DRV8432_15 Datasheet, PDF (24/42 Pages) Texas Instruments – DRV84x2 Dual Full-Bridge PWM Motor Driver

DRV8412, DRV8432
SLES242G – DECEMBER 2009 – REVISED DECEMBER 2014
9 Power Supply Recommendations
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9.1 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 power supply’s capacitance and ability to source current
• 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.
Power Supply
Parasitic Wire
Inductance
Motor Drive System
VM
+
+
Motor
±
Driver
GND
Local
Bulk Capacitor
IC Bypass
Capacitor
Figure 19. 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.
9.2 Power Supplies
To facilitate system design, the DRV841x2 needs only a 12-V supply in addition to H-Bridge power supply
(PVDD). An internal voltage regulator provides suitable voltage levels for the digital and low-voltage analog
circuitry. Additionally, the high-side gate drive requires a floating voltage supply, which is accommodated by built-
in bootstrap circuitry requiring external bootstrap capacitor.
To provide symmetrical electrical characteristics, the PWM signal path, including gate drive and output stage, is
designed as identical, independent half-bridges. For this reason, each half-bridge has a separate gate drive
supply (GVDD_X), a bootstrap pin (BST_X), and a power-stage supply pin (PVDD_X). Furthermore, an additional
pin (VDD) is provided as supply for all common circuits. Special attention should be paid to place all decoupling
capacitors as close to their associated pins as possible. In general, inductance between the power supply pins
and decoupling capacitors must be avoided. Furthermore, decoupling capacitors need a short ground path back
to the device.
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