TPS7A53-Q1: Queries in the datasheet

Hi Viswa,

See my responses to your questions below, I've put my responses in green to make them easy to find. 

1)In the datasheet pg no:6, accuracy of output voltage is provided.

     a)What is accuracy with Bias? Is it when bias voltage is used

Yes, you are correct any time you seethe notation "with Bias" that means that a bias voltage was provided. 

     b)In the accuracy with Bias for 125C Junction, -0.75% and 75% is provided. Whether this -0.75% and 0.75% is the accuracy of internal reference voltage(0.8V)? If not, what is the variation of 0.8V?

The +-0.75% accuracy shows how much error there will be at the output of the LDO, so these specs remove the any inaccuracy due to external resistors. The reason we give this value and not the accuracy of the internal voltage reference (0.8V) is because the internal reference has a much tighter accuracy but ultimately a user needs to know how the output voltage will behave since there are other sources of error beyond just the reference voltage. 

2)When the input voltage is above 3.3V, is it ok to use bias voltage?

Yes you can connect a bias voltage when Vin>3.3V, many customers do this and it will not alter the performance of the LDO. 

3)What is the maximum limit of soft -start voltage? When simulated using the Pspice model, it is found that the voltage on SS pin capacitor keeps on increasing.

Yes, the model is behavioral and doesn't always mimic every aspect of the actual LDO. The voltage on the SS pin is the reference voltage so the maximum you will see on this pin is 0.8V plus the max accuracy spec which aligns with your application.  So in the worst case you should not see more than ~810mV. 

4)Whether using 12.7kohm resistor instead of 12.1kohm resistor will cause any problem?

No this will not cause any problems. 12.1k is recommended to have a similar impedance as the internal node however small changes in the external resistor will not noticeably affect the PSRR and Noise performance. Also note that the internal impedance will vary due to normal process variation which is likely to see worst case value shifts of+-20%.