DRV8843_15 Datasheet, PDF (9/20 Pages) Texas Instruments – DUAL H-BRIDGE DRIVER IC

DRV8843
www.ti.com
SLVSAS8C – APRIL 2011 – REVISED AUGUST 2013
Bridge Control
The AIN1 and AIN2 input pins directly control the state of the AOUT1 and AOUT2 outputs; similarly, the BIN1
and BIN2 input pins directly control the state of the BOUT1 and BOUT2 outputs. Either input can also be used
for PWM control of the load. Table 2 shows the logic.
Table 2. H-Bridge Logic
xIN1
0
0
1
1
xIN2
0
1
0
1
xOUT1
Z
L
H
L
xOUT2
Z
H
L
L
The inputs can also be used for PWM control of the motor speed. When controlling a winding with PWM, when
the drive current is interrupted, the inductive nature of the motor requires that the current must continue to flow.
This is called recirculation current. To handle this recirculation current, the H-bridge can operate in two different
states, fast decay or slow decay. In fast decay mode, the H-bridge is disabled and recirculation current flows
through the body diodes; in slow decay, the motor winding is shorted.
To PWM using fast decay, the PWM signal is applied to one xIN pin while the other is held low; to use slow
decay, one xIN pin is held high.
The control inputs have internal pulldown resistors of approximately 100 kΩ.
xIN1
PWM
1
0
PWM
Table 3. PWM Function
xIN2
0
PWM
PWM
1
FUNCTION
Forward PWM, fast decay
Forward PWM, slow decay
Reverse PWM, fast decay
Reverse PWM, slow decay
The drawings below show the current paths in different drive and decay modes:
VM
VM
1
xOUT1
2
3
1 Forward drive
2 Fast decay
1
xOUT2 _{3 Slow decay}
xOUT1
2
3
xOUT2
1 Reverse drive
2 Fast decay
3 Slow decay
FORWARD
REVERSE
Figure 2. Current Paths
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