RT7253A
Typical Application Circuit
V
IN
4.5V to 17V
2
C
IN
10µF x 2
R
EN
100k
VIN
BOOT
RT7253A
SW 3
7 EN
8 SS
GND
1
C
BOOT
L
100nF 10µH
R1
75k
FB 5
COMP
6
C
C
3.3nF
R
C
13k
R2
24k
V
OUT
3.3V/2A
C
OUT
22µF x 2
C
SS
0.1µF
4, 9 (Exposed Pad)
C
P
Open
V
OUT
(V) R1 (kΩ)
8
27
5
62
3.3
75
2.5
25.5
1.5
10.5
1.2
12
1
3
R2 (kΩ)
3
11.8
24
12
12
24
12
R
C
(kΩ)
24
18
12
8.2
3.6
3
2.7
C
C
(nF)
4.7
4.7
4.7
4.7
4.7
4.7
4.7
L (μH)
22
15
10
6.8
3.6
3.6
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
Functional Pin Description
Pin No.
1
2
3
4,
9 (Exposed Pad)
5
Pin Name
BOOT
VIN
SW
GND
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 17V. Must bypass with a suitably large ceramic
capacitor.
Phase 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 pin. This pin is connected to the converter output. It is used to
set the output of the converter to regulate to the desired value via an internal
resistive voltage divider. For an adjustable output, an external resistive
voltage divider is connected to this pin.
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
RT7253A into shutdown mode reducing the supply current to less than 3μA.
Attach this pin to VIN with a 100kΩ pull up resistor for automatic startup.
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 13.5ms.
FB
6
COMP
7
EN
8
SS
www.richtek.com
2
DS7253A-02 March 2011
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
