Other Parts Discussed in Thread: DRV8871
I am replacing the DRV8871 with the DRV8256P to drive a DC motor. The DRV8871 uses a slow decay current regulation method: I would like to continue using the slow decay method on the DRV88256P.
Per the data sheet:
7.3.3 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 7-4, 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 7-4, 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 7-4, Item 3.
The DRV88256P has a quad-level Decay pin. It has four options:
Table 7-5. Decay Mode Settings
DECAY DECAY MODE
0 Smart tune Dynamic Decay
1 Smart tune Ripple Control
Hi-Z Mixed decay: 30% fast
330k to GND Fast decay
How do I select Slow decay?
Thank you.