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MIC4043_14 Datasheet, PDF (1/14 Pages) Micrel Semiconductor – Low-Voltage, Secondary-Side Shunt Regulator | |||
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MIC4043
Low-Voltage, Secondary-Side
Shunt Regulator
General Description
The MIC4043 is a shunt regulator optimized for secondary-
side regulation in low-voltage power supplies. Featuring an
output stage guaranteed to swing within 400mV of ground,
the MIC4043 can be used in power supplies operating
down to 1.8V, even with opto-isolators requiring greater
than 1.2V of headroom.
In power supply applications, the MIC4043 normally drives
the LED of an optically isolated feedback circuit. The
MIC4043 monitors a resistively-divided output voltage and
sinks error current through the opto-isolatorâs LED
(secondary side); the opto-isolatorâs transistor (primary
side) provides this signal to the controllerâs feedback input.
The MIC4043 is also practical for other voltage-monitoring
applications requiring an open- collector output.
The MIC4043 replaces conventional â431-type shunt
regulators to allow low-voltage applications where there is
inadequate headroom for a 2.5V regulator in series with an
opto-isolator. Replacing â431-type devices requires only a
minor change to the way that the resistive-divider values
are calculated.
Datasheets and support documentation are available on
Micrelâs web site at: www.micrel.com.
Features
⢠Ideal for 1.8V switching converters
⢠Low-voltage operation:
â 400mV maximum saturation over operating
temperature range
⢠Easy-to-use
â Voltage in, current out
⢠2% voltage tolerance over operating temperature range
Applications
⢠Optically-isolated, low-voltage power supplies
⢠Low-voltage discrete regulator control
Typical Application
200kHz DC-to-DC Flyback Converter
Micrel Inc. ⢠2180 Fortune Drive ⢠San Jose, CA 95131 ⢠USA ⢠tel +1 (408) 944-0800 ⢠fax + 1 (408) 474-1000 ⢠http://www.micrel.com
October 10, 2014
Revision 2.0
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