INA239 datasheet(16/44 Pages) TI

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Settings for the conversion time and number of conversions averaged impact the effective measurement

resolution. For more detailed information on how averaging reduces noise and increases the effective number of

bits (ENOB) see Section 8.1.3.

7.3.5 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. 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.

7.3.6 Multi-Alert Monitoring and Fault Detection

The INA239 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

INA239 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.

INA239

SLYS027 – JANUARY 2021

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