DRV8307: BLDC starts and spins up to speed, but then shuts off and coasts

Russell Troxel

Part Number: DRV8307

The motor spins up and the 8307 outputs LOCKn. Then the device loses lock and coasts down to almost stopped. then it starts again on its own and repeats the process. These repeats until I stop the motor. The repeated stop and start produces excessive motor and FET heat.I am supplying a 20kHz PWM. I am using a 0.01 ohm R sense.

over 6 years ago

0 Rick Duncan over 6 years ago

TI__Guru** 114905 points

Hi Russell,

Are you using the DRV8307EVM? If not, can you provide a schematic?
What is your system voltage?
What is the time between LOCKn and the device losing lock? Are you monitoring FAULTn?
What are you motor parameters?

0 Russell Troxel over 6 years ago in reply to Rick Duncan

Prodigy 70 points

I am not using the EVM. I am attaching that art of the board schematic. Note that I have changed the FETs to CDS18535KCS with heat sinks. I have also lowered the gate resistors to 100 ohms. FET Temps are staying below 100F.

System VM voltage is 24V.

I am monitoring fault. It is not happening.

The lock time varies depending on speed and how long it has been running.

Motor datasheet is uploaded

0 Russell Troxel over 6 years ago in reply to Russell Troxel

Prodigy 70 points

ec057c brushless_dc_motor.pdf FAN_DRIVER.pdf

0 Russell Troxel over 6 years ago in reply to Russell Troxel

Prodigy 70 points

1586.FAN_DRIVER.pdf

0 Rick Duncan over 6 years ago in reply to Russell Troxel

TI__Guru** 114905 points

Hi Russell,

Thank you for the additional information. Since you are not seeing a fault, please:

1) examine the ENABLEn signal for glitches
2) examine the DIR signal for glitches
3) examine the BRAKE signal for glitches
4) examine the VINT and VREG for voltage droops
5) provide the exact PWM input frequency and duty cycle when the slow down occurs

Motor drivers

Motor drivers forum

DRV8307: BLDC starts and spins up to speed, but then shuts off and coasts