SENSE

SENSE

Total Offset Error (V)

Total Offset Error (%) =

100%

I

R

u

u

INA180

2.7 V to 5.5 V

Load

Supply

GND

VS

Load

IN±

IN+

OUT

+

±

0.1 µF

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21

INA180, INA2180

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SBOS741A – APRIL 2017 – REVISED AUGUST 2017

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9.2 Typical Application

Figure 41. Low-Side Sensing

9.2.1 Design Requirements

The design requirements for the circuit shown in Figure 41, are listed in Table 3

Table 3. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

5 V

Low-side current sensing

Mode of operation

Unidirectional

< 900 mW

40 A

Accuracy

Small-signal bandwidth

> 80 kHz

9.2.2 Detailed Design Procedure

The maximum value of the current sense resistor is calculated based on the maximum power loss requirement.

By applying Equation 1, the maximum value of the current-sense resistor is calculated to be 0.563 mΩ. This is

standard resistor value that meets the power-loss requirement.

sense gain calculated to avoid the positive swing-to-rail limitations on the output is 248.5. To maximize the output

signal range, the INA180A4 (gain = 200) device is selected for this application.

To calculate the accuracy at peak current, the two factors that must be determined are the gain error and the

offset error. The gain error of the INAx180 is specified to be a maximum of 1%. The error due to the offset is

Equation 6, the percentage error contribution of the offset voltage is calculated to be 0.75%, with total offset error

(6)