DRV8842 Datasheet, PDF (8/18 Pages) Texas Instruments – DC MOTOR DRIVER IC

DRV8842
SLVSAB8D – MAY 2010 – REVISED JANUARY 2012
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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.
The full-scale (100%) chopping current is calculated in Equation 1.
V
I = ₅^¾ _{R CHOP}
REFX
· _ISENSE
(1)
Example:
If a 0.25-Ω sense resistor is used and the VREFx pin is 2.5 V, the full-scale (100%) chopping current will be
2.5 V / (5 x 0.25 Ω) = 2 A.
Five input pins (I0 - I4) are used to scale the current in the bridge as a percentage of the full-scale current set by
the VREF input pin and sense resistance. The I0 - I4 pins have internal pulldown resistors of approximately
100 kΩ. The function of the pins is shown in Table 3.
I[4..0]
0x00h
0x01h
0x02h
0x03h
0x04h
0x05h
0x06h
0x07h
0x08h
0x09h
0x0Ah
0x0Bh
0x0Ch
0x0Dh
0x0Eh
0x0Fh
0x10h
0x11h
0x12h
0x13h
0x14h
0x15h
0x16h
0x17h
0x18h
0x19h
0x1Ah
0x1Bh
0x1Ch
0x1Dh
0x1Eh
0x1Fh
Table 3. Pin Functions
RELATIVE CURRENT
(% FULL-SCALE CHOPPING CURRENT)
0%
5%
10%
15%
20%
24%
29%
34%
38%
43%
47%
51%
56%
60%
63%
67%
71%
74%
77%
80%
83%
86%
88%
90%
92%
94%
96%
97%
98%
99%
100%
100%
8
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