Datasheet

V
OS
RTI (Referred−To−Input) +
ǒ
V
OUT1
G
Ǔ
* 100 mV
G +
V
OUT1
* V
OUT2
100 mV * 20 mV
INA193A-EP
www.ti.com SBOS400A –MAY 2007–REVISED SEPTEMBER 2013
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
Normal Case 1: V
SENSE
≥ 20 mV, V
CM
≥ V
S
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).
(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).
(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.
Normal Case 2: V
SENSE
≥ 20 mV, V
CM
< V
S
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.
Low V
SENSE
Case 1: V
SENSE
< 20 mV, –16 V ≤ V
CM
< 0; and Low V
SENSE
Case 3: V
SENSE
< 20 mV,
V
S
< V
CM
≤ 80 V
Although the INA193A is 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. 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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