Paul and others mention a power sequencing issue in post http://e2e.ti.com/support/dsp/sitara_arm174_microprocessors/f/791/t/151486.aspx :

The EXT_WAKEUP output buffer is powered by the VDDS_RTC power domain. This signal is what controls the TPS65910 when operating in the sleep mode where only the AM335x RTC is powered on.

Therefore, you must have a separate voltage regulator to source the VDDS-RTC supply form the battery if you plan to use the EXT_WAKEUP output to control the TPS65910.

 

Is the above also required when using the TPS65217B + AM3352 ?

Or can I just power VRTC by the always on VLDO1?

 

thank you,

Gregory