MCF8316C-Q1: DAC OUT 1 For Bus Current output

Hi John,

I have explained to difference thread regarding configuring DAC 

From old thread

1. The PWM referred here is Switching PWM frequency used for Inverter, if you are using 20KHz then DAC update rate is every 20KHz

2. Yes, Both DAC can be used to map the Algorithm variables listed in the data sheet. The farthest address is 75Ch (Table 8-21 in the data sheet) which is still within 12 bits space.

3.  In Bi Polar mode 0 to 16 scaling is divided into two halves, 0 to 8 and 8 to 15 to represent positive and Negative direction and hence the scaling is /8 for Bi Polar and /16 for Unipolar.

4.  For this example we will use UNIPOLAR configuration since Bus Voltage is always positive. 

BASE DC Bus Voltage is 60V

VM = 13.5V and normalizing with 60V, In Unipolar 0 Pu = 0V, 1 Pu = 3V.

In your setting DACOUT2 scaling is 8/8, hence DACOUT = 3 * 0.225 (Variable Pu  13.5/60) * Scaling (8/8) and hence output voltage is 0.675V

Please refer to the thread (last answer) and let me know if this helps .

Thanks and Best regards

Venkatadri S

Hi Venkatadrri,

    1.The variable I want to monitor is Bus Current. Is the Base Current in MCF8316C 10A? So, 1 pu = 10A (dac output = 3V); However, the voltage output by the current DAC does not match the value of the Bus Current;

     (a)Dac Out 1 Volt = 1.39V;

    The Reg of bus current(0x410) = 773863, iBus = (773863/2^27)*BaseCurrent(10A)/8=0.00720A, Scalling=(2^2=4)Therefore, the theoretical calculated value of dac_out = 0.00720 * 3V * 4 =  0.08648V，which is ≠ 1.39V;

     (b)

 Dac Out 1 Volt = 0.900V;

    The Reg of bus current(0x410) = 2190792, iBus = (2190792/2^27)*BaseCurrent(10A)/8=0.0103A, Scalling=(2^2=4)Therefore, the theoretical calculated value of dac_out = 0.0103* 3V * 4 =  0.124V，which is ≠ 0.900V;

     (c)

 Dac Out 1 Volt = 0.118V;

    The Reg of bus current(0x410) = 1112346, iBus = (1112346/2^27)*BaseCurrent(10A)/8=0.020403A, Scalling=(2^2=4)Therefore, the theoretical calculated value of dac_out = 0.020403* 3V * 4 =  0.244V，which is ≠ 0.118V;

      2. I haven't found a linear relationship between the actual output voltage of the DAC out and the Bus current. But I'm not sure what the reason is. Do you have any suggestions?

   Thank for your time.

   Best Regard

   John Wu

Hi John,

I will try to create a example calculator and share you.

I request some time today.

Thanks and Best regards

Venkatadri S

Hi Venkatadri，

    Get it.DAC output 1 has successfully mapped the Bus Current.Thank you for your help.

   Another Question:In the datasheet, dac out 1 corresponds to Pin 36, and dacout 2 corresponds to Pin 37.

But in fact, the dac out 1 output is on Pin 37, and the dac out 2 output is on Pin 36,which is different from datasheet(MCF8316C Q1).Is this a writing error in the datasheet?

  Best Regard

   John Wu

Hi John,

Can you recheck

MCF8315C-Q1 data sheet MCF8315C-Q1 Sensorless Field Oriented Control (FOC) Integrated FET BLDC Driver datasheet (Rev. A)

MCF8316C-Q1 data sheet MCF8316C-Q1 Sensorless Field Oriented Control (FOC)Integrated FET BLDC Driver datasheet

Thanks and Best regards

Venkatadri S

HI Venkatadri,

          The chip used is MCF8316C. I tested three PCBA boards(Not Ti EVM) and the results were the same each time. I configured Dac out 1 to monitor the bus current, but in fact, it was outputting from Pin 37,,which is different from datasheet(MCF8316C Q1).Is this a writing error in the datasheet.

        Any idea?Could this be caused by the configuration on our software?Here is our  configure/cfs-file/__key/communityserver-discussions-components-files/38/1881.M0M2_5F00_DACOUT1_5F00_register_5F00_0812.zip

   Best Regard

   John Wu

Hi John,

Let me verify and get back to you by tomorrow.

Thanks and Best regards

Venkatadri S