TLE987X BLDC_SENSORLESS_FOC/Current sensing/ CSA gain computation

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User19528
Level 2
Level 2
First like received
Hello,
In the "BLDC_SENSORLESS_FOC_LIN_EXAMPLE_TLE987X" SW example, in Emo.c the gain of the CSA is computed as follow:
Could you please tell me to what correspond the value of 1.25 and how it is obtained ? give me please more details
Thanks in advance
OpGain = 10.0;
CSA_Set_Gain(0u);
/* 1.25 => 125mV, secured OpAmp differential input voltage range */
x = Emo_Focpar_Cfg.NominalCurrent * Emo_Focpar_Cfg.Rshunt * 10.0;

if (x < 1.25)
{
OpGain = 10.0;
CSA_Set_Gain(0u);
}

x = Emo_Focpar_Cfg.NominalCurrent * Emo_Focpar_Cfg.Rshunt * 20.0;

if (x < 1.25)
{
OpGain = 20.0;
CSA_Set_Gain(1u);
}

x = Emo_Focpar_Cfg.NominalCurrent * Emo_Focpar_Cfg.Rshunt * 40.0;

if (x < 1.25)
{
OpGain = 40.0;
CSA_Set_Gain(2u);
}

x = Emo_Focpar_Cfg.NominalCurrent * Emo_Focpar_Cfg.Rshunt * 60.0;

if (x < 1.25)
{
OpGain = 60.0;
CSA_Set_Gain(3u);
}
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1 Reply
User17952
Level 3
Level 3
Hi,
You can refer to the the chapter of CSA in Manual,you will find the limitation of CSA differential input voltage is 1.5V.
1.25V is secured OpAmp differential input voltage range .
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