L11815A

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

4 of 4

www.unisonic.com.tw

QW-R502-346.F

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.

TYPICAL APPLICATION CIRCUIT

L11815A

GND

C1=1µF

C2=4.7µF

UTC assumes no responsibility for equipment failures that result from using products at values that

exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or

other parameters) listed in products specifications of any and all UTC products described or contained

herein. UTC products are not designed for use in life support appliances, devices or systems where

malfunction of these products can be reasonably expected to result in personal injury. Reproduction in

whole or in part is prohibited without the prior written consent of the copyright owner. The information

presented in this document does not form part of any quotation or contract, is believed to be accurate

and reliable and may be changed without notice.