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SBOS374B − NOVEMBER 2006 − REVISED OCTOBER 2007
www.ti.com
11
In the Typical Characteristics, the Output Error vs
Common-Mode Voltage curve shows the highest
accuracy for the this region of operation. In this plot,
VS= 12V; for VCM ≥ 12V, the output error is at its minimum.
This cas e i s a l s o u s e d t o create the VSENSE ≥ 20mV output
specifications in the Electrical Characteristics table.
Normal Case 2: VSENSE ≥ 20mV, VCM < VS
This region of operation has slightly less accuracy than
Normal Case 1 as a result of the common-mode operating
area i n which the part functions, as seen in the Output Error
vs Common-Mode Voltage curve. As noted, for this graph
VS = 12V ; for VCM < 1 2 V, the Output Error increases as VCM
becomes less than 12V, with a typical maximum error of
0.005% at the most negative VCM = −16V.
Low VSENSE Case 1:
VSENSE < 20mV, −16V ≤ VCM < 0; and
Low VSENSE Case 3:
VSENSE < 20mV, VS < VCM ≤ 80V
Although the INA200 family of devices are not designed for
accurate operation in either of these regions, some
applications are exposed to these conditions. For
example, when monitoring power supplies that are
switched on and of f while VS is still applied to the INA200,
INA201, or INA202, it is important to know what the
behavior of the devices will be in these regions.
As VSENSE approaches 0mV, in these VCM regions, the
device output accuracy degrades. A larger-than-normal
offset can appear at the current shunt monitor output with
a typical maximum value of VOUT = 300mV for
VSENSE = 0mV. As VSENSE approaches 20mV, VOUT
returns to the expected output value with accuracy as
specified in the Electrical Characteristics. Figure 3
illustrates this effect using the INA202 (Gain = 100).
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0024 6 8 1012141618
VOUT (V)
VSENSE (mV)
20
Actual
Ideal
Figure 3. Example for Low VSENSE Cases 1 and 3
(INA202, Gain = 100)
Low VSENSE Case 2: VSENSE < 20mV, 0V ≤ VCM ≤ VS
This region of operation is the least accurate for the
INA200 family. To achieve the wide input common-mode
voltage range, these devices use two op amp front ends in
parallel. One op amp front end operates in the positive
input common-mode voltage range, and the other in the
negative input region. For this case, neither of these two
internal amplifiers dominates and overall loop gain is very
low. Within this region, VOUT approaches voltages close to
linear operation levels for Normal Case 2. This deviation
from linear operation becomes greatest the closer VSENSE
approaches 0V. Within this region, as VSENSE approaches
20mV, device operation is closer to that described by
Normal Case 2. Figure 4 illustrates this behavior for the
INA202. The VOUT maximum peak for this case is tested
by maintaining a constant VS, setting VSENSE = 0mV and
sweeping VCM from 0V to V S. The exact VCM at which VOUT
peaks during this test varies from part to part, but the VOUT
maximum peak is tested to be less than the specified VOUT
tested limit.
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
00 2 4 6 8 10 12 14 16 18 20 22
VOUT (V)
VSENSE (mV)
24
INA202 VOUT Tested Limit(1)
VCM2
VCM1
VCM3
VCM4
VCM2,V
CM3,andV
CM4 illustrate the variance
frompart to part of theVCM that can cause
maximumVOUT with VSENSE < 20mV.
VOUT tested limit at
VSENSE =0mV,0≤VCM1 ≤VS.
NOTE: (1) INA200VOUT Tested Limit = 0.4V. INA201 VOUT Tested Limit = 1V.
Ideal
Figure 4. Example for Low VSENSE Case 2
(INA202, Gain = 100)
SELECTING RS
The value chosen for the shunt resistor, RS, depends on
the application and is a compromise between small-signal
accuracy and maximum permissible voltage loss in the
measurement line. High values of RS provide better
accuracy at lower currents by minimizing the effects of
offset, while low values of RS minimize voltage loss in the
supply line. For most applications, best performance is
attained with an RS value that provides a full-scale shunt
voltage range of 50mV to 100mV. Maximum input voltage
for accurate measurements is 500mV.
TRANSIENT PROTECTION
The −16V to +80V common-mode range of the INA200,
INA201, and INA202 is ideal for withstanding automotive
fault conditions ranging from 12V battery reversal up to
+80V transients, since no additional protective
components are needed up to those levels. In the event
that the INA200, INA201, and INA202 are exposed to
transients on the inputs in excess of their ratings, then
external transient absorption with semiconductor transient
absorbers (such as zeners) will be necessary. Use of