RT9182ACE RICHTEK [Richtek Technology Corporation], RT9182ACE Datasheet - Page 6

• Manufacturer Part Number: RT9182ACE
• Description: DUAL, LOW-NOISE, 200mA LDO REGULATOR
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9182
Functional Description
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 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).
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 minimum.
Thermal-overload
dissipation in the RT9182. When the junction
temperature exceeds T
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
protection is designed to protect the RT9182 in the
www.richtek-ic.com.tw
6
conditions.
protection
J
= +140°C, the thermal
limits
Thermal-overloaded
total
power
Preliminary
event of fault conditions. Do not exceed the absolute
maximum junction-temperature rating of T
for continuous operation. The output can be shorted
to ground for an indefinite amount 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
The maximum power dissipation is:
where T
the RT9182 die junction and the surrounding
environment, θ
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.
Low-Noise Operation
An external 10nF bypass capacitor at BP, in
conjunction with an internal resistor, creates a
lowpass filter. The RT9182 exhibits 29µVRMS of
output voltage noise with C
2.2µF.
PMAX = (T
P = I
OUT
J
- T
(V
A
J
IN
is the temperature difference between
- T
JA
- V
A
is the thermal resistance from the
) / θ
OUT
JA
).
BP
= 10nF and C
DS9182-02 April 2002
J
= +150°C
OUT
=