ZHCSD45 December   2014 OPA2277-EP

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用范围
  3. 3 说明
  4. 4 称重放大器原理图
  5. 5 修订历史记录
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Offset Voltage Adjustment
        2. 9.2.2.2 Input Protection
        3. 9.2.2.3 Input Bias Current Cancellation
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
      1. 11.2.1 Board Layout
      2. 11.2.2 Measurement Tips
  12. 12器件和文档支持
    1. 12.1 商标
    2. 12.2 静电放电警告
    3. 12.3 术语表
  13. 13机械封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

11 Layout

11.1 Layout Guidelines

Solder the lead-frame die pad to a thermal pad on the PCB. Mechanical drawings in 机械封装和可订购信息 show the physical dimensions for the package and pad.

Soldering the exposed pad significantly improves board-level reliability during temperature cycling, key push, package shear, and similar board-level tests. Even with applications that have low-power dissipation, the exposed pad must be soldered to the PCB to provide structural integrity and long-term reliability.

The OPA2277 has very-low offset voltage and drift. To achieve highest performance, optimize circuit layout and mechanical conditions. Offset voltage and drift can be degraded by small thermoelectric potentials at the operational amplifier inputs. Connections of dissimilar metals generate thermal potential which can degrade the ultimate performance of the OPA2277. These thermal potentials can be made to cancel by assuring that they are equal in both input terminals.

  • Keep thermal mass of the connections made to the two input terminals similar.
  • Locate heat sources as far as possible from the critical input circuitry.
  • Shield operational amplifier and input circuitry from air currents such as cooling fans.

11.2 Layout Example

11.2.1 Board Layout

This demonstration fixture is a two-layer PCB. It uses a ground plane on the bottom, and signal and power traces on the top. The ground plane has been opened up around Op Amp pins sensitive to capacitive loading. Power-supply traces are laid out to keep current loop areas to a minimum. The SMA (or SMB) connectors may be mounted either vertically or horizontally.

The location and type of capacitors used for power-supply bypassing are crucial to high-frequency amplifiers. The tantalum capacitors, C1 and C2, do not need to be as close to pins 7 and 4 on your PCB, and may be shared with other amplifiers.

11.2.2 Measurement Tips

This demonstration fixture and the component values shown are designed to operate in a 50Ω environment. Most data sheet plots are obtained in this manner. Change the component values for different input and output impedance levels.

Do not use high-impedance probes; they represent a heavy capacitive load to the Op Amps, and will alter the amplifier response. Instead, use low impedance (≤ 500Ω) probes with adequate bandwidth. The probe input capacitance and resistance set an upper limit on the measurement bandwidth. If a high-impedance probe must be used, place a 100Ω resistor on the probe tip to isolate its capacitance from the circuit.

layout_ex_bos700.gifFigure 27. Decoupling Capacitors and DUT Area