Infineon iMOTION EVAL-M7-D111T, User Manual, Page: 16 / 25

User guide 16 of 24 V1.0
2021-04-15
EVAL-M7-D111T user guide
iMOTION™ evaluation board for smart driver
System and functional description
In the example circuit, the gain calculated from the analysis with Rs
≈
0, is given by:
𝐺_𝑒𝑥𝑡 =
𝑅2
𝑅1 + 𝑅2
So the current input scaling can be calculated as:
𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑖𝑛𝑝𝑢𝑡 𝑠𝑐𝑎𝑙𝑖𝑛𝑔 = 𝐺
𝑒𝑥𝑡
× 𝑅𝑠 =
𝑅2
𝑅1 + 𝑅2
× 𝑅𝑠
For this evaluation board ’s inverter current feedback circuit, the R1 is 2 k Ω , R2 is 22.1 k Ω , and the Rs is 75 m Ω .
So the inverter current input scaling can be calculated as 68.8 mA/V.
Figure 10 Current feedback offset and gain
2.2.2.2 Offset voltage calculation
We can conclude from Figure 10 that users can also calculate the offset voltage needed to enter into MCEWizard.
This parameter is the voltage in mV at the current sense pin when the shunt current is zero. In the evaluation
board design example, R1 is 2 k
Ω and R2 is 22.1 k Ω . So the offset voltage is:
𝑉𝑜𝑓𝑓 =
R1
R1 + R2
× 𝑉𝐷𝐷 =
2
2 + 22.1
× 5 = 0.415 𝑉 = 415 𝑚𝑉
Current sensing on board