mBrane: that's if you think of those two 2pin pwm channels. You CAN control MCP35X using 4th 4-pin channel that can regulate both pwm and analogous mode. If your wish to regulate two pumps, you have to use pwm Y wire splitter or buy AA5-LT to get another PWM channel (yes, i don't like much the fact AA5 having only one proper pwm channel, but it's better then other alternatives having none at all).