DRV10987: Tuning Issues from DRV10983 to DRV10987

Hey nishanth, 

1) When there is no motor connected to the DRV10987, the device should draw max 16mA. So if it is drawing 490mA, this indicates there is a problem with either the chip or layout. Are you using the DRV10987 evm or a customer pcb? If you are using a custom pcb, I recommend checking the circuit to make sure it follows the typical application schematic in the datasheet http://www.ti.com/lit/ds/symlink/drv10987.pdf .

First focus on getting rid of the high current draw with no motor load. We will worry about tuning later.

Thanks for your reply....

1. Only Motor running condition only it takes 490mA. (WITHOUT GIVING LOAD TO THE MOTOR)

2. In no motor condition it takes 20mA only.

3. I am using custom board only...... In the same board itself DRV10983 working well. I just change the chip and EEPROM data to work in DRV10987.

4. The DRV10987 itself starts to run the motor, but VCC need to below 22VDC. But my motor is designed for 24V.

5. With the same setup if I run the motor using DRV10983 means in no-load condition of motor itself it takes 20mA, but in DRV10987 it takes 490mA. No- load condition of motor means i am not giving any load to motor, it is free running.

Please help me to solve this problem................

For DRV10987, why does vcc need to be below 22V?

thanks for reply...........

if I keep more VCC to 24VDC means, DRV10987 takes more current at start up so hardware current limit is set. If i run same motor with DRV10983 with same hardware current limit means its working well........

1) In order to use 24V Vcc, you can lower the open loop current setting for startup so the hardware current limit isn't set. If possible, you can also increase the hardware current limit.

2) One possible issue, and it could be a reason why the DRV10987 is getting hot, is you need to make sure the dead time is set appropriately relative to the slew rate control you set. Please refer to Table 3. Dead-Time Settings in DRV10987 tuning guide http://www.ti.com/lit/ug/slou477/slou477.pdf .

3) If you are still having trouble, please send me both the DRV10983 tuning settings and DRV10987 tuning settings, and I can recommend a DRV10987 setting to try

Thanks for reply.......

Finally I found the problem that following:-

1. DRV10987 taking a peak current more than 2A for 2.6ms at motor start-up, so my power supply is not able to give that much current.

2. I added 470uF/50V capacitor at 24VCC line due to adding of capacitor problem solved. But same setup without capacitor the DRV10983 is running perfectly.

Why DRV10987 is taking more peak current at initial motor start up.....

DRV10983:-

0x20 0x3E

0x21 0xDE

0x22 0x3A

0x23 0x0C

0x24 0xDC

0x25 0xFE

0x26 0x87

0x27 0xE1

0x28 0x0F

0x29 0xF7

0x2A 0xAF

0x2B 0x0E

DRV10987:-

0x90 0x003E

0x91 0x5E3A

0x92 0x1CDC

0x93 0x4387

0x94 0x3F0F

0x95 0xA177

0x96 0x2B69

Help me to solve this problem..............

thanks for your reply.......

I already using a capacitors at VCC line........

Please find my schematic

1) I compared your schematic with that of the recommended circuit, and these are the differences I see:

a)  C1 is 100nF instead of 10nF (I dont think this is the issue)

b) L3 has to have 1.15-A current rating and have dc resistance less than 1 ohm (check "table 36. external components" in datasheet). This might be an issue.

2) What is the current draw fo the device when there is no motor? Is it as expected?

3) Is there any differences in the boards between DRV10987 and DRV10983, other than the actual IC?

4) If you want me to explore this further, please take a waveform of the motor phase current during startup so I could get  a better idea of what is going on.

Thanks for your reply....

1) I compared your schematic with that of the recommended circuit, and these are the differences I see:  

a)  C1 is 100nF instead of 10nF (I dont think this is the issue)  --> Changed to 10nF problem still there.

b) L3 has to have 1.15-A current rating and have dc resistance less than 1 ohm (check "table 36. external components" in datasheet). This might be an issue. --> L3 matches the SPECS

2) What is the current draw fo the device when there is no motor? Is it as expected? -->Current drawing at without motor <10mA. (8.4mA) only

3) Is there any differences in the boards between DRV10987 and DRV10983, other than the actual IC?  -->No difference. I am using same board for both the part numbers.

4) If you want me to explore this further, please take a waveform of the motor phase current during startup so I could get  a better idea of what is going on. Please find it below:-

Current  Probe Waveform. 100mv/1A . At 24VCC of the DRV Chip.

Any possibility to run the Motor dependent on input current.

 For a example:-

1. if input current limit is 0.5A means Speed of the motor is 25%.

2. if input current limit is 1.0A means Speed of the motor is 50%.

2. if input current limit is 1.5A means Speed of the motor is 75%

Without any external sensing the DRV need to self-Run.

1) I am confused by the current waveform because usually, I would expect motor phase current to look sinusoidal like below:

2) You can use the software current limit to limit duty cycle based on current.

Any followup needed on this?

Hi, are there any updates on this?