DRV421_15 Datasheet, PDF (18/44 Pages) Texas Instruments – DRV421 Integrated Magnetic Fluxgate Sensor for Closed-Loop Current Sensing

DRV421
SBOS704A – MAY 2015 – REVISED JULY 2015
www.ti.com
Feature Description (continued)
Table 1. DRV421 Loop Gain Filter Settings and Relation to Magnetic Core Parameters
GSEL1
0
0
1
1
GSEL0
0
1
0
1
COMPENSATION LOOP PROPERTIES
INTEGRATOR CORNER
FREQUENCY
AC OPEN-LOOP GAIN
3.8 kHz
8.5
3.8 kHz
38
1.9 kHz
25
1.9 kHz
70
RANGE OF
MODIFIED GAIN
FACTOR G_MOD
3 < G_MOD < 12
1 < G_MOD < 3
1 < G_MOD <3
0.3 < G_MOD < 1
RANGE OF COMPENSATION
COIL INDUCTANCE L
(N_WINDING = 1000
and G_CORE = 0.6 mT/A)
100 mH < L < 200 mH
200 mH < L < 600 mH
200 mH < L < 600 mH
600 mH < L < 2 H
Table 1 gives an initial gain-setting recommendation based on a simulation model of a generic magnetic core.
Secondary magnetic effects, such as eddy current losses and core hysteresis, can lead to different optimal
settings. Therefore, make sure to verify the correct gain setting by measuring the response of the current sensor
to an input current step at compensation driver output pins ICOMP1 and ICOMP2. Examples of measurement
results with a magnetic core of 300 mH, 1000 compensation coil windings, and different DRV421 gain settings
are shown in Figure 53 to Figure 56.
ICOMP1
ICOMP2
VOUT
ER
ICOMP1
ICOMP2
VOUT
ER
Figure 53. Settling of ICOMP1 and ICOMP2
with GSEL[1:0] = 00
ICOMP1
ICOMP2
VOUT
ER
Figure 54. Settling of ICOMP1 and ICOMP2
with GSEL[1:0] = 01
ICOMP1
ICOMP2
VOUT
ER
Figure 55. Settling of ICOMP1 and ICOMP2
with GSEL[1:0] = 10
Figure 56. Settling of ICOMP1 and ICOMP2
with GSEL[1:0] = 11
These measurement examples show a stable response for both GSEL[1:0] = 10 and 11 settings. However,
inductive coupling between the primary current and compensation coil makes it difficult to measure high-
frequency instability. Therefore, use the lowest gain setting that yields a stable response; in this case, use gain
setting 10.
18
Submit Documentation Feedback
Product Folder Links: DRV421
Copyright © 2015, Texas Instruments Incorporated