Figure 8-3 shows the complete OPA2186 high-side current monitor. The circuit is capable of monitoring a current

range of < 1 A to 11 A, with a VCM very close to the 24-V supply voltage.

+

–

+ 24 V –

VO = 300 mV to 3.3 V

+

24 V

–

RL = 10 m

R1 = 1 k

R2 = 30 k

R3 = 1 k

R4 = 30 k

OPA2186

IL

Load Current

1 A to 11 A

µController

ADC

+ 3.3 V –

Figure 8-3. OPA2186 Configured as a High-Side Current Monitor

In this example, the OPA2186 output voltage is intentionally limited to 3.3 V. However, because of the 24-V

supply, the output voltage can be much higher to allow for a higher-voltage data converter with a higher dynamic

range.

The circuit in Figure 8-3 was checked using the TINA Spice circuit simulation tool to verify the correct operation

of the OPA2186 high-side current monitor. The simulation results are seen in Figure 8-4. The performance is

exactly as expected. Upon careful inspection of the plots, one possible surprise is that VO continues towards

zero as the sense current drops below 1 A, where VO is 300 mV and less.

+

–

+ 24 V –

VO = 300 mV to 3.3 V

+

24 V

–

RL = 10 m

R1 = 1 k

R2 = 30 k

R3 = 1 k

R4 = 30 k

OPA2186

IL

Load Current

1 A to 11 A

µController

ADC

+ 3.3 V –

Figure 8-4. OPA2186 High-Side Current-Monitor Simulation Schematic

The OPA2186 output, as well as other CMOS output amplifiers, often swing closer to 0 V than the linear

output parameters suggest. The voltage output swing, VO (see the Electrical Characteristics table), is not an

indication of the linear output range, but rather how close the output can move towards the supply rail. In that

region, the amplifier output approaches saturation, and the amplifier ceases to operate linearly. Thus, in the

current-monitor application, the current-measurement capability can continue to much less than the 300-mV

output level. However, keep in mind that the linearity errors are becoming large.

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OPA2186

SBOS968A – JUNE 2022 – REVISED SEPTEMBER 2022

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