INA219: About specification of ADC timing

Hello Satoshi,

1. The target measurement for the conversion times listed under "ADC Timing" is the applied shunt voltage of 32mV listed in the testing conditions at top of the Electrical Characteristics table.

2. The "Minimum convert input low time" spec is for a device with an external Convert pin that needs to be pulsed low to trigger a conversion. I noticed in the data sheet on page 10 that there is reference to a convert pin, but the package drawing doesn’t show a Convert pin as this is a serial I2C interface device. I will have to get back to you on this.

3. If the data changes significantly during a single ADC Conversion time (for example, signal is a DC 32mV, but then jumps to 100mV very quickly halfway through conversion time), then these 100mV input values will be sampled and averaged along with the 32mV values to create a single ouput value in between 32mV and 100mV. So overall, the INA219 output cannot change at the same time the input changes, there will be some latecncy. This latency should be greater for higher conversion time and lower shorter conversion times. If conversion time is increase and latency also increased, then noise will go down. So there is tradeoff between latency and noise.

Peter Iliya
Current Sense Applications