AIC1085_15 Datasheet, PDF (6/9 Pages) Analog Intergrations Corporation – 3A Low Dropout Positive Regulator

AIC1085
 APPLICATION INFORMATION
INPUT-OUTPUT CAPACITORS
Linear regulators require input and output
capacitors to maintain stability. Input capacitor at
10F with a 10F aluminum electrolytic output
capacitor is recommended.
POWER DISSIPATION
The AIC1085 obtains thermal-limiting circuitry,
which is designed to protect the device against
overload condition. For continuous load
condition, maximum rating of junction
temperature must not be exceeded. It is
important to pay more attention in thermal
resistance. It includes junction to case, junction
to ambient. The maximum power dissipation of
AIC1085 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

(T_J-max - T_A )
Rθ _JA
Where T_J-max is the maximum allowable junction
temperature (125C), and T_A is the ambient
temperature suitable in application.
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.
 APPLICATION EXAMPLES
Vin
3 _AIC1085 ²
Vout
5V
+ _C1
1 ADJ
R1
3.3V
125 ⁺ C2
10uF
10uF
TTL
R3
MMBT2222A ^R2
1k
R4
205
1k
Fig. 5 V_OUT=3.3V with Shutdown
Vin
3 _AIC1085 2
5V
+ _C1
10uF
1 ADJ
Vout
R1
1.25V
125 ⁺ C2
10uF
Fig. 7 V_OUT=1.25V Application Circuit
Vin
3
2
AIC1085
5V
+
C1
1 ADJ
10uF
Cadj
Vout
R1
125
3.3V
+ _C2
100uF
R2
205
* Cadj can improve ripple rejection
Fig. 6 Improving Ripple Rejection
T1
Vin
D1
3
AIC1085-33
2
+
C1
1
10uF
FLOATING INPUT
+ _C2
100uF
Vout
-3.3V
Fig. 8 Low Dropout Negative Supply
6