User guide
18 of 35
Revision 1.4
2021-09-10
EVAL-M1-IM818-A user guide
Evaluation power board with MADK M1 connector
System and functional description
2.6.2
Motor External Current feedback configuration and calculation
The current input value is product of the shunt resistance in milliohms and gain of External current sense
amplifier for EVAL-M1-101T as shown in Figure 12.
Figure 12
Current shunt feedback and sample timing for EVAL-M1-101T
The external amplifier gain circuit can be found in the schematics or user manual for the control board (For
example, EVAL-M1-101T see Figure 13).
Figure 13 depicts IU+ current feedback sensing circuity on EVAL-M1-101T evaluation board. Please note that the
default external amplification gain is less than 1 for current sense in this evaluation board.
Figure 13
The part of Current feedback on the EVAL-M1-101T evaluation board
Based on the principle of Kirchhoff's voltage law,
𝑉
2
≈
𝑉
1
≈
(
𝑉
𝐷𝐷
−
𝐼
𝑠ℎ
∗
𝑅
𝑠ℎ
)
∗
𝑅
7
𝑅
6
+
𝑅
7
+
𝐼
𝑠ℎ
∗
𝑅
𝑠ℎ
=
𝑅
7
𝑅
6
+
𝑅
7
𝑉
𝐷𝐷
+
𝑅
6
𝑅
6
+
𝑅
7
𝑅
𝑠ℎ
∗
𝐼
𝑠ℎ
𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑖𝑛𝑝𝑢𝑡
=
𝑅
6
𝑅
6
+
𝑅
7
𝑅
𝑠ℎ
=
5
6
𝑅
𝑠ℎ
Based on this calculation, the current input for the MADK combination of EVAL-M1-101T and EVAL-M1-IM818-A
is 20.83 mV/A.
Please use same procedure to calculate the current input for other combinations of MADK boards and enter it
into MCEWizard as shown in Figure 14
R7
2k, 1%
C15
220pF
IU+
R6
10k, 1%
+3.3V
R8
100R
Rsh
iMOTION
IU
Controller
V1
V2
6
Current Shunt
Resistor on power board
1sh
