AIC1730_15 Datasheet, PDF (10/12 Pages) Analog Intergrations Corporation – 150mA, Low Noise, Low Dropout Linear Regulator

AIC1730
„ APPLICATION INFORMATION
INPUT-OUTPUT CAPACITORS
Linear regulators require input and output
capacitors to maintain stability. Input capacitor
at 1μF with 1uF aluminum electrolytic output
capacitor is recommended. And it should be
selected within the Equivalent Series Resistance
(ESR) range as shown in the figure 21, 22, 23,
and 24. ESR of ceramic capacitor is lower and
its electrical characteristics (capacitance and
ESR) vary widely over temperature. In general,
tantalum or electric output capacitor is
suggested for heavy load.
Normally, the output capacitor should be 1μF
(aluminum electrolytic) at least and rates for
operating temperature range. Note that it’s
important to check selected manufactures
electrical characteristics (capacitance and ESR)
over temperature.
NOISE BYPASS CAPACITOR
0.1μF bypass capacitor at BP pin reduces output
voltage noise. And the BP pin has to connect a
capacitor to GND.
POWER DISSIPATION
The maximum power dissipation of AIC1742
depends on the thermal resistance of its case
and circuit board, the temperature difference
between the die junction and ambient air, and
the rate of airflow. The rate of temperature rise is
greatly affected by the mounting pad
configuration on the PCB, the board material,
and the ambient temperature. When the IC
mounting with good thermal conductivity is used,
the junction temperature will be low even when
large power dissipation applies.
The power dissipation across the device is
P = I_OUT (V_IN-V_OUT).
The maximum power dissipation is:
PMAX = ^{(TJ − TA)}
(RθJB + RθBA)
Where T_J-T_A is the temperature difference
between the die junction and the surrounding air,
Rθ_JB is the thermal resistance of the package,
and Rθ_BA is the thermal resistance through the
PCB, copper traces, and other materials to the
surrounding air.
As a general rule, the lower temperature is, the
better reliability of the device is. So the PCB
mounting pad should provide maximum thermal
conductivity to maintain low device temperature.
GND pin performs a dual function of providing
an electrical connection to ground and
channeling heat away. Therefore, connecting the
GND pin to ground with a large pad or ground
plane would increase the power dissipation and
reduce the device temperature.
10