Grove I2C Mini Motor Driver v1.0 has massive voltage drop/not outputting enough current

I am using the DRV8830 based motor driver:

I have 2 motors attached to the board and am powering the board with 6V. I have soldered an additional 220mR resistor to both spare pads (R6 and R13 in the link above) in order to raise the current limit for each motor to 1A.

When I drive just one motor at its maximum voltage (i.e. sending 0b111111 in the voltage bits) I only see the voltage to the motor go to 5V at 150mA.

I have measured the supply voltage to the motor driver board and it stays constant at 6V while the motor is being driven. I always check for errors and do not see any undervoltage errors. My 6V PSU that powers the board can handle 3A output no problem.

Surely it should be much closer to 6V and a higher current? I have this micro motor connected which is specced for 6V and about 1A.

Please could someone help me understand why I cannot give 6V to my motor? Why does it cap at 5V and 150mA?

Many thanks.

This Grove - Mini I2C motor driver includes two DRV8830. The DRV8830 provides an integrated motor driver solution for battery-powered motion control applications. There is a voltage stabilizing circuit inside the module, which can convert the input voltage into a 5V voltage for output through the circuit. Because the voltage of 5V allows the IIC bus to provide a stable and safe working environment, but 6V cannot.

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Thanks. I just read the DRV8830 datasheet again. It is misleading as only on page 8 does it have a table of output voltages vs. register values and I can see the maximum voltage is 5.06v. I am annoyed by the poor documentation by TI.