DRV8426PWPR datasheet(17/49 Pages) TI1

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DRV8426

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SLOSE55 – MAY 2020

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7.3.6 Decay Modes

During PWM current chopping, the H-bridge is enabled to drive through the motor winding until the PWM current

chopping threshold is reached. This is shown in Figure 8, Item 1.

Once the chopping current threshold is reached, the H-bridge can operate in two different states, fast decay or

slow decay. In fast decay mode, once the PWM chopping current level has been reached, the H-bridge reverses

state to allow winding current to flow in a reverse direction. The opposite FETs are turned on; as the winding

current approaches zero, the bridge is disabled to prevent any reverse current flow. Fast decay mode is shown in

Figure 8, item 2. In slow decay mode, winding current is re-circulated by enabling both of the low-side FETs in

the bridge. This is shown in Figure 8, Item 3.

Figure 8. Decay Modes

The decay mode of the DRV8426 is selected by the DECAY0 and DECAY1 pins as shown in Table 8. If

DECAY1 pin is Hi-Z, irrespective of the DECAY0 pin voltage, the decay mode will be smart tune dynamic decay.

The decay modes can be changed on the fly. After a decay mode change, the new decay mode is applied after a

10 µs de-glitch time.

Table 8. Decay Mode Settings

DECAY0

DECAY1

INCREASING STEPS

DECREASING

STEPS

Smart tune Dynamic

Decay

Smart tune Dynamic

Decay

Smart tune Ripple

Control

Smart tune Ripple

Control

Mixed decay: 30%

fast

Mixed decay: 30%

fast

Slow decay

Mixed decay: 30%

fast

Hi-Z

Mixed decay: 60%

fast

Mixed decay: 60%

fast

Hi-Z

Slow decay

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