DRV8702D-Q1 Datasheet, PDF (51/66 Pages) Texas Instruments – Automotive Half-Bridge Gate Driver

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DRV8702D-Q1, DRV8703D-Q1
SLVSDX8 – MARCH 2017
9 Power Supply Recommendations
The DRV8702D-Q1 device is designed to operate with an input voltage supply (VM) rangefrom 5.5 V to 45 V. A
0.1-µF ceramic capacitor rated for VM must be placed as close to the DRV8702D-Q1 device as possible. Also, a
bulk capacitor valued at least 10 µF must be placed on the VM pin.
Additional bulk capacitance is required to bypass the external half-bridge FETs.
9.1 Bulk Capacitance Sizing
Bulk capacitance sizing is an important factor in motor drive system design. It is 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 of the power supply and the ability of the power supply 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, and stepper).
• The motor braking method.
The inductance between the power supply and motor drive system limits the rate that 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 sufficient bulk capacitance is used, the motor voltage
remains stable, and high current can be quickly supplied.
The data sheet 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
Copyright © 2016, Texas Instruments Incorporated
Figure 59. 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 a margin for cases
when the motor transfers energy to the supply.
Copyright © 2017, Texas Instruments Incorporated
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