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RT9167A-45CB 参数 Datasheet PDF下载

RT9167A-45CB图片预览
型号: RT9167A-45CB
PDF下载: 下载PDF文件 查看货源
内容描述: 低噪声固定输出电压200MA / 500MA LDO稳压器 [LOW NOISE FIXED OUTPUT VOLTAGE 200MA/500MA LDO REGULATOR]
分类和应用: 稳压器输出元件
文件页数/大小: 14 页 / 257 K
品牌: ETC [ ETC ]
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RT9167/A
Internal P-Channel Pass Transistor
C
BP
= 1nF
The RT9167/A features a typical 1.1Ω P-channel
MOSFET
pass
transistor.
It
provides
several
advantages over similar designs using PNP pass
transistors, including longer battery life. The P-channel
MOSFET requires no base drive, which reduces
quiescent current considerably. PNP-based regulators
waste considerable current in dropout when the pass
transistor saturates. They also use high base-drive
currents under large loads. The RT9167/A does not
V
OUT
= 3.0V
Voltage (0.5V / DIV)
C
BP
= 10nF
suffer from these problems and consume only 80µA of
quiescent current whether in dropout, light-load, or
heavy-load applications.
Input-Output (Dropout) Voltage
A
regulator’s
minimum
input-output
voltage
differential (or dropout voltage) determines the
lowest usable supply voltage. In battery-powered
systems, this will determine the useful end-of-life
battery voltage. Because the RT9167/A uses a P-
channel MOSFET pass transistor, the dropout
voltage is a function of drain-to-source on-resistance
[R
DS(ON)
] multiplied by the load current.
Reverse Current Path
The power transistor used in the RT9167/A has an
inherent diode connected between the regulator
input and output (see Fig.3). If the output is forced
above the input by more than a diode-drop, this
diode will become forward biased and current will
flow from the V
OUT
terminal to V
IN
. This diode will
also be turned on by abruptly stepping the input
voltage to a value below the output voltage. To
prevent regulator mis-operation, a Schottky diode
should
be
used
in
any
applications
where
input/output voltage conditions can cause the
internal diode to be turned on (see Fig.4). As shown,
the Schottky diode is connected in parallel with the
internal parasitic diode and prevents it from being
turned on by limiting the voltage drop across it to
about 0.3V. < 100 mA to prevent damage to the part.
0
5.0
10.0
15.0
Time (ms)
Fig. 2
Load-Transient Considerations
The RT9167/A load-transient response graphs (see
Typical
Operating
Characteristics)
show
two
components of the output response: a DC shift from
the output impedance due to the load current
change, and the transient response. The DC shift is
quite small due to the excellent load regulation of the
IC. Typical output voltage transient spike for a step
change in the load current from 0mA to 50mA is tens
mV, depending on the ESR of the output capacitor.
Increasing
the
output
capacitor’s
value
and
decreasing the ESR attenuates the overshoot.
Shutdown Input Operation
The RT9167/A is shutdown by pulling the SHDN
input low, and turned on by driving the input high. If
this feature is not to be used, the SHDN input should
be tied to VIN to keep the regulator on at all times
(the SHDN input must
not
be left floating).
To ensure proper operation, the signal source used to
drive the SHDN input must be able to swing above and
below the specified turn-on/turn-off voltage thresholds
which guarantee an ON or OFF state (see Electrical
Characteristics). The ON/OFF signal may come from
either CMOS output, or an open-collector output with
pull-up resistor to the RT9167/A input voltage or
another logic supply. The high-level voltage may
exceed the RT9167/A input voltage, but must remain
within the absolute maximum ratings for the SHDN pin.
DS9167/A-10 July 2001
www.richtek-ic.com.tw
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