DRV8841_15 Datasheet, PDF (17/28 Pages) Texas Instruments – Dual H-Bridge Driver IC

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DRV8841
SLVSAC0F – MAY 2010 – REVISED DECEMBER 2015
9 Power Supply Recommendations
The DRV8841 is designed to operate from an input voltage supply (VMx) range from 8.2 to 45 V. Two
0.1-µF ceramic capacitors rated for VMx must be placed as close as possible to the VMA and VMB pins
respectively (one on each pin). In addition to the local decoupling caps, additional bulk capacitance is required
and must be sized accordingly to the application requirements.
9.1 Bulk Capacitance
Bulk capacitance sizing is an important factor in motor drive system design. It is dependent on a variety of factors
including:
• Type of power supply
• Acceptable supply voltage ripple
• Parasitic inductance in the power supply wiring
• Type of motor (brushed DC, brushless DC, stepper)
• Motor start-up current
• 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. You should size the bulk capacitance to meet acceptable
voltage ripple levels.
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
+
+
MMoottoorr
–
D^Dr^riⁱv^vee^rr
GND
Local
Bulk Capacitor
IC Bypass
Capacitor
Figure 10. Setup of Motor Drive System With External Power Supply
9.2 Power Supply and Logic Sequencing
There is no specific sequence for powering-up the DRV8841. It is okay for digital input signals to be present
before VMx is applied. After VMx is applied to the DRV8841, it begins operation based on the status of the
control pins.
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