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EMB1499Q: several questions on driver

Given Ding
Expert 7405 points
Part Number: EMB1499Q

Hi team,

here are several questions: 

1. in datasheet, there is such timing in charging. Gate_LS and PWM_clamp seems will make corresponding FETs turn on at same time in red area. But for normal ACF, those 2 FETs should not turn on at same time. Please kindly check. 

2. There is a start up circuit which will make soft-start. In datasheet, only a short description that,  the ramp generator charges an internal Cstart capacitor during startup, generating a gradually increasing voltage ramp until the voltage reaches VSET value and is clamped by it.So the turn on time of gate_LS is gradually bigger, how about the other gate signal? If there is a sequence picture, it will be better to make it clear. Thanks. 

BRs

Given 

  • 0
    TI__Genius 17370 points

    Hi Given,

    For 1) Please see the note below the figure 7, where it mentions about the delay for PWM_CLAMP. We recommend following this datasheet spec.

    For 2) We do not have a diagram for this, however, this is explained in section PWM Controller Blocks to explain the ramp. 

    Regards,

    Taylor

  • 0 in reply to Taylor Vogt
    TI__Expert 7405 points

    Hi Taylor,

    Thanks for your reply.

    For #2, I understand from PWM controller blocks that there is an internal soft start ramp which is as Vref during start-up to force LS_gate turn on gradually, but I still want to know for other signals,  such as PWM_clamp, will it turn on gradually or keep complementary? Thanks.

    BRs

    Given 

  • 0 in reply to Given Ding
    TI__Genius 17370 points

    Hi Given,

    This is explained for all of the gate driver signals in the timing generator section of the datasheet. " In reality, these gate signals would have finite rise and fall times and are dictated by the CG of the external MOSFET and the output resistance of the internal driver" so this depends on your system configuration. I would recommend you take some scope plots depending on your FETs etc. and characterize this for your system if it is concerning.

    Regards,

    Taylor