01-Jun-2002 Rev. A

Page 6 of 6

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Any changing of specification will not be informed individual

Elektronische Bauelemente

SSC2128

CMOS Low Dropout

Voltage Regulator

Detailed Description

The SSC2128 of COMS regulators contain a PMOS pass transistor,voltage reference, error amplifier,over-current protection and thermal

shutdown.The P-channel pass transistor receives data from the error amplifier, over-current shutdown, and thermal protection circuits.

During normal operation, the error amplifier compares the output voltage to a precision reference. Over-current and Thermal shutdown circuits

become active when the junction temperature exceeds140 C, or the current exceeds 2.2A.During thermal shutdown, the output voltage

remains low. Normal operation is restored when the junction temperature drops below 120 C.The SSC2128 behaves like a current

source when the load reaches 2.2A. However, if the load impedance drops below 0.3

, the current drops back to 600mA to prevent

excessive power dissipation. Normal operation is restored when the load resistance exceeds of 0.75

.

o

o

External Capacitors

The SSC2128 is stable with an output capacitance to ground of 4.7uF or greater. Ceramic capacitors have the lowest ESR, and will offer

the best AC performance. Conversely, Aluminum Electrolytic capacitors exhibit the highest ESR, resulting in the poorest AC response.

Unfortunately, large value ceramic capacitors are comparatively expensive. One option is to parallel a 0.1uF ceramic capacitor with a

10uF Aluminum Electrolytic. The benefit is low ESR, high capacitance, and low overall cost. A second capacitor is recommended between

The input capacitor should be at least 0.1uF to have a beneficial effect. A third capacitor can be

ground termination is desirable. This can be achieved with a "Star" connection.

Enable

When pulled low, the PMOS pass transistor shuts off, and all internal circuits are powered down. In this state, the quiescent

source and EN

Ω

Ω

Ω

connected between the BY-PASS pin and GND. This capacitor can be a low cost Polyester Film variety between the value of

0.001~0.01uF. A large capcacitor improves the AC ripple rejection, but also makes the output come up slowly. This "Soft" turn-on

is desirable in some applications to limit turn-on surges. All capacitors should be placed in closed proximity to the pins. A "Quiet"

current is