User guide
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V 1.0.1
2021-01-27
REF-AIRCON-C302A-IM564 user guide
Air conditioner application reference design kits
System and functional description
2.2.6
Design tips for PFC current sensing
As mentioned in the motor current sensing section, common mode noise rejection (CMR) is vitally important for
direct current AD sample. The PFC current sensing shunt resistor is located at a long distance from the IMC302A
IC in the REF-AIRCON-C302A-IM564 board, i.e. PFC current sensing cannot use the direct AD sample mode any
more.
An 11 MHz rail-to rail I/O CMOS OPA SGM8968-1 is used for PFC current sensing to achieve enough common
mode noise rejection ability.
A 15 mOhm 5 W shunt resistor (50110 package) and 14.7X external-gain OPA is the default configuration for the
REF-AIRCON-C302A-IM564 reference design, i.e., 1 A PFC current produces 220.5 mV voltage to ADC input. So
MCEWizard’s “PFC Current Measurement Input Scaling” needs an input of 220.5 mV/A, as shown in Figure 18.
Figure 18
PFC current sensing configuration in MCEWizard for REF-AIRCON-C302A-IM564
