LTC6242I voltage follower output saturation voltage

I used LTC6242 as a voltage follower configuration: - power to IC is 4.2V

- measured V+ to IC is 3.8V

- V- is feedback to Vout, measured about 3.6V

- output is set at high impedance for testing

(Note that I wanted output to be 3.8V)

When the power is at 4.2V, output seems to be saturated at 3.6V even I increased the V+ voltage higher.

Has anyone tested the saturation level of this op amp?

Other than increasing the power supply, any other method?