Using a Schmitt-Trigger to transform sine to square wave
Presuming that pin5 is output of LM393 (not sure where you got that model for LM393).  Also presuming pin2 is the (+) input.  

LM393 is an open collector output op-amp.  This means that the output of LM393 cannot go high (towards Vdd) without an external pull up resistor.  

You could simply tie R4 to the positive rail, Vdd, instead of to ground.  

Your resistors R1, R2, R3, are very low value.  Things might work in a simulator with those low values. However, low resistance values require higher current and will effect the output transistor in a bad way. Look at the current required with 5v/100 ohms, that's 50mA current.  

The LM393 output transistor isn't going to like that 50mA.  Maximum sink current is 18mA.  

EDIT  :  I made assumption R4 would change to value of 100 ohms so that output could pull higher. That is why I mentioned the caution on sinking high current.  

2nd EDIT :   The LTC6241 has maximum TOTAL supply voltage of 7 volts. You are using total of 10 volts.  Move up to the LTC6241HV.