ZHCSH32 November   2017 TLA2021 , TLA2022 , TLA2024

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      系统监控应用示例
  4. 4 修订历史记录
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin 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 Electrical Characteristics
    6. 7.6 I2C Timing Requirements
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagrams
    3. 8.3 Feature Description
      1. 8.3.1 Multiplexer
      2. 8.3.2 Analog Inputs
      3. 8.3.3 Full-Scale Range (FSR) and LSB Size
      4. 8.3.4 Voltage Reference
      5. 8.3.5 Oscillator
      6. 8.3.6 Output Data Rate and Conversion Time
    4. 8.4 Device Functional Modes
      1. 8.4.1 Reset and Power-Up
      2. 8.4.2 Operating Modes
        1. 8.4.2.1 Single-Shot Conversion Mode
        2. 8.4.2.2 Continuous-Conversion Mode
    5. 8.5 Programming
      1. 8.5.1 I2C Interface
        1. 8.5.1.1 I2C Address Selection
        2. 8.5.1.2 I2C Interface Speed
        3. 8.5.1.3 Serial Clock (SCL) and Serial Data (SDA)
        4. 8.5.1.4 I2C Data Transfer Protocol
        5. 8.5.1.5 Timeout
        6. 8.5.1.6 I2C General-Call (Software Reset)
      2. 8.5.2 Reading and Writing Register Data
        1. 8.5.2.1 Reading Conversion Data or the Configuration Register
        2. 8.5.2.2 Writing the Configuration Register
      3. 8.5.3 Data Format
  9. 9 Register Maps
    1. 9.1 Conversion Data Register (RP = 00h) [reset = 0000h]
      1. Table 6. Conversion Data Register Field Descriptions
    2. 9.2 Configuration Register (RP = 01h) [reset = 8583h]
      1. Table 7. Configuration Register Field Descriptions
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Basic Interface Connections
      2. 10.1.2 Connecting Multiple Devices
      3. 10.1.3 Single-Ended Signal Measurements
      4. 10.1.4 Analog Input Filtering
      5. 10.1.5 Duty Cycling To Reduce Power Consumption
      6. 10.1.6 I2C Communication Sequence Example
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curve
  11. 11Power Supply Recommendations
    1. 11.1 Power-Supply Sequencing
    2. 11.2 Power-Supply Decoupling
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13器件和文档支持
    1. 13.1 器件支持
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 相关链接
    3. 13.3 接收文档更新通知
    4. 13.4 社区资源
    5. 13.5 商标
    6. 13.6 静电放电警告
    7. 13.7 Glossary
  14. 14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

8.3.2 Analog Inputs

The TLA202x use a switched-capacitor input stage where capacitors are continuously charged and then discharged to measure the voltage between AINP and AINN. The frequency at which the input signal is sampled is referred to as the sampling frequency or the modulator frequency (fMOD). The TLA202x have a 1-MHz internal oscillator that is further divided by a factor of 4 to generate fMOD at 250 kHz. The capacitors used in this input stage are small, and to external circuitry, the average loading appears resistive. Figure 9 shows this structure. The capacitor values set the resistance and switching rate. Figure 10 shows the timing for the switches in Figure 9. During the sampling phase, switches S1 are closed. This event charges CA1 to VAINP, CA2 to VAINN, and CB to (VAINP – VAINN). During the discharge phase, S1 is first opened and then S2 is closed. CA1 and CA2 then discharge to approximately 0.7 V and CB discharges to 0 V. This charging draws a very small transient current from the source driving the TLA202x analog inputs. The average value of this current can be used to calculate the effective impedance (Zeff), where Zeff = VIN / IAVERAGE.

TLA2021 TLA2022 TLA2024 ai_simple_ana_in_cir_bas444.gifFigure 9. Simplified Analog Input Circuit
TLA2021 TLA2022 TLA2024 ai_tim_s1s2_bas457.gifFigure 10. S1 and S2 Switch Timing

The common-mode input impedance is measured by applying a common-mode signal to the shorted AINP and AINN inputs and measuring the average current consumed by each pin. The common-mode input impedance changes depending on the full-scale range, but is approximately 6 MΩ for the default full-scale range. In Figure 9, the common-mode input impedance is ZCM.

The differential input impedance is measured by applying a differential signal to the AINP and AINN inputs where one input is held at 0.7 V. The current that flows through the pin connected to 0.7 V is the differential current and scales with the full-scale range. In Figure 9, the differential input impedance is ZDIFF.

Consider the typical value of the input impedance. Unless the input source has a low impedance, the TLA202x input impedance may affect the measurement accuracy. For sources with high-output impedance, buffering may be necessary. Active buffers introduce noise, offset, and gain errors. Consider all of these factors in high-accuracy applications.

The clock oscillator frequency drifts slightly with temperature; therefore, the input impedances also drift. For most applications, this input impedance drift is negligible and can be ignored.