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DRV8872-Q1: Current trip value calculation

s91240719
Intellectual 340 points
Part Number: DRV8872-Q1

Hi Sir.:

I am verifying trip function. (Itrip =Vtrip/Risen) 

But I can't get correct result.

(for example:)

VM =>24V

IN2 input signal => Logic High level

IN2 input signal => Logic Low level

winding inductance => 220uH

Motor current =>1.65A ,

RISEN =>1 ohm

Itrip  = 0.35/1 ==> Itrip = 0.35 A

When I measure motor winding current I got Ipeak = 1.65A

Why?

CH1 Motor winding current

CH2 nFault

CH3 OUT2

CH4 ISEN


Andrew

  • 0
    TI__Guru** 114905 points
    Hi s91240719,

    Can you provide a zoomed in scope capture of the current as the outputs are initially enabled?

    There are two items to note:
    1) The current is increasing by >1.25A during the blanking time of 2us, and reducing by ~1.25 during the off time. Capturing the initial current build up will help determine how the current regulation is operating.
    2) Please note the absolute maximum of the ISEN pin is being violated.