描述 Description

The MPC9774 utilizes PLL technology to frequency lock its outputs onto an input reference clock. Normal operation of the MPC9774 requires the connection of the PLL feedback output QFB to feedback input FB_IN to close the PLL feedback path. The reference clock frequency and the divider for the feedback path determine the VCO frequency. Both must be selected to match the VCO frequency range. The MPC9774 features frequency programmability between the three output banks outputs as well as the output to input relationships. Output frequency ratios of 1:1, 2:1, 3:1, 3:2 and 3:2:1 can be realized. Additionally, the device supports a separate configurable feedback output which allows for a wide variety of of input/output frequency multiplication alternatives. The VCO_SEL pin provides an extended PLL input reference frequency range. The REF_SEL pin selects the internal crystal oscillator or the LVCMOS compatible inputs as the reference clock signal. Two alternative LVCMOS compatible clock inputs are provided for clock redundancy support. The PLL_EN control selects the PLL bypass configuration for test and diagnosis. In this configuration, the selected input reference clock is routed directly to the output dividers bypassing the PLL. The PLL bypass is fully static and the minimum clock frequency specification and all other PLL characteristics do not apply. The MPC9774 has an internal power–on reset. The MPC9774 is fully 3.3V compatible and requires no external loop filter components. All inputs (except XTAL) accept LVCMOS signals while the outputs provide LVCMOS compatible levels with the capability to drive terminated 50 ? transmission lines. For series terminated transmission lines, each of the MPC9774 outputs can drive one or two traces giving the devices an effective fanout of 1:12. The device is pin and function compatible to the MPC974 and is packaged in a 52-lead LQFP package.

特性 Features

1:14 PLL based low-voltage clock generator
3.3V power supply
Internal power–on reset
Generates clock signals up to 125 MHz
Maximum output skew of 175 ps
Two LVCMOS PLL reference clock inputs
External PLL feedback supports zero-delay capability
Various feedback and output dividers (see application section)
Supports up to three individual generated output clock frequencies
Drives up to 28 clock lines
Ambient temperature range 0°C to +70°C
Pin and function compatible to the MPC974