Power-up circuit for analog circuits

A start-up circuit for providing a current to an analog circuit in response to a power-down signal wherein the start-up circuit comprises:

• at least five transistors each having a gate, a drain and a source;
• a capacitor having a first electrode and a second electrode, the first capacitor electrode receiving an input voltage and the second capacitor electrode connected in series to the first transistor drain;
• the first transistor source connected to ground;
• the first transistor gate receiving a power-down signal input;
• the second capacitor electrode further connected to the second transistor drain;
• the second transistor drain further connected to the third transistor drain;
• the second transistor gate receiving the power-down signal;
• the third transistor source connected to the fourth transistor source;
• the fourth transistor source receiving a voltage input;
• the fourth transistor drain connected to the fifth transistor gate and to the third transistor gate;
• the fourth transistor gate receiving an inverted power-down signal;
• the fifth transistor gate further connected to the third transistor gate;
• the fifth transistor source receiving a voltage input;
• and
• the fifth transistor drain providing a start-up current to the analog circuit.

A start-up circuit for supplying current to an analog circuit comprising:

• means for receiving a power-down signal, the receiving means charging to a voltage;
• means for providing a reference current wherein the reference current means is supplied with a current from the receiving means;
• and
• means for mirroring current from the reference means;
• wherein the current mirroring means charges one or more nodes of the analog circuit.