The output voltage problem of battery charger BQ24075

Hello, I want to build a charger circuit by using BQ24075, but I’m so clear about its function and usage, so I want to ask for your suggestion.

According to the datasheet of BQ24075 (http://www.kynix.com/uploadfiles/pdf/BQ24075QRGTRQ1.pdf), I found the introduction of the OUT part:

“System Supply Output. OUT provides a regulated output when the input is below the OVP threshold and above the regulation voltage. When the input is out of the operation range, OUT is connected to VBAT except when SYSOFF is high (BQ24075 and BQ24079 only). Connect OUT to the system load. Bypass OUT to VSS with a 4.7 μF to 47 μF ceramic capacitor.“

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Question:

It is said that OUT is connected to VBAT except when SYSOFF is high. I don’t know that when there’s no input, will the output voltage be stable?

Also, our system requires adapter power supply voltage to 4.5-5.5 v. And without the power supply, the voltage should be stabilized to 4.5-5.5v with battery power. If BQ24075 can not achieve this , do you have any other suggestions of solution?

Sorry for my poor English, but any suggestions will be much appreciated!

Rosie