DRV8842_15 Datasheet, PDF (9/27 Pages) Texas Instruments – DC Motor Driver IC

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Feature Description (continued)
DRV8842
SLVSAB8F – MAY 2010 – REVISED DECEMBER 2015
IN1
IN2
DECAY
I[4:0]
VREF
VCP, VGD
OCP
Pre-
drive
PWM
DAC
5
OCP
-
+
A =5
VM
VM
OUT1
OUT2
DCM
ISEN
Figure 5. Motor Control Circuitry
Note that there are multiple VM, ISEN, OUT, and VREF pins. All like-named pins must be connected together on
the PCB.
7.3.2 Bridge Control
The IN1 and IN2 input pins directly control the state of the OUT1 and OUT2 outputs. Either input can also be
used for PWM control of the load. Table 1 shows the logic.
Table 1. H-Bridge Logic
xIN1
0
0
1
1
xIN2
0
1
0
1
xOUT1
L
L
H
H
xOUT2
L
H
L
H
The control inputs have internal pulldown resistors of approximately 100 kΩ.
7.3.3 Current Regulation
The maximum current through the load is regulated by a fixed-frequency PWM current regulation, or current
chopping. When the H-bridge is enabled, current rises through the winding at a rate dependent on the DC
voltage and inductance of the winding. Once the current hits the current chopping threshold, the bridge disables
the current until the beginning of the next PWM cycle.
For DC motors, current regulation is used to limit the start-up and stall current of the motor. Speed control is
typically performed by providing an external PWM signal to the xIN1 or xIN2 input pins.
If the current regulation feature is not needed, it can be disabled by connecting the ISENSE pins directly to
ground and the VREF pins to V3P3.
The PWM chopping current is set by a comparator which compares the voltage across a current sense resistor
connected to the ISEN pin, multiplied by a factor of 5, with a reference voltage. The reference voltage is input
from the VREF pin, and is scaled by a 5-bit DAC that allows current settings of zero to 100% in an approximately
sinusoidal sequence.
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