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http://www.union-ic.com

Rev.01 Sep.2010

5/7

UM177XX

Pin Function

SHDN

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(Pin 1): Shutdown, Active Low. This pin is used to put the UM177XX into shutdown. The

SHDN

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pin cannot be left floating and must be tied to the input pin if not used.

GND (Pin 2): Ground and Heat Sink. Solder to a ground plane or large pad to maximize heat

dissipation.

VIN (Pin 3): Power for UM177XX and Load. Power is supplied to the devices through the IN pin.

The IN pin should be locally bypassed to ground if the UM177XX series are more than a few

inches away from another source of bulk capacitance. In general, the output impedance of a

battery rises with frequency, so it is usually advisable to include an input bypass capacitor in

battery-powered circuits. A capacitor in the range of 0.1μF to 1μF is usually sufficient. The

UM177XX series are designed to withstand reverse voltages on the IN pin with respect to both

ground and the output pin. In the case of a reversed input, which can happen if a battery is

plugged in backwards, the UM177XX will act as if there is a large resistor in series with its input

with only a small amount of current flow.

VOUT (Pin 4): Voltage Regulated Output. The OUT pin supplies power to the load. A minimum

output capacitor of 1μF is required to ensure stability. Larger output capacitors may be required

for applications with large transient loads to limit peak voltage transients. See the Applications

Information section for more information on output capacitance.

NC (Pin 5，6): Not Connected.

Typical Application Circuit