SBOS659B January 2022 – August 2022 OPA593

ADVANCE INFORMATION

- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
- 8 Application and Implementation
- 9 Device and Documentation Support
- 10Mechanical, Packaging, and Orderable Information

- DNT|12

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 (R_{CL}) 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:

Equation 1.
${I}_{LIMIT}=\frac{3.687V\times 4000}{56.7k\Omega +{R}_{CL}}$

Equation 2.
${R}_{CL}=\frac{3.687V\times 4000}{{I}_{LIMIT}}\mathrm{\u201356.7}k\Omega $

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.

CAUTION: With this configuration, the output of the DAC must not exceed the ILIMIT
specification in Section 6.1 to avoid reverse biasing the internal current limit circuitry and potentially damaging
the device.

Use Equation 3 to set the
current limit when a DAC is used (V_{LIMIT} = DAC output voltage):

Equation 3.
${V}_{LIMIT}=3.687V\u2013\frac{{I}_{LIMIT}\times 56.7k\Omega}{4000}$

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) |
---|---|---|

50 | 237 | 2.98 |

100 | 90.9 | 2.27 |

200 | 16.9 | 0.85 |

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.