SLVSDS7B August 2019 – November 2019 DRV8876
The DRV887x family of devices provide integrated regulation and sensing out the output current.
The current sense feedback is configured by scaling the RIPROPI resistor to properly sense the scaled down output current from IPROPI within the dynamic voltage range of the controller ADC. An example of this is shown.
If VADC = 2.5 V, ITRIP = 1 A, and AIPROPI = 1000 µA/A then to maximize the dynamic IPROPI voltage range an RIPROPI of approximately 2.5 kΩ should be selected.
The accuracy tolerance of RIPROPI can be selected based on the application requirements. 10%, 5%, 1%, 0.1% are all valid tolerance values. The typical recommendation is 1% for best tradeoff between performance and cost.
The output current regulation trip point (ITRIP) is configured with a combination of VREF and RIPROPI. Since RIPROPI was previously calculated and AIPROPI is a constant, all the remains is to calculate VREF.
If RIPROPI = 2.5 kΩ, ITRIP = 1 A, and AIPROPI = 1000 µA/A then VREF should be set to 2.5 V.
VREF can be generated with a simple resistor divider (RREF1 and RREF2) from the controller supply voltage. The resistor sizing can be achieved by selecting a value for RREF1 and calculating the required value for RREF2.