How to extend watchdog timeout interval to 5sec for TMS320F28335?

I am using watchdog to wake up MCU from the standby mode. the requirement timeout period is 5s.

With the oscclk = 50MHz, the maximum timout we can attain is 167.7ms (1/f*512*64*256). 

is there any option we can extend the watchdog timer to 5s?

best,

Jie