MSP430 IO Pin Output Voltage too low to supply TLV2780 OP Amplifier

Dear Friends:

  I followed the SLAA335 "Implementing A Smoke Detector With The MSP430F2012" use one IO pin P1.3 to power TLV2780.

   I found that IO output voltage only 0.9V, but it is 3.3V if I disconnect IO Pin P1.3 from TLV2780.

  I use MSP430G2232 instead of MSP430F2012.

 Who can kindly tell me what the problem is ?

and how to soult the problem ?

Thanks !

Marshall Wu