Question on Allegro a1308 output filter

[trilerian]

Hello, as the title states, I have a question on the Allegro a1308 hall effect sensor output rc filter.  In the data sheet it call for a pulldown resistor on the output followed by a cap.
They label these as RL and CL.  CL can have a max value of 10nf and RL needs to min of 4.7kΩ.  I have defaulted these in my schematic to 10kΩ and 4.7nf.  But how do I calculate the filter -3db with a pulldown resistor instead of a series resistor?  I realize this is a very beginner question, and I am sorry, but my searches have evaded me. 

[srb1954]

Hello, as the title states, I have a question on the Allegro a1308 hall effect sensor output rc filter.  In the data sheet it call for a pulldown resistor on the output followed by a cap.
They label these as RL and CL.  CL can have a max value of 10nf and RL needs to min of 4.7kΩ.  I have defaulted these in my schematic to 10kΩ and 4.7nf.  But how do I calculate the filter -3db with a pulldown resistor instead of a series resistor?  I realize this is a very beginner question, and I am sorry, but my searches have evaded me.

The pulldown resistor is not relevant to calculating the -3dB point as it is the internal O/P resistance of the A1308 driver stage that should be used to calculate  the roll-off frequency. The O/P resistance is listed in the datasheet as 3 typical so the filtering obtained with the 4n7 capacitor is pretty minimal. If you need filtering it would be better to add a suitable series resistor rather than relying on the not very well controlled internal O/P resistance.

The minimum value  for R_L and the maximum value for C_L specified in the datasheet are there to ensure that excessive load is not put on the output driver; you don't need to use these specified values to make the chip function.