I need to generate one sine wave of 40 hz by timer A using an  20 Khz carrier frequency, if the lenght of timer A is 8 bits , i need one clock frequency  of  5.12 Mhz ( Fclock = Fpwm*2^n), n=8, Fpwm=20000 hz.

If i  use one sine table of 120 points  the least frequency that i can see is 160 Hz, ( Fpwm/ 120),  my question is, how can i get a 40 hz sine wave without vary the carrier frequency and the point of the sine table?

Thanks

Gastón