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DRV8145-Q1: Inductive load current re-circulates

Che Wen Yeh
Intellectual 900 points
Part Number: DRV8145-Q1

Tool/software:

Hi Teams,

Please help to check DRV8145 inductive load current re-circulates questions as following, thanks.

1. Will the current flow in the direction of D1?

2. Is there a risk of IC damage if reverse current flows through the HS body diode?

  • +1
    TI__Mastermind 44525 points

    Hi Che Wen,

    Thanks for your question. 

    Che Wen Yeh said:
    1. Will the current flow in the direction of D1?

    The load current or recirculation current will not flow via D1. 

    Che Wen Yeh said:
    2. Is there a risk of IC damage if reverse current flows through the HS body diode?

    No risk with this as long as the absolute specifications are not exceeded. See below control table from the datasheet. Assuming the inductive load is connected as low-side load, while IN = 1 the HS-FET will conduct and drive the inductive load and while IN = 0 the LS-FET will conduct and provide a path for the recirculation current. See diagram. If the inductive load is connected to the outputs via long cable harness using an optional Schottky diode would provide a shorter path for the recirculation current in the event the half-bridge is rendered HiZ, for example by DRVOFF = 1 or a loss of power. If no Schottky diode the LS-FET body diode will complete the recirculation path with no issues. If the inductance in high it could lead to an increased voltage above absolute max. ratings of the driver and in this case using a Schottky diode close to the inductive load as shown would address this scenario. For most common applications such as BDC motor an external Schottky diode is rarely needed. Thank you.

    Regards Murugavel 

  • 0 in reply to Murugavel4637
    Intellectual 900 points

    Hi Murugavel,

    Is there more detail information as following? thanks.

    1. Voltage level detect OLA.

    2. motor driver configuration in OLA mode

    3. Test report for OLA mode

  • +1 in reply to Che Wen Yeh
    TI__Mastermind 44525 points

    Hi Che Wen,

    Please see the below specifications in the datasheet as well as the section 7.3.4.4 On-State Diagnostics (OLA) - SPI Variant Only. The OLA comparator looks for the inductive voltage spike during the dead time of the PWM transitions. If the spike > VOLA_REF it means the load is normal. Because this detection is dependent on dead time a PWM duty cycle > 0 and < 100 % is necessary for this detection. Configuration is explained in this section.

    The specifications are derived based on tests and validation of this function. No other test report is available. All the relevant information is provided in the datasheet. Thank you.

    Regards, Murugavel