SLOSE98A December 2022 – September 2023 DRV8461
PRODUCTION DATA
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 7-12, 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, as soon as the PWM chopping current level is reached, the H-bridge reverses state by switching on the opposite arm MOSFETs to allow the winding current to flow in the opposite direction. As the winding current approaches zero, the H-bridge is disabled to prevent further reverse current flow. Fast decay mode is shown in Figure 7-12, item 3.
In slow decay mode, the winding current is re-circulated by enabling both low-side MOSFETs in the H-bridge. This is shown in Figure 7-12, Item 2.
The decay mode is selected by the DECAY register or the DECAY0 and DECAY1 pins, as shown in Table 7-19. The decay modes can be changed on the fly.
SPI Interface | H/W Interface | Decay Mode | |
---|---|---|---|
DECAY | DECAY0 | DECAY1 | |
000b | Hi-Z | 1 | Slow decay |
100b | 1 | 0 | Mixed decay: 30% fast |
101b | Hi-Z | 0 | Mixed decay: 60% fast |
110b | 0 | 0 | Smart tune Dynamic Decay |
111b (default) | 0 | 1 | Smart tune Ripple Control |
The remaining settings of DECAY bit (001b, 010b, 011b) and the (DECAY0 = 1, DECAY1 = 1) setting are reserved.
The DRV8461 also features the silent step decay mode for ultra-silent operation at low speed and standstill. See Section 7.3.12 for details.