DRV8428E: change of KV with different VREF

user1292453

Prodigy 105 points

Part Number: DRV8428E

Good morning,

Today, I will use the DRV8428E with a 0.330 A curent in the stepper motor.

I chopping current = VREF / KV

with KV : transimpedance gain and VREF = DVDD * Rref2/( Rref2 + Rref1)

DVDD=5V Rref2 = 4.99 K Rref1= 20 K --> VREF= 5 *4.99(4.99+20) = 0.998V

the result is : I chopping current = 0.998/3= 0.333 A

The problem is that KV ( transimpedance gain) is defined only for VREF = 3V ( data sheet page 8 SLOSE51A – JUNE 2020 – REVISED NOVEMBER 2020) KV= 3V/A +- 0.195

Could you please tell me if the value of KV is the same with different value of VREF

Thanks in advance for your answer

Michel Thiébaut

over 4 years ago

0 Ryan Kehr over 4 years ago

TI__Guru 55595 points

Michel,

Not sure why the specification is only given at VREF = 3V. Kv should be the same over the range of VREF. It is just an attenuation factor and should not be dependent on VREF.

0 user1292453 over 4 years ago in reply to Ryan Kehr

Prodigy 105 points

Ryan,

Thanks a lot for your answer.

Are you absolutely sure about the independence of KV in VREF ?

Do you have someone in mind, who could be sure about that ?

Thanks in advance for your answer

Michel Thiébaut

0 Ryan Kehr over 4 years ago in reply to user1292453

TI__Guru 55595 points

Michel,

I am verifying, but a lot of people are out for the holidays. It may not be until next week until I get a confirmation.

0 Dipankar Mitra over 4 years ago in reply to Ryan Kehr

TI__Prodigy 110 points

Michel,

The typical value of Kv is independent of the VREF voltage - it will be 3 V/A at any VREF. However, the accuracy of the Kv parameter will vary as a function of the VREF - +/-6.5% when VREF is between 2V and 3V; +/-11% when VREF is between 600mV and 2V etc. So, for your use case, Kv will be 3 V/A with +/-11% accuracy.

Best Regards,

Dipankar Mitra

Motor Drive Team

Motor drivers

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DRV8428E: change of KV with different VREF