INA228 datasheet(17/50 Pages) TI

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7.3.6 Integrated Precision Oscillator

The internal timebase of the device is provided by an internal oscillator that is trimmed to less than 0.5%

tolerance at room temperature. The precision oscillator is the timing source for ADC conversions, as well as

the time-count used for calculation of energy and charge. The digital filter response varies with conversion time;

therefore, the precise clock ensures filter response and notch frequency consistency across temperature. On

power up, the internal oscillator and ADC take roughly 300 µs to reach <1% error stability. Once the clock

stabilizes, the ADC data output will be accurate to the electrical specifications provided in Section 6.

7.3.7 Multi-Alert Monitoring and Fault Detection

The INA228-Q1 includes a multipurpose, open-drain ALERT output pin that can be used to report multiple

diagnostics or as an indicator that the ADC conversion is complete when the device is operating in both

triggered and continuous conversion mode. The diagnostics listed in Table 7-1 are constantly monitored and can

be reported through the ALERT pin whenever the monitored output value crosses its associated out-of-range

threshold.

Table 7-1. ALERT Diagnostics Description

INA228-Q1 DIAGNOSTIC

STATUS BIT IN DIAG_ALRT REGISTER

(RO)

OUT-OF-RANGE

THRESHOLD

VALUE

Shunt Under Voltage Limit

SHNTUL

SUVL

0x8000 h

(two's complement)

Shunt Over Voltage Limit

SHNTOL

SOVL

0x7FFF h

(two's complement)

Bus Voltage Over-Limit

BUSOL

BOVL

0x7FFF h

(two's complement,

positive values only)

Bus Voltage Under-Limit

BUSUL

BUVL

0x0000 h

(two's complement,

positive values only)

Temperature Over-Limit

TMPOL

TEMP_LIMIT

0xFFFF h

(two's complement,

positive values only)

Power Over-Limit

POL

PWR_LIMIT

0x7FFF h

(two's complement)

A read of the DIAG_ALRT register is used to determine which diagnostic has triggered the ALERT pin. This

ALERT pin functions.

• Alert latch enable — In case the ALERT pin is triggered, this function will hold the value of the pin even after

all diagnostic conditions have cleared. A read of the DIAG_ALRT register will reset the status of the ALERT

pin. This function is enabled by setting the ALATCH bit.

• Conversion ready enable — Enables the ALERT pin to assert when an ADC conversion has completed and

output values are ready to be read through the digital interface. This function is enabled by setting the CNVR

bit. The conversion completed events can also be read through the CNVRF bit regardless of the CNVR bit

setting.

• Alert comparison on averaged output — Allows the out-of-range threshold value to be compared to the

averaged data values produced by the ADC. This helps to additionally remove noise from the output data

when compared to the out-of-range threshold to avoid false alerts due to noise. However, the diagnostic will

be delayed due to the time needed for averaging. This function is enabled by setting the SLOWALERT bit.

• Alert polarity — Allows the device to invert the active state of the ALERT pin. Note that the ALERT pin is an

open-drain output that must be pulled-up by a resistor. The ALERT pin is active-low by default and can be

configured for active high function using the APOL control bit.

Other diagnostic functions that are not reported by the ALERT pin but are available by reading the DIAG_ALRT

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INA228-Q1

SLYS022A – JUNE 2020 – REVISED JUNE 2021

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