APE8837_16 Datasheet, PDF (9/10 Pages) Advanced Power Electronics Corp. – DUAL CHANNEL LDO REGULATORS WITH ENABLE

Advanced Power
Electronics Corp.
APE8837
APPLICATION INFORMATION
Like any low-dropout regulator, the APE8837 requires input and output decoupling capacitors. The device is
specifically designed for portable applications requiring minimum board space and smallest components.
These capacitors must be correctly selected for good performance (see Capacitor Characteristics Section).
Please note that linear regulators with a low dropout voltage have high internal loop gains which require care
in guarding against oscillation caused by insufficient decoupling capacitance.
Input Capacitor
An input capacitance of 2.2uF is required between input pin and ground directly (the amount of the
capacitance may be increased without limit). The input capacitor must be located less than 1cm from the
device to assure input stability. A lower ESR capacitor allows the use of less capacitance, while higher ESR
type (like aluminum electrolytic) requires more capacitance. Capacitor types (aluminum, ceramic and
tantalum) can be mixed in parallel, but the total equivalent input capacitance/ ESR must be defined as above
to stable operation. There are no requirements for the ESR on the input capacitor, but tolerance and
temperature coefficient must be considered when selecting the capacitor to ensure the capacitance will be
1uF over the entire operating temperature range.
Output Capacitor
The APE8837 is designed specifically to work with very small ceramic output capacitors. A ceramic capacitor
. ^{(temperature characteristics X7R, X5R) in 1uF is suitable for the APE8837 application. The recommended}
minimum capacitance for the device is 2.2uF, X5R or X7R dielectric ceramic, between V_OUT and GND for
stability, but it may be increased without limit. Higher capacitance values help to improve transient. The output
capacitor's ESR is critical because it forms a zero to provide phase lead which is required for loop stability.
Thermal Considerations
The APE8837 series can deliver a current of up to 200mA/channel over the full operating junction temperature
range. However, the maximum output current must be debated 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_OUT + V_IN x I_GND
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 thermal resistance from junction to ambient (Rθ_JA) of SOT-26 package at recommended
minimum footprint is 250°C/W.
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