TLC5940 for mosfet driving

Hi,

for a project I currently am working on I am using the TLC5940
To use this I've been using the standart library supplied by arduino.

As high powers will be flowing through the mosfets im driving, I want to create a signal of 20kHz instead of the standard 1kHz. For this I had to go to tlc_config.h to change TLC_PWM_PERIOD. however, if I should set this using the formulas, I would get 400. This would mean that the grayscale clock would drop below 0, which won't work.

Does anyone know how I should fix this? or what values I should change to upgrade the frequency?

Kind Regards