DRV8824_16 Datasheet, PDF (22/35 Pages) Texas Instruments – Stepper Motor Controller IC

DRV8824
SLVSA06J – OCTOBER 2009 – REVISED JULY 2014
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10 Power Supply Recommendations
The DRV8824 is designed to operate from an input voltage supply (V_(VMx)) range between 8.2 and 45 V. Two
0.01-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.
10.1 Bulk Capacitance
Bulk capacitance sizing is an important factor in motor drive system design. It depends 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 startup current
• Motor braking method
The inductance between the power supply and 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. The designer must 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
+
+
Motor
±
Driver
GND
Local
Bulk Capacitor
IC Bypass
Capacitor
Figure 11. Example Setup of Motor Drive System With External Power Supply
10.2 Power Supply and Logic Sequencing
There is no specific sequence for powering-up the DRV8824. It is okay for digital input signals to be present
before VMx is applied. After VMx is applied to the DRV8824, it begins operation based on the status of the
control pins.
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