TPS2663: Different behavior between resistive and inductive load

Antoine Gingras1

Part Number: TPS2663
Other Parts Discussed in Thread: LMG1210

Hi,

Does anyone sees a reason why the eFuse would behave differently with an inductive load (BLDC motor) and a resistive load. Below is the eFuse current and fault signals for a 1.5 to 3A step. We can see the efuse lets the current go throught unrestricted for 25ms then limit the the current to 2.18 A for 160ms (Rlim = 8.45K , 0.1%).

This is all as expected.

But with a motor torquing at stall with a current command of 2.3A, i get two different things. Below is the case with the motor load when overcurrent condition does seem to be detected.

Sometimes the overcurrent is detected but after more than 180ms.

Does the rate of change of current has an impact on overcurrent detection delay?

In the tests:

Rlim = 8.45K

Plim = 0R

Cdvdt= 100nF

Default ULVO

Auto-retry mode

no input reverse blocking.

Cin = 10uF

Cout= 340uF

Thanks and best regards,

Antoine

over 5 years ago

0 Rakesh over 5 years ago

TI__Guru** 105361 points

Hi Antoine,

Welcome to E2E and thanks for considering TPS2663.

For the second case i.e., with BLDC motor, can you share test waveform with Vin, Vout, Input current and FLTb in a single scopeshot.

Thanks, Rakesh

0 Antoine Gingras1 over 5 years ago in reply to Rakesh

Prodigy 65 points

Hi Rakesh,

Here are the scopeshot you requested.

Yellow = Vin

Blue = Vout

Pink = FLTb

Green = Iin

Thanks,

Antoine

0 Rakesh over 5 years ago in reply to Antoine Gingras1

TI__Guru** 105361 points

Hi Antoine,

Thanks for the test waveforms. It looks the motor stalled current makes the device to hover near the current limit (in and out of it). We usually similar behavior when we test using e-load in CC mode (a case where two current regulation loops are in series, one by the eFuse and other by the e-load in cc mode)

What is happening if the motor current command is increased to 3A ?

Did you get a chance to look how is the current when motor stalled with a current command of 2.3A when powered from DC supply ?

Best Regards, Rakesh