ICL7663S

The ICL7663S is a CMOS integrated circuit incorporating all the functions of a voltage regulator plus protection circuitry on a single monolithic chip. Referring to the Functional Diagram, the main blocks are a bandgap-type voltage reference, an error amplifier, and an output driver with both PMOS and NPN pass transistors.

The bandgap output voltage, trimmed to 1.29V ±15mV for the ICL7663SA, and the input voltage at the V  terminal SET are compared in amplifier A. Error amplifier A drives a P-channel pass transistor which is sufficient for low (under about 5mA) currents. The high current output is passed by an NPN bipolar transistor connected as a follower. This configuration gives more gain and lower output impedance.

Logic-controlled shutdown is implemented via a N-Channel MOS transistor. Current-sensing is achieved with comparator C, which functions with the V_OUT2  terminal. The ICL7663S has an output (V_TC) from a buffer amplifier (B), which can be used in combination with amplifier A to generate programmable-temperature-coefficient output voltages.

The amplifier, reference and comparator circuitry all operate at bias levels well below 1A to achieve extremely low quiescent current. This does limit the dynamic response of  the circuits, however, and transients are best dealt with outside the regulator loop.