The TL497AC and TL497AI incorporate on a single monolithic chip all the active functions required in the construction of switching voltage regulators. They can also be used as the control element to drive external components for high-power-output applications. The TL497AC and TL497AI were designed for ease of use in step-up, step-down, or voltage inversion applications requiring high efficiency. The TL497AC and TL497AI are fixed-on-time variable-frequency switching-voltage-regulator control circuits. The switch-on time is programmed by a single external capacitor connected between FREQ CONTROL and GND. This capacitor, CT, is charged by an internal constant-current generator to a predetermined threshold. The charging current and the threshold vary proportionally with VCC. Thus, the switch-on time remains constant over the specified range of input voltage (4.5 V to 12 V). Typical on times for various values of CT are as follows: TIMING CAPACITOR, CT (pF)