7.3 Feature Description

7.3.1 Current Limit

The OPA593 current limit is set through the ILIMIT pin and is programmable from ±25 mA to ±250 mA, typical.

The device is specified and tested for current limits of ±25 mA, ±50 mA, ±100 mA, ±250 mA. 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.

56.7 k

RCL

DAC

V– Supply

3.687 V

V–

ILIMIT

56.7 k

V– Supply

3.687 V

V–

ILIMIT

Figure 7-1. OPA593 Internal Current Limit Configurations

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:

ILIMIT= 3.687 V × 4000

56.7 kΩ+RCL

(1)

RCL= 3.687 V × 4000

ILIMIT  –56.7 kΩ

(2)

An alternative to fixing the current limit to a single value using an external resistor is to use a source measure

unit (SMU) or digital-to-analog converter (DAC), which enables a variable current limit.

CAUTION

With this configuration, the output of the SMU or 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 (VLIMIT = DAC output voltage):

VLIMIT= 3.687 V – ILIMIT × 56.7 kΩ

4000

(3)

Be aware that the SMU or DAC output voltage must be referenced to the negative supply of the OPA593.

Several nominal current-limit values along with the respective external resistor values and DAC output voltages

are listed in Table 7-1.

Table 7-1. Nominal Current-Limit Values

CURRENT LIMIT, ILIMIT(mA)

RESISTOR, RCL (kΩ)

DAC VOLTAGE, VLIMIT (V)(1)

25

536

3.33

50

237

2.98

100

90.9

2.27

200

16.9

0.85

250

2.29

0.14

(1)

Voltages are referenced to the negative supply, V−

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OPA593

SBOS659C – JANUARY 2022 – REVISED DECEMBER 2022

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