ZHCSBL1B September 2013 – October 2014 DRV8816
PRODUCTION DATA.
10 Power Supply Recommendations
10.1 Bulk Capacitance
Having appropriate local bulk capacitance is an important factor in motor drive system design. It is generally beneficial to have more bulk capacitance, while the disadvantages are increased cost and physical size.
The amount of local capacitance needed depends on a variety of factors, including:
- The highest current required by the motor system.
- The power supply's capacitance and ability to source current.
- The amount of parasitic inductance between the power supply and motor systems.
- The acceptable voltage ripple.
- The type of motor used (Brushed DC, Brushless DC, Stepper).
- The motor braking method.
The inductance between the power supply and motor drive system will limit the rate current can change from the power supply. If the local bulk capacitance is too small, the system will respond to excessive current demands or dumps from the motor with a change in voltage. When adequate bulk capacitance is used, the motor voltage remains stable and high current can be quickly supplied.
The datasheet generally provides a recommended value, but system-level testing is required to determine the appropriate sized bulk capacitor.
Figure 12. Example Setup of Motor Drive System with External Power Supply
10.2 Power Supervisor
Control input nSLEEP is used to minimize power consumption when the DRV8816 is not in use. This disables much of the internal circuitry, including the internal voltage rails and charge pump. nSLEEP is asserted low. A logic high on this input pin results in normal operation. When switching from low to high, the user should allow a 1-ms delay before applying PWM signals. This time is needed for the charge pump to stabilize.