The DACx760 voltage output includes an internal circuit to typically regulate the load current to about 30 mA. However, this parameter is not production tested or trimmed. Optionally, use an external current limiting circuit on VOUT. However, if the VOUT, IOUT and +VSENSE pins are tied together, this circuit must be placed in the VOUT path before the circuit is tied together to the other pins at the common pin. The nature of the current-limiting circuit depends on the application and load. An example of a unidirectional current limiter is shown in Figure 9-5.

Figure 9-5 Unidirectional Current Limiter Circuit

Under normal operation, most current in this circuit flows through Q1 and into R₃. As current increases through R₃, so does the voltage drop across R₃, which increases the base-emitter voltage of Q₂. Eventually the base-emitter voltage of Q₂ becomes high enough to turn on Q₂, which turns off Q₁ and reduce the current that can pass from VIN to VOUT. The value of R₃ sets the current limit. Be aware that this example is very simple and only applies for sourcing current into a resistive load. For cases involving both sourcing and sinking current as well as nonresistive loads, more complex circuits are required to achieve bidirectional current limiting.