Power

Valid

Output

High

Low

All Enabled Channel Bus

Voltages Are Not Above

Power Valid Upper Limit

All Enabled Channel Bus

Voltages Are Above

Power Valid Upper Limit

At Least One Bus Voltage

Channel Has Dropped Below

Power Valid Lower Limit

All Enabled Channel Bus

Voltages Are Above

Power Valid Upper Limit

INA3221

www.ti.com

SBOS576 – MAY 2012

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.

Copyright © 2012, Texas Instruments Incorporated

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