I have my circuit configured this way because I'll be hooking up my 8051 microcontroller GPIO pin to the point where three resistors (R2, R3, and R4) intersect, and the microcontroller only outputs my choice of high-impedance and ground, never VCC. The 500K was included in this circuit because I was simulating that the micro was producing a high-impedance output.
Other than 500K, what would be the absolute maximum resistor values I can use for R1, R2, and R3? The target device needs at least 3.5V input for a logic high and less than 3V for logic low.
Is my logic sort-of right if I did the following math?:
Target voltage wanted for logic high (3.5V) divided by Target device leakage current Then Result divided by sum of Result + R1 times 5V = Target voltage?
I ask because I'll be running this circuit off of a regulated 5V source which is powered by batteries.