An overcurrent threshold is set by programming the Current Over-Limit Threshold register (COL). The value that

must be programmed into this register is calculated by dividing the over current limit value by the current LSB

size. For this example, the target value for the COL register is 9 A ÷ 480 μA = 18750d (493Eh).

An overvoltage fault threshold on the bus voltage is set by programming the bus over voltage limit register

(BOVL). In this example the desired overvoltage threshold is 14 V. The value that must be programmed into this

register is calculated by dividing the target threshold voltage by the bus voltage fault limit LSB value of 3.125 mV.

For this example, the target value for the BOVL register is 14 V ÷3.125 mV = 4480d (1180h).

When setting the power over-limit value, the LSB size used to calculate the value needed in the limit registers

will be 256 times greater than the power LSB. This is because the power register is a 24 bits in length while the

power fault limit register is 16 bits.

Values stored in the alert limit registers are set to the default values after VS power cycle events and must be

reprogrammed each time power is applied.

8.2.2.3 Calculate Returned Values

Parametric values are calculated by multiplying the returned value by the LSB value. Table 8-4 shows the

returned values for this application example, assuming the design requirements shown in Table 8-3.

Table 8-4. Calculating Returned Values

PARAMETER

RETURNED VALUE

LSB VALUE

CALCULATED VALUE

Current (A)

10417d

480 µA/LSB

5.00016 A

Bus voltage (V)

3840d

3.125 mV/LSB

12 V

Power (W)

625020d

96 µW/LSB

60.00192 W

Energy (J)

8789344d

24.576 mJ/LSB

216.007 kJ

Charge (C)

3750120d

480 µC/LSB

18000.576 C

Temperature (°C)

320d

125 mºC/LSB

40°C

Current, Bus Voltage (positive only), Charge, and Temperature 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 should then be converted to decimal with the negative sign applied. For

example, assume a current reading returns 1011 0100 0001 0000. This is a negative value due to the MSB

having a value of one. Inverting the bits and adding one results in 0100 1011 1111 0000 (19440d) which from

the current value example in Table 8-4 correlates to a current of 9.3312 A. The returned value was negative,

therefore the measured current value is –9.3312 A.

INA700

SBOSAB4 – MAY 2023

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