RT8089A データシートの表示（PDF） - Richtek Technology
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コンポーネント説明
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RT8089A Datasheet PDF : 15 Pages
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Function Block Diagram
EN
PGOOD
FB
PGOOD
VREF
0.6V
EA
EN
OSC
Output
Clamp
Slope
Com
ISEN
OC
Limit
RT8089A
VIN
Int-SS
POR
0.54V
0.2V
PGOOD
UV
Control
Logic
OTP
Driver
NISEN
Current Limit
SW
GND
VCC
Operation
The RT8089A is a synchronous low voltage Buck Converter
that can support the input voltage range from 2.7V to 5.5V
and the output current can be up to 3A. The RT8089A
uses a constant frequency, current mode architecture. In
normal operation, the high side P-MOSFET is turned on
when the Switch Controller is set by the oscillator (OSC)
and is turned off when the current comparator resets the
switch controller. High side MOSFET peak current is
measured by internal RSENSE. The Current Signal is
where Slope Compensator works together with sensing
voltage of RSENSE. The error amplifier EA adjusts COMP
voltage by comparing the feedback signal (VFB) from the
output voltage with the internal 0.6V reference. When the
load current increases, it causes a drop in the feedback
voltage relative to the reference, the COMP voltage then
rises to allow higher inductor current to match the load
current.
UV Comparator
If the feedback voltage (VFB) is lower than threshold voltage
0.2V, the UV Comparator's output will go high and the
Switch Controller will turn off the high side MOSFET.
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8089A-01 March 2013
Oscillator (OSC)
The internal oscillator runs at nominal frequency 1MHz.
PGOOD Comparator
When the feedback voltage (VFB) is higher than threshold
voltage 0.54V, the PGOOD open drain output will be high
impedance.
Enable
There is an internal pull down 500kΩ resistor at EN pin.
When the EN pin is higher than 1.6V, the converter will be
turned on. The EN pin can be connected to VIN through a
100kΩ resistor for automatic startup.
Soft-Start (SS)
An internal current source charges an internal capacitor
to build the soft-start ramp voltage. The VFB voltage will
track the internal ramp voltage during soft-start interval.
The typical soft-start time is 700μs.
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