V

RTI(Referred-To-Input)=

OS

V

OUT1

G

- 100mV

G=

V

V

-

OUT1

OUT2

100mV

20mV

-

17

INA203-Q1

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SBOS539A – DECEMBER 2010 – REVISED APRIL 2016

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Application Information (continued)

9.1.4.1 Normal Case 1: VSENSE ≥ 20 mV, VCM ≥ VS

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 3.

where

•

VOUT1 = output voltage with VSENSE = 100 mV

•

VOUT2 = output voltage with VSENSE = 20 mV

(3)

Then the offset voltage is measured at VSENSE = 100 mV and referred to the input (RTI) of the current shunt

monitor, as shown in Equation 4.

(4)

In the Typical Characteristics section, the Output Error vs Common-Mode Voltage curve (Figure 7) shows the

highest accuracy for this region of operation. In this plot, VS = 12 V; for VCM ≥ 12 V, the output error is at its

minimum. This case is also used to create the VSENSE ≥ 20 mV output specifications in the Electrical

Characteristics table.

9.1.4.2 Normal Case 2: VSENSE ≥ 20 mV, VCM < VS

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

(Figure 7). As noted, for this graph VS = 12 V; for VCM < 12 V, the output error increases as VCM becomes less

than 12 V, with a typical maximum error of 0.005% at the most negative VCM = –16 V.

9.1.4.3 Low VSENSE Case 1:

VSENSE < 20 mV, –16 V ≤ VCM < 0; and

Low VSENSE Case 3:

VSENSE < 20 mV, VS < VCM ≤ 80 V

Although the INA203-Q1 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 VS

is still applied to the INA203-Q1. It is important to know what the behavior of the devices will be in these regions.

As VSENSE approaches 0 mV, 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 = 300 mV for VSENSE

= 0 mV. As VSENSE approaches 20 mV, VOUT returns to the expected output value with accuracy as specified in

the Electrical Characteristics. Figure 32 illustrates this effect (Gain = 100).