The TQ2061 provides optional 200-ohm on-chip pull-down resistors which are useful if the output is AC-coupled to the device being driven. In order to use these resistors, pin 20 (PDR2) should be connected to pin 21 (QN), and pin 23 (PDR1) should be connected to pin 22 (Q). Various test modes on the chip simplify debug and testing of systems by slowing the clock output or by bypassing the PLL.