The input clock frequency requirements are all included in the Hardware Specification for each part and differ across the product line. If an LCD Controller has a built-in PLL, then typically a lower input clock source is sufficient as all internal clocks are driven by the PLL. If an LCD Controller does not contain a PLL, then a higher frequency input clock source is typically required as all of the internal clocks are generated from this single source. Please refer to the specific LCD Controller documentation for details.