SE5509_12 Datasheet, PDF (5/7 Pages) Seaward Electronics Inc. – Low Power Low Noise LDO CMOS Voltage Regulator

Low Power Low Noise LDO
CMOS Voltage Regulator
SE5509
Application Hints
Like any low dropout regulator, SE5509 requires
external capacitors to ensure stability. The
external capacitors must be carefully selected to
ensure performance.
Input Capacitor
An input capacitor of at least 1μF is required.
Ceramic or Tantalum can be used. The value can
be increase 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. Electrolytical capacitor is recommended. The
minimum value is 1μF but may be increase without
limit. Ceramic can be used. But the value should not
be more than 2.2μF.
Thermal Considerations
It is important that the thermal limit of the package is
not exceeded. The SE5509 has built-in thermal
protection. When the thermal limit is exceeded,
the IC will enter protection, and V_OUT will be pulled
to ground. The power dissipation for a given
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 SE5509. SE5509 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.
Application Diagram
Revision 9/26/2012
Preliminary and all contents are subject to change without prior notice
© Seaward Electronics Inc., 2006. • www.seawardinc.com.cn • Page 5