RT8287A 데이터 시트보기 (PDF) - Richtek Technology
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RT8287A Datasheet PDF : 14 Pages
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RT8287A
Typical Application Circuit
VIN
PGOOD
ON/OFF
CIN
22µF
1 VIN
BOOT 6
RT8287A
SW 2, 3, 4, 5
9 PGOOD
CBOOT
0.1µF L
VOUT
1.2V/4A
R3
100k
CC
0.1µF
11
VCC
FB 8
SS 10
RT
CSS
47nF
R1
COUT
R2
7 EN
AGND GND
14 12, 13, 15 (Exposed Pad)
VOUT (V)
5
3.3
2.5
1.8
1.5
1.2
1.05
Table 1. Recommended Components Selection
R1 (kΩ)
75
R2 (kΩ)
14.46
RT (kΩ)
0
L (μH)
4.7
75
24.32
0
3.6
75
35.82
0
3.6
5
4.07
30
2
5
5.84
39
2
5
10.31
47
2
5
16.69
47
1.5
COUT (μF)
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
Function Pin Description
Pin No.
Pin Name
Pin Function
Supply Input. VIN supplies the power to the IC, as well as the step-down converter
1
VIN
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.
2, 3, 4, 5
6
7
8
9
10
SW
BOOT
EN
FB
PGOOD
SS
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.
Power Good Output. The output of this pin is open-drain. Power good threshold is
90% low to high and 70% high to low of regulation value.
Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from
SS to GND to set the soft-start period.
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
is a registered trademark of Richtek Technology Corporation.
DS8287A-03 June 2012
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