DRV8823-Q1_15 Datasheet, PDF (10/22 Pages) Texas Instruments – 4-BRIDGE SERIAL INTERFACE MOTOR DRIVER

DRV8823-Q1
SLVSBH2B – JUNE 2012 – REVISED JANUARY 2013
www.ti.com
Decay Mode
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 3 as case 1. The current flow direction shown indicates
positive current flow in the step table below.
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. As the winding current approaches zero, the bridge is
disabled to prevent any reverse current flow. Fast decay mode is shown in Figure 3 as case 2.
In slow decay mode, winding current is recirculated by enabling both of the low-side FETs in the bridge. This is
shown in Figure 3 as case 3.
VM
1
xOUT1
3
2
xOUT2
1 Drive current
2 Fast decay (reverse)
3 Slow decay (brake)
Figure 3. Decay Mode
The DRV8823-Q1 device supports slow decay and a mixed decay mode. Mixed decay mode begins as fast
decay, but at a fixed period of time (75% of the PWM cycle) switches to slow decay mode for the remainder of
the fixed PWM period.
Slow or mixed decay mode is selected by the state of the xDECAY bits in the serial interface registers. If the
xDECAY bit is 0, slow decay is selected. If the xDECAY bit is 1, mixed decay is selected.
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