RT8278GSP データシートの表示（PDF） - Richtek Technology
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RT8278GSP Datasheet PDF : 16 Pages
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RT8278
VOUT (V)
10
8
5
3.3
2.5
1.8
1.5
1.2
Table 1. Recommended Component Selection for fSW = 2.2MHz
R1 (kΩ)
115
R2 (kΩ)
10
RC (kΩ)
82
CC (nF)
0.56
L (μH)
8.2
91
10
68
0.56
6.8
52.3
10
56
1.8
4.7
31.6
10
36
1
2.2
21.5
10
27
1.2
2
12.4
10
20
1.8
1.5
8.87
10
16
3.3
1.5
4.99
10
24
1
1
COUT (μF)
22
22
22
22
22
22
22
22
Functional Pin Description
Pin No.
1
2
Pin Name
BOOT
VIN
Pin Function
Bootstrap Power Pin. BOOT supplies the drive for the high side N-MOSFET
switch. Connect a 10nF or greater capacitor from SW to BOOT to power the high
side switch.
Supply Input. VIN supplies the power to the IC, as well as the step-down
converter switches. Drive VIN with a 4.5V to 24V power source. Bypass VIN to
GND with a suitably large capacitor to eliminate noise on the input to the IC.
3
SW
4,
9 (Exposed Pad)
GND
5
FB
6
COMP
7
EN
8
RT
Switch Node. SW is the switching node that supplies power to the output.
Connect the output LC filter from SW to the output load. Note that a capacitor is
required from SW to BOOT to power the high side switch.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Feedback Input. FB senses the output voltage to regulate. Drive FB with a
resistive voltage divider from the output voltage.
Compensation Node. COMP is used to compensate the regulation control loop.
Connect a series RC network from COMP to GND to compensate the regulation
control loop. In some cases, an additional capacitor from COMP to GND is
required.
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN
higher than 1.4V to turn on the regulator, lower than 0.4V to turn off. For
automatic startup, leave EN unconnected.
Oscillator Resistor Input. Connecting a resistor to ground from this pin sets the
switching frequency.
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DS8278-02 March 2011
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