SLOS825E December 2012 – April 2018 DRV2605
The rated voltage is the driving voltage that the driver will output during steady state. However, in closed-loop drive mode, temporarily having an output voltage that is higher than the rated voltage is possible. See the Overdrive Voltage-Clamp Programming section for details.
The RATED_VOLTAGE[7:0] bit in register 0x16 sets the rated voltage for the closed-loop drive modes. For the ERM, Equation 2 calculates the average steady-state voltage when a full-scale input signal is provided. For the LRA,Equation 3 calculates the root-mean-square (RMS) voltage when driven to steady state with a full-scale input signal.
In open-loop mode, the RATED_VOLTAGE[7:0] bit is ignored. Instead, the OD_CLAMP[7:0] bit (in register 0x17) is used to set the rated voltage for the open-loop drive modes. For the ERM, Equation 4 calculates the rated voltage with a full-scale input signal. For the LRA,Equation 5 calculates the RMS voltage with a full-scale input signal.
The auto-calibration routine uses the RATED_VOLTAGE[7:0] and OD_CLAMP[7:0] bits as inputs and therefore these registers must be written before calibration is performed. Any modification of this register value should be followed by calibration to appropriately set A_CAL_BEMF[7:0].