The AD9553 is a phase-locked loop （PLL） based clock translator designed to address the needs of passive optical networks （PON） and base stations. The device employs an integer-N PLL to accommodate the applicable frequency translation requirements. The user supplies up to two single-ended input reference signals or one differential input reference signal via the REFA and REFB inputs. The device supports holdover applications by allowing the user to connect a 25 MHz crystal resonator to the XTAL input. The AD9553 is pin programmable， providing a matrix of standard input/output frequency translations from a list of 15 possible input frequencies to a list of 52 possible output frequency pairs （OUT1 and OUT2）。 The device also has a 3-wire SPI interface， enabling the user to program custom input-to-output frequency translations. The AD9553 output drivers are compatible with LVPECL， LVDS， or single-ended CMOS logic levels， although the AD9553 is implemented in a strictly CMOS process. The AD9553 operates over the extended industrial temperature range of ?40°C to +85°C.