DAC7760 Datasheet, PDF (46/63 Pages) Texas Instruments – Single-Channel, 12- and 16-Bit Programmable Current Output and Voltage Output Digital-to-Analog Converters for 4-mA to 20-mA Current Loop Applications

DAC7760, DAC8760
SBAS528B – JUNE 2013 – REVISED JUNE 2016
Application Information (continued)
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R₂
R₃
VIN
D₁
Q₁
R₁
VOUT
Q₂
R₄
Figure 95. 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. Note that this is a very simple example 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.
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