Power_LSB = 20 Current_LSB

15

Maximum Expected Current

Current _ LSB

2

=

Cal = trunc

0.04096

Current_LSB

R

´

SHUNT

Supply

Load

R

10

FILTER

R

10

FILTER

0.1µF to 1µF

Ceramic Capacitor

R

SHUNT

Data (SDA)

3.3V Supply

Clock (SCL)

×

Power Register

Current Register

I C-/SMBUS

2

Compatible

Interface

Voltage Register

V

IN+

ADC

INA220

GND

A0

A1

Supply Voltage

V

IN-

V

S

V

BUS

11

INA220

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SBOS459E – JUNE 2009 – REVISED JANUARY 2016

Product Folder Links: INA220

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Device Functional Modes (continued)

In applications that do not have large energy storage electrolytics on one or both sides of the shunt, an input

overstress condition may result from an excessive dV/dt of the voltage applied to the input. A hard physical short

is the most likely cause of this event, particularly in applications with no large electrolytics present. This problem

occurs because an excessive dV/dt can activate the ESD protection in the INA220 in systems where large

currents are available. Testing has demonstrated that the addition of 10-

Ω resistors in series with each input of

the INA220 sufficiently protects the inputs against dV/dt failure up to the 26-V rating of the INA220. These

resistors have no significant effect on accuracy.

Figure 14. INA220 With Input Filtering

8.5 Programming

8.5.1 Programming the INA220 Calibration Register

Register Details shows the default power-up states of the registers. These registers are volatile, and if

programmed to anything other than default values, they must be reprogrammed at every device power-up. The

Calibration Register is calculated based on Equation 1. This equation includes the term Current_LSB, which is

the programmed value for the LSB for the Current Register (04h). The Current_LSB value is used to convert the

value in the Current Register (04h) to the actual current in amperes. The highest resolution for the Current

Register (04h) can be obtained by using the smallest allowable Current_LSB based on the maximum expected

current as shown in Equation 2. While this value yields the highest resolution, it is common to select a value for

the Current_LSB to the nearest round number above this value to simplify the conversion of the Current Register

shunt used to develop the differential voltage across the input pins. The Power Register (03h) is internally set to

be 20 times the programmed Current_LSB (see Equation 3).

where

•

0.04096 is an internal fixed value used to ensure scaling is maintained properly

•

Current_LSB is the programmed value for the LSB for the Current Register (04h)

(1)

(2)

(3)