Datasheet

I =
CHOP
V
REFX
5 · R
ISENSE
¾
DRV8842
SLVSAB8E –MAY 2010–REVISED AUGUST 2013 www.ti.com
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.
(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.
Table 3. Pin Functions
RELATIVE CURRENT
I[4..0]
(% FULL-SCALE CHOPPING CURRENT)
0x00h 0%
0x01h 5%
0x02h 10%
0x03h 15%
0x04h 20%
0x05h 24%
0x06h 29%
0x07h 34%
0x08h 38%
0x09h 43%
0x0Ah 47%
0x0Bh 51%
0x0Ch 56%
0x0Dh 60%
0x0Eh 63%
0x0Fh 67%
0x10h 71%
0x11h 74%
0x12h 77%
0x13h 80%
0x14h 83%
0x15h 86%
0x16h 88%
0x17h 90%
0x18h 92%
0x19h 94%
0x1Ah 96%
0x1Bh 97%
0x1Ch 98%
0x1Dh 99%
0x1Eh 100%
0x1Fh 100%
8 Submit Documentation Feedback Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links: DRV8842