Data Sheet

TRIP

0mA

Fast

Mixed

25%

Slow

PWM cycle

PWM on PWM off (t

OFF

)

25% 50% 75% 100%

DRV8834

SLVSB19D –FEBRUARY 2012–REVISED MARCH 2015

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Feature Description (continued)

The DRV8834 supports fast, slow, and also mixed decay modes. With DC motors, slow decay is nearly always

used to minimize current ripple and optimize speed control; with stepper motors, the decay mode is chosen for a

given stepper motor and operating conditions to minimize mechanical noise and vibration.

In mixed decay mode, the current recirculation begins as fast decay, but at a fixed period of time (determined by

the state of the xDECAY pins shown in Table 1) switches to slow decay mode for the remainder of the fixed

PWM period.

Table 1. Decay Pin Configuration

RESISTANCE ON xDECAY PIN -OR- VOLTAGE FORCED ON xDECAY PIN % OF PWM CYCLE IS FAST DECAY

< 1 kΩ < 0.1 V 0%

20 kΩ ±5% 0.2 V ±5% 25%

50 kΩ ±5% 0.5 V ±5% 50%

100 kΩ ±5% 1 V ±5% 75%

> 200 kΩ > 2 V 100%

Figure 8 shows the current waveforms in slow, 25% mixed, and fast decay modes.

Figure 8. Current Decay Modes

Decay mode is selected by the voltage present on the xDECAY pins. Internal current sources of 10 µA (typical)

are connected to the pins, which allows setting of the decay mode by a resistor connected to ground if desired.

It is possible to drive the xDECAY pin with a tristate GPIO pin and also place the resistor to ground. This allows a

microcontroller to select fast, slow, or mixed decay modes by driving the pin high, low, or high-impedance. The

logic-low voltage must be less than 0.1 V with 10-µA of current sourced from the DRV8834 to attain slow decay.

In indexer mode, only the ADECAY pin is used, and slow decay mode is always used when at any point in the

step table where the current is increasing. When current is decreasing or remaining constant, the decay mode

used will be fast, slow, or mixed, as commanded by the ADECAY pin.

8.3.3 Protection Circuits

The DRV8834 is fully protected against undervoltage, overcurrent and overtemperature events.

Product Folder Links: DRV8834