DRV8305_15 Datasheet, PDF (44/53 Pages) Texas Instruments – DRV8305 Three Phase Gate Driver With Current Shunt Amplifiers and Voltage Regulator

DRV8305
SLVSCX2A – AUGUST 2015 – REVISED SEPTEMBER 2015
9 Power Supply Recommendations
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9.1 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
• Power supply’s capacitance and ability to source or sink current
• Amount of parasitic inductance between the power supply and motor system
• Acceptable voltage ripple
• Type of motor used (brushed DC, brushless DC, stepper)
• 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 data sheet generally provides a recommended value, but system-level testing is required to determine the
appropriate-sized bulk capacitor.
Power Supply
Parasitic Wire
Inductance
Motor Drive System
VM
+
+
Motor
±
Driver
GND
Local
Bulk Capacitor
IC Bypass
Capacitor
Figure 16. 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.
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