Infineon REF-Vacuum-C101-2ED, Руководство пользователя

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User Guide www.Infineon.com/iMotion 27 of 43 www.Infineon.com/SOI Revision 1.0
2020-5-22
UG2020-11 REF-Vacuum-C101-2ED User Guide
𝐴𝐷 𝑖𝑛𝑝𝑢𝑡 =
𝑅
29
𝑅
29
+ 𝑅
34
𝑅𝑆
1
∗ 𝐼
𝑏𝑢𝑠
=
5.1𝐾
5.1𝐾 + 0.1𝐾
𝑅𝑆
1
∗ 𝐼
𝑏𝑢𝑠
= 0.98 ∗ 𝑅𝑆
1
∗ 𝐼
𝑏𝑢𝑠
Figure 23 Current feedback without external op-amp
R29 & R34 also determine the ADC operational bias for current sensing, which corresponds to the motor
regeneration operation range. For those applications that only work in motoring mode, the bias can be as low
as possible to reserve enough ADC range for motoring mode, since negative input would not occur.
Please note that in direct AD sample mode (without external op-amp):

The external RC network’s input gain is less than 1. Normally ADC internal gain needs to be configured to
X3, X6 or X12 to lower the required input signal range and reduce shunt resistor power dissipation. RS1
must be much higher than 2 mOhm to achieve enough current sensing signal-to-noise ratio (SNR) and
improve control performance: For example, to achieve sufficiently high SNR, motor current sensing counts
need be over 30~50% of AD range (traced Iu peak over 600 cts~1000 cts) at rate motor current, and PCB
ground noise lower than 5% of total sampled signal in MCEDesigner trace result.

There is NO common mode noise rejection ability, compared to external op-amp sample mode. Directly AD
current sensing mode needs to deal with PCB GND network very carefully to reduce grounding noise as low
as possible. Please note that any voltage difference between IMC101T’s ADC ground and shunt resistor
ground will be considered as an “input signal” and deteriorate control performance or increase motor
audible noise.
For the power rating of the shunt resistor, the following list should be considered:

Maximum input current of inverter (I
busRMS
)

Maximum motor current output (I
motorRMS
)

Shunt resistor value at Tc = 25  C (R
SH
)

Power derating ratio of shunt resistor at T
SH
=100  C according to the manufacturer’s datasheet

Safety margin and measure margin (total 50%~60% derating)

Power supply for IMC101T (3.3 V or 5 V)
An example for shunt resistor and ADC internal gain selection: