RT7270
Typical Application Circuit
V
IN
4.5V to 18V
2
C
IN
10µF x 2
R
EN
100k
VIN
BOOT
RT7270
SW 3
7 EN
8 SS
GND
1
C
BOOT
L
0.1µF 10µH
R1
26.1k
FB 5
COMP
6
C
C
R
C
3.9nF 6.8k
R2
10k
V
OUT
3.3V
C
OUT
22µF x 2
C
SS
0.1µF
4, 9 (Exposed Pad)
C
P
Open
Table 1. Recommended Component Selection
V
OUT
(V)
15
10
8
5
3.3
2.5
1.8
1.2
R1 (kΩ)
153
97.6
76.8
45.3
26.1
16.9
9.53
3
R2 (kΩ)
10
10
10
10
10
10
10
10
R
C
(kΩ)
30
20
15
13
6.8
6.2
4.3
3
C
C
(nF)
3.9
3.9
3.9
3.9
3.9
3.9
3.9
3.9
L (μH)
33
22
22
15
10
6.8
4.7
3.6
C
OUT
(μF)
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
Functional Pin Description
Pin No.
1
2
3
4,
9 (Exposed Pad)
5
6
7
8
Pin Name
BOOT
VIN
SW
GND
FB
COMP
EN
SS
Pin Function
Bootstrap for High Side Gate Driver. Connect a 0.1μF or greater ceramic
capacitor from BOOT to SW pins.
Input Supply Voltage, 4.5V to 18V. Must bypass with a suitable large ceramic
capacitor.
Switch Node. Connect this pin to an external L-C filter.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Feedback Input. It is used to regulate the output of the converter to a set value
via an external resistive voltage divider.
Compensation Node. COMP is used to compensate the regulation control
loop. Connect a series RC network from COMP to GND. In some cases, an
additional capacitor from COMP to GND is required.
Enable Input Pin. A logic high enables the converter; a logic low forces the IC
into shutdown mode reducing the supply current to less than 3μA.
Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor
from SS to GND to set the soft-start period. A 0.1μF capacitor sets the
soft-start period to 15.5ms.
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS7270-01
September 2012
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
