EUP7981
On/Off Input Operation
The EUP7981 is turned off by pulling the V
EN
pin low,
and turned on by pulling it high. If this feature is not
used, the V
EN
pin should be tied to V
IN
to keep the
regulator output on at all time. To assure proper
operation, the signal source used to drive the V
EN
input must be able to swing above and below the
specified turn-on/off voltage thresholds listed in the
Electrical Characteristics section under V
IL
and V
IH
.
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 ]
