300mA Low Power Low Noise
LDO CMOS Voltage Regulator
Application Hints
Like any low dropout regulator, SE5509B requires
external capacitors to ensure stability.
ensure performance.
The
external capacitors must be carefully selected to
SE5509B
Thermal Considerations
It is important that the thermal limit of the package is
not exceeded. The SE5509B has built-in thermal
protection.
to ground.
When the thermal limit is exceeded,
The power dissipation for a given
the IC will enter protection, and V
OUT
will be pulled
application can be calculated as following:
The power dissipation (P
D
) is
P
D
= I
OUT
* [V
IN
– V
OUT
]
The thermal limit of the package is then limited to
P
D(MAX)
= [T
J
– T
A
]/Θ
JA
where T
J
is the junction
temperature, TA is the ambient temperature, and
Θ
JA
is around 230°C/W for SE5509B. SE5509B is
designed to enter thermal protection at 150°C. For
example, if T
A
is 25°C then the maximum P
D
is
limited to about 0.6W. In other words, if I
OUT(MAX)
=
300mA, then [V
IN
– V
OUT
] cannot exceed 2V.
Input Capacitor
An input capacitor of at least 1μF is required. The
inexpensive Electrolytic capacitor is preferred. The
value can be increased without upper limit.
Output Capacitor
An output capacitor is required for stability. It must
be placed no more than 1 cm away from the V
OUT
pin, and connected directly between V
OUT
and GND
pins. The inexpensive Electrolytic capacitor is
recommended. The minimum value is 1μF but may
be increased without limit.
Application Diagram
Revision 5/4/2009
Preliminary and all contents are subject to change without prior notice
© Seaward Electronics Inc., 2006. • www.seawardinc.com.cn • Page 5
SEAWARD [ Seaward Electronics Inc. ]
