LM18298 used for our project

hey i'm building a satellite tracker for a project. We were using an LM18298 to drive a stepper motor, but the motor we had ended up bein too weak for the gear ratio that we are using.

So now we are usin a DC motor.Can i use a PWM on the enable pin of one of the channels? ie direction will be set by the two input pins and the enable used pin to drive

please help, this is a last minute change to our project
thanks

edit--
as well the data sheet says the typical commutator frequency is 25kHz.....is this the optimum PWM freq?

The frequency doesn't matter, the motor will respond to the average DC. You could parallel the inputs and outputs for more current drive. This IC has been discontinued since 1994! I hope you don't burn it out. The only problem I see is that Veb of NPN transistors is 5 to 7 volts; when the upper transistor is turned off, the back emf of the motor will cause the base-emitter to break down if Vs is higher than about 8 volts.