RT8280 RICHTEK [Richtek Technology Corporation], RT8280 Datasheet - Page 2

• Manufacturer Part Number: RT8280
• Description: 3A, 24V, 3MHz Step-Down Converter
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT8280
Typical Application Circuit
Copyright
www.richtek.com
2
Functional Pin Description
9 (Exposed Pad)
V
OUT
Pin No.
3.3
2.5
1.8
1.5
1.2
10
©
8
5
2012 Richtek Technology Corporation. All rights reserved.
4,
1
2
3
5
6
7
8
(V)
4.5V to 24V
Chip Enable
V
BOOT
VIN
SW
GND
FB
COMP
EN
RT
R1 (kΩ)
Pin Name
IN
52.3
31.6
21.5
12.4
8.87
4.99
115
91
Table 1. Recommended Component Selection for f
R
24k
RT
9 (Exposed Pad)
Bootstrap Power. 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. V
converter switches. Drive V
GND with a suitably large capacitor to eliminate noise on the input to the IC.
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.
10µF
C
R2 (kΩ)
IN
10
10
10
10
10
10
10
10
4,
2
7
8
VIN
EN
RT
GND
IN
RT8280
supplies the power to the IC, as well as the step-down
R
C
COMP
BOOT
68
51
36
24
18
13
12
(kΩ)
9
SW
FB
IN
6
1
3
5
with a 4.5V to 24V power source. Bypass V
is a registered trademark of Richtek Technology Corporation.
Pin Function
C
1.8nF
C
C
0.82
1.2
1.8
2.2
2.2
2.2
1.8
NC
C
1
C
(nF)
B330A
10nF
BOOT
C
P
24k
SW
R
C
2.2µH
= 2.2MHz
L
L (μH)
10k
R1
31.6k
R2
8.2
6.8
4.7
2.2
1.5
1.5
2
1
DS8280-02 March 2012
C
22µF
OUT
V
3.3V/3A
OUT
C
OUT
22
22
22
22
22
22
22
22
(μF)
IN
to