DRV8829_15 Datasheet, PDF (11/27 Pages) Texas Instruments – DRV8829 5-A 45-V Single H-Bridge Motor Driver

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DRV8829
SLVSA74E – MAY 2010 – REVISED SEPTEMBER 2015
Table 1. Current Scalar Logic (continued)
I[4..0]
0x0Dh
0x0Eh
0x0Fh
0x10h
0x11h
0x12h
0x13h
0x14h
0x15h
0x16h
0x17h
0x18h
0x19h
0x1Ah
0x1Bh
0x1Ch
0x1Dh
0x1Eh
0x1Fh
RELATIVE CURRENT
(% FULL-SCALE CHOPPING CURRENT)
60%
63%
67%
71%
74%
77%
80%
83%
86%
88%
90%
92%
94%
96%
97%
98%
99%
100%
100%
7.4 Device Functional Modes
7.4.1 Bridge Control
The PHASE input pin controls the direction of current flow through the H-bridge. The ENBL input pin enables the
H-bridge outputs when active high. Table 2 shows the logic.
ENBL
0
1
1
Table 2. H-Bridge Logic
PHASE
X
1
0
OUT1
Z
H
L
OUT2
Z
L
H
The control inputs have internal pulldown resistors of approximately 100 kΩ.
7.4.2 Decay Mode
During PWM current chopping, the H-bridge is enabled to drive current through the motor winding until the PWM
current chopping threshold is reached. This is shown in Figure 4 as case 1. The current flow direction shown
indicates the state when the PHASE pin is high.
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 4 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 4 as case 3.
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