RT8252A Datasheet, PDF (2/14 Pages) Richtek Technology Corporation – 2A, 23V, 340kHz Synchronous Step-Down Converter

RT8252A
Typical Application Circuit
V_IN
4.5V to 23V
C_SS
0.1µF
C_IN
10µF
2 _VIN
BOOT ¹
RT8252A
SW ³
C_{BOOT L}
100nF 10µH
R_EN 100k
7 _EN
R1
75k
8 _SS
FB ⁵
4, 9 (Exposed Pad)
GND
COMP ⁶
C_C
3.3nF
R_C
13k
R2
24k
V_OUT
3.3V/2A
C_OUT
22µF x 2
C_P
Open
Recommended Component Selection
V_OUT (V) R1 (kΩ) R2 (kΩ) R_C (kΩ)
8
27
3
27
5
62
11.8
20
3.3
75
24
13
2.5
25.5
12
9.1
1.5
10.5
12
4.7
1.2
12
24
3.6
1
3
12
3
C_C (nF)
3.3
3.3
3.3
3.3
3.3
3.3
3.3
L (μH)
22
15
10
6.8
3.6
3.6
2
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
Pin Name
BOOT
VIN
SW
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 23V. Must bypass with a suitably large ceramic
capacitor.
Phase Node--Connect this pin to an external L-C filter.
4,
9 (Exposed Pad)
GND
5
FB
6
COMP
7
EN
8
SS
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Feedback Input. 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 divider. For an adjustable output, an external resistive 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.
Chip Enable (Active High). A logic high enables the converter; a logic low
forces the RT8252A 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.
www.richtek.com
2
DS8252A-02 March 2011