RT8289 データシートの表示（PDF） - Richtek Technology
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RT8289 Datasheet PDF : 13 Pages
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RT8289
Functional Pin Description
Pin No.
Pin Name
Pin Function
High Side Gate Drive Bootstrap Input. BOOT supplies the drive for the high side
1
BOOT
N-MOSFET switch. Connect a 10nF or greater capacitor from SW to BOOT to
power the high side switch.
2, 3
NC
No Internal Connection.
Feedback Input. FB senses the output voltage to regulate said voltage. Drive FB
4
FB
with a resistive voltage divider from the output voltage. The value of the divider
resistors also sets loop bandwidth. The feedback threshold is 1.222V.
5
EN
6,
9 (Exposed Pad)
GND
7
VIN
8
SW
Chip Enable (Active High). EN is a digital input that turns the regulator on or off.
Drive EN higher than 1.4V to turn on the regulator, lower than 0.4V to turn it off.
For automatic startup, leave EN unconnected.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Power Input. VIN supplies the power to the IC, as well as the step-down
converter switches. Drive VIN with a 5.5V to 32V power source. Bypass VIN to
GND with a suitably large capacitor to eliminate noise on the input to the IC.
Power Switching Output. 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.
Function Block Diagram
VIN
Current Sense
Ramp
Amplifier -
Generator
+
EN
Regulator
Oscillator
500kHz
S
Q Driver
+
R
Reference
Error
+ Amplifier
-
PWM
Comparator
FB
-
12k
400k 30pF
OC Limit
Clamp
Bootstrap
Control
13pF
BOOT
SW
GND
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DS8289-01 March 2011
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