LM2662M/TR-HG

The LM2662 CMOS charge pump voltage converter inverts positive voltages in the range of 1.5 V to 5.5 V to the corresponding negative voltage. Using two low-cost capacitors, the LM2662 delivers 200 mA of output current without the cost, size, and EMI issues associated with inductor-based converters. With a quiescent current of only 300 μA and efficiency exceeding 90% under most load conditions, it provides ideal performance for battery-powered systems. The LM2662 can also be used as a positive voltage doubler. The oscillator frequency can be reduced by adding an external capacitor to the OSC pin. In addition, the OSC pin can be used to drive the LM2662 with an external clock. For the LM2662, the oscillator frequency of 20 kHz or 150 kHz can be selected via the frequency control (FC) pin. The LM2662 contains four large CMOS switches that are sequentially switched to invert the input supply voltage. Energy transfer and storage are provided by external capacitors. When S1 and S3 are closed, C1 charges to the supply voltage V+. During this period, switches S2 and S4 are open. In the second time interval, S1 and S3 open and S2 and S4 close, allowing C1 to charge C2. After multiple cycles, the voltage across C2 is boosted to V+. Since the anode of C2 is connected to ground, assuming no load on C2, lossless switches, and no ESR in the capacitors, the output at the cathode of C2 equals −(V+). In practice, charge transfer efficiency depends on the switching frequency, switch on-resistance, and capacitor ESR.

Applications

• Laptops
• Mobile phones
• Medical instruments
• Op-amp power supplies
• Interface power supplies
• Handheld instruments

Key features

• Inverts or doubles input supply voltage
• Typical output resistance: 9 Ω
• Typical conversion efficiency: 86% at 200 mA
• Selectable oscillator frequency: 20 kHz/150 kHz