PL0501
APPLICATION INFORMATION
Quick Charging Mode
The PL0501 has a quick charge block to get the
reference up very quickly by charging the BYP capacitor
with very high current when the chip comes out of shut
down. This quick charge block stops charging the BYP
capacitor when the reference reaches 95% of its nominal
value and then the chip switches out of quick charging
mode to normal operating mode.
Capacitor Selection And Regulator Stability
Use a 1.0μF capacitor on the PL0501 input and a 1.0μF
capacitor on the output. Large input capacitor values and
lower ESR provide better noise rejection and line-
transient response.
Reduce output noise and improve load-transient
response, stability and power-supply rejection by using
large output capacitors. Note that some ceramic
dielectrics exhibit large capacitance and ESR variation
with temperature. With dielectrics such as Z5U and Y5V,
it may be necessary to use a 2.2μF or larger output
capacitor to ensure stability at temperatures below -10°C.
With X7R or X5R dielectrics, 1μF is sufficient at all
operating temperatures.
Over Temperature Protection
Over temperature protection limits the total power
dissipation in the PL0501. When the junction
temperature exceeds TJ = +165°C, the thermal sensor
signals the shutdown logic and turns off the pass
transistor. The thermal sensor turns the pass transistor
on again after the IC’s junction temperature drops by
20°C, resulting in a pulsed output during continuous
thermal-overload conditions.
Use a 0.01μF bypass capacitor at BYP (PL0501-BYP) for
low-output voltage noise. The leakage current going into
the BYP pin should be less than 10nA.
Thermal-overload protection is designed to protect the
PL0501 in the event of a fault condition. For continuous
operation, do not exceed the absolute maximum junction
temperature rating of TJ = +150°C.
Noise, PSRR and Transient Response
The PL0501 is designed to deliver ultra-low noise and
high PSRR, as well as low dropout and low quiescent
currents in battery-powered systems. The PL0501 PSRR
is 75dB at 100Hz and 70dB at 10KHz.
When operating from sources other than batteries,
improved supply-noise rejection and transient response
can be achieved by increasing the values of the input and
output bypass capacitors and through passive filtering
techniques.
Operating Region and Power Dissipation
The PL0501’s maximum power dissipation depends on
(1) the thermal resistance of the case and circuit board,
(2) the temperature difference between the die junction
and ambient and (3) the rate of airflow. The power
dissipation across the device is:
P = IOUT × (VIN – VOUT
)
Dropout Voltage
The maximum power dissipation is:
A regulator’s minimum dropout voltage determines the
lowest usable supply voltage. In battery-powered
systems, this determines the useful end-of-life battery
voltage. Because the PL0501 uses a P-channel MOSFET
pass transistor, its dropout voltage is a function of drain-
to-source on resistance (RDSON) multiplied by the load
current.
PMAX = (TJ – TA)/(θJC + θCA)
Where (TJ – TA) is the temperature difference between
the PL0501 die junction and the surrounding air, θJC is
the thermal resistance of the package and θCA is the
thermal resistance through the PC board, copper traces
and other materials to the surrounding air.
The GND pin of the PL0501 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.
Noise Reduction
For the PL0501, an external 0.01μF bypass capacitor
between BYP and GND with innovative noise bypass
scheme reduces the output noises dramatically, exhibiting
100μV (RMS) of output voltage noise with CBYP = 0.01μF
and COUT = 10μF.
8
July 2007
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