CMOS Micro-Power Comparator plus Voltage Follower

The MC14578 is an analog building block consisting of a very-high input impedance comparator. The voltage follower allows monitoring the noninverting input of the comparator without loading.

Four enhancement-mode MOSFETs are also included on chip. These FETs can be externally configured as open-drain or totem-pole outputs. The drains have on-chip static-protecting diodes. Therefore, the output voltage must be maintained between VSS and VDD.

The chip requires one external component. A 3.9 MΩ ±10 resistor must be connected from the Rbias pin to VDD. This circuit is designed to operate in smoke detector systems that comply with UL217 and UL268 specifications.

Features

• Applications:

Pulse Shapers Line-Powered Smoke Detectors

Threshold Detectors Liquid/Moisture Sensors

Low-Battery Detectors CO Detector and Micro Interface

• Operating Voltage Range: 3.5 to 14 V

• Operating Temperature Range: -30° to 70°C

• Input Current (IN + Pin): ±1 pA @ 25°C (DIP Only)

• Quiescent Current: 10 µA @ 25°C

• Electrostatic Discharge (ESD) Protection Circuitry on All Pins