Table 8-4. Register Values (continued)

Register

Contents

LSB Value

Calculated Value

Bus_Voltage_CH1 (01h)

7500d (1D4Ch)

1.6mV

7500 × 1.6mV = 12V

Current_CH1 (02h)

12000d (2EE0h)

Current LSB = 500µA

12000 × 500µA = 6A

Power_CH1 (03h)

4500d (1194h)

Current LSB x 32 = 16mW

4500 × 16mW = 72W

Energy_CH1 (04h)

16200000d (00F7

3140h)

Current LSB x 32 = 16mJ

16200000 × 16mJ = 259.2kJ

Shunt Voltage and Current return values in two's complement format. In two's complement format a negative

value in binary is represented by having a 1 in the most significant bit of the returned value. These values can

be converted to decimal by first inverting all the bits and adding 1 to obtain the unsigned binary value. This value

must then be converted to decimal with the negative sign applied.

8.2.3 Application Curves

Figure 8-4 and Figure 8-5 show the ALERT pin response to a BUS over voltage fault with a conversion time

of 140μs for the bus voltage measurements with averaging set to 1. For these scope shots, persistence is

enabled on the ALERT channel to show the variation in the alert response for many sequential fault events. The

alert response time can change depending on the value of the current before fault occurs as well as the how

much the fault condition exceeds the programmed fault threshold. Figure 8-4 shows the response time for an

overcurrent fault when the fault condition greatly exceeds the programmed threshold. While Figure 8-5 shows

the over voltage response time when the fault slightly exceeds the programmed threshold. Variation in the alert

response exists because the external fault event is not synchronized to the internal ADC conversion start. Also

the ADC is constantly sampling to get a result, so the response time for fault events starting from zero are slower

than fault events starting from values near the set fault threshold. In applications where the alert timing is critical,

the worst-case alert response is equal to 2 × (tconv_shunt + tconv_voltage) × number of channels enabled. When

alerting on over power conditions, an additional 60μs needed to allow for background math calculations.

Minimum Delay: 54µs

TIME (50µs / div)

Fault Threshold: 0.2V

Maximum Delay: 193µs

Figure 8-4. Alert Response Time (Sampled Values

Significantly Above Threshold)

Minimum Delay: 136µs

TIME (50µs / div)

Fault Threshold: 1.9V

Maximum Delay: 275µs

Figure 8-5. Alert Response Time (Sampled Values

Slightly Above Threshold)

8.3 Power Supply Recommendations

Figure 8-3 shows that the device input circuitry can accurately measure signals on common-mode voltages

beyond the power-supply voltage, VS. For example, the voltage applied to the VS power supply pin can be 5V,

whereas the bus power-supply voltage being monitored (the common-mode voltage) can be as high as 48V. The

device can also withstand the full -0.3V to 48V range at the input pins, regardless of whether the device has

power applied or not.

INA2227

SBOSAL5 – JUNE 2025

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