Triple Capacitive Voltage Inverter with the MAX871

Published:2012/11/9 0:10:00 Author:muriel | Keyword: Triple Capacitive Voltage , Inverter, MAX871 | From:SeekIC

This design idea is based on a customer request for a cheap, and not very accurate, negative voltage supply of about -12V to -15V with a low output current of < 5mA and an input voltage of 5V. This application might be used for negative op-amp supply. Figure 1 shows the typical operation circuit with the flying capacitor C1 and C2. The output voltage on pin 1 is -VIN. Four additional capacitors (C3 to C6) and four additional diodes (D1 to D4) triple the negative output voltage at the OUT pin from -VIN to -3VIN. C5 and C6 decreases the voltage with every step by -VIN. Without any diode voltage drop C3 got -2VIN and C4 charges ideally to -3VIN. It is possible to add more of these cascades but with every step the voltage drop of the diodes will reduce the effort.



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