APE8875 Datasheet, PDF (4/9 Pages) Advanced Power Electronics Corp. – 1.6X LINEAR REGULATOR FOR DC FAN DRIVER

Advanced Power
Electronics Corp.
APE8875
FUNCTION DESCRIPTIONS
Current-Limit
The APE8875 monitors the current via the output PMOS and limits the maximum
current to prevent load and APE8875 from damages during overload or short circuit
conditions.
Short Current Protection
When the output voltage drops below 0.6V (typical), which is caused by over
load or short circuit, the fold back current limit circuitry limits the output current to
250mA. The fold back current limit is used to reduce the power dissipation during
short circuit condition.
Thermal Shutdown
A thermal shutdown circuit limits the junction temperature of APE8875. When the
junction temperature exceeds +150 °C, a thermal sensor turns off the output PMOS,
allowing the device to cool down. The regulator regulates the output again through
initiation of a new soft-start cycle after the junction temperature cools by 30 ° C,
resulting in a pulsed output during continuous thermal overload conditions.
APPLICATION INFORMATION
Capacitor Selection
Normally, use a 2.2µF capacitor on the input and a 2.2µF capacitor on the output
of the APE8875. In order to insure the circuit stability, the proper output capacitor
value should be larger than 1uF. With X5R and X7R dielectrics, 2.2uF is sufficient at
all operating temperatures.
Thermal Considerations
The APE8875 series can deliver a current of up to 600mA over the full operating
junction temperature range. However, the maximum output current must be dated at
higher ambient temperature to ensure the junction temperature does not exceed 125°
C. With all possible conditions, the junction temperature must be within the range
specified under operating conditions. Power dissipation can be calculated based on
the output current and the voltage drop across regulator.
P_D = (V_IN - V_OUT) I_O
The final operating junction temperature for any set of conditions can be
estimated by the following thermal equation:
P_{D (MAX)} = (T_{J (MAX)} - T_A) / Rth_JA
Where T_J(MAX) is the maximum junction temperature of the die (125°C) and T_A is
the maximum ambient temperature. The junction to ambient thermal resistance
(Rth_JA) for TSOT-26 package at recommended minimum footprint is 100°C/W.
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