How much voltage are BRA and BRB absolute maximum ratings on TMC5130?

BRA and BRB shall be tied to GND via the sense resistors. The internal current regulation senses voltage on these pins and will keep a maximum voltage of roughly 325mV (full scale setting). You should not apply additional external voltage. With a given sense resistor, a certain voltage corresponds to a certain bridge current. The internally determined full scale setting will be kept when operating the motor with SpreadCycle, respectively when operating with StealthChop and sufficiently set current regulation parameters. The pins are designed to carry the nominal / maximum motor current.

Therefore there is no maximum rating given.

The internal circuitry is designed to withstand short time pulses occurring due to chopper operation of the motor bridge and due to trace inductivity. In case sense resistors have a high inductivity or in case motor outputs have a high capacitive load, apply ceramic capacitors in parallel to the sense resistor to suppress peak voltages. 

BRA and BRB shall be tied to GND via the sense resistors. The internal current regulation senses voltage on these pins and will keep a maximum voltage of roughly 325mV (full scale setting). You should not apply additional external voltage. With a given sense resistor, a certain voltage corresponds to a certain bridge current. The internally determined full scale setting will be kept when operating the motor with SpreadCycle, respectively when operating with StealthChop and sufficiently set current regulation parameters. The pins are designed to carry the nominal / maximum motor current.

Therefore there is no maximum rating given.

The internal circuitry is designed to withstand short time pulses occurring due to chopper operation of the motor bridge and due to trace inductivity. In case sense resistors have a high inductivity or in case motor outputs have a high capacitive load, apply ceramic capacitors in parallel to the sense resistor to suppress peak voltages.