ZHCSDO0A March   2015  – May 2015 DRV8701

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Bridge Control
      2. 7.3.2  Half-Bridge Operation
      3. 7.3.3  Current Regulation
      4. 7.3.4  Amplifier Output SO
        1. 7.3.4.1 SNSOUT
      5. 7.3.5  PWM Motor Gate Drivers
      6. 7.3.6  IDRIVE Pin
      7. 7.3.7  Dead Time
      8. 7.3.8  Propagation Delay
      9. 7.3.9  Overcurrent VDS Monitor
      10. 7.3.10 Charge Pump
      11. 7.3.11 LDO Voltage Regulators
      12. 7.3.12 Gate Drive Clamp
      13. 7.3.13 Protection Circuits
        1. 7.3.13.1 VM Undervoltage Lockout (UVLO)
        2. 7.3.13.2 VCP Undervoltage Lockout (CPUV)
        3. 7.3.13.3 Overcurrent Protection (OCP)
        4. 7.3.13.4 Pre-Driver Fault (PDF)
        5. 7.3.13.5 Thermal Shutdown (TSD)
      14. 7.3.14 Reverse Supply Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operating DRV8701 and H-Bridge on Separate Supplies
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Brushed-DC Motor Control
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 External FET Selection
          2. 8.2.1.2.2 IDRIVE Configuration
          3. 8.2.1.2.3 Current Chopping Configuration
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Alternate Application
        1. 8.2.2.1 Design Requirements
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1 IDRIVE Configuration
        2. 8.2.3.2 VM Boost Voltage
  9. 9 Power Supply Recommendations
    1. 9.1 Bulk Capacitance Sizing
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 文档支持
      1. 11.1.1 相关文档
    2. 11.2 社区资源
    3. 11.3 商标
    4. 11.4 静电放电警告
    5. 11.5 术语表
  12. 12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 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

The DRV8701 is used in brushed-DC, solenoid, or relay control.

8.2 Typical Applications

8.2.1 Brushed-DC Motor Control

The following design procedure can be used to configure the DRV8701.

DRV8701 typ_app_LVSCX5.gifFigure 34. Typical Application Schematic

8.2.1.1 Design Requirements

Table 10 gives design input parameters for system design.

Table 10. Design Parameters

Design Parameter Reference Example Value
Nominal supply voltage VM 18 V
Supply voltage range VMMIN, VMMAX 12 to 24 V
FET total gate charge(1) QG 14 nC (typically)
FET gate-to-drain charge(1) QGD 2.3 nC (typically)
Target FET gate rise time RT 100 to 300 ns
Motor current chopping level ICHOP 3 A
(1) FET part number is CSD88537ND.

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 External FET Selection

The DRV8701 FET support is based on the charge pump capacity and output PWM frequency. For a quick calculation of FET driving capacity, use the following equations when drive and brake (slow decay) are the primary modes of operation:

Equation 5. DRV8701 eq_03_LVSCX5.gif

where

  • fPWM is the maximum desired PWM frequency to be applied to the DRV8701 inputs or the current chopping frequency, whichever is larger.
  • IVCP is the charge pump capacity, which depends on VM.

The internal current chopping frequency is at most:

Equation 6. DRV8701 eq_04_LVSCX5.gif

Example: If a system at VM = 7 V (IVCP = 8 mA) uses a maximum PWM frequency of 40 kHz, then the DRV8701 will support QG < 200 nC FETs.

If the application will require a forced fast decay (or alternating between drive and reverse drive), the maximum FET driving capacity is given by:

Equation 7. DRV8701 eq_05_LVSCX5.gif

8.2.1.2.2 IDRIVE Configuration

Select IDRIVE based on the gate charge of the FETs. Configure this pin so that the FET gates are charged completely during tDRIVE. If the designer chooses an IDRIVE that is too low for a given FET, then the FET may not turn on completely. TI suggests to adjust these values in-system with the required external FETs and motor to determine the best possible setting for any application.

For FETs with a known gate-to-drain charge (QGD) and desired rise time (RT), select IDRIVE based on:

Equation 8. DRV8701 eq_06_LVSCX5.gif

Example: If the gate-to-drain charge is 2.3 nC, and the desired rise time is around 100 to 300 ns,

IDRIVE1 = 2.3 nC / 100 ns = 23 mA

IDRIVE2 = 2.3 nC / 300 ns = 7.7 mA

Select IDRIVE between 7.7 and 23 mA

Select IDRIVE as 12.5-mA source (25-mA sink)

Requires a 33-kΩ resistor from the IDRIVE pin to GND

8.2.1.2.3 Current Chopping Configuration

The chopping current is set based on the sense resistor value and the analog voltage at VREF. Calculate the current using Equation 9. The amplifier gain AV is 20 V/V and VOFF is typically 50 mV.

Example: If the desired chopping current is 3 A,

Set RSENSE = 50 mΩ

Equation 9. DRV8701 eq_07_LVSCX5.gif

VREF would have to be 3.05 V.

Create a resistor divider from AVDD (4.8 V) to set VREF ≈ 3 V

Set R2 = 3.3 kΩ; set R1 = 2 kΩ.

8.2.1.3 Application Curves

DRV8701 app_curve_01_LVSCX5.gifFigure 35. SH1 Rise Time (12.5-mA Source, 25-mA Sink)
DRV8701 app_curve_03_LVSCX5.gifFigure 37. Current Regulating at 3 A on Motor Startup
DRV8701 app_curve_05_LVSCX5.gifFigure 39. Current Profile on Motor Startup Without Regulation
DRV8701 app_curve_02_LVSCX5.gifFigure 36. SH1 Fall Time (12.5-mA Source, 25-mA Sink)
DRV8701 app_curve_04_LVSCX5.gifFigure 38. Current Profile on Motor Startup With Regulation

8.2.2 Alternate Application

In this example, the DRV8701 is powered from a supply that is boosted above VBAT. This allows the system to work at lower VBAT voltages, but requires the user to disable OCP monitoring.

DRV8701 alt_app_LVSCX5.gifFigure 40. DRV8701 on Boosted Supply

8.2.2.1 Design Requirements

Table 11 gives design input parameters for system design.

Table 11. Design Parameters

Design Parameter Reference Example Value
Battery voltage VBAT 12 V nominal
Minimum operation: 4.0 V
DRV8701 supply voltage VM VM = 7 V when VBAT < 7 V
VM = VBAT when VBAT ≥ 7 V
FET total gate charge QG 42 nC
FET gate-to-drain charge QGD 11 nC
Motor current chopping level ICHOP 3 A

8.2.3 Detailed Design Procedure

8.2.3.1 IDRIVE Configuration

Because the VM supply to the DRV8701 is different from the external H-bridge supply VBAT, the designer must disable the overcurrent monitor to prevent false overcurrent detection. The designer must place a 68-kΩ resistor between the IDRIVE pin and AVDD.

IDRIVE is fixed at 25-mA source and 50-mA sink in this mode.

So, the rise time is 11 nC / 25 mA = 440 ns.

8.2.3.2 VM Boost Voltage

To determine an effective voltage to boost VM, first determine the minimum VBAT at which the system must operate. Select VM such that the gate driver clamps do not turn on during normal operation.

Equation 10. DRV8701 eq_VM_LVSCX5.gif

Example: If VBAT minimum is 4.0 V,

VM < 7.75 V

So VM = 7 V is selected to allow for adequate margin.