INA780B datasheet(12/42 Pages) TI1

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The INA780x measures the die temperature, current, and bus voltage. An internal temperature measurement is

made before each current measurement. Temperature compensation is then applied to the current measurement

to achieve low drift performance. The MODE bits setting in the ADC_CONFIG register permit selecting modes

to convert only the current or bus voltage to further allow the user to configure the monitoring function to fit

the specific application requirements. After an ADC conversion is complete, the converted values independently

update in their corresponding registers where they can be read through the digital interface at the time of

conversion end if no averaging is selected. The conversion time for shunt voltage, bus voltage, and temperature

inputs are set independently from 50 µs to 4.12 ms depending on the values programmed in the ADC_CONFIG

made. The total time to get the current measurement is the sum of the conversion times for these two

parameters. Enabled measurement inputs are converted sequentially, which means the total time to convert

all inputs depends on the conversion time for each input and the number of inputs enabled. When averaging

is used, the intermediate values are subsequently stored in an averaging accumulator, and the conversion

sequence repeats until the number of averages is reached. After all of the averaging is complete, the final

values are updated in the corresponding registers that can then be read. These values remain in the data output

registers until they are replaced by the next fully completed conversion results. In this case, reading the data

output registers does not affect a conversion in progress.

The ADC has two conversion modes—continuous and triggered—set by the MODE bits in the ADC_CONFIG

the output registers as described above in an indefinite loop. In triggered-conversion mode, the ADC will convert

the input measurements as described above, after which the ADC will go into shutdown mode until another

single-shot trigger is generated by writing to the MODE bits. Writing the MODE bits will interrupt and restart

triggered or continuous conversions that are in progress. The values from the device can be read at any time

because data from the last conversion remains available until the next conversion is complete. The Conversion

Ready flag is set after all conversions and averaging are complete.

The Conversion Ready flag (CNVRF) clears under these conditions:

• Writing to the ADC_CONFIG register (except for selecting shutdown mode); or

• Reading the DIAG_ALRT Register

While the INA780x device is used in either one of the conversion modes, a dedicated digital engine is calculating

the current, power, charge and energy values in the background as described in Internal Measurement

and Calculation Engine. In triggered mode, the accumulation registers (ENERGY and CHARGE) are invalid,

as the device does not keep track of elapsed time. For applications that require critical measurements in

regards to accumulation of time for energy and charge measurements, the device must be configured to use

continuous conversion mode, as the accumulated results are continuously updated and can provide true system

representation of charge and energy consumption in a system. All of the calculations are performed in the

background and do not contribute to conversion time.

For applications that must synchronize with other components in the system, the INA780x conversion can be

delayed by programming the CONVDLY bits in the CONFIG register in the range between 0 ms (no delay)

and 510 ms. The resolution in programming the conversion delay is 2 ms. The conversion delay is set to 0

ms by default. Conversion delay can assist in measurement synchronization when multiple external devices

are used for voltage or current monitoring purposes. In applications where time-aligned voltage and current

measurements are needed, two devices can be used with the current measurement delayed such that the

external voltage and current measurements will occur at approximately the same time. Keep in mind that even

though the internal time base for the ADC is precise, synchronization will be lost over time due to internal and

external time base mismatch.

7.3.5.1 Low Latency Digital Filter

The device integrates a low-pass digital filter that performs both decimation and filtering on the ADC output

data, which helps with noise reduction. The digital filter is automatically adjusted for the different output data

rates and always settles within one conversion cycle. The user has the flexibility to choose different output

conversion time periods TCT from 50 µs to 4.12 ms. With this configuration the first amplitude notch appears

at the Nyquist frequency of the output signal which is determined by the selected conversion time period and

defined as fNOTCH= 1 / (2 x TCT). This means that the filter cut-off frequency will scale proportionally with the

INA780A, INA780B

SBOSAB6 – JULY 2023

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