INA226-Q1

www.ti.com

SBOS743 – JULY 2015

Feature Description (continued)

The device has two operating modes, continuous and triggered, that determine how the ADC operates following

these conversions. When the device is in the normal operating mode (that is, MODE bits of the Configuration

Register (00h) are set to '111'), it continuously converts a shunt voltage reading followed by a bus voltage

reading. After the shunt voltage reading, the current value is calculated (based on Equation 3). This current value

is then used to calculate the power result (using Equation 4). These values are subsequently stored in an

accumulator, and the measurement/calculation sequence repeats until the number of averages set in the

Configuration Register (00h) is reached. Following every sequence, the present set of values measured and

calculated are appended to previously collected values. After all of the averaging has been completed, the final

values for shunt voltage, bus voltage, current, and power 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. Reading the data output registers does not affect a conversion in progress.

The mode control in the Conversion Register (00h) also permits selecting modes to convert only the shunt

voltage or the bus voltage in order to further allow the user to configure the monitoring function to fit the specific

application requirements.

All current and power calculations are performed in the background and do not contribute to conversion time.

In triggered mode, writing any of the triggered convert modes into the Configuration Register (00h) (that is,

MODE bits of the Configuration Register (00h) are set to ‘001’, ‘010’, or ‘011’) triggers a single-shot conversion.

This action produces a single set of measurements; thus, to trigger another single-shot conversion, the

Configuration Register (00h) must be written to a second time, even if the mode does not change.

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

reduces the quiescent current and turns off current into the device inputs, reducing the impact of supply drain

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

device 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 (00h) .

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

Conversion Ready flag bit (Mask/Enable Register, CVRF bit) is provided to help coordinate one-shot or triggered

conversions. The Conversion Ready flag (CVRF) bit is set after all conversions, averaging, and multiplication

operations are complete.

The Conversion Ready flag (CVRF) bit clears under these conditions:

•

Writing to the Configuration Register (00h) , except when configuring the MODE bits for power-down mode; or

•

Reading the Mask/Enable Register (06h)

7.3.1.1 Power Calculation

The Current and Power are calculated following shunt voltage and bus voltage measurements as shown in

Figure 19. Current is calculated following 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. Again,

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 (00h) .

Copyright © 2015, Texas Instruments Incorporated

Submit Documentation Feedback

11

Product Folder Links: INA226-Q1