SBOS659B January 2022 – August 2022 OPA593
The OPA593 has a high-accuracy, externally programmable current limit that has a ±5% tolerance for output currents ≥ 50 mA. The current limit is set through the ILIMIT pin and is programmable from 10 mA to 250 mA (typical). A resistor can be used to limit the current to a fixed value or a digital-to-analog converter (DAC) can be used to vary the current limit during operation. Figure 7-1 shows a simplified diagram of the current-limit mirror configurations, as well as common resistor or DAC settings and the respective output current limit.
The most common configuration is to set the current limit using a resistor (RCL) connected between the ILIMIT pin and the negative supply (V–). With this configuration, Equation 1 and Equation 2 are used to calculate the current limit based on the external resistor value or the resistor needed given the desired current limit value:
An alternative to fixing the current limit to a single value using an external resistor is to use a DAC, which enables a variable current limit.
Use Equation 3 to set the current limit when a DAC is used (VLIMIT = DAC output voltage):
Several nominal current limit values along with their respective external resistor values and DAC output voltages are listed in Table 7-1.
|OUTPUT CURRENT LIMIT (mA)||RESISTOR (kΩ)||DAC VOLTAGE (V)|
The current limit of the OPA593 has a ±10% tolerance for output currents between 25 mA and 50 mA, and is ±5% accurate for currents ≥ 50 mA. Any resistor or DAC tolerances add to the OPA593 tolerance, so take care when selecting the external components to make sure and provide the desired system level accuracy. Figure 7-2 shows a correlation between the ideal or calculated output current limit and the actual current limit as measured on the OPA593.