INA230_17 Datasheet, PDF (14/37 Pages) Texas Instruments – High- or Low-Side Measurement, Bidirectional CURRENT/POWER MONITOR with I2C Interface

INA230
SBOS601 – FEBRUARY 2012
www.ti.com
ALERT PIN
The INA230 has a single Alert Limit register (07h) that allows the ALERT pin to be programmed to respond to a
single user-defined event or to a conversion ready notification if desired. The Mask/Enable register allows for
selecton from one of the five available functions to monitor and/or set the conversion ready bit (CNVR,
Mask/Enable register) to control the response of the ALERT pin. Based on the function being monitored, a value
would then be entered into the Alert Limit register to set the corresponding threshold value that asserts the
ALERT pin.
The ALERT pin allows for one of several available alert functions to be monitored to determine if a user-defined
threshold has been exceeded. The five alert functions that can be monitored are:
• Shunt Voltage Over Limit (SOL)
• Shunt Voltage Under Limit (SUL)
• Bus Voltage Over Limit (BOL)
• Bus Voltage Under Limit (BUL)
• Power Over Limit (POL)
The ALERT pin is an open-drain output. This pin is asserted when the alert function selected in the Mask/Enable
register exceeds the value programmed into the Alert Limit register. Only one of these alert functions can be
enabled and monitored at a time. If multiple alert functions are enabled, the selected function in the highest
significant bit position takes priority and responds to the Alert Limit register value. For example, if the SOL and
the SUL are both selected, the ALERT pin asserts when the Shunt Voltage Over Limit register exceeds the value
in the Alert Limit register.
The conversion ready state of the device can also be monitored at the ALERT pin to inform the user when the
device has completed the previous conversion and is ready to begin a new conversion. The conversion ready
flag (CVRF) bit can be monitored at the ALERT pin along with one of the alert functions. If an alert function and
the CNVR bit are both enabled to be monitored at the ALERT pin, then after the ALERT pin is asserted, the
Mask/Enable register must be read following the alert to determine the source of the alert. By reading the CVRF
bit (D3), and the AFF bit (D4) in the Mask/Enable register, the source of the alert can be determined. If the
conversion ready feature is not desired, and the CNVR bit is not set, the ALERT pin only responds to an
exceeded alert limit based on the alert function enabled.
If the alert function is not used, the ALERT pin can be left floating without impacting the operation of the device.
Refer to Figure 20 to see the relative timing of when the value in the Alert Limit register is compared to the
corresponding converted value. For example, if the alert function that is enabled is Shunt Voltage Over Limit
(SOL), following every shunt voltage conversion the value in the Alert Limit register is compared to the measured
shunt voltage to determine if the measurements have exceeded the programmed limit. The AFF bit (D4,
Mask/Enable register) asserts high any time the measured voltage exceeds the value programmed into the Alert
Limit register. In addition to the AFF bit being asserted, the ALERT pin is asserted based on the Alert Polarity bit
(APOL, D1, Mask/Enable register). If the Alert Latch is enabled, the AFF bit and ALERT pin remain asserted until
either the Configuration register is written to or the Mask/Enable register is read.
The bus voltage alert functions (BOL and BUL, Mask/Enable register) compare the measured bus voltage to the
Alert Limit register following every bus voltage conversion and assert the AFF bit and ALERT pin if the limit
threshold is exceeded.
The power over limit alert function (POL, Mask/Enable Regsiter) is also compared to the calculated power value
following every bus voltage measurement conversion and asserts the AFF bit and ALERT pin if the limit
threshold is exceeded.
With the alert function comparing the programmed alert limit value to the result of each corresponding
conversion, it is possible to have an alert issued during a conversion cycle where the averaged value of the
signal does not exceed the alert limit. The triggering of the alert based on this intermediate conversion allows for
out-of-range events to be detected more quickly than the averaged output data registers are updated. This can
be used to create alert limits for quickly changing conditions through the use of the alert function, as well as to
create limits to longer-duration conditions through software monitoring of the averaged output values.
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