of the samples have been measured and the corresponding current and power calculations have been made,

the accumulated average for each of these parameters is then loaded to the corresponding output registers

where they can then be read. These calculations are performed in the background and do not add to the overall

conversion time.

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Current Limit Detect Following

Every Shunt Voltage Conversion

Bus and Power Limit Detect

Following Every Bus Voltage Conversion

Power Average

Bus Voltage Average

Shunt Voltage Average

Figure 7-1. Power Calculation Scheme

7.3.3 Low Bias Current

When performing a current measurement, the INA232 features very low input bias current which provides

several benefits. The low input bias current of the INA232 reduces the current consumed by the device in both

active and shutdown state. Another benefit of low bias current is that it allows the use of input filters to reject

high-frequency noise before the signal is converted to digital data. In traditional digital current-sense monitors,

the addition of input filters comes at the cost of reduced accuracy. However, as a result of the low bias current,

the reduction in accuracy due to input filters is minimized. An additional benefit of low bias current is the ability

to use a larger shunt resistor to accurately sense smaller currents. Use of a larger value for the shunt resistor

allows the device to accurately monitor currents in the sub-mA range.

The bias current in the INA232 is the smallest when the sensed current is zero. As the current starts to increase,

the differential voltage drop across the shunt resistor increases which results in an increase in the bias current

(see Figure 6-9).

The INA232 has low bias current only when making a current measurement, when bus voltage measurements

are made the impedance of the IN– will decrease. During bus voltage measurements the IN– pin will be

connected to an internal resistor divider with an impedance of approximately 1 MΩ. Configuring the ADC to

perform only current measurements will allow the device to always have low bias current.

7.3.4 Low Voltage Supply and Wide Common-Mode Voltage Range

The supply voltage range of the INA232 is 1.7 V to 5.5 V. The ability to operate at 1.7 V enables the device to be

used in 1.8-V supply rails. Even with a supply voltage of 1.7 V, the device can monitor currents on voltage rails

as high as 48 V. This wide common-mode range of operation allows the device to be used in many applications

where the common-mode voltage exceeds the supply voltage rail.

7.3.5 ALERT Pin

The INA232 has a single Mask/Enable register (06h) that allows the ALERT pin to be programmed to respond

to a single user-defined event or to a conversion ready notification if desired. The Mask/Enable register allows

the selection from one of the five available functions to monitor and set the conversion ready bit (CNVR, Mask/

Enable register) to control the response of the ALERT pin. Based on the function being monitored, a value

would then be entered into the Alert Limit register (07h) to set the corresponding threshold value that asserts the

ALERT pin.

The ALERT pin allows for one of several available alert functions to be monitored to determine if a user-defined

threshold has been exceeded. The five alert functions that can be monitored are:

• Shunt voltage overlimit (SOL)

INA232

SBOSAA2 – DECEMBER 2022

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