Datasheet

Power
Valid
Output
High
Low
All enabled channel bus voltages are
above the power valid upper limit.
All enabled channel
bus voltages are not above
the power valid upper limit.
At least one bus voltage channel has
dropped below the power valid lower limit.
All enabled channel bus voltages are
above the power valid upper limit.
INA3221
www.ti.com SBOS576A –MAY 2012–REVISED JUNE 2013
Warning Alert
The Warning Alert monitors the averaged value of each shunt voltage channel. The averaged value of each
shunt voltage channel is based on the number of averages set with the Average Mode bits in the Configuration
Register. The average value is updated in the shunt voltage output register each time there is a conversion on
the corresponding channel. The averaged value is compared to the value programmed in the corresponding
channel Warning Alert Limit register to determine if the averaged value has been exceeded, which indicates if the
average current is too high. The default Warning Alert Limit value for each channel is set to a positive full-scale
value to effectively disable this alert at power-up. The corresponding limit registers can be programmed at any
time to begin monitoring for out-of-range conditions. The Warning Alert pin is asserted and pulled low if any
channel measurements exceed the limit present in the corresponding channel Warning Alert Limit. When the
Warning Alert pin is asserted, the Mask/Enable Register can be read to determine which channel Warning Flag
Bit is asserted.
Power Valid Alert
The Power Valid Alert verifies if all power rails are above the required levels. This feature allows the INA3221 to
ensure power sequencing is properly managed and that the reported measurements are valid based on system
configuration. The Power Valid mode starts at power-up to detect when all channels exceed a 10-V threshold.
This 10-V level is the default value programmed into the Power Valid Upper Limit register. This value can be
reprogrammed when the INA3221 is powered up to a valid supply voltage level of at least 2.7 V. When all three
bus voltage measurements reach the programmed value loaded to the Power Valid Upper Limit register, the
Power Valid Alert pin is pulled high. The Power Valid Alert powers up in a low state and is not pulled high until
the Power Valid conditions are met, indicating all bus voltage rails are above the Power Valid Upper Limit value.
This sequence is shown in Figure 24.
Figure 24. Power Valid State Diagram
When the Power Valid conditions are met and the Power Valid Alert pin is pulled high, the INA3221 switches to a
mode that detects if any bus voltage measurements drop below 9 V. This 9-V level is the default value
programmed into the Power Valid Lower Limit register. This value can also be reprogrammed when the INA3221
powers up to a supply voltage of at least 2.7 V. If any bus voltage measurement on the three channels drops
below the Power Valid Lower Limit register, the Power Valid Alert pin goes low, indicating that the Power Valid
condition is no longer met. At this point, the INA3221 switches back to a mode that identifies a Power Valid
condition when all power rails again reach the Power Valid Upper Limit register values.
The Power Valid Alert function is based on the Power Valid conditions requirement that all three channels reach
the intended Power Valid Upper Limit value. If all three channels are not used, the unused channel VIN– pin
must be externally connected to one of the used channels in order to use the Power Valid Alert function. If the
unused channel is not connected to a valid rail, the Power Valid Alert function cannot detect if all three channels
reach the Power Valid level. The unused channel VIN+ pin should be left floating.
The Power Valid function also requires bus voltage measurements to be monitored. Bus voltage measurements
must be enabled through one of the corresponding MODE settings set in the Configuration Register to be able to
detect changes in the Power Valid state. The Single-Shot Bus Voltage mode can periodically cycle between the
bus voltage measurements to ensure that the Power Valid conditions are met.
When all three bus voltage measurements are completed, the results are compared to the Power Valid threshold
values to determine the Power Valid state. The bus voltage measurement values remain in the corresponding
channel output registers until the bus voltage measurements are taken again, which updates the output registers.
When the output registers are updated, the values are again compared to the Power Valid thresholds. Without
taking periodic bus voltage measurements, the INA3221 is unable to determine if the Power Valid conditions are
maintained.
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