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EVAL-IMM101T
Smart IPM evaluation board application note
Schematics and Layout
In leg shunt configuration, the resistors RS1, RS2 and RS3 are purposed to generate voltages proportional to the
source currents of the low side power MOSFETs. These voltages are shifted using the shift stages in Figure 13 and
they are measured at pins P2.9, P2.6, P2.2 respectively.
In single shunt configuration, resistor RS1 is purposed to generate a voltage proportional to the sum of the source
currents of the low side power MOSFETs. This voltage is shifted using the shift stage in Figure 13 and it is
measured at pin P2.9 (P2.6, P2.2 are used only for leg shunt).
The shift stage is made of a voltage divider and a low pass filter; using the superposition theorem, it is possible
to calculate the input current scaling and the shift stage offset. The input current scaling can be calculated using
the following formula:
𝐼𝑛𝑝𝑢𝑡 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑆𝑐𝑎𝑙𝑖𝑛𝑔 = 𝑅𝑆
1,2,3
𝑅
1,4,7
𝑅
1,4,7
+ 𝑅
2,5,8
𝑉/𝐴
The ADC dynamic range can be calculated using the following formula:
𝐴𝐷𝐶 𝑟𝑎𝑛𝑔𝑒 =
𝐼𝑛𝑝𝑢𝑡 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑆𝑐𝑎𝑙𝑖𝑛𝑔
3.3 𝑉
× 𝐼𝑛𝑡𝑒𝑟𝑛𝑎𝑙 𝐺𝑎𝑖𝑛 × (2
12
− 1) 𝑐𝑜𝑢𝑛𝑡𝑠/𝐴
The Internal Gain can be set via MCEWizard and the default value for the EVAL-IMM101T is equal to 3. Particular
attention has to be paid in setting the Internal Gain to avoid to saturate the ADC; this causes a continuos GateKill
fault status in MCEDesigner.
The shift stage offset can be calculated using the following formula:
𝑆ℎ𝑖𝑓𝑡 𝑆𝑡𝑎𝑔𝑒 𝑂𝑓𝑓𝑠𝑒𝑡 =
𝑅
2,5,8
𝑅
1,4,7
+ 𝑅
2,5,8
× 3.3 𝑉
In single shunt configuration, RS2, RS3, R5 and R8 are not inserted.
The overcurrent comparator reference voltage can be calculate using the following formula:
𝑂𝑉𝐶 𝑇ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑 = (𝐼
𝑢,𝑣,𝑤 𝑀𝐴𝑋 𝑝𝑒𝑎𝑘
× 𝐼𝑛𝑝𝑢𝑡 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑆𝑐𝑎𝑙𝑖𝑛𝑔 + 𝑆ℎ𝑖𝑓𝑡 𝑆𝑡𝑎𝑔𝑒 𝑂𝑓𝑓𝑒𝑠𝑡) 𝑉
