SLES267C August   2011  – March 2016 DRV8302

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  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 Gate Timing and Protection Characteristics
    7. 6.7 Current Shunt Amplifier Characteristics
    8. 6.8 Buck Converter Characteristics
    9. 6.9 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Function Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Three-Phase Gate Driver
      2. 7.3.2 Current Shunt Amplifiers
      3. 7.3.3 Buck Converter
      4. 7.3.4 Protection Features
        1. 7.3.4.1 Overcurrent Protection (OCP) and Reporting
          1. 7.3.4.1.1 Current Limit Mode (M_OC = LOW)
          2. 7.3.4.1.2 OC Latch Shutdown Mode
        2. 7.3.4.2 OC_ADJ
        3. 7.3.4.3 Undervoltage Protection (UVLO)
        4. 7.3.4.4 Overvoltage Protection (GVDD_OV)
        5. 7.3.4.5 Overtemperature Protection
        6. 7.3.4.6 Fault and Protection Handling
    4. 7.4 Device Functional Modes
      1. 7.4.1 EN_GATE
      2. 7.4.2 DTC
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Gate Driver Power Up Sequencing Errdata
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Gate Drive Average Current Load
        2. 8.2.2.2 Overcurrent Protection Setup
        3. 8.2.2.3 Sense Amplifier Setup
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 Bulk Capacitance
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

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 DRV8302 is a gate driver designed to drive a 3-phase BLDC motor in combination with external power MOSFETs. The device provides a high level of integration with three half-bridge gate drivers, two current shunt amplifiers, overcurrent protection, and a step-down buck regulator.

8.1.1 Gate Driver Power Up Sequencing Errdata

The DRV8301 gate drivers may not correctly power-up if a voltage greater than 8.5 V is present on any SH_X pin when EN_GATE is brought logic high (device enabled) after PVDD1 power is applied (PVDD1 > PVDD_UV). This sequence should be avoided by ensuring the voltage levels on the SH_X pins are less than 8.5 V when the DRV8301 is enabled through EN_GATE.

8.2 Typical Application

DRV8302 typ_app_combined_sles267.gif Figure 6. Typical Application Schematic

Example:
Buck: PVDD = 3.5 V – 40 V, Iout_max = 1.5 A, Vo = 3.3 V, Fs = 570 kHz

8.2.1 Design Requirements

Table 6. Design Parameters

DESIGN PARAMETER REFERENCE VALUE
Supply voltage PVDD 24 V
Motor winding resistance MR 0.5 Ω
Motor winding inductance ML 0.28 mH
Motor poles MP 16 poles
Motor rated RPM MRPM 4000 RPM
Target full-scale current IMAX 14 A
Sense resistor RSENSE 0.01 Ω
MOSFET Qg Qg 29 nC
MOSFET RDS(on) RDS(on) 4.7 mΩ
VDS trip level OC_ADJ_SET 0.123 V
Switching frequency ƒSW 45 kHz
Series gate resistance RGATE 10 Ω
Amplifier reference VREF 3.3 V
Amplifier gain Gain 10 V/V

8.2.2 Detailed Design Procedure

8.2.2.1 Gate Drive Average Current Load

The gate drive supply (GVDD) of the DRV8302 can deliver up to 30 mA (RMS) of current to the external power MOSFETs. Use Equation 5 to determine the approximate RMS load on the gate drive supply:

Equation 5. Gate Drive RMS Current = MOSFET Qg × Number of Switching MOSFETs × Switching Frequency

Example:

Equation 6. 7.83 mA = 29 nC × 6 × 45 kHz

This is a rough approximation only.

8.2.2.2 Overcurrent Protection Setup

The DRV8302 provides overcurrent protection for the external power MOSFETs through the use of VDS monitors for both the high side and low side MOSFETs. These are intended for protecting the MOSFET in overcurrent conditions and not for precise current regulation.

The overcurrent protection works by monitoring the VDS voltage of the external MOSFET and comparing it against the OC_ADJ pin voltage. If the VDS exceeds the OC_ADJ pin voltage the DRV8302 takes action according to the M_OC pin.

Equation 7. Overcurrent Trip = OC_ADJ_SET / MOSFET RDS(on)

Example:

Equation 8. 26.17 A = 0.123 V/ 4.7 mΩ

MOSFET RDS(on) changes with temperature and this will affect the overcurrent trip level.

8.2.2.3 Sense Amplifier Setup

The DRV8302 provides two bidirectional low-side current shunt amplifiers. These can be used to sense a sum of the three half-bridges, two of the half-bridges individually, or in conjunction with an additional shunt amplifier to sense all three half-bridges individually.

  1. Determine the peak current that the motor will demand (IMAX). This will be dependent on the motor parameters and your specific application. I(MAX) in this example is 14 A.
  2. Determine the available voltage range for the current shunt amplifier. This will be ± half of the amplifier reference voltage (VREF). In this case the available range is ±1.65 V.
  3. Determine the sense resistor value and amplifier gain settings. There are common tradeoffs for both the sense resistor value and amplifier gain. The larger the sense resistor value, the better the resolution of the half-bridge current. This comes at the cost of additional power dissipated from the sense resistor. A larger gain value will allow you to decrease the sense resistor, but at the cost of increased noise in the output signal. This example uses a 0.01-Ω sense resistor and the minimum gain setting of the DRV8302 (10 V/V). These values allow the current shunt amplifiers to measure ±16.5 A (some additional margin on the 14-A requirement).

8.2.3 Application Curves

DRV8302 wvfrm01_los719.png
Figure 7. Motor Spinning 2000 RPM
DRV8302 wvfrm03_los719.png
Figure 9. Gate Drive 20% Duty Cycle
DRV8302 wvfrm02_los719.png
Figure 8. Motor Spinning 4000 RPM
DRV8302 wvfrm04_los719.png
Figure 10. Gate Drive 80% Duty Cycle