Boost/Buck Converter Supplies Negative Bias

Because it provides a fixed output voltage from -3 vdc to -5 vdc (adjustable in 1V increments) over an input voltage range of 2.5 vdc to 5.5 vdc, the TC1142 boost/buck dc-dc converter is well suited for regulated negative dc bias applications. The 20-mA device can be connected directly to a 3.6V single-cell Li-ion battery and requires no inductors, thereby saving space and cost and reducing EMI effects.With its built-in voltage reference and comparator, a minimum number of external components can be teamed with the TC1142 converter in applications demanding a regulated negative dc bias, such as GaAs power amplifiers in cellular handsets. It requires only three external capacitors. Active feedback circuitry maintains a 2 ohm (typical) output impedance while in regulation. The unit can be clocked from its on-board, 200-kHz oscillator or an external clock.