The TPS6040x is a family of devices that generate an unregulated negative output voltage from an input voltage
ranging from 1.6 V to 5.5 V. The devices are typically supplied by a preregulated supply rail of 5 V or 3.3 V. Due
to its wide input voltage range, two or three NiCd, NiMH, or alkaline battery cells, as well as one Li-Ion cell can
also power them.
Only three external 1-μF capacitors are required to build a complete dc/dc charge pump inverter. Assembled
in a 5-pin SOT23 package, the complete converter can be built on a 50 mm2 board area. Additional board area
and component count reduction is achieved by replacing the Schottky diode that is typically needed for start-up
into load by integrated circuitry.
The TPS6040x can deliver a maximum output current of 60 mA with a typical conversion efficiency of greater
than 90% over a wide output current range. Three device options with 20-kHz, 50-kHz, and 250-kHz fixed
frequency operation are available. One device comes with a variable switching frequency to reduce operating
current in applications with a wide load range and enables the design with low-value capacitors.