參數(shù)資料
      型號: ATT3020-50J84I
      廠商: Electronic Theatre Controls, Inc.
      元件分類: FPGA
      英文描述: Field-Programmable Gate Arrays
      中文描述: 現(xiàn)場可編程門陣列
      文件頁數(shù): 16/80頁
      文件大?。?/td> 528K
      代理商: ATT3020-50J84I
      Data Sheet
      February 1997
      ATT3000 Series Field-Programmable Gate Arrays
      16
      Lucent Technologies Inc.
      Programmable Interconnect
      (continued)
      Crystal Oscillator
      Figure 16 shows the location of an internal high-speed
      inverting amplifier which may be used to implement an
      on-chip crystal oscillator. It is associated with the auxil-
      iary buffer in the lower right corner of the die. When the
      oscillator is configured and connected as a signal
      source, two special user IOBs are also configured to
      connect the oscillator amplifier with external crystal
      oscillator components as shown in Figure 17. A divide-
      by-two option is available to ensure symmetry. The
      oscillator circuit becomes active before configuration is
      complete in order to allow the oscillator to stabilize.
      Actual internal connection is delayed until completion
      of configuration. In Figure 17, the feedback resistor,
      R1, between output and input biases the amplifier at
      threshold. The value should be as large as is practical
      to minimize loading of the crystal. The inversion of the
      amplifier, together with the R-C networks and an AT cut
      series resonant crystal, produces the 360° phase shift
      of the Pierce oscillator. A series resistor, R2, may be
      included to add to the amplifier output impedance when
      needed for phase shift control or crystal resistance
      matching, or to limit the amplifier input swing to control
      clipping at large amplitudes. Excess feedback voltage
      may be corrected by the ratio of C2/C1. The amplifier is
      designed to be used from 1 MHz to one-half the speci-
      fied CLB toggle frequency. Use at frequencies below
      1 MHz may require individual characterization with
      respect to a series resistance. Crystal oscillators above
      20 MHz generally require a crystal which operates in a
      third overtone mode, where the fundamental frequency
      must be suppressed by an inductor across C2. When
      the oscillator inverter is not used, these IOBs and their
      package pins are available for general user I/O.
      Suggested component values:
      R1—0.5 M
      to 1 M
      R2—0 k
      to 1 k
      (may be required for low frequency, phase shift, and/or compensation level for Crystal Q)
      C1, C2—10 pF to 40 pF
      Y1—1 MHz to 20 MHz AT cut series resonant
      Figure 17. Crystal Oscillator Inverter
      Pin
      44-Pin
      PLCC
      68-Pin
      PLCC
      84-Pin
      PLCC
      100-Pin
      132-Pin
      PPGA
      144-Pin
      TQFP
      160-Pin
      QFP
      175-Pin
      PPGA
      208-Pin
      SQFP
      QFP
      TQFP
      XTAL1 (OUT)
      XTAL2 (IN)
      30
      26
      47
      43
      57
      53
      82
      76
      79
      73
      P13
      M13
      75
      69
      82
      76
      T14
      P15
      110
      100
      R1
      R2
      C2
      C1
      XTAL1 (OUT)
      XTAL2
      (IN)
      ALTERNATE
      CLOCK BUFFER
      INTERNAL
      EXTERNAL
      D
      Q
      Y1
      L
      THIRD
      OVERTONE
      ONLY
      5-3109(F)
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