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Current Limit Detect Following

Every Shunt Voltage Conversion

Bus and Power Limit Detect

Following Every Bus Voltage Conversion

Power Average

Bus Voltage Average

Shunt Voltage Average

INA231

www.ti.com

SBOS644 – FEBRUARY 2013

In addition to the two operating modes (continuous and triggered), the INA231 also has a power-down mode that

reduces the quiescent current and turns off current into the INA231 inputs, which reduces the impact of supply

drain when the device is not being used. Full recovery from power-down mode requires 40 ms. The registers of

the INA231 can be written to and read from while the device is in power-down mode. The device remains in

power-down mode until one of the active modes settings are written into the Configuration register.

Although the INA231 can be read at any time, and the data from the last conversion remain available, the

conversion ready flag bit (CVRF bit, Mask/Enable register) is provided to help coordinate single-shot or triggered

conversions. The CVRF bit is set after all conversions, averaging, and multiplication operations are complete for

a single cycle.

The CVRF bit clears under these conditions:

1. Writing to the Configuration register, except when configuring the MODE bits for power-down mode; or

2. Reading the Status register.

Power Calculation

The current and power are calculated after shunt voltage and bus voltage measurements, as shown in Figure 20.

The current is calculated after a shunt voltage measurement based on the value set in the Calibration register. If

there is no value loaded into the Calibration register, the current value stored is zero. Power is calculated

following the bus voltage measurement based on the previous current calculation and bus voltage measurement.

If there is no value loaded in the Calibration register, the power value stored is also zero. These calculations are

performed in the background and do not add to the overall conversion time. These current and power values are

considered intermediate results (unless the averaging is set to 1) and are stored in an internal accumulation

register, not the corresponding output registers. Following every measured sample, the newly-calculated values

for current and power are appended to this accumulation register until all of the samples have been measured

and averaged based on the number of averages set in the Configuration register.

Figure 20. Power Calculation Scheme

In addition to the current and power accumulating after every sample, the shunt and bus voltage measurements

are also collected. After all of the samples have been measured and the corresponding current and power

calculations have been made, the accumulated average for each of these parameters is then loaded to the

corresponding output registers where they can then be read.

Copyright © 2013, Texas Instruments Incorporated

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