MIC4043_14 Datasheet, PDF (7/14 Pages) Micrel Semiconductor – Low-Voltage, Secondary-Side Shunt Regulator

Micrel, Inc.
Functional Description
The MIC4043 combines a G_M amplifier, precision 1.245V
reference, and a pass transistor in a single package.
The operation of the MIC4043 is similar to conventional
shunt regulators such as the industry standard ’431. In a
closed loop system, the MIC4043 maintains the desired
feedback voltage at the FB pin by sinking current onto the
SNK pin proportional to the error voltage at the FB pin.
The ratio of sink current to error voltage is the
transconductance of the device.
Reference
The MIC4043 uses a high-side reference. External
voltage dividers providing feedback to the MIC4043 will
be inverted when compared to those used with ’431-
equivalent devices.
Behavior
The external feedback voltage is compared to the internal
high-side 1.245V reference.
If the feedback voltage, V_FB, is less than V_IN – V_REF, the
amplifier provides no drive to the sink transistor. If the
feedback voltages are greater than V_IN – V_REF, the
amplifier drives the pass transistor which sinks current to
ground.
MIC4043
October 10, 2014
7
Revision 2.0