What will happen if the CE is at high impedance?

LDO Linear RegulatorsDC/DC Switching RegulatorsHow to use

• If the EN(CE,CONTROL) pin is pulled up or down by a constant current circuit or an internal resistor inside the IC shown in Fig. 1 or Fig. 2, the IC can be set to standby state even though the input voltage is at high impedance.
  However, if the EN(CE,CONTROL) pin is not pulled up nor down inside the IC shown in Fig. 3, the IC status may be indefinite, and therefore the operation may be unstable. In this case, pull up or down the EN(CE,CONTROL) pin with an external resistor.

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