Unexpected BAL_SWITCH_STAT Register Values on MC33774A

[MarkFan]

Hello,

I am working with the MC33774 and have encountered unexpected results when configuring the balancing switch monitor.

• Configuration:

  • Register: MC33774_BAL_SWITCH_MON_CFG0_OFFSET (0x1006)

  • Value written: 0x1F

• Observation:
  When I read back from the status registers:

  • MC33774_BAL_SWITCH_STAT0_OFFSET (0x1010) → returns 0xAAAA or 0x5555

  These values are different from what I expected (e.g., 0x15 or 0xA0).

Question:
Could you please clarify why the status registers return 0xAAAA and 0x5555 instead of reflecting the configured value? Is this the correct behavior, or am I missing a step in the configuration procedure?

Thank you for your support.

Mark

[TomasVaverka]

Hello Mark,

These returned values are expected and reflect the real-time physical state of the balancing switches. 

0xAAAA = 1010101010101010
0x5555 = 0101010101010101

This alternating pattern indicates that the MC33774A is performing automatic odd/even balancing, which is a normal part of its operation. The status register shows which switches are currently closed (balancing active) or open (inactive) and does not directly reflect the configuration value written to the monitoring enable register.

BRs, Tomas

[MarkFan]

Hi Tomas,

    Thasnk for your reply, Actually, only 5 cell connect to MC33774A in our design, according to Missing cell case, I have to coofig BAL_SWITCH_MON_CFG0 and BAL_SWITCH_MON_CFG1 to 0x1f.

    So the balancing switches should be

    10101  = 0x15  not  0x5555

    0101   = 0xa  not 0xaaaa

am I misinterpreting how the monitor configuration maps to the STAT registers?

Thank you for your support.

Mark

[TomasVaverka · Accepted solution]

Hello Mark,

Your configuration is correct for a 5-cell setup. The status register shows what the switches are doing in real time, not just the ones you are monitoring. Seeing 0xAAAA or 0x5555 is normal during active balancing.

BRs, Tomas