JAJSHW2A August   2019  – April 2020 DRV425-Q1

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      概略回路図
  4. 4 改訂履歴
  5. 5 概要（続き）
  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 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Fluxgate Sensor Front-End
        1. 8.3.1.1 Fluxgate Sensor
        2. 8.3.1.2 Bandwidth
        3. 8.3.1.3 Differential Driver for the Internal Compensation Coil
        4. 8.3.1.4 Magnetic Field Range, Overrange Indicator, and Error Flag
      2. 8.3.2 Shunt-Sense Amplifier
      3. 8.3.3 Voltage Reference
      4. 8.3.4 Low-Power Operation
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Linear Position Sensing
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Current Sensing in Busbars
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Power Supply Decoupling
    2. 10.2 Power-On Start-Up and Brownout
    3. 10.3 Power Dissipation
      1. 10.3.1 Thermal Pad
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12デバイスおよびドキュメントのサポート
    1. 12.1 ドキュメントのサポート
      1. 12.1.1 関連資料
    2. 12.2 ドキュメントの更新通知を受け取る方法
    3. 12.3 サポート・リソース
    4. 12.4 商標
    5. 12.5 静電気放電に関する注意事項
    6. 12.6 Glossary
  13. 13メカニカル、パッケージ、および注文情報

8.1 Overview

Magnetic sensors are used in a broad range of applications, such as position, indirect ac and dc current, or torque measurement.  Hall-effect sensors are most commonly used in magnetic field sensing, but offset, noise, gain variation, and nonlinearity limit the achievable resolution and accuracy of the system. Fluxgate sensors offer significantly higher sensitivity, lower drift, lower noise, high linearity, and enable up to 1000-times better measurement accuracy.

As shown in the Functional Block Diagram section, the DRV425-Q1 consists of a magnetic fluxgate sensor with the necessary sensor conditioning and compensation coil to internally close the control loop. The fluxgate sensor is repeatedly driven in and out of saturation, and supports hysteresis-free operation with excellent accuracy. The internal compensation coil assures stable gain and high linearity.

The magnetic field, B, is detected by the internal fluxgate sensor in the DRV425-Q1. The device integrates the sensor output to assure high-loop gain. The integrator output connects to the built-in differential driver that drives an opposing compensation current through the internal compensation coil. The compensation coil generates an opposite magnetic field that brings the original magnetic field at the sensor back to zero.

The compensation current is proportional to the external magnetic field, with a value of 12.2 mA/mT. This compensation current generates a voltage drop across an external shunt resistor, RSHUNT. An integrated difference amplifier with a fixed gain of 4 V/V measures this voltage and generates an output voltage that is referenced to REFIN, and is proportional to the magnetic field. The value of the output voltage at the VOUT pin (VVOUT) is calculated using Equation 1:

Equation 1. VVOUT [V] = B × G × RSHUNT × GAMP = B [mT] × 12.2 mA/mT × RSHUNT [Ω] × 4 [V/V]