MSP430FR5989: Use of VLO in ACLK for ESI Config

Dear Ti team,

I have an application flow meter with ESI that runs well on a FR5989 with 32kHz external crystal (based on FLOW ESI GUI). I wanted to check current consumption if i use internal VLO (so I save space on PCB).

	// ACLK Clock configuration
    //Set external clock frequency to ACLK frequency
	//CS_setExternalClockSource(32768,0);

	CS_initClockSignal(CS_ACLK, CS_VLOCLK_SELECT, CS_CLOCK_DIVIDER_1);  
	//CS_turnOnLFXT(CS_LFXT_DRIVE_3);

I've commented the external crystal code and used VLOCLK as source but when I turn on the device it doesn't start calibration, is it possible that ESI is restricted to 32Khz? Something that I can change in ESI config?

I've tried to use LFMODOSC as ACLK source at it runs well (of course it consumes more), so i suppose ESI has a minimum CLK for its operation.

Best regards

Samuel