SLVSD19A June 2015 – July 2015 DRV8881
PRODUCTION DATA.
In a stepper motor, the full-scale current (IFS) is the maximum current driven through either winding. This quantity will depend on the TRQ pins, the xVREF analog voltage, and the sense resistor value (RSENSE). AVREF and BVREF can be configured to drive different currents, but in this example the same full-scale current is used in both coils.
TRQ is a DAC used to scale the output current. The current scalar value for different inputs is shown in Table 10.
TRQ1 | TRQ0 | CURRENT SCALAR (TRQ) |
---|---|---|
1 | 1 | 25% |
1 | 0 | 50% |
0 | 1 | 75% |
0 | 0 | 100% |
Example: If the desired full-scale current is 800 mA | ||
Set RSENSE = 250 mΩ, assume TRQ = 100%. | ||
xVREF would have to be 1.32 V. | ||
Create a resistor divider from V3P3 (3.3 V) to set AVREF and BVREF ≈ 1.32 V. | ||
Set R2 = 10 kΩ, set R1 = 15 kΩ |
Note that IFS must also follow Equation 3 in order to avoid saturating the motor. VM is the motor supply voltage, and RL is the motor winding resistance.