EUP7981
On/Off Input Operation
The EUP7981 is turned off by pulling the VEN pin low,
and turned on by pulling it high. If this feature is not
used, the VEN pin should be tied to VIN to keep the
regulator output on at all time. To assure proper
operation, the signal source used to drive the VEN
input must be able to swing above and below the
specified turn-on/off voltage thresholds listed in the
Electrical Characteristics section under VIL and VIH.
Fast Start up
The EUP7981 output starts up after Vref voltage
reaches its final value (1.2V nomial). The start-up time
is determined by the time constant of the bypass
capacitor. The smaller the capacitor value., the shorter
the start-up time, but less noise gets reduced. As a
result, start-up time and noise reduction need to be
taken into design consideration when choosing the
value of the bypass capacitor.
DS7981 Ver1.0 Jan. 2008
9
EUTECH [ EUTECH MICROELECTRONICS INC ]
