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RT9182JPES 参数 Datasheet PDF下载

RT9182JPES图片预览
型号: RT9182JPES
PDF下载: 下载PDF文件 查看货源
内容描述: 双通道,低噪声型,200mA LDO稳压器 [Dual, Low-Noise, 200mA LDO Regulator]
分类和应用: 稳压器
文件页数/大小: 9 页 / 113 K
品牌: RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
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RT9182
Applications Information
The RT9182 is integrated with two low noise, low dropout,
and low quiescent current linear regulators designed
primarily for battery-powered applications. Output
voltages are optional ranging from 1.5V to 3.3V, and each
channel can supply current up to 200mA.
Shutdown
The RT9182 is shutdown by pulling the EN input low,
and turned on by driving the input high. If this feature is
not to be used, the EN input should be tied to VIN to
keep the regulator on at all times (the EN input must
not
be floating).
Internal P-Channel Pass Transistor
The RT9182 features double typical 1.5Ω P-Channel
MOSFET pass transistors. 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
RT9182 does not suffer from these problems and
consume only 165μA of quiescent current whether in
dropout, light-load, or heavy-load applications.
Current Limit and Thermal Protection
The RT9182 includes two independent current limit
structure which monitor and control each pass transistor's
gate voltage limiting the guaranteed maximum output
current to 200mA.
Thermal-overload protection limits total power dissipation
in the RT9182. When the junction temperature exceeds
T
J
= +140°C, the thermal sensor signals the shutdown
logic turning off the pass transistor and allowing the IC to
cool. The thermal sensor will turn the pass transistor on
again after the IC's junction temperature cools by 10°C,
resulting in a pulsed output during continuous thermal-
overload conditions. Thermal-overloaded protection is
designed to protect the RT9182 in the event of fault
conditions.
Do not exceed the absolute maximum junction tempera-
ture rating
of T
J
= + 125°C for continuous
operation. The
output can be shorted to ground for an indefinite amount
DS9182-18 April 2008
of time without damaging the part by cooperation of current
limit and thermal protection.
Operating Region and Power Dissipation
The maximum power dissipation of RT9182 depends on
the thermal resistance of the case and circuit board, the
temperature difference between the die junction and
ambient air, and the rate of airflow. The power dissipation
across the device is
P = I
OUT
(V
IN
- V
OUT
).
The maximum power dissipation is :
P
(MAX)
= (T
J
- T
A
) /
θ
JA
where T
J
- T
A
is the temperature difference between the
RT9182 die junction and the surrounding environment,
θ
JA
is the thermal resistance from the junction to the
surrounding environment. The GND pin of the RT9182
performs the dual function of providing an electrical
connection to ground and channeling heat away. Connect
the GND pin to ground using a large pad or ground plane.
Capacitor Selection and Regulator Stability
Like any low-dropout regulator, the external capacitors
used with the RT9182 must be carefully selected for
regulator stability and performance.
Using a capacitor whose value is > 1uF on the RT9182
input and the amount of capacitance can be increased
without limit. The input capacitor must be located a
distance of not more than 0.5" from the input pin of the
IC and returned to a clean analog ground. Any good
quality ceramic or tantalum can be used for this capacitor.
The capacitor with larger value and lower ESR (equivalent
series resistance) provides better PSRR and line-
transient response.
The output capacitor must meet both requirements for
minimum amount of capacitance and ESR in all LDO
applications (see Figure1). The RT9182 is designed
specifically to work with low ESR ceramic output capacitor
in space-saving and performance consideration. Using
a ceramic capacitor whose value is at least 1uF with ESR
is > 5mΩ on the RT9182 output ensures stability. The
RT9182 still works well with output capacitor of other
types due to the wide stable ESR range. Output capacitor
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