RT8287 Ver la hoja de datos (PDF) - Richtek Technology
Número de pieza
componentes Descripción
Fabricante
RT8287 Datasheet PDF : 14 Pages
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RT8287
Typical Application Circuit
VIN
PGOOD
ON/OFF
1 VIN
BOOT 6
CIN
22µF
RT8287
SW 2, 3, 4, 5
9 PGOOD
CBOOT
0.1µF L
VOUT
1.2V/3A
R3
100k 11
FB 8
RT
VCC
R1
COUT
CC
CSS
R2
0.1µF
7 EN
47nF
SS 10
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.
1
Pin Name
VIN
2, 3, 4, 5
SW
6
BOOT
7
EN
8
FB
9
PGOOD
10
SS
11
VCC
12, 13
15 (Exposed Pad)
GND
14
AGND
Pin Function
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.
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.
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.
Analog Ground. Connect this pin to the system ground in PCB layout.
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
is a registered trademark of Richtek Technology Corporation.
DS8287-03 June 2012
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