The DRV8842-EP is designed to operate from an input voltage supply (VM) range between 8.2 and 45 V. Two 0.1-µF ceramic capacitors rated for VM must be placed as close as possible to the VM pins respectively (one on each pin). In addition to the local decoupling caps, additional bulk capacitance is required and must be sized according 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 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.

Figure 10. 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 DRV8842-EP. It is okay for digital input signals to be present before VM is applied. After VM is applied to the DRV8842-EP, the device begins operation based on the status of the control pins.