L11815A_11 Datasheet, PDF (5/6 Pages) Unisonic Technologies – 1.5A CMOS LDO

L11815A
Preliminary
CMOS IC
„ DETAILED DESCRIPATION
The UTC L11815A of CMOS regulators insist of a PMOS pass transistor, voltage reference, error amplifier,
over-current protection, and thermal shutdown.
The error amplifier, over-current shutdown, and thermal protection circuits provides data for P-channel pass
transistor. The error amplifier takes output voltage for a precision reference in the normal operation and the normal
operation is restored when the junction temperature drops below 120°C.Over-current and Thermal shutdown circuits
start to work when the junction temperature is higher than 150 °C, or the current exceeds 2.2A. The output voltage
stays low when the thermal shutdown is in active.
The UTC L11815A behaves like a current source when the load reaches 2.2A. But the current would fall back to
600mA to prevent excessive power loss when the load impedance value is below 0.3Ω.Normal operation is restored
when the load resistance value is higher than 0.75 Ω.
„ EXTERNAL CAPACITORS
The UTC L11815A has an output capacitor to ground of 4.7μF or more in the stable operation. Ceramic
capacitors can provide the lowest ESR with the best AC performance. Aluminum Electrolytic capacitors, in contrast,
have the highest ESR with poorest AC response. Unfortunately, large value ceramic capacitors are comparatively
expensive. So we can parallel a 0.1μF ceramic capacitor with a 10μF Aluminum Electrolytic. The result is low ESR,
high capacitance, and low overall cost.
A second capacitor is recommended between the input and ground to stabilize input voltage. To get an ideal
effect the value of the input capacitor should be at least 0.1μF.
All capacitors should be placed in close proximity to the pins. This can be achieved with a star connection.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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