L1188

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

5 of 6

www.unisonic.com.tw

QW-R502-324.b

TYPICAL APPLICATION CIRCUIT

APPLICATION INFORMATION

1. Detailed Description

Internal circuits include: a PMOS pass transistor, voltage reference, error amplifier, over-current protection, and

thermal shutdown.

The data through the error amplifier, over-current shutdown, and thermal protection circuits, then to the

P-channel pass transistor.

As soon as the junction temperature exceeds 150°C or the current exceeds 900mA, over-current and thermal

shutdown circuits start working. When the junction temperature drops below 120°C, normal operation is restored.

When the load exceeds the rated output current, for preventing the over stress, the chip switches from voltage

mode to current mode.

2. External Information

When considering the external capacitors, the L1188 is stable with an output capacitor to ground of 2.2μF or

greater. As we know, the ceramic capacitors have the lowest ESR but can offer the best AC performance; the

aluminum electrolytic capacitors exhibit the highest ESR but offer the poorest AC response. And also large value

ceramic capacitors are expensive. Consider all the situation, the best way is to parallel a 0.1μF ceramic capacitor with

a 10μF Aluminum Electrolytic (low ESR, high capacitance, and low overall cost).

For better beneficial effecting, the input capacitor should be at least 0.1μF.