アプリケーションノート3659

Simple Circuit Converts +5V to -10V


Abstract: This simple charge-pump voltage inverter produces more than -10V at no load, and more than 200mA while the output voltage remains greater than the input.

The versatile switched-capacitor charge pump is easy to use and requires no inductor. It can double a positive voltage or convert a positive voltage to negative.

For some applications in which only a positive supply is available, the system must generate a negative voltage of larger magnitude than the positive rail. For that purpose, the circuit of Figure 1 inverts the input voltage and doubles the resulting negative output at the same time. The voltage inverter shown (IC1) converts a positive input to a negative output voltage, normally with an absolute magnitude lower than that of the input. But in this circuit, the two Schottky diodes and the two capacitors at the output produce a higher output voltage.

Figure 1. This simple circuit derives -10V from +5V.
Figure 1. This simple circuit derives -10V from +5V.

The expected output is VOUT = -(2xVIN - 2VD- IOUT* RO), where VD is the voltage drop across a diode, IOUT is the output current, and RO is the output resistance. While the maximum expected voltage is -10V, overshoot across the capacitors due to parasitic inductance in the capacitors and traces produces more than -11V at no load (Figure 2).

Figure 2. The circuit in Figure 1 above produces more than -10V at no load, and more than 200mA while the output voltage remains greater than the input.
Figure 2. The circuit in Figure 1 above produces more than -10V at no load, and more than 200mA while the output voltage remains greater than the input.

This design idea appeared in the May 26, 2005 issue of EDN magazine.

関連製品
MAX889 高周波、安定化、200mA、反転チャージポンプ 無料
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© Dec 14, 2005, Maxim Integrated Products, Inc.
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APP 3659: Dec 14, 2005
アプリケーションノート3659, AN3659, AN 3659, APP3659, Appnote3659, Appnote 3659