Datasheet
Normal Case 1: V
SENSE
≥ 20 mV, V
CM
≥ V
S
G +
V
OUT1
* V
OUT2
100 mV * 20 mV
(1)
V
OS
RTI (Referred−To−Input) +
ǒ
V
OUT1
G
Ǔ
* 100 mV
(2)
Normal Case 2: V
SENSE
≥ 20 mV, V
CM
< V
S
Low V
SENSE
Case 1: V
SENSE
< 20 mV, – 16 V ≤ V
CM
< 0; and Low V
SENSE
Case 3: V
SENSE
< 20 mV,
INA193A-Q1 , INA194A-Q1 , INA195A-Q1
INA196A-Q1 , INA197A-Q1 , INA198A-Q1
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............................................................................................................................................... SBOS366C – AUGUST 2006 – REVISED OCTOBER 2008
This section addresses the accuracy of these specific operating regions:
Normal Case 1: V
SENSE
≥ 20 mV, V
CM
≥ V
S
Normal Case 2: V
SENSE
≥ 20 mV, V
CM
< V
S
Low V
SENSE
Case 1: V
SENSE
< 20 mV, – 16 V ≤ V
CM
< 0
Low V
SENSE
Case 2: V
SENSE
< 20 mV, 0 V ≤ V
CM
≤ V
S
Low V
SENSE
Case 3: V
SENSE
< 20 mV, V
S
< V
CM
≤ 80 V
This region of operation provides the highest accuracy. Here, the input offset voltage is characterized and
measured using a two-step method. First, the gain is determined by (Equation 1 ).
Where:
V
OUT1
= Output voltage with V
SENSE
= 100 mV
V
OUT2
= Output voltage with V
SENSE
= 20 mV
The offset voltage is then measured at V
SENSE
= 100 mV and referred to the input (RTI) of the current shunt
monitor, as shown in (Equation 2 ).
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, V
S
= 12 V; for V
CM
≥ 12 V, the output error is at its minimum. This case is
also used to create the V
SENSE
≥ 20 mV output specifications in the Electrical Characteristics table.
This region of operation has slightly less accuracy than Normal Case 1 as a result of the common-mode
operating area in which the part functions, as seen in the Output Error vs Common-Mode Voltage curve. As
noted, for this graph V
S
= 12 V; for V
CM
< 12 V, the Output Error increases as V
CM
becomes less than 12 V, with
a typical maximum error of 0.005% at the most negative V
CM
= – 16 V.
V
S
< V
CM
≤ 80 V
Although the INA193A – INA198A 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 off while V
S
is still applied to the INA193A – INA198A. It is important to know what the
behavior of the devices will be in these regions.
As V
SENSE
approaches 0 mV, in these V
CM
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 V
OUT
= 300 mV for
V
SENSE
= 0 mV. As V
SENSE
approaches 20 mV, V
OUT
returns to the expected output value with accuracy as
specified in the Electrical Characteristics. Figure 2 illustrates this effect using the INA195A and INA198A
(Gain = 100).
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