rt8288 Richtek Technology Corporation, rt8288 Datasheet - Page 2

• Manufacturer Part Number: rt8288
• Description: 3a, 21v 500khz Synchronous Step-down Converter
• Manufacturer: Richtek Technology Corporation

RT8288
Typical Application Circuit
Function Pin Description
www.richtek.com
2
9 (Exposed Pad)
Pin No.
2, 3
8,
1
4
5
6
7
V
OUT
1.05
3.3
2.5
1.8
1.5
1.2
5
(V)
VIN
SW
BOOT
EN
FB
VCC
GND
Chip Enable
Pin Name
V
IN
8, 9 (Exposed Pad)
R1 (kΩ)
75
75
75
5
5
5
5
Supply Input. VIN supplies the power to the IC, as well as the step-down converter
switches. Drive VIN with a 4.5V to 21V power source. Bypass VIN to 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.
High Side Gate Drive Boost Input. BOOT supplies the drive for the high side
N-MOSFET switch. Connect a 100nF or greater capacitor from SW to BOOT to
power the high side switch.
Chip Enable (Active High). For automatic start-up, connect the EN pin to VIN with a
100kΩ resistor.
Feedback Input. FB senses the output voltage to regulate said voltage. Drive FB
with a resistive voltage divider from the output voltage. The feedback threshold is
0.808V.
Bias Supply. Decouple with 0.1μF to 0.22μF capacitor. The capacitance should be
no more than 0.22μF.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Table 1. Recommended Components Selection
C
22µF
IN
1
5
VIN
EN
GND
R2 (kΩ)
14.46
24.32
35.82
10.31
16.69
4.07
5.84
RT8288
BOOT
VCC
SW
FB
4
2, 3
6
7
R
T
30
39
47
47
0
0
0
(kΩ)
C
0.1µF
R
Pin Function
C
C
100nF
T
BOOT
R2
L
L (μH)
4.7
3.6
3.6
1.5
R1
2
2
2
C
DS8288-01 August 2011
OUT
V
C
OUT
OUT
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
(μF)