Diodes AP2202 - Manual (Page 24)

150mA RF ULDO REGULATOR AP2202
Data Sheet
24
Jul. 2011 Rev. 2. 2 BCD Semiconductor Manufacturing Limited
Input Capacitor
A 1
µ F minimum capacitor is recommended to be
placed between V
IN
and GND.
Output Capacitor
It is required to prevent oscillation. 1.0
µ F minimum
is recommended when C
BYP
is unused. 2.2 µ F mini-
mum is recommended when C
BYP
is 100pF. The out-
put capacitor may be increased to improve transient
response.
Noise Bypass Capacitor
Bypass capacitor is connected to the internal voltage
reference. A 100pF capacitor connected from BYP to
GND make this reference quiet, resulting in a
significant reduction in output noise, but the ESR
stable area will be narrowed.
The start-up speed of the AP2202 is inversely
proportional to the value of reference bypass
capacitor. In some cases, if output noise is not a
major concern and rapid turn-on is necessary, omit
C
BYP
and leave BYP open.
Power Dissipation
Thermal shutdown may take place if exceeding the
maximum power dissipation in application. Under all
possible operating conditions, the junction tempera-
ture must be within the range specified under abso-
lute maximum ratings to avoid thermal shutdown.
To determine if the power dissipated in the regulator
reaches the maximum power dissipation (see figure
16,17), using:
T
J
= P
D
* θ
JA
+ T
A
P
D
=(V
IN
-V
OUT
)*I
OUT
+V
IN
*I
GND
Where: T
J
≤ T
J(max)
, T
J(max)
is absolute maximum rat-
ings for the junction temperature; V
IN
*I
GND
can be
ignored due to its small value.
T
J(max)
is 150 o C , θ
JA
is 200 o C /W for SOT-23-5 pack-
age and 165 o C /W for SOT-89 package, no heatsink is
required since the package alone will dissipate
enough heat to satisfy these requirements unless the
calculated value for power dissipation exceeds the
limit.
Example: For 2.8V version packaged in SOT-23-5,
I
OUT
=150mA, T
A
=50
o
C, V
IN(Max)
is:
(150 o C -50 o C )/(0.15A*200 o C/W )+2.8V=6.133V
Therefore, for good performance, please make sure
that input voltage is less than 6.133V without heat-
sink when T
A
=50
o
C.
Application Information