L6482H

arocca · ‎2013-06-19

Posted on June 19, 2013 at 16:54

Hi,

I'm using L6482H in my board. I changed original MOSFET (eval6482h) and now I use STP35NF10.

My board work ok with default parameters.

Im working in STEP_MODE with 1/8 microstep. Rsense = 0.1R / VS = 43V

At low revolution, torque is really great but I cant to get good torque (or similar at low speed) when my board is set at 260RPM for example.

Question1: Predictive current control is working in step_mode ???

Question2: Is possible to modify tcc,tdt,tblank registers to get better torque at high revolution?

I checked setting board in full step. of course, torque is better but i cant to get a desired torque in high speed.

Is very important to me solve this. I have a lot of machines waiting for this design.

I have in mind, check all time step frequency and modify tval_hold in different speed and get equal torque in all range of my application.

Please, ST Team...Help with this. Im sorry for my english!!!

Thanks!!!

#l6482h #l6482h #l6482

Enrico Poli · ‎2013-07-02

Posted on July 02, 2013 at 11:06

Hi,

the default configuration of the L6482H doesn't allow good performance.

First of all, the gate driving configuration (GATECFG1 and GATECFG2) is not suitable for the STP35NF10 MOSFETs.

I suggest the following configuration:

- IGATE = 64mA

- TCC = 1us (IGATE x TCC should be > of Qg of the MOS)

- TDT = 250 ns

- TBLANK = 375 ns

The current control configuration should also be adjusted:

- TON_MIN = 3.5 us

- TOFF_MIN = 21 us

- TOFF_FAST = 10 us

- FAST_STEP = 16 us

- TSW = 48 us

Using this configuration you should obtain better results.

Question1: Predictive current control is working in step_mode ???

Yes, when it is enabled it is always active.

Question2: Is possible to modify tcc,tdt,tblank registers to get better torque at high revolution?

The high speed torque is usually limited by the supply voltage and the motor characteristics (higher the rotation speed, higher is difficulty to force the current into the motor phases). For the TCC, IGATE, etc. configuration see the previous point.

BR

Enrico

arocca · ‎2013-07-02

Posted on July 03, 2013 at 00:30

Hi Enrico!!!

I have tested your configuration. but my parameters with bridge in ON mode are:

ABS_POS = 0

EL_POS = 0

MARK = 0

SPEED = 0

ACC = 0x08A

DEC = 0x08A

MAX_SPEED = 0x041

MIN_SPEED = 0

FS_SPD = 0x027

TVAL_HOLD = 0x50

VAL_RUN = 2

TVAL_ACC = 2

TVAL_DEC = 2

T_FAST = 0x48

TON_MIN = 6

TOFF_MIN = 0x29

OCD_TH = 0x1F

STEP_MODE = 0x0B

ALARM_EN = 0xFF

GATECFG1 = 0x0028

GATECFG2 = 0x41

CONFIG = 0xB000

if Try set IGATE = 64mA, bridge never turn on. Only in 4mA bridge is on.

In 8mA, motor try to move and in one sec, the bridge turn off.

Other problem is OC_SD bit. My board work only if OC_SD = 0.

Try to set OCD_TH = 0x1F and TVAL_HOLD = 2 but nothing.

With IGATE = 4mA and OC_SD = 0, My system work but when my motor try to move, it move with sound really bad. is like ''interference''.

Attach video!!!

Some idea about oc_sd and Igate?

Best Regards,

________________

Attachments :

MOV_0151.rar : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzHT&d=%2Fa%2F0X0000000bJB%2FHCS.LV3graKxI1tyiAx00joBExOXmm4DnUioEAon3as&asPdf=false

Enrico Poli · ‎2013-07-12

Posted on July 12, 2013 at 17:31

This is very strange. An higher gate current should allow you to turn-on the MOSFETs in shorter time and with better performance.

The fact that the device stops is OC_SD is high (probably even if no load is connected to the power stage) confirms that the MOSFETs are not properly driven.

Please, try again my configuration setting the VCC to 15 V (I missed this point in my previous post) and let me know.

arocca · ‎2013-07-15

Posted on July 15, 2013 at 14:23

Dear Enrico,

Your configuration is ok with 15VCC. Im really happy!!! Thanks

I need you help with this:

(1) at low speed, torque is very high and high speed, torque decrease because is difficult force current into phases motor. I need same torque in all my range of speed. My solution: I can supervise frequency in step signal and modify tval_hold to try get same torque in all my range of speed. is it correct? or can I get same torque in other better way?

(2) when motor stop...sometimes...I can hear noise in the motor. My machines need four, five or six stepper motors working at same time and is not acceptable too much noise. Is possible delete noise in motor when it is stopped? maybe tsw register in other value?

Best Regards,

Andres

Enrico Poli · ‎2013-07-18

Posted on July 18, 2013 at 15:40

Hi Andres,

(1)The torque limit at high speed is not related to the TVAL value. In fact the TVAL set the target current (i.e. torque) which you need to force into the motor.

If cause the BEMF you cannot react this target value, there is no other way that increase the supply voltage of your application. This way you should be able to force higher current at high speed.

(2) You can reduce the noise adjusting the current control parameters. In particular you can obtain lower noise:

- Reducing the TOFF_FAST value

- Reducing the TSW value

I suggest you to follow the application note AN4158 for details about the current control algorithm.

Kind Regards

Enrico