產品詳細資料

Technology family LS Bits (#) 1 Rating Catalog Operating temperature range (°C) 0 to 70
Technology family LS Bits (#) 1 Rating Catalog Operating temperature range (°C) 0 to 70
PDIP (N) 16 181.42 mm² 19.3 x 9.4
  • Digital Design Avoids Analog Compensation Errors
  • Easily Cascadable for Higher Order Loops
  • Useful Frequency from DC to:
    • 50 MHz Typical (K Clock)
    • 35 MHz Typical (I/D Clock)

 

  • Digital Design Avoids Analog Compensation Errors
  • Easily Cascadable for Higher Order Loops
  • Useful Frequency from DC to:
    • 50 MHz Typical (K Clock)
    • 35 MHz Typical (I/D Clock)

 

The SN54LS297 and SN74LS297 devices are designed to provide a simple, cost-effective solution to high-accuracy, digital, phase-locked-loop applications. These devices contain all the necessary circuits, with the exception of the divide-by-N counter, to build first order phase-locked loops as described in Figure 1.

Both exclusive-OR (XORPD) and edge-controlled (ECPD) phase detectors are provided for maximum flexibility.

Proper partitioning of the loop function, with many of the building blocks external to the package, makes it easy for the designer to incorporate ripple cancellation or to cascade to higher order phase-locked loops.

The length of the up/down K counter is digitally programmable according to the K counter function table. With A, B, C, and D all low, the K counter is disabled. With A high and B, C, and D low, the K counter is only three stages long, which widens the bandwidth or capture range and shortens the lock time of the loop. When A, B, C, and D are all programmed high, the K counter becomes seventeen stages long, which narrows the bandwidth or capture range and lengthens the lock time. Real-time control of loop bandwidth by manipulating the A through D inputs can maximize the overall performance of the digital phase-locked loop.FIGURE 1-SIMPLIFIED BLOCK DIAGRAM

The 'LS297 can perform the classic first-order phase-locked loop function without using analog components. The accuracy of the digital phase-locked loop (DPLL) is not affected by VCC and temperature variations, but depends solely on accuracies of the K clock, I/D clock, and loop propagation delays. The I/D clock frequency and the divide-by-N modulos will determine the center frequency of the DPLL. The center frequency is defined by the relationship fc = I/D Clock /2N(Hz).

 

The SN54LS297 and SN74LS297 devices are designed to provide a simple, cost-effective solution to high-accuracy, digital, phase-locked-loop applications. These devices contain all the necessary circuits, with the exception of the divide-by-N counter, to build first order phase-locked loops as described in Figure 1.

Both exclusive-OR (XORPD) and edge-controlled (ECPD) phase detectors are provided for maximum flexibility.

Proper partitioning of the loop function, with many of the building blocks external to the package, makes it easy for the designer to incorporate ripple cancellation or to cascade to higher order phase-locked loops.

The length of the up/down K counter is digitally programmable according to the K counter function table. With A, B, C, and D all low, the K counter is disabled. With A high and B, C, and D low, the K counter is only three stages long, which widens the bandwidth or capture range and shortens the lock time of the loop. When A, B, C, and D are all programmed high, the K counter becomes seventeen stages long, which narrows the bandwidth or capture range and lengthens the lock time. Real-time control of loop bandwidth by manipulating the A through D inputs can maximize the overall performance of the digital phase-locked loop.FIGURE 1-SIMPLIFIED BLOCK DIAGRAM

The 'LS297 can perform the classic first-order phase-locked loop function without using analog components. The accuracy of the digital phase-locked loop (DPLL) is not affected by VCC and temperature variations, but depends solely on accuracies of the K clock, I/D clock, and loop propagation delays. The I/D clock frequency and the divide-by-N modulos will determine the center frequency of the DPLL. The center frequency is defined by the relationship fc = I/D Clock /2N(Hz).

 

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類型 標題 日期
* Data sheet Digital Phase-Locked-Loop Filters datasheet 1988年 3月 1日
Selection guide Logic Guide (Rev. AB) 2017年 6月 12日
Application note Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) 2015年 12月 2日
User guide LOGIC Pocket Data Book (Rev. B) 2007年 1月 16日
Application note Semiconductor Packing Material Electrostatic Discharge (ESD) Protection 2004年 7月 8日
Application note TI IBIS File Creation, Validation, and Distribution Processes 2002年 8月 29日
Application note Designing With Logic (Rev. C) 1997年 6月 1日
Application note Designing with the SN54/74LS123 (Rev. A) 1997年 3月 1日
Application note Digital PLL Design Using the SN54/74LS297 (Rev. B) 1997年 3月 1日
Application note Input and Output Characteristics of Digital Integrated Circuits 1996年 10月 1日
Application note Live Insertion 1996年 10月 1日

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