DRV8317 datasheet(60/69 Pages) TI

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10 Power Supply Recommendations

10.1 Bulk Capacitance

Having an 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 capacitance and current capability of the power supply

• The amount of parasitic inductance between the power supply and motor system

• 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 the motor drive system limits the rate current can change from

the power supply. If the local bulk capacitance is too small, the system responds 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 data sheet generally provides a recommended value, but system-level testing is required to determine the

appropriate sized bulk capacitor.

Local

Bulk Capacitor

Parasitic Wire

Inductance

Motor Driver

Power Supply

Motor Drive System

GND

IC Bypass

Capacitor

Figure 10-1. Example Setup of Motor Drive System With External Power Supply

The voltage rating for bulk capacitors should be higher than the operating voltage, to provide margin for cases

when the motor transfers energy to the supply.

DRV8317

SLVSGT3 – DECEMBER 2022

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