull low the SD shutdown pin voltage.
110mV
68mV
43mV
2µH
V
2.5V
I
V
i
i
i
D
L
Q
L
44mV
28mV
18mV
C.C.M.
5µH
Q
Table 1
T
ON
T
S
V
I
D
T
93mV
58mV
37mV
-
µI
OFF
2µH
V
V
L
L
O
L
Fig.4
-
V
C
1.5V
O
37mV
23mV
15mV
5µH
µQ
www.richtek-ic.com.tw
R
RT9204
I
I
I
D
L
Q
V
O
= I
O
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