MM9Z1 Shunt Resistor Open Detection Issue

[Shaojun]

Dear support/community,

I'm working MM9Z1_638 microcontroller to measure current. So far everything looks fine. But once I enable open circuit detection for Shunt Resistor with 

B_COMP_CTL = B_COMP_CTL_OPENEM_MASK | B_COMP_CTL_OPENE_MASK.

The sensor always outputs a constant current (0.6A for 50uOhm Shunt Resistor), even though the actual current is changing. And the OPEN bit in COMP_SR Register always indicates, the Shunt resistor is disconnected(OPEN = 1). Writing 1 also has no effect on this flag.

Please give me some suggestions or information about this issue.

Thanks!

Best regards,

Shaojun